diff --git a/design-system/AGENTS.md b/design-system/AGENTS.md
index 1e21892aec..49f3d6bb32 100644
--- a/design-system/AGENTS.md
+++ b/design-system/AGENTS.md
@@ -42,4 +42,10 @@ pnpm run design-system:check
 
 Run `pnpm run design-system:check` for cross-package or release-boundary changes. Token and theme changes must also run the repository-level `pnpm run theme:color-audit:all`.
 
+For shared icon rendering or geometry changes, use the focused package checks:
+
+```bash
+pnpm --dir design-system run build:ui && node --test design-system/packages/ui/tests/icon.test.mjs design-system/packages/ui/tests/icon-slots.test.mjs
+```
+
 Do not use browser automation or mock screenshots as visual proof. Design Lab is the manual authoring surface; source, build, HTTP, and package checks do not establish final visual fidelity.
diff --git a/design-system/apps/design-lab/src/i18n/messages.ts b/design-system/apps/design-lab/src/i18n/messages.ts
index 3c3fd7c1f7..e143ff2acc 100644
--- a/design-system/apps/design-lab/src/i18n/messages.ts
+++ b/design-system/apps/design-lab/src/i18n/messages.ts
@@ -163,7 +163,8 @@ export const enUSMessages = {
   "component.GitToolCard.description": "A prominent Git command card with output, warning, failure, and execution metadata.",
   "component.GlobSearchToolCard.description": "An ambient file-pattern search card with reusable result-list anatomy.",
   "component.GrepSearchToolCard.description": "An ambient text-search card with query metadata and a scrollable result preview.",
-  "component.IconButton.description": "A labeled icon-only action with annotation, quiet, outlined, filled, and primary variants. An annotation provides a small, muted entry to supplemental help.",
+  "component.IconButton.description": "A labeled icon action with annotation, quiet, glass, outlined, filled, and primary variants. Glass actions float over intact content.",
+  "component.Capsule.description": "A capsule with a circular glass action floating over intact text and equal edge spacing.",
   "component.Input.description": "A native text field with independent leading and trailing content slots.",
   "component.KeyHint.description": "A semantic keyboard hint with optional decorative icon content.",
   "component.LoadingState.description": "A centered loading composition with an activity indicator and optional support copy.",
@@ -186,7 +187,7 @@ export const enUSMessages = {
   "component.SkillToolCard.description": "An ambient trace for skill loading progress and outcomes.",
   "component.Spinner.description": "A compact activity indicator with matrix and bar presentations.",
   "component.Switch.description": "Toggles a single setting between on and off with native checkbox semantics.",
-  "component.TabGroup.description": "A compact single-selection tab list with optional leading icons, end actions, and automatic keyboard activation.",
+  "component.TabGroup.description": "A compact single-selection tab list with leading icons, glass end actions over intact labels, and automatic keyboard activation.",
   "component.RollingText.description": "Vertical text replacement with coordinated width, interruption handling, and reduced-motion support. Try repeated clicks in the replacement specimen.",
   "component.ShimmerText.description": "A soft fade moves slowly across activity text, keeping every glyph visible. Reduced motion, high contrast and print keep the text static and readable.",
   "components.preview.replaceText": "Replace title",
@@ -557,6 +558,7 @@ export const enUSMessages = {
   "detail.option.primary": "Primary",
   "detail.option.quiet": "Quiet",
   "detail.option.annotation": "Annotation",
+  "detail.option.glass": "Glass",
   "detail.option.text": "Text",
   "detail.option.sm": "Small",
   "detail.option.start": "Start",
@@ -969,7 +971,8 @@ export const zhCNMessages = {
   "component.GitToolCard.description": "关注型 Git 命令卡片，统一呈现输出、警告、失败与执行元数据。",
   "component.GlobSearchToolCard.description": "复用结果列表结构的低关注文件模式搜索卡片。",
   "component.GrepSearchToolCard.description": "带查询元数据和可滚动结果预览的低关注文本搜索卡片。",
-  "component.IconButton.description": "带无障碍标签的纯图标组件，支持标注、安静、描边、填充和主要呈现方式。标注以小尺寸、弱化颜色提供补充说明入口。",
+  "component.IconButton.description": "带无障碍标签的纯图标组件，支持标注、安静、毛玻璃、描边、填充和主要呈现方式。毛玻璃操作悬浮在完整内容上方。",
+  "component.Capsule.description": "胶囊内容保持完整，圆形毛玻璃操作悬浮其上，边缘间距一致。",
   "component.Input.description": "使用原生输入语义，并提供独立前置与后置内容槽的文本字段。",
   "component.KeyHint.description": "使用键盘提示语义，并支持可选装饰图标的基础组件。",
   "component.LoadingState.description": "由活动指示器与可选说明文字组成的居中加载状态。",
@@ -992,7 +995,7 @@ export const zhCNMessages = {
   "component.SkillToolCard.description": "低关注 Skill 轨迹，用于呈现加载进度和执行结果。",
   "component.Spinner.description": "提供点阵与条形样式的紧凑活动指示器。",
   "component.Switch.description": "通过原生复选框语义在开启与关闭之间切换单项设置。",
-  "component.TabGroup.description": "紧凑的单选标签组，支持前置图标、尾部操作与方向键自动切换。",
+  "component.TabGroup.description": "紧凑的单选标签组，支持前置图标、悬浮于完整标签上的毛玻璃尾部操作与方向键自动切换。",
   "component.RollingText.description": "垂直滚动替换文本，宽度同步过渡，支持连续切换与减少动态效果。可在替换示例中连续点击体验。",
   "component.ShimmerText.description": "柔和的渐隐在运行文字间缓慢流动，始终保留完整字形；减少动态效果、高对比度和打印时保持静态可读。",
   "components.preview.replaceText": "替换标题",
@@ -1363,6 +1366,7 @@ export const zhCNMessages = {
   "detail.option.primary": "主要",
   "detail.option.quiet": "安静",
   "detail.option.annotation": "标注",
+  "detail.option.glass": "毛玻璃",
   "detail.option.text": "文字",
   "detail.option.sm": "小",
   "detail.option.start": "起始",
@@ -1772,7 +1776,8 @@ export const zhTWMessages = {
   "meta.category.primitive": "基礎元件",
   "meta.category.other": "元件",
   "component.ActionCard.description": "可獨立設定前置內容、標題、說明、選取狀態和同級尾端操作的可互動卡片。",
-  "component.IconButton.description": "帶無障礙標籤的純圖示元件，支援標註、安靜、描邊、填滿和主要呈現方式。標註以小尺寸、弱化顏色提供補充說明入口。",
+  "component.IconButton.description": "帶無障礙標籤的純圖示元件，支援標註、安靜、毛玻璃、描邊、填滿和主要呈現方式。毛玻璃操作懸浮在完整內容上方。",
+  "component.Capsule.description": "膠囊內容保持完整，圓形毛玻璃操作懸浮其上，邊緣間距一致。",
   "component.MobileActionSheet.description": "用於統一呈現一般和危險操作清單的可關閉行動端彈層。",
   "component.MobileBadge.description": "用於狀態、身分與中繼資料的緊湊行動端標籤。",
   "component.MobileBanner.description": "支援語義色調和可選操作的行動端行內狀態橫幅。",
@@ -1839,7 +1844,7 @@ export const zhTWMessages = {
   "component.SkillToolCard.description": "低關注 Skill 軌跡，用於呈現載入進度和執行結果。",
   "component.Spinner.description": "提供點陣與條形樣式的緊湊活動指示器。",
   "component.Switch.description": "以原生核取方塊語意在開啟與關閉之間切換單一設定。",
-  "component.TabGroup.description": "緊湊的單選標籤群組，支援前置圖示、尾端操作與方向鍵自動切換。",
+  "component.TabGroup.description": "緊湊的單選標籤群組，支援前置圖示、懸浮於完整標籤上的毛玻璃尾端操作與方向鍵自動切換。",
   "component.RollingText.description": "垂直捲動替換文字，寬度同步過渡，支援連續切換與減少動態效果。可在替換範例中連續點擊體驗。",
   "component.ShimmerText.description": "柔和的漸隱在執行文字間緩慢流動，始終保留完整字形；減少動態效果、高對比度和列印時保持靜態可讀。",
   "components.preview.replaceText": "替換標題",
@@ -2113,6 +2118,7 @@ export const zhTWMessages = {
   "detail.iconPosition": "圖示位置",
   "detail.option.outline": "描邊",
   "detail.option.annotation": "標註",
+  "detail.option.glass": "毛玻璃",
   "detail.option.fill": "填滿",
   "detail.option.sm": "小",
   "detail.option.start": "起始",
diff --git a/design-system/apps/design-lab/src/pages/ComponentDetailPage.tsx b/design-system/apps/design-lab/src/pages/ComponentDetailPage.tsx
index f9aec4b64b..e041290432 100644
--- a/design-system/apps/design-lab/src/pages/ComponentDetailPage.tsx
+++ b/design-system/apps/design-lab/src/pages/ComponentDetailPage.tsx
@@ -1,3 +1,4 @@
+import { CapsulePreview } from "../preview/CapsulePreview";
 import { Fragment, useEffect, useMemo, useState, type CSSProperties } from "react";
 import { ComponentOverview } from "../preview/ComponentOverview";
 import { getComponentPresentation, getInitialPreviewState, hasComponentOverview } from "../preview/componentPresentation";
@@ -163,7 +164,7 @@ type PageHeaderAlign = "center" | "start";
 type PageHeaderSize = "display" | "lg" | "md" | "sm";
 
 const buttonVariants = ["outline", "fill", "secondary", "primary", "text"] as const;
-const iconButtonVariants = ["annotation", "quiet", "outline", "fill", "primary"] as const;
+const iconButtonVariants = ["annotation", "quiet", "glass", "outline", "fill", "primary"] as const;
 const iconButtonSizes = ["xs", "standard", "sm", "md", "lg"] as const;
 const buttonInspectorStates = ["default", "hover", "active"] as const;
 const fieldOrientations = ["vertical", "horizontal"] as const;
@@ -231,6 +232,7 @@ const optionLabelKeys: Readonly<Record<string, MessageKey>> = {
   open: "detail.option.open",
   outline: "detail.option.outline",
   annotation: "detail.option.annotation",
+  glass: "detail.option.glass",
   primary: "detail.option.primary",
   quiet: "detail.option.quiet",
   raised: "detail.option.raised",
@@ -537,6 +539,9 @@ export function ComponentDetailPage({
       return `import { Icon } from "@openbitfun/ui";\n\n<Icon name="${iconName}" size="${iconSize}" tone="${iconTone}" />`;
     }
 
+    if (component.name === "Capsule") {
+      return `import { Button, Capsule, Icon, IconButton } from "@openbitfun/ui";\n\n<Capsule size="sm" action={\n  <IconButton aria-label="${t("components.preview.close")}" icon={<Icon name="xmark" />} onClick={remove} />\n}>\n  <Button size="sm" variant="outline">${t("components.preview.modalProviderName")}</Button>\n</Capsule>`;
+    }
     if (component.name === "IconButton") {
       const stateProps = `${inspectorDisabled ? " disabled" : ""}${inspectorLoading ? " loading" : ""}`;
       const annotation = iconButtonVariant === "annotation";
@@ -904,6 +909,7 @@ export function ComponentDetailPage({
       );
     }
 
+    if (component.name === "Capsule") return <CapsulePreview key={state} state={state} />;
     if (component.name === "Icon") {
       return <Icon name={iconName} size={iconSize} tone={iconTone} />;
     }
diff --git a/design-system/apps/design-lab/src/pages/ComponentsPage.tsx b/design-system/apps/design-lab/src/pages/ComponentsPage.tsx
index 77b6dbcc40..41e187d0b5 100644
--- a/design-system/apps/design-lab/src/pages/ComponentsPage.tsx
+++ b/design-system/apps/design-lab/src/pages/ComponentsPage.tsx
@@ -1,6 +1,7 @@
 import { useEffect, useRef, useState } from "react";
 import { ComponentDetailPage } from "./ComponentDetailPage";
 import { BrandPreview } from "../preview/BrandPreview";
+import { CapsulePreview } from "../preview/CapsulePreview";
 import { AppWindow, Heading, Keyboard, List, Rows3, MousePointerClick, PanelTop, ToggleLeft } from "lucide-react";
 import { VoiceCallPreview, VoiceParticlePreview } from "../components/VoiceCallPreview";
 import {
@@ -607,6 +608,8 @@ export function ComponentCardPreview({ component }: { component: ComponentMeta }
           shortcut={<KeyHint icon={<CatalogIcon name="command-mac" size="lg" aria-hidden="true" />}>K</KeyHint>}
         />
       );
+    case "Capsule":
+      return <CapsulePreview state="hover" />;
     case "StatusPill":
       return (
         <StatusPill leading={<CatalogIcon name="unselected" />}>
diff --git a/design-system/apps/design-lab/src/preview/CapsulePreview.tsx b/design-system/apps/design-lab/src/preview/CapsulePreview.tsx
new file mode 100644
index 0000000000..18844261dd
--- /dev/null
+++ b/design-system/apps/design-lab/src/preview/CapsulePreview.tsx
@@ -0,0 +1,22 @@
+import { useState } from "react";
+import { Button, Capsule, Icon, IconButton, Stack, Tooltip } from "@openbitfun/ui";
+import { useI18n } from "../i18n";
+
+export function CapsulePreview({ state = "default" }: { state?: string }) {
+  const { t } = useI18n();
+  const [removed, setRemoved] = useState<string[]>([]);
+  const disabled = state === "disabled";
+  return <Stack direction="horizontal" align="center" gap="3">
+    {(["xs", "sm"] as const).filter(size => !removed.includes(size)).map(size => (
+      <Capsule key={size} size={size} data-openbitfun-preview-state={state} action={(
+        <Tooltip content={t("components.preview.close")} trigger="hover-focus">
+          <IconButton aria-label={t("components.preview.close")} icon={<Icon name="xmark" />}
+            disabled={disabled} onClick={() => setRemoved(current => [...current, size])} />
+        </Tooltip>
+      )}>
+        <Button size={size} variant="outline" disabled={disabled}>{t("components.preview.modalProviderName")}</Button>
+      </Capsule>
+    ))}
+    {removed.length > 0 && <Button size="sm" onClick={() => setRemoved([])}>{t("components.preview.add")}</Button>}
+  </Stack>;
+}
diff --git a/design-system/apps/design-lab/src/preview/FlowChatMockTools.tsx b/design-system/apps/design-lab/src/preview/FlowChatMockTools.tsx
index 153e2d4a56..29c362a661 100644
--- a/design-system/apps/design-lab/src/preview/FlowChatMockTools.tsx
+++ b/design-system/apps/design-lab/src/preview/FlowChatMockTools.tsx
@@ -9,14 +9,14 @@ export type MockToolScope = 'all' | ToolGroup;
 
 // Only grouping is Lab-owned. Names and component bindings come from production.
 const groupForTool = {
-  get_goal: 'collaboration', create_goal: 'collaboration', update_goal: 'collaboration', AgentList: 'collaboration', AgentDelete: 'collaboration',
+  get_goal: 'collaboration', create_goal: 'collaboration', update_goal: 'collaboration', AgentList: 'collaboration',
   SessionHistory: 'collaboration', analyze_image: 'files', GetTime: 'execution',
   ListMCPResources: 'execution', ReadMCPResource: 'execution', ListMCPPrompts: 'execution', GetMCPPrompt: 'execution',
   Worktree: 'files', PortForward: 'execution', ReviewPlatform: 'collaboration', FrontendWorkbench: 'web',
   FinalizeMiniApp: 'web', PublishMiniApp: 'web', PublishAppearance: 'web', Playbook: 'execution',
   Read: 'files', Write: 'files', Edit: 'files', Delete: 'files', Grep: 'files', Glob: 'files', LS: 'files',
   GetFileDiff: 'files', view_image: 'files',
-  ListModels: 'execution', ControlHub: 'web', AgentInterrupt: 'collaboration',
+  ListModels: 'execution', ControlHub: 'web',
   RunCode: 'execution', ExecCommand: 'execution', WriteStdin: 'execution', ExecControl: 'execution', Cron: 'execution', GetToolSpec: 'execution', Skill: 'execution',
   WebSearch: 'web', WebFetch: 'web', PageDeploy: 'web', PagePublish: 'web',
   AgentSpawn: 'collaboration', AgentSendInput: 'collaboration', AgentWait: 'collaboration', TodoWrite: 'collaboration',
diff --git a/design-system/apps/design-lab/src/preview/FlowChatPreviewRegistry.tsx b/design-system/apps/design-lab/src/preview/FlowChatPreviewRegistry.tsx
index 23cd63c772..c76860ea89 100644
--- a/design-system/apps/design-lab/src/preview/FlowChatPreviewRegistry.tsx
+++ b/design-system/apps/design-lab/src/preview/FlowChatPreviewRegistry.tsx
@@ -1,4 +1,4 @@
-import { LayersPlusIcon } from "@openbitfun/ui";
+import { Icon, LayersPlusIcon } from "@openbitfun/ui";
 import { toolsForComponent } from '@openbitfun/flow-chat-presentation/registry';
 import { semanticToolCardPreviews } from './SemanticToolCardPreview';
 import { createScenarioClock, execScenarios, execSnapshot, type ExecToolName } from '@openbitfun/flow-chat-presentation/scenarios';
@@ -35,7 +35,6 @@ import {
   Monitor,
   MousePointer,
   Plus,
-  Pencil,
   Rocket,
   Search,
   SearchCheck,
@@ -257,7 +256,7 @@ function ChatComposerPreview({ interactive, state }: PreviewProps) {
                   />
                   <IconButton
                     aria-label="Edit"
-                    icon={<Pencil />}
+                    icon={<Icon name="edit" />}
                     size="xs"
                   />
                 </ChatComposerQueueItemActions>
diff --git a/design-system/apps/design-lab/src/preview/componentPresentation.ts b/design-system/apps/design-lab/src/preview/componentPresentation.ts
index 87fa3537a5..55041f0071 100644
--- a/design-system/apps/design-lab/src/preview/componentPresentation.ts
+++ b/design-system/apps/design-lab/src/preview/componentPresentation.ts
@@ -7,7 +7,7 @@ export type ComponentPresentation =
 // These are website presentation choices. The public registry still owns the
 // component inventory, properties and supported states.
 const presentations: Record<string, ComponentPresentation> = {
-  Button: "matrix", IconButton: "matrix",
+  Button: "matrix", IconButton: "matrix", Capsule: "compact",
   Avatar: "compact", Checkbox: "compact", Radio: "compact", Switch: "compact",
   StatusPill: "compact", Spinner: "compact", LoadingState: "compact",
   LauncherButton: "compact", NumberBadge: "compact", KeyHint: "compact",
diff --git a/design-system/apps/design-lab/vite/component-detail-contract.test.mjs b/design-system/apps/design-lab/vite/component-detail-contract.test.mjs
index 31108cde29..062fc4b94c 100644
--- a/design-system/apps/design-lab/vite/component-detail-contract.test.mjs
+++ b/design-system/apps/design-lab/vite/component-detail-contract.test.mjs
@@ -201,7 +201,7 @@ test("IconButton preview exposes its icon-only presentation contract", async ()
   assert.ok(declaration);
   assert.deepEqual(
     [...declaration[1].matchAll(/"([^"]+)"/g)].map((match) => match[1]),
-    ["annotation", "quiet", "outline", "fill", "primary"],
+    ["annotation", "quiet", "glass", "outline", "fill", "primary"],
   );
   assert.match(source, /data-component="icon-button"/);
   assert.match(source, /aria-label=\{t\(annotation \? "components\.preview\.fieldHelp" : "components\.preview\.listView"\)\}/);
diff --git a/design-system/apps/design-lab/vite/component-preview-render.test.mjs b/design-system/apps/design-lab/vite/component-preview-render.test.mjs
index 4ee8eb342f..578a9bffe3 100644
--- a/design-system/apps/design-lab/vite/component-preview-render.test.mjs
+++ b/design-system/apps/design-lab/vite/component-preview-render.test.mjs
@@ -75,6 +75,16 @@ test("color and pattern directories expose one labelled panel while retaining ot
   }
 });
 
+test("Capsule previews publish the glass action composition in every supported state", () => {
+  const { html, preview } = render("Capsule");
+  assert.match(preview, /data-openbitfun-component="capsule"/);
+  assert.match(preview, /data-openbitfun-variant="glass"/);
+  assert.match(preview, /data-openbitfun-shape="circle"/);
+  assert.match(preview, /data-openbitfun-preview-state="disabled"/);
+  assert.match(html, /import \{ Button, Capsule, Icon, IconButton \}/);
+  assert.doesNotMatch(html, />component\.Capsule\.description</);
+});
+
 test("Textarea opens with its editable, validation and disabled examples visible", () => {
   const { html, preview } = render("Textarea");
   assert.equal((preview.match(/data-openbitfun-component="textarea"/g) ?? []).length, 5);
diff --git a/design-system/packages/ui/README.md b/design-system/packages/ui/README.md
index b4f7593d3c..e27c81804c 100644
--- a/design-system/packages/ui/README.md
+++ b/design-system/packages/ui/README.md
@@ -133,7 +133,9 @@ by the component that needs them.
 ## Icons
 
 Use `Icon` for shared size, tone and accessible labels. General-purpose symbols
-use Lucide. Automatic reasoning uses the authored `reasoning-auto` SVG mark with
+use Lucide. The named `edit` icon uses the simple `Pen` outline without Pencil's
+cap divider, keeping compact action groups visually light.
+Automatic reasoning uses the authored `reasoning-auto` SVG mark with
 a `currentColor` mask so it follows the active theme. Manual reasoning levels use
 the product slider and text labels.
 Product consumers own capability filtering, translated names and
@@ -392,6 +394,41 @@ focus ring. Use it for toolbar, dialog, and row utilities. `fill` and `primary`
 keep an opaque backing surface for persistent emphasis. Disabled quiet actions
 remain transparent and do not show hover or pressed feedback.
 
+`IconButton variant="glass"` is a translucent, blurred action over existing
+content. It uses a low-opacity tint of the shared raised surface, a softened
+subtle border and subtle blur, without an outer shadow. Hover and pressed states
+retain translucency. Unsupported blur, increased contrast and reduced transparency
+use a solid surface.
+The button itself owns the glass material and its reveal transition so an opaque
+backing or fading parent cannot prevent it from sampling the content behind it.
+
+### Capsule actions
+
+Wrap a pill-shaped `Button`, inline `Input`, or tag label in `Capsule`, matching
+its `size` to the child. Pass one `IconButton` (optionally inside `Tooltip`) to
+`action`. The slot selects circular glass presentation and compact geometry;
+the consumer keeps the action's accessible label, tone, disabled/loading state,
+and callbacks. The action is a sibling of the primary control, never a nested
+button. Pointer hover or focus within the capsule reveals it; touch keeps it
+available. Its right inset equals the top and bottom clearance at every density.
+
+```tsx
+<Capsule size="sm" action={
+  <IconButton aria-label="Remove provider" icon={<Icon name="delete" />}
+    tone="danger" onClick={requestRemoval} />
+}>
+  <Button size="sm" variant="outline" onClick={editProvider}>Provider name</Button>
+</Capsule>
+```
+
+The action floats over the intact label: do not clip, mask, hide, resize, or add
+action padding to its text when revealing the icon. Normal constrained-width
+`OverflowText` behavior remains available. `TabGroup.endAction` and removable
+`MultiSelect` tags share this contract, including existing native tab buttons.
+Leading identity icons stay in their label layout; this contract governs the
+independent trailing actions. Product CSS owns placement of capsules, not their
+action offsets, backgrounds, or visibility.
+
 For supplemental label annotations, compose `Tooltip trigger="hover-focus"
 openOnClick` with `IconButton variant="annotation" size="xs"` and an `info`
 icon. The annotation uses `color.content.muted` at rest and
diff --git a/design-system/packages/ui/src/components/Capsule/Capsule.meta.ts b/design-system/packages/ui/src/components/Capsule/Capsule.meta.ts
new file mode 100644
index 0000000000..10cd8e4d7d
--- /dev/null
+++ b/design-system/packages/ui/src/components/Capsule/Capsule.meta.ts
@@ -0,0 +1,15 @@
+import type { ComponentMeta } from "../../registry.types";
+
+export const capsuleMeta = {
+  category: "action",
+  description: "A capsule composition with a circular glass action floating over its unmodified label. Pointer hover and keyboard focus reveal the action; touch keeps it available.",
+  maturity: "stable",
+  name: "Capsule",
+  props: [
+    { name: "children", type: "ReactNode" },
+    { name: "action", type: "ReactNode" },
+    { name: "size", type: "xs | sm | md | lg", defaultValue: "sm" },
+  ],
+  states: ["default", "hover", "focus-visible", "disabled"],
+  tokens: ["control.button.xsHeight", "control.height.sm", "control.height.md", "control.height.lg", "control.iconButton.xsSize", "color.surface.raised", "color.border.subtle", "effect.blur.subtle", "radius.pill"],
+} as const satisfies ComponentMeta;
diff --git a/design-system/packages/ui/src/components/Capsule/Capsule.module.css b/design-system/packages/ui/src/components/Capsule/Capsule.module.css
new file mode 100644
index 0000000000..496a721189
--- /dev/null
+++ b/design-system/packages/ui/src/components/Capsule/Capsule.module.css
@@ -0,0 +1,14 @@
+@layer openbitfun.components {
+  .root {
+    --_floating-action-host-height: var(--openbitfun-control-height-sm);
+    display: inline-flex;
+    flex: 0 1 auto;
+    align-items: center;
+    min-inline-size: 0;
+    max-inline-size: 100%;
+  }
+
+  .root[data-size="xs"] { --_floating-action-host-height: var(--openbitfun-control-button-xs-height); }
+  .root[data-size="md"] { --_floating-action-host-height: var(--openbitfun-control-height-md); }
+  .root[data-size="lg"] { --_floating-action-host-height: var(--openbitfun-control-height-lg); }
+}
diff --git a/design-system/packages/ui/src/components/Capsule/Capsule.tsx b/design-system/packages/ui/src/components/Capsule/Capsule.tsx
new file mode 100644
index 0000000000..fe957e7a63
--- /dev/null
+++ b/design-system/packages/ui/src/components/Capsule/Capsule.tsx
@@ -0,0 +1,29 @@
+import { forwardRef, type HTMLAttributes, type ReactNode } from "react";
+import { classNames } from "../../internal/classNames";
+import { FloatingAction } from "../../internal/FloatingAction";
+import actionStyles from "../../internal/FloatingAction.module.css";
+import styles from "./Capsule.module.css";
+
+export interface CapsuleProps extends HTMLAttributes<HTMLSpanElement> {
+  /** One IconButton (optionally wrapped in Tooltip), rendered beside the content. */
+  action?: ReactNode;
+  /** Match the size of the child Button, Input, or label surface. */
+  size?: "xs" | "sm" | "md" | "lg";
+}
+
+/** Keeps label layout intact beneath a circular glass action with equal edge gaps. */
+export const Capsule = forwardRef<HTMLSpanElement, CapsuleProps>(function Capsule({
+  action,
+  children,
+  className,
+  size = "sm",
+  ...props
+}, ref) {
+  return (
+    <span {...props} className={classNames(actionStyles.host, styles.root, className)}
+      data-openbitfun-component="capsule" data-size={size} data-overflow-trigger ref={ref}>
+      {children}
+      {action != null && <FloatingAction data-openbitfun-part="action">{action}</FloatingAction>}
+    </span>
+  );
+});
diff --git a/design-system/packages/ui/src/components/Capsule/index.ts b/design-system/packages/ui/src/components/Capsule/index.ts
new file mode 100644
index 0000000000..6262586ca6
--- /dev/null
+++ b/design-system/packages/ui/src/components/Capsule/index.ts
@@ -0,0 +1 @@
+export { Capsule, type CapsuleProps } from "./Capsule";
diff --git a/design-system/packages/ui/src/components/Combobox/Combobox.module.css b/design-system/packages/ui/src/components/Combobox/Combobox.module.css
index 8bc63530f3..1ec8876520 100644
--- a/design-system/packages/ui/src/components/Combobox/Combobox.module.css
+++ b/design-system/packages/ui/src/components/Combobox/Combobox.module.css
@@ -225,7 +225,7 @@
     overflow: hidden;
     align-items: center;
     max-inline-size: 10rem;
-    min-block-size: var(--openbitfun-control-icon-button-xs-size);
+    block-size: var(--openbitfun-control-button-xs-height);
     gap: var(--openbitfun-space-1);
     padding-inline: var(--openbitfun-space-2);
     border: var(--openbitfun-border-width-default) solid var(--openbitfun-color-border-subtle);
@@ -236,10 +236,6 @@
     white-space: nowrap;
   }
 
-  .tag:has(button) {
-    padding-inline-end: 0;
-  }
-
   .tag > span {
     overflow: hidden;
   }
diff --git a/design-system/packages/ui/src/components/Combobox/Combobox.tsx b/design-system/packages/ui/src/components/Combobox/Combobox.tsx
index e3f73cb43f..5f65da32ea 100644
--- a/design-system/packages/ui/src/components/Combobox/Combobox.tsx
+++ b/design-system/packages/ui/src/components/Combobox/Combobox.tsx
@@ -22,6 +22,7 @@ import { Portal } from "../../overlay/Portal";
 import { useDesignSystem } from "../../overlay/useDesignSystem";
 import { useDismissibleLayer } from "../../overlay/useDismissibleLayer";
 import { IconButton } from "../IconButton";
+import { Capsule } from "../Capsule";
 import {
   Listbox,
   ListboxEmpty,
@@ -656,8 +657,7 @@ const CollectionPicker = forwardRef<HTMLDivElement, PickerProps>(function Collec
         {showTags && (
           <span className={styles.tags} data-openbitfun-part="tags">
             {selectedOptions.slice(0, Math.max(1, maxVisibleTags)).map((option) => (
-              <span className={styles.tag} data-openbitfun-part="tag" key={`${typeof option.value}:${option.value}`}>
-                <OverflowText>{option.label}</OverflowText>
+              <Capsule size="xs" data-openbitfun-part="tag" key={`${typeof option.value}:${option.value}`} action={(
                 <IconButton
                   aria-label={`${designSystem.messages.clearSelection}: ${option.label}`}
                   disabled={disabled}
@@ -672,7 +672,9 @@ const CollectionPicker = forwardRef<HTMLDivElement, PickerProps>(function Collec
                   tabIndex={resolvedOpen ? -1 : undefined}
                   variant="quiet"
                 />
-              </span>
+              )}>
+                <span className={styles.tag}><OverflowText>{option.label}</OverflowText></span>
+              </Capsule>
             ))}
             {selectedOptions.length > Math.max(1, maxVisibleTags) && (
               <span className={styles.tag}>+{selectedOptions.length - Math.max(1, maxVisibleTags)}</span>
diff --git a/design-system/packages/ui/src/components/Icon/Icon.tsx b/design-system/packages/ui/src/components/Icon/Icon.tsx
index 2714bd8588..97badfc451 100644
--- a/design-system/packages/ui/src/components/Icon/Icon.tsx
+++ b/design-system/packages/ui/src/components/Icon/Icon.tsx
@@ -62,7 +62,7 @@ import {
   PanelLeft,
   PanelRight,
   PanelsTopLeft,
-  Pencil,
+  Pen,
   Pin,
   Plus,
   Plug,
@@ -270,7 +270,7 @@ const lineGlyphs = {
   "device-mac": Monitor,
   "download": ArrowDown,
   "duplicate": Copy,
-  "edit": Pencil,
+  "edit": Pen,
   "extension": Puzzle,
   "eye": Eye,
   "file-search-corner": FileSearchCorner,
diff --git a/design-system/packages/ui/src/components/IconButton/IconButton.meta.ts b/design-system/packages/ui/src/components/IconButton/IconButton.meta.ts
index 6a044ae694..1c690639e1 100644
--- a/design-system/packages/ui/src/components/IconButton/IconButton.meta.ts
+++ b/design-system/packages/ui/src/components/IconButton/IconButton.meta.ts
@@ -2,13 +2,13 @@ import type { ComponentMeta } from "../../registry.types";
 
 export const iconButtonMeta = {
   category: "action",
-  description: "A labeled icon-only action with annotation, quiet, outlined, filled, and primary variants. Annotation pairs a muted 12px mark with the existing 22px xs target for supplemental label help.",
+  description: "A labeled icon-only action with annotation, quiet, glass, outlined, filled, and primary variants. Glass floats over intact content; capsule and tab action slots select it automatically.",
   maturity: "stable",
   name: "IconButton",
   props: [
     { name: "aria-label", type: "string" },
     { name: "icon", type: "ReactNode" },
-    { defaultValue: "quiet", name: "variant", type: "annotation | quiet | outline | fill | primary" },
+    { defaultValue: "quiet", name: "variant", type: "annotation | quiet | glass | outline | fill | primary" },
     { defaultValue: "square", name: "shape", type: "square | circle" },
     { defaultValue: "sm", name: "size", type: "xs | standard | sm | md | lg" },
     { defaultValue: "neutral", name: "tone", type: "neutral | danger" },
@@ -16,6 +16,9 @@ export const iconButtonMeta = {
   ],
   states: ["default", "hover", "active", "focus-visible", "disabled", "loading"],
   tokens: [
+    "color.surface.raised",
+    "color.border.subtle",
+    "effect.blur.subtle",
     "opacity.iconArtwork",
     "color.content.primary",
     "color.content.secondary",
diff --git a/design-system/packages/ui/src/components/IconButton/IconButton.tsx b/design-system/packages/ui/src/components/IconButton/IconButton.tsx
index be5b18a01a..c41a124ffa 100644
--- a/design-system/packages/ui/src/components/IconButton/IconButton.tsx
+++ b/design-system/packages/ui/src/components/IconButton/IconButton.tsx
@@ -1,9 +1,12 @@
 import {
   forwardRef,
+  useContext,
   type ButtonHTMLAttributes,
   type ReactNode,
 } from "react";
 import { classNames } from "../../internal/classNames";
+import { FloatingActionContext } from "../../internal/floatingActionContext";
+import glassStyles from "../../internal/GlassAction.module.css";
 import styles from "./IconButton.module.css";
 
 export interface IconButtonProps
@@ -15,7 +18,7 @@ export interface IconButtonProps
   size?: "xs" | "standard" | "sm" | "md" | "lg";
   tone?: "danger" | "neutral";
   /** Use annotation with an xs size and Tooltip for supplemental label help. */
-  variant?: "annotation" | "fill" | "outline" | "primary" | "quiet";
+  variant?: "annotation" | "fill" | "glass" | "outline" | "primary" | "quiet";
 }
 
 export const IconButton = forwardRef<HTMLButtonElement, IconButtonProps>(function IconButton({
@@ -31,18 +34,20 @@ export const IconButton = forwardRef<HTMLButtonElement, IconButtonProps>(functio
   variant = "quiet",
   ...props
 }, ref) {
+  const floating = useContext(FloatingActionContext);
+  const resolvedVariant = floating ? "glass" : variant;
   return (
     <button
       {...props}
       aria-busy={loading || undefined}
       aria-label={ariaLabel}
-      className={classNames(styles.button, className)}
+      className={classNames(styles.button, resolvedVariant === "glass" && glassStyles.surface, className)}
       data-openbitfun-component="icon-button"
-      data-openbitfun-shape={shape}
+      data-openbitfun-shape={floating ? "circle" : shape}
       data-openbitfun-tone={tone}
-      data-openbitfun-variant={variant}
+      data-openbitfun-variant={resolvedVariant}
       data-loading={loading ? "true" : "false"}
-      data-size={size}
+      data-size={floating ? "xs" : size}
       disabled={disabled || loading}
       ref={ref}
       type={type}
diff --git a/design-system/packages/ui/src/components/TabGroup/TabGroup.meta.ts b/design-system/packages/ui/src/components/TabGroup/TabGroup.meta.ts
index f55e8e50e4..9ea22f538d 100644
--- a/design-system/packages/ui/src/components/TabGroup/TabGroup.meta.ts
+++ b/design-system/packages/ui/src/components/TabGroup/TabGroup.meta.ts
@@ -2,7 +2,7 @@ import type { ComponentMeta } from "../../registry.types";
 
 export const tabGroupMeta = {
   category: "navigation",
-  description: "A compact single-selection tab list with optional leading icons, end actions, and automatic keyboard activation.",
+  description: "A compact single-selection tab list with leading icons, glass end actions floating over intact labels, and automatic keyboard activation.",
   maturity: "stable",
   name: "TabGroup",
   props: [
@@ -40,7 +40,9 @@ export const tabGroupMeta = {
     "control.tabGroup.itemPaddingBlockSm",
     "control.tabGroup.itemPaddingInlineSm",
     "control.tabGroup.itemActionSize",
-    "control.tabGroup.itemActionInset",
+    "color.surface.raised",
+    "color.border.subtle",
+    "effect.blur.subtle",
     "control.tabGroup.itemRadius",
     "type.label.md.fontSize",
     "type.label.md.lineHeight",
diff --git a/design-system/packages/ui/src/components/TabGroup/TabGroup.module.css b/design-system/packages/ui/src/components/TabGroup/TabGroup.module.css
index 86d78bdd9e..69438b2bea 100644
--- a/design-system/packages/ui/src/components/TabGroup/TabGroup.module.css
+++ b/design-system/packages/ui/src/components/TabGroup/TabGroup.module.css
@@ -5,11 +5,6 @@
     --_tab-group-item-padding-inline: var(--openbitfun-control-tab-group-item-padding-inline);
     --_tab-group-item-gap: var(--openbitfun-control-tab-group-item-gap);
     --_tab-group-item-icon-size: var(--openbitfun-control-tab-group-item-icon-size);
-    --_tab-group-item-action-reserve: calc(
-      var(--openbitfun-control-tab-group-item-action-size)
-      + var(--openbitfun-control-tab-group-item-action-inset)
-      + var(--_tab-group-item-gap)
-    );
 
     display: inline-flex;
     align-items: center;
@@ -25,6 +20,8 @@
   }
 
   .item {
+    --_floating-action-host-height: var(--_tab-group-item-height);
+    --_floating-action-size: var(--openbitfun-control-tab-group-item-action-size);
     position: relative;
     display: inline-flex;
     flex: 0 0 auto;
@@ -64,16 +61,6 @@
       color var(--openbitfun-motion-duration-fast) var(--openbitfun-motion-easing-standard);
   }
 
-  .item[data-has-end-action="true"] .tab {
-    padding-inline-end: var(--_tab-group-item-action-reserve);
-  }
-
-  .item[data-has-end-action="true"][data-has-icon="false"] .tab {
-    /* Mirror the trailing action reserve so a text-only label remains centered
-       within the complete tab while the overlaid action fades in and out. */
-    padding-inline-start: var(--_tab-group-item-action-reserve);
-  }
-
   .tab[aria-selected="true"] {
     --_tab-background: var(--openbitfun-color-selection-surface);
     --_tab-background-hover: var(--openbitfun-color-action-neutral-surface-hover);
@@ -132,17 +119,7 @@
   }
 
   .endAction {
-    position: absolute;
-    inset-block-start: 50%;
-    inset-inline-end: var(--openbitfun-control-tab-group-item-action-inset);
-    display: inline-flex;
-    align-items: center;
-    justify-content: center;
-    inline-size: var(--openbitfun-control-tab-group-item-action-size);
-    block-size: var(--openbitfun-control-tab-group-item-action-size);
     color: var(--openbitfun-color-action-neutral-content);
-    transform: translateY(-50%);
-    transition: opacity var(--openbitfun-motion-duration-fast) var(--openbitfun-motion-easing-standard);
   }
 
   .labelSuffix {
@@ -151,7 +128,7 @@
     align-items: center;
   }
 
-  /* Composed IconButtons own their variants, geometry and interaction states. */
+  /* Native tab actions share the glass material; IconButtons keep their tone and states. */
   .endAction > :where(button, [role="button"]):where(:not([data-openbitfun-component="icon-button"])) {
     display: inline-flex;
     align-items: center;
@@ -163,7 +140,6 @@
     border: 0;
     border-radius: var(--openbitfun-radius-pill);
     color: inherit;
-    background: transparent;
     font: inherit;
     cursor: pointer;
     transition:
@@ -173,11 +149,6 @@
 
   .endAction > :where(button, [role="button"]):where(:not([data-openbitfun-component="icon-button"])):hover {
     color: var(--openbitfun-color-action-neutral-content);
-    background: var(--openbitfun-color-action-neutral-surface-hover);
-  }
-
-  .endAction > :where(button, [role="button"]):where(:not([data-openbitfun-component="icon-button"])):active {
-    background: var(--openbitfun-color-action-neutral-surface-pressed);
   }
 
   .endAction > :where(button, [role="button"]):where(:not([data-openbitfun-component="icon-button"])):focus-visible {
@@ -190,18 +161,6 @@
     cursor: not-allowed;
   }
 
-  @media (hover: hover) and (pointer: fine) {
-    .endAction {
-      opacity: 0;
-      pointer-events: none;
-    }
-
-    .item:is(:hover, :focus-within) .endAction {
-      opacity: 1;
-      pointer-events: auto;
-    }
-  }
-
   @media (prefers-reduced-motion: reduce) {
     .tab,
     .endAction,
diff --git a/design-system/packages/ui/src/components/TabGroup/TabGroup.tsx b/design-system/packages/ui/src/components/TabGroup/TabGroup.tsx
index a7ac7e9ad6..3224ea4b99 100644
--- a/design-system/packages/ui/src/components/TabGroup/TabGroup.tsx
+++ b/design-system/packages/ui/src/components/TabGroup/TabGroup.tsx
@@ -9,6 +9,8 @@ import {
   type ReactNode,
 } from "react";
 import { classNames } from "../../internal/classNames";
+import { FloatingAction } from "../../internal/FloatingAction";
+import actionStyles from "../../internal/FloatingAction.module.css";
 import { OverflowText } from "../../primitives/OverflowText";
 import { RollingText } from "../RollingText";
 import styles from "./TabGroup.module.css";
@@ -139,7 +141,7 @@ export const TabGroup = forwardRef<HTMLDivElement, TabGroupProps>(function TabGr
         const hasIcon = Boolean(item.icon);
         const node = (
           <div
-            className={styles.item}
+            className={classNames(actionStyles.host, styles.item)}
             data-openbitfun-part="item"
             data-overflow-trigger
             data-has-end-action={hasEndAction ? "true" : "false"}
@@ -191,9 +193,9 @@ export const TabGroup = forwardRef<HTMLDivElement, TabGroupProps>(function TabGr
               )}
             </button>
             {hasEndAction && (
-              <span className={styles.endAction} data-openbitfun-part="endAction">
+              <FloatingAction className={styles.endAction} data-openbitfun-part="endAction">
                 {item.endAction}
-              </span>
+              </FloatingAction>
             )}
           </div>
         );
diff --git a/design-system/packages/ui/src/index.ts b/design-system/packages/ui/src/index.ts
index 842ff7c1c1..f511c0784f 100644
--- a/design-system/packages/ui/src/index.ts
+++ b/design-system/packages/ui/src/index.ts
@@ -57,6 +57,7 @@ export {
 export { Alert, type AlertProps, type AlertTone } from "./components/Alert";
 export { Avatar, AvatarGroup, type AvatarGroupProps, type AvatarProps, type AvatarSize } from "./components/Avatar";
 export { Button, type ButtonProps } from "./components/Button";
+export { Capsule, type CapsuleProps } from "./components/Capsule";
 export { Checkbox, type CheckboxProps, type CheckboxSize } from "./components/Checkbox";
 export {
   Card,
diff --git a/design-system/packages/ui/src/internal/FloatingAction.module.css b/design-system/packages/ui/src/internal/FloatingAction.module.css
new file mode 100644
index 0000000000..29985f6673
--- /dev/null
+++ b/design-system/packages/ui/src/internal/FloatingAction.module.css
@@ -0,0 +1,50 @@
+@layer openbitfun.components {
+  .host {
+    --_floating-action-size: var(--openbitfun-control-icon-button-xs-size);
+    position: relative;
+  }
+
+  .action {
+    pointer-events: auto;
+    position: absolute;
+    inset-block-start: 50%;
+    inset-inline-end: calc((var(--_floating-action-host-height) - var(--_floating-action-size)) / 2);
+    display: inline-flex;
+    align-items: center;
+    justify-content: center;
+    inline-size: var(--_floating-action-size);
+    block-size: var(--_floating-action-size);
+    transform: translateY(-50%);
+  }
+
+  .action > button {
+    inline-size: 100%;
+    block-size: 100%;
+    border-radius: var(--openbitfun-radius-pill);
+    transition: opacity var(--openbitfun-motion-duration-fast) var(--openbitfun-motion-easing-standard);
+  }
+
+  @media (hover: hover) and (pointer: fine) {
+    .action {
+      pointer-events: none;
+    }
+
+    .action > button {
+      opacity: 0;
+    }
+
+    .host:is(:hover, :focus-within, [data-openbitfun-preview-state="hover"], [data-openbitfun-preview-state="focus-visible"]) > .action {
+      pointer-events: auto;
+    }
+
+    .host:is(:hover, :focus-within, [data-openbitfun-preview-state="hover"], [data-openbitfun-preview-state="focus-visible"]) > .action > button {
+      opacity: 1;
+    }
+  }
+
+  @media (prefers-reduced-motion: reduce) {
+    .action > button {
+      transition: none;
+    }
+  }
+}
diff --git a/design-system/packages/ui/src/internal/FloatingAction.tsx b/design-system/packages/ui/src/internal/FloatingAction.tsx
new file mode 100644
index 0000000000..5525c51f29
--- /dev/null
+++ b/design-system/packages/ui/src/internal/FloatingAction.tsx
@@ -0,0 +1,19 @@
+import { Children, cloneElement, isValidElement, type HTMLAttributes, type ReactNode } from "react";
+import { classNames } from "./classNames";
+import { FloatingActionContext } from "./floatingActionContext";
+import glassStyles from "./GlassAction.module.css";
+import styles from "./FloatingAction.module.css";
+
+export function FloatingAction({ children, className, ...props }: HTMLAttributes<HTMLSpanElement>) {
+  return (
+    <FloatingActionContext.Provider value>
+      <span {...props} className={classNames(styles.action, className)}>
+        {Children.map(children, (child: ReactNode) => (
+          isValidElement<HTMLAttributes<HTMLButtonElement>>(child) && child.type === "button"
+            ? cloneElement(child, { className: classNames(child.props.className, glassStyles.surface) })
+            : child
+        ))}
+      </span>
+    </FloatingActionContext.Provider>
+  );
+}
diff --git a/design-system/packages/ui/src/internal/GlassAction.module.css b/design-system/packages/ui/src/internal/GlassAction.module.css
new file mode 100644
index 0000000000..405ef24d24
--- /dev/null
+++ b/design-system/packages/ui/src/internal/GlassAction.module.css
@@ -0,0 +1,54 @@
+@layer openbitfun.components {
+  .surface[data-openbitfun-variant="glass"],
+  .surface:not([data-openbitfun-component="icon-button"]) {
+    background: var(--openbitfun-color-surface-raised);
+    box-shadow: inset 0 0 0 var(--openbitfun-border-width-default) color-mix(in srgb, var(--openbitfun-color-border-subtle) 60%, transparent);
+  }
+
+  @supports ((backdrop-filter: blur(0)) or (-webkit-backdrop-filter: blur(0))) {
+    .surface[data-openbitfun-variant="glass"],
+    .surface:not([data-openbitfun-component="icon-button"]) {
+      background: color-mix(in srgb, var(--openbitfun-color-surface-raised) 28%, transparent);
+      -webkit-backdrop-filter: var(--openbitfun-effect-blur-subtle);
+      backdrop-filter: var(--openbitfun-effect-blur-subtle);
+    }
+
+    .surface[data-openbitfun-variant="glass"]:where(:not(:disabled):is(:hover, [data-openbitfun-preview-state="hover"])),
+    .surface:not([data-openbitfun-component="icon-button"]):where(:not(:disabled):is(:hover, [data-openbitfun-preview-state="hover"])) {
+      background: color-mix(in srgb, var(--openbitfun-color-surface-raised) 40%, transparent);
+    }
+
+    .surface[data-openbitfun-variant="glass"]:where(:not(:disabled):is(:active, [data-openbitfun-preview-state="active"])),
+    .surface:not([data-openbitfun-component="icon-button"]):where(:not(:disabled):is(:active, [data-openbitfun-preview-state="active"])) {
+      background: color-mix(in srgb, var(--openbitfun-color-surface-raised) 48%, transparent);
+    }
+  }
+
+  :where([data-contrast="high"]) .surface[data-openbitfun-variant="glass"],
+  :where([data-contrast="high"]) .surface:not([data-openbitfun-component="icon-button"]) {
+    background: var(--openbitfun-color-surface-raised);
+    -webkit-backdrop-filter: none;
+    backdrop-filter: none;
+  }
+
+  @media (prefers-reduced-transparency: reduce), (prefers-contrast: more) {
+    .surface[data-openbitfun-variant="glass"],
+    .surface:not([data-openbitfun-component="icon-button"]) {
+      background: var(--openbitfun-color-surface-raised);
+      -webkit-backdrop-filter: none;
+      backdrop-filter: none;
+    }
+  }
+
+  @media (forced-colors: active) {
+    .surface[data-openbitfun-variant="glass"],
+    .surface:not([data-openbitfun-component="icon-button"]) {
+      color: ButtonText;
+      background: Canvas;
+      box-shadow: none;
+      -webkit-backdrop-filter: none;
+      backdrop-filter: none;
+      outline: var(--openbitfun-border-width-default) solid ButtonText;
+    }
+  }
+}
diff --git a/design-system/packages/ui/src/internal/floatingActionContext.ts b/design-system/packages/ui/src/internal/floatingActionContext.ts
new file mode 100644
index 0000000000..ec2f7864c0
--- /dev/null
+++ b/design-system/packages/ui/src/internal/floatingActionContext.ts
@@ -0,0 +1,4 @@
+import { createContext } from "react";
+
+/** Capsule and tab action slots own their floating presentation and geometry. */
+export const FloatingActionContext = createContext(false);
diff --git a/design-system/packages/ui/src/registry.ts b/design-system/packages/ui/src/registry.ts
index cad1627db1..abda186802 100644
--- a/design-system/packages/ui/src/registry.ts
+++ b/design-system/packages/ui/src/registry.ts
@@ -4,6 +4,7 @@ import { activityItemMeta } from "./components/ActivityItem/ActivityItem.meta";
 import { alertMeta } from "./components/Alert/Alert.meta";
 import { avatarMeta } from "./components/Avatar/Avatar.meta";
 import { buttonMeta } from "./components/Button/Button.meta";
+import { capsuleMeta } from "./components/Capsule/Capsule.meta";
 import { checkboxMeta } from "./components/Checkbox/Checkbox.meta";
 import { cardMeta } from "./components/Card/Card.meta";
 import { composerMeta } from "./components/Composer/Composer.meta";
@@ -127,6 +128,7 @@ export const componentRegistry = [
   askUserMeta,
   avatarMeta,
   buttonMeta,
+  capsuleMeta,
   cardMeta,
   checkboxMeta,
   chatComposerMeta,
diff --git a/design-system/packages/ui/tests/capsule.test.mjs b/design-system/packages/ui/tests/capsule.test.mjs
new file mode 100644
index 0000000000..7de04336c7
--- /dev/null
+++ b/design-system/packages/ui/tests/capsule.test.mjs
@@ -0,0 +1,54 @@
+import assert from "node:assert/strict";
+import { createElement as h } from "react";
+import { renderToStaticMarkup } from "react-dom/server";
+import test from "node:test";
+import { Button, Capsule, Icon, IconButton, MultiSelect, TabGroup, Tooltip } from "../dist/index.js";
+
+const action = (props = {}) => h(IconButton, {
+  "aria-label": "Remove provider", icon: h(Icon, { name: "delete" }), ...props,
+});
+
+test("a tooltip-wrapped capsule action keeps its accessible name and destructive state with shared glass presentation", () => {
+  const markup = renderToStaticMarkup(h(Capsule, {
+    size: "sm",
+    action: h(Tooltip, { content: "Remove provider" }, action({ tone: "danger", variant: "fill", loading: true })),
+  }, h(Button, { size: "sm", "aria-label": "Edit provider" }, "Long provider name")));
+  assert.match(markup, /data-openbitfun-component="capsule"/);
+  assert.match(markup, /data-openbitfun-part="action"/);
+  assert.match(markup, /data-openbitfun-variant="glass"/);
+  assert.match(markup, /data-openbitfun-shape="circle"/);
+  assert.match(markup, /data-openbitfun-tone="danger"/);
+  assert.match(markup, /aria-label="Remove provider"/);
+  assert.match(markup, /aria-busy="true"/);
+  assert.match(markup, /disabled=""/);
+  assert.match(markup, /Long provider name/);
+  assert.equal((markup.match(/<button\b/g) ?? []).length, 2);
+  assert.ok(markup.indexOf("</button>") < markup.lastIndexOf("<button"), "Primary and secondary actions must be siblings");
+});
+
+test("capsules without actions preserve ordinary content and do not add a focus target", () => {
+  const markup = renderToStaticMarkup(h(Capsule, { size: "xs" }, "A tag"));
+  assert.match(markup, />A tag<\/span>/);
+  assert.doesNotMatch(markup, /tabindex|role=|data-openbitfun-part="action"/);
+});
+
+test("tab actions and removable MultiSelect labels adopt the same glass presentation", () => {
+  const tabs = renderToStaticMarkup(h(TabGroup, { items: [{ value: "a", label: "A long tab", endAction: action({ variant: "outline" }) }] }));
+  assert.match(tabs, /data-openbitfun-variant="glass"/);
+  assert.match(tabs, /role="tab"/);
+  assert.match(tabs, /A long tab/);
+
+  const select = renderToStaticMarkup(h(MultiSelect, {
+    "aria-label": "Tags", value: ["a"], options: [{ value: "a", label: "A long tag" }], disabled: true,
+  }));
+  assert.match(select, /data-openbitfun-component="capsule"/);
+  assert.match(select, /data-openbitfun-variant="glass"/);
+  assert.match(select, /A long tag/);
+  assert.match(select, /disabled=""/);
+});
+
+test("a standalone icon retains its chosen variant outside a floating action slot", () => {
+  const markup = renderToStaticMarkup(action({ variant: "outline" }));
+  assert.match(markup, /data-openbitfun-variant="outline"/);
+  assert.doesNotMatch(markup, /data-openbitfun-variant="glass"/);
+});
diff --git a/design-system/packages/ui/tests/registry.test.mjs b/design-system/packages/ui/tests/registry.test.mjs
index 858094e302..e7539b8c92 100644
--- a/design-system/packages/ui/tests/registry.test.mjs
+++ b/design-system/packages/ui/tests/registry.test.mjs
@@ -24,6 +24,7 @@ test("registry exposes only the formal stable components", () => {
       "AskUser",
       "Avatar",
       "Button",
+      "Capsule",
       "Card",
       "Checkbox",
       "ChatComposer",
diff --git a/design-system/packages/ui/tests/tab-group.test.mjs b/design-system/packages/ui/tests/tab-group.test.mjs
index acaeb2ef83..9c7d6e4eab 100644
--- a/design-system/packages/ui/tests/tab-group.test.mjs
+++ b/design-system/packages/ui/tests/tab-group.test.mjs
@@ -102,7 +102,7 @@ test("product wrappers preserve the standard tablist, selection and end-action a
   assert.equal((markup.match(/role="tab"/g) ?? []).length, 2);
   assert.equal((markup.match(/aria-selected="true"/g) ?? []).length, 1);
   assert.match(markup, /data-document="settings" data-index="1" draggable="true"/);
-  assert.match(markup, /<\/button><span[^>]+data-openbitfun-part="endAction"><button/);
+  assert.match(markup, /<\/button><span[^>]+data-openbitfun-part="endAction"[^>]*><button/);
 });
 
 test("label metadata remains inside the accessible tab and outside rolling text", () => {
@@ -163,24 +163,14 @@ test("end actions are rendered beside tabs instead of nesting interactive contro
   assert.equal((markup.match(/data-has-icon="true"/g) ?? []).length, 1);
   assert.equal((markup.match(/data-has-icon="false"/g) ?? []).length, 1);
   assert.match(markup, /data-openbitfun-part="endAction"/);
-  assert.match(markup, /<\/button><span[^>]+data-openbitfun-part="endAction"><button/);
+  assert.match(markup, /<\/button><span[^>]+data-openbitfun-part="endAction"[^>]*><button/);
   assert.equal((markup.match(/type="button"/g) ?? []).length, 3);
 });
 
-test("text-only tabs mirror the end-action reserve to keep labels centered", async () => {
-  const styles = await readFile(
-    new URL("../src/components/TabGroup/TabGroup.module.css", import.meta.url),
-    "utf8",
-  );
-
-  assert.match(
-    styles,
-    /\.item\[data-has-end-action="true"\] \.tab\s*\{[^}]*padding-inline-end:\s*var\(--_tab-group-item-action-reserve\);/s,
-  );
-  assert.match(
-    styles,
-    /\.item\[data-has-end-action="true"\]\[data-has-icon="false"\] \.tab\s*\{[^}]*padding-inline-start:\s*var\(--_tab-group-item-action-reserve\);/s,
-  );
+test("end actions float over the label without reserving or clipping text", async () => {
+  const styles = await readFile(new URL("../src/components/TabGroup/TabGroup.module.css", import.meta.url), "utf8");
+  assert.doesNotMatch(styles, /action-reserve|clip-path|mask-image/);
+  assert.doesNotMatch(styles, /data-has-end-action[^}]*padding-inline/s);
 });
 
 test("TabGroup styling uses its geometry contract and Button semantic colors", async () => {
@@ -195,7 +185,6 @@ test("TabGroup styling uses its geometry contract and Button semantic colors", a
   assert.match(styles, /--openbitfun-control-tab-group-item-padding-block-sm/);
   assert.match(styles, /--openbitfun-control-tab-group-item-padding-inline-sm/);
   assert.match(styles, /--openbitfun-control-tab-group-item-action-size/);
-  assert.match(styles, /--openbitfun-control-tab-group-item-action-inset/);
   assert.match(styles, /--openbitfun-control-tab-group-item-radius/);
   assert.match(styles, /--openbitfun-color-action-neutral-border/);
   assert.match(styles, /--openbitfun-color-action-neutral-content/);
diff --git a/scripts/core-boundaries/cargo-dependency-boundaries.mjs b/scripts/core-boundaries/cargo-dependency-boundaries.mjs
index 8c7f961976..26178ca5de 100644
--- a/scripts/core-boundaries/cargo-dependency-boundaries.mjs
+++ b/scripts/core-boundaries/cargo-dependency-boundaries.mjs
@@ -145,7 +145,8 @@ function isProcMacroPackage(pkg) {
 const SERVICES_INTEGRATIONS_TOKIO_FEATURES = new Map([
   ['account-identity', ['rt', 'sync']],
   ['announcement', ['fs', 'sync']],
-  ['models-dev', ['fs', 'sync', 'time']],
+  // Large catalog validation/hash work uses spawn_blocking, outside async IO workers.
+  ['models-dev', ['fs', 'rt', 'sync', 'time']],
   ['browser-control', ['time']],
   ['canvas-runtime', ['fs']],
   ['deep-research', []],
diff --git a/src/apps/cli/src/peer_host/commands/session.rs b/src/apps/cli/src/peer_host/commands/session.rs
index 57d7af74ba..79eafa5348 100644
--- a/src/apps/cli/src/peer_host/commands/session.rs
+++ b/src/apps/cli/src/peer_host/commands/session.rs
@@ -757,7 +757,20 @@ pub(crate) async fn update_session_model(
         .map(|preset| preset.trim().to_string())
         .filter(|preset| !preset.is_empty());
     if has_session_workspace_scope(request) {
-        ensure_coordinator_session(state, args).await?;
+        ensure_session_workspace_runtime_ownership(state, request).await?;
+        let storage = resolved_session_storage_path(state, request).await?;
+        state
+            .compatibility
+            .update_session_model_selection_from_storage_path(
+                &storage,
+                &session_id,
+                &model_name,
+                reasoning_preset.as_deref(),
+                optional_bool(request, "includeInternal").unwrap_or(false),
+            )
+            .await
+            .map_err(|error| peer_core_session_error("Failed to update session model", error))?;
+        return Ok(Value::Null);
     }
     state
         .agent_runtime
diff --git a/src/apps/desktop/AGENTS.md b/src/apps/desktop/AGENTS.md
index 9fa16df9fe..864bfd590e 100644
--- a/src/apps/desktop/AGENTS.md
+++ b/src/apps/desktop/AGENTS.md
@@ -124,6 +124,17 @@ For session storage directory access, run
 for session storage directory resolution (these tests do not launch a file manager),
 and `cargo test -p openbitfun-desktop --lib remote_workspace_policy` after registration changes.
 
+For model selector request compatibility and configuration effect routing:
+
+```bash
+cargo test --locked -p openbitfun-desktop --lib update_session_model_distinguishes_omitted_null_and_explicit_reasoning_presets
+cargo test --locked -p openbitfun-desktop --lib backend_effect_routing_is_owned_by_the_control_transaction
+```
+
+Use the Core guide's session-model tests for cold persistence, no-op writes,
+rollback, and ownership; the Desktop adapter must not restore history for a
+model selection alone.
+
 For MiniApp Agent session and context changes, run
 `cargo test --locked -p openbitfun-desktop --lib api::miniapp_agent_api::tests`.
 This covers legacy payloads, exact context paths, trust instructions, and snapshot cleanup.
diff --git a/src/apps/desktop/src/api/agentic_api.rs b/src/apps/desktop/src/api/agentic_api.rs
index 5e23546f5f..eea76c20b8 100644
--- a/src/apps/desktop/src/api/agentic_api.rs
+++ b/src/apps/desktop/src/api/agentic_api.rs
@@ -2102,16 +2102,28 @@ pub async fn update_session_model(
     if session_id.is_empty() {
         return Err("session_id is required".to_string());
     }
-    ensure_session_loaded_for_selector_update(
-        runtime.inner(),
-        &session_id,
-        request.workspace_id,
-        request.workspace_path,
-        request.remote_connection_id,
-        request.remote_ssh_host,
-        request.include_internal,
-    )
-    .await?;
+    if runtime
+        .session_application()
+        .update_unloaded_session_model(
+            DesktopSessionScopeRequest {
+                workspace_id: request.workspace_id,
+                workspace_path: request.workspace_path.unwrap_or_default(),
+                remote_connection_id: request.remote_connection_id,
+                remote_ssh_host: request.remote_ssh_host,
+            },
+            &session_id,
+            &request.model_name,
+            request
+                .reasoning_preset
+                .as_ref()
+                .and_then(|value| value.as_deref()),
+            request.include_internal,
+        )
+        .await
+        .map_err(|error| error.to_string())?
+    {
+        return Ok(());
+    }
     let update_result = match request.reasoning_preset {
         Some(reasoning_preset) => {
             let reasoning_preset = reasoning_preset
diff --git a/src/apps/desktop/src/api/clipboard_file_api.rs b/src/apps/desktop/src/api/clipboard_file_api.rs
index f5bfc66d44..08d8897930 100644
--- a/src/apps/desktop/src/api/clipboard_file_api.rs
+++ b/src/apps/desktop/src/api/clipboard_file_api.rs
@@ -342,6 +342,7 @@ impl Default for ClipboardImageResponse {
 
 /// Sniffs the image format from magic bytes so a tool that misreports success
 /// cannot inject arbitrary text as an attachment payload.
+#[cfg(any(target_os = "linux", test))]
 pub(crate) fn sniff_image_mime(bytes: &[u8]) -> Option<&'static str> {
     if bytes.starts_with(&[0x89, b'P', b'N', b'G', 0x0D, 0x0A, 0x1A, 0x0A]) {
         Some("image/png")
@@ -355,12 +356,14 @@ pub(crate) fn sniff_image_mime(bytes: &[u8]) -> Option<&'static str> {
 /// Outcome of a Linux clipboard-image probe.
 enum ClipboardImageRead {
     /// An image payload, base64-encoded with its sniffed MIME type.
+    #[cfg(target_os = "linux")]
     Image(String, String),
     /// The reader tools ran; the clipboard simply holds no image payload.
     Empty,
     /// Neither `wl-paste` nor `xclip` could be spawned. Surfaced to the user
     /// instead of silently reporting "no image": a plain-text clipboard and a
     /// machine missing the reader tools must stay distinguishable.
+    #[cfg(target_os = "linux")]
     ToolsUnavailable(String),
 }
 
@@ -440,11 +443,13 @@ fn get_clipboard_image_internal() -> ClipboardImageRead {
 #[tauri::command]
 pub async fn get_clipboard_image() -> Result<ClipboardImageResponse, String> {
     match get_clipboard_image_internal() {
+        #[cfg(target_os = "linux")]
         ClipboardImageRead::Image(base64, mime_type) => Ok(ClipboardImageResponse {
             base64: Some(base64),
             mime_type: Some(mime_type),
         }),
         ClipboardImageRead::Empty => Ok(ClipboardImageResponse::default()),
+        #[cfg(target_os = "linux")]
         ClipboardImageRead::ToolsUnavailable(error) => {
             log::warn!("Clipboard image read unsupported: {}", error);
             Err(error)
diff --git a/src/apps/desktop/src/computer_use/control_session.rs b/src/apps/desktop/src/computer_use/control_session.rs
index 5ceb4299d9..3349f6f42f 100644
--- a/src/apps/desktop/src/computer_use/control_session.rs
+++ b/src/apps/desktop/src/computer_use/control_session.rs
@@ -288,6 +288,7 @@ fn cleanup_async(ticket: u64) {
 }
 /// Native delegates pass the identity captured when their stream was created.
 /// Never call an unscoped "stop current" from a delayed native callback.
+#[cfg(target_os = "linux")]
 pub(crate) fn native_stopped_generation(generation: u64, reason: &str) {
     native_stopped_inner(generation, None, reason);
 }
diff --git a/src/apps/desktop/src/computer_use/macos_ax_ui.rs b/src/apps/desktop/src/computer_use/macos_ax_ui.rs
index cb571f8126..8f02c62b61 100644
--- a/src/apps/desktop/src/computer_use/macos_ax_ui.rs
+++ b/src/apps/desktop/src/computer_use/macos_ax_ui.rs
@@ -50,19 +50,6 @@ unsafe extern "C" {
 const K_AX_VALUE_CGPOINT: u32 = 1;
 const K_AX_VALUE_CGSIZE: u32 = 2;
 
-/// Pid of the frontmost application, via `NSWorkspace.frontmostApplication`.
-///
-/// Reads in-process in microseconds. The previous implementation shelled out to
-/// `osascript` on every call — and this is on the hot path for
-/// `describe_screen` (which reaches it up to three times per call), so a single
-/// observation used to cost several hundred milliseconds of process spawns plus
-/// the risk of a System Events AppleEvent timeout.
-fn frontmost_pid() -> OpenBitFunResult<i32> {
-    crate::computer_use::macos_bg_input::frontmost_pid_macos().ok_or_else(|| {
-        OpenBitFunError::tool("NSWorkspace reported no frontmost application.".to_string())
-    })
-}
-
 unsafe fn ax_release(v: CFTypeRef) {
     unsafe {
         if !v.is_null() {
@@ -540,14 +527,6 @@ fn element_short_desc(role: Option<&str>, title: Option<&str>) -> String {
 
 const MAX_CANDIDATES: usize = 10;
 
-/// Search the **frontmost** app's accessibility tree (BFS) for elements matching filters.
-/// Collects all matches, filters invisible/off-screen ones, ranks by relevance, returns the best.
-pub(super) fn locate_ui_element_center(
-    query: &UiElementLocateQuery,
-) -> OpenBitFunResult<UiElementLocateResult> {
-    locate_ui_element_center_for_pid(frontmost_pid()?, query)
-}
-
 /// Search only the explicitly selected application, even while another app is active.
 pub(super) fn locate_ui_element_center_for_pid(
     pid: i32,
@@ -890,13 +869,8 @@ unsafe fn is_ax_interactive(elem: AXUIElementRef, role: &str) -> bool {
     }
 }
 
-/// Enumerate visible interactive elements in the frontmost app's AX tree
-/// and return a condensed text representation of the UI for context (no
-/// numbered labels rendered on the screenshot).
-pub(super) fn enumerate_ui_tree_text(max_elements: usize) -> Option<String> {
-    enumerate_ui_tree_text_for_pid(frontmost_pid().ok()?, max_elements)
-}
-
+/// Enumerate visible interactive elements in the selected app's AX tree
+/// and return a condensed text representation of the UI for context.
 pub(super) fn enumerate_ui_tree_text_for_pid(pid: i32, max_elements: usize) -> Option<String> {
     let root = unsafe { AXUIElementCreateApplication(pid) };
     if root.is_null() {
@@ -1055,13 +1029,6 @@ unsafe fn ax_parent_context_line(elem: AXUIElementRef) -> Option<String> {
 }
 
 /// Hit-test the accessibility element at global screen coordinates (OCR `move_to_text` disambiguation).
-pub(super) fn accessibility_hit_at_global_point(gx: f64, gy: f64) -> Option<OcrAccessibilityHit> {
-    unsafe {
-        let sys = AXUIElementCreateSystemWide();
-        accessibility_hit_from_root(sys, None, gx, gy)
-    }
-}
-
 pub(super) fn accessibility_hit_at_global_point_for_pid(
     pid: i32,
     gx: f64,
@@ -1116,15 +1083,6 @@ unsafe fn accessibility_hit_from_root(
     }
 }
 
-// ── Raw OCR: frontmost window bounds (separate from agent screenshot pipeline) ─────────────────
-
-/// Bounds of the foreground app's focused or main window in global screen coordinates (same space as pointer / screen capture).
-/// Used to crop **raw** pixels for Vision OCR without pointer overlays from the agent screenshot path.
-pub(super) fn frontmost_window_bounds_global() -> OpenBitFunResult<(i32, i32, u32, u32)> {
-    let pid = frontmost_pid()?;
-    window_bounds_global_for_pid(pid)
-}
-
 /// Number of windows the app currently owns, per the AX `AXWindows` attribute.
 ///
 /// A launched-but-windowless app — common for Electron clients whose window was
diff --git a/src/apps/desktop/src/computer_use/macos_capture.rs b/src/apps/desktop/src/computer_use/macos_capture.rs
index 0a5c158d5a..8167ced873 100644
--- a/src/apps/desktop/src/computer_use/macos_capture.rs
+++ b/src/apps/desktop/src/computer_use/macos_capture.rs
@@ -56,7 +56,6 @@ pub(super) struct CaptureFrame {
     pub height: u32,
     pub window_id: u32,
     pub bounds: [f64; 4],
-    pub sequence: u64,
     pub generation: u64,
 }
 
@@ -144,7 +143,6 @@ impl CaptureSession {
             height,
             window_id,
             bounds,
-            sequence,
             generation: self.generation,
         })
     }
diff --git a/src/apps/desktop/src/computer_use/macos_list_apps.rs b/src/apps/desktop/src/computer_use/macos_list_apps.rs
index 2e5edf55d3..9a3a8ee222 100644
--- a/src/apps/desktop/src/computer_use/macos_list_apps.rs
+++ b/src/apps/desktop/src/computer_use/macos_list_apps.rs
@@ -127,9 +127,6 @@ pub(super) fn list_running_apps(include_hidden: bool) -> OpenBitFunResult<Vec<Ap
     Ok(apps)
 }
 
-/// Compatibility for launch/quit call sites. Discovery is always fresh now.
-pub(super) fn invalidate_cache() {}
-
 #[cfg(test)]
 mod tests {
     use super::*;
diff --git a/src/apps/desktop/src/embedded_relay_host.rs b/src/apps/desktop/src/embedded_relay_host.rs
index d9677fa69b..e3f43d7354 100644
--- a/src/apps/desktop/src/embedded_relay_host.rs
+++ b/src/apps/desktop/src/embedded_relay_host.rs
@@ -220,15 +220,14 @@ mod tests {
     /// milliseconds.
     async fn assert_port_released(port: u16, what: &str) {
         let deadline = std::time::Instant::now() + std::time::Duration::from_secs(5);
-        let mut last_err = None;
         loop {
-            match tokio::net::TcpListener::bind(("0.0.0.0", port)).await {
+            let last_err = match tokio::net::TcpListener::bind(("0.0.0.0", port)).await {
                 Ok(l) => {
                     drop(l);
                     return;
                 }
-                Err(e) => last_err = Some(e),
-            }
+                Err(e) => e,
+            };
             if std::time::Instant::now() >= deadline {
                 panic!("{what}: port {port} never became bindable again: {last_err:?}");
             }
diff --git a/src/apps/desktop/src/openbitfun_control_host.rs b/src/apps/desktop/src/openbitfun_control_host.rs
index 559dc2bb12..310b2133aa 100644
--- a/src/apps/desktop/src/openbitfun_control_host.rs
+++ b/src/apps/desktop/src/openbitfun_control_host.rs
@@ -266,8 +266,6 @@ fn option_requires_presentation_commit(option: &ProductCapabilityOption) -> bool
 fn config_path_invalidates_ai_client(path: &str) -> bool {
     [
         "ai.models",
-        "ai.default_models",
-        "ai.agent_model_defaults",
         "ai.stream_idle_timeout_secs",
         "ai.stream_ttft_timeout_secs",
         "ai.proxy",
@@ -710,6 +708,17 @@ pub(crate) async fn set_config_from_gui(
     let state = app.state::<AppState>();
     let previous_value = state.config_service.get_config(Some(path)).await.ok();
     let applied = apply_legacy_config_mutation(&state.config_service, path, value).await?;
+    if !applied.changed {
+        return Ok(json!({
+            "catalogDigest": openbitfun_product_domains::product_control::catalog()?.digest.clone(),
+            "configured": true,
+            "changedPaths": [],
+            "controlledBindings": applied.controlled_bindings,
+            "effectiveValue": applied.effective_value,
+            "revision": current_revision(),
+            "presentationSync": [],
+        }));
+    }
     let backend_effect_result =
         match apply_backend_config_effects(app, &state, path, &applied.effective_value).await {
             Ok(()) => {
@@ -1233,8 +1242,6 @@ mod tests {
         for path in [
             "ai.models",
             "ai.models.providers.openai",
-            "ai.default_models.primary",
-            "ai.agent_model_defaults",
             "ai.stream_idle_timeout_secs",
             "ai.stream_ttft_timeout_secs",
             "ai.proxy",
@@ -1247,6 +1254,9 @@ mod tests {
         assert!(!config_path_invalidates_ai_client(
             "ai.tool_execution_timeout_secs"
         ));
+        for path in ["ai.default_models.primary", "ai.agent_model_defaults.mode"] {
+            assert!(!config_path_invalidates_ai_client(path));
+        }
 
         let appearance = product_capability("setting.application.appearance")
             .unwrap()
diff --git a/src/apps/desktop/src/runtime/session_application.rs b/src/apps/desktop/src/runtime/session_application.rs
index 2360c8bc73..55b029ddc8 100644
--- a/src/apps/desktop/src/runtime/session_application.rs
+++ b/src/apps/desktop/src/runtime/session_application.rs
@@ -739,6 +739,36 @@ impl DesktopSessionApplication {
         Ok(updated_title)
     }
 
+    pub(crate) async fn update_unloaded_session_model(
+        &self,
+        request: DesktopSessionScopeRequest,
+        session_id: &str,
+        model_id: &str,
+        reasoning_preset: Option<&str>,
+        include_internal: bool,
+    ) -> DesktopSessionApplicationResult<bool> {
+        if self
+            .compatibility
+            .is_session_loaded_in_memory(session_id)
+            .map_err(desktop_core_session_error)?
+        {
+            return Ok(false);
+        }
+        let scope = self.resolved_scope(request).await?;
+        self.ensure_runtime_ownership(&scope)?;
+        self.compatibility
+            .update_session_model_selection_from_storage_path(
+                &self.storage_path(&scope),
+                session_id,
+                model_id,
+                reasoning_preset,
+                include_internal,
+            )
+            .await
+            .map_err(desktop_core_session_error)?;
+        Ok(true)
+    }
+
     pub(crate) async fn ensure_session_loaded(
         &self,
         request: DesktopSessionScopeRequest,
diff --git a/src/apps/desktop/src/webview_recovery.rs b/src/apps/desktop/src/webview_recovery.rs
index 8816038b77..4e8e30d57e 100644
--- a/src/apps/desktop/src/webview_recovery.rs
+++ b/src/apps/desktop/src/webview_recovery.rs
@@ -1,9 +1,14 @@
+#[cfg(any(target_os = "windows", test))]
 use serde::{Deserialize, Serialize};
+#[cfg(any(target_os = "windows", test))]
 use std::time::Duration;
 
+#[cfg(any(target_os = "windows", test))]
 const RENDERER_FAILURE_WINDOW: Duration = Duration::from_secs(10 * 60);
+#[cfg(any(target_os = "windows", test))]
 const RESTART_FAILURE_WINDOW: Duration = Duration::from_secs(10 * 60);
 
+#[cfg(any(target_os = "windows", test))]
 #[derive(Debug, Clone, Copy, PartialEq, Eq)]
 enum FailureKind {
     BrowserExited,
@@ -13,6 +18,7 @@ enum FailureKind {
     Other,
 }
 
+#[cfg(any(target_os = "windows", test))]
 #[derive(Debug, Clone, Copy, PartialEq, Eq)]
 enum RecoveryAction {
     Reload,
@@ -21,6 +27,7 @@ enum RecoveryAction {
     Observe,
 }
 
+#[cfg(any(target_os = "windows", test))]
 #[derive(Debug, Default, Serialize, Deserialize)]
 #[serde(rename_all = "camelCase", default)]
 struct RecoveryHistory {
@@ -28,6 +35,7 @@ struct RecoveryHistory {
     restart_attempts_ms: Vec<u64>,
 }
 
+#[cfg(any(target_os = "windows", test))]
 fn decide_recovery(
     history: &mut RecoveryHistory,
     failure: FailureKind,
@@ -50,6 +58,7 @@ fn decide_recovery(
     }
 }
 
+#[cfg(any(target_os = "windows", test))]
 fn restart_or_block(history: &mut RecoveryHistory, now_ms: u64) -> RecoveryAction {
     let window_ms = RESTART_FAILURE_WINDOW.as_millis() as u64;
     history
@@ -63,6 +72,7 @@ fn restart_or_block(history: &mut RecoveryHistory, now_ms: u64) -> RecoveryActio
     }
 }
 
+#[cfg(any(target_os = "windows", test))]
 fn restart_after_failed_reload(history: &mut RecoveryHistory, now_ms: u64) -> RecoveryAction {
     restart_or_block(history, now_ms)
 }
diff --git a/src/crates/adapters/agent-runtime-ipc/src/client.rs b/src/crates/adapters/agent-runtime-ipc/src/client.rs
index 8a8affdce3..fe227c5663 100644
--- a/src/crates/adapters/agent-runtime-ipc/src/client.rs
+++ b/src/crates/adapters/agent-runtime-ipc/src/client.rs
@@ -196,7 +196,7 @@ impl RuntimeIpcClient {
         let release_gate_after_write = operation.is_interruptible_lineage_read();
         let request_id = self
             .next_request_id
-            .fetch_update(Ordering::Relaxed, Ordering::Relaxed, |value| {
+            .try_update(Ordering::Relaxed, Ordering::Relaxed, |value| {
                 value.checked_add(1)
             })
             .map_err(|_| RuntimeIpcClientError::RequestIdExhausted)?;
diff --git a/src/crates/assembly/core/AGENTS.md b/src/crates/assembly/core/AGENTS.md
index 203829187b..d1888c999d 100644
--- a/src/crates/assembly/core/AGENTS.md
+++ b/src/crates/assembly/core/AGENTS.md
@@ -257,6 +257,20 @@ For built-in provider overlay, trusted endpoint validation, and reasoning catalo
 cargo test -p openbitfun-core --no-default-features --features ai-adapter-runtime --lib infrastructure::ai::
 ```
 
+For model selector latency, run the catalog and session mutation owner fixtures:
+
+```bash
+cargo test --locked -p openbitfun-core --no-default-features --features model-catalog --lib infrastructure::ai::reasoning_catalog::tests
+cargo test --locked -p openbitfun-core --no-default-features --features agent-runtime,git --lib session_model_update
+cargo test --locked -p openbitfun-core --no-default-features --features remote-connect,git --lib remote_attach_and_mutation_paths_preserve_workspace_ownership_facts
+```
+
+Catalog snapshots remain usable during background refresh. Selector mutations
+must not restore cold transcripts or reserve active-session capacity; preserve
+writer ownership, unknown persisted fields, legacy metadata-only sessions, and
+both state/metadata projections on failure. These fixtures cover local storage
+and remote routing contracts, not live SSH/relay/peer/dispatch connections.
+
 Configuration persistence, account settings import, backup restore, legacy
 field/deletion compatibility, local-change notifications, and save/reload/model
 concurrency regressions have feature-free fixtures:
diff --git a/src/crates/assembly/core/src/agentic/coordination/coordinator.rs b/src/crates/assembly/core/src/agentic/coordination/coordinator.rs
index 6cb62bca19..62ad18c4a3 100644
--- a/src/crates/assembly/core/src/agentic/coordination/coordinator.rs
+++ b/src/crates/assembly/core/src/agentic/coordination/coordinator.rs
@@ -2602,6 +2602,41 @@ Update the persona files and delete BOOTSTRAP.md as soon as bootstrap is complet
         Ok(())
     }
 
+    /// A selector mutation can edit a historical header without admitting a
+    /// runtime session. Ownership is checked against the persisted binding
+    /// while the session mutation and writer permits are held.
+    pub(crate) async fn update_session_model_selection_from_storage_path(
+        &self,
+        storage_path: &Path,
+        session_id: &str,
+        model_id: &str,
+        reasoning_preset: Option<&str>,
+        include_internal: bool,
+    ) -> OpenBitFunResult<Session> {
+        let model_id = normalize_model_selection(model_id).await?;
+        self.session_manager
+            .update_session_model_selection_in_storage(
+                Some(storage_path),
+                session_id,
+                &model_id,
+                reasoning_preset,
+                include_internal,
+                |session| {
+                    let workspace = session.config.workspace_path.as_deref().ok_or_else(|| {
+                        OpenBitFunError::Validation(format!(
+                            "Session workspace_path is missing: {session_id}"
+                        ))
+                    })?;
+                    self.ensure_runtime_ownership(
+                        Path::new(workspace),
+                        session.config.remote_connection_id.as_deref(),
+                        session.config.remote_ssh_host.as_deref(),
+                    )
+                },
+            )
+            .await
+    }
+
     /// Re-enable (or disable) the tool loop of an already persisted session.
     ///
     /// Session configs are written once at creation, so a host that changes its
diff --git a/src/crates/assembly/core/src/agentic/persistence/manager.rs b/src/crates/assembly/core/src/agentic/persistence/manager.rs
index 7c150b37cd..c8e4fb64d3 100644
--- a/src/crates/assembly/core/src/agentic/persistence/manager.rs
+++ b/src/crates/assembly/core/src/agentic/persistence/manager.rs
@@ -1795,7 +1795,7 @@ impl PersistenceManager {
         &self,
         workspace_path: &Path,
         session_id: &str,
-        state: &StoredSessionStateFile,
+        state: &(impl serde::Serialize + Sync),
     ) -> OpenBitFunResult<()> {
         #[cfg(test)]
         {
@@ -2492,6 +2492,118 @@ impl PersistenceManager {
         Ok(())
     }
 
+    /// Persist only selector facts. Historical sessions need neither transcript
+    /// loading nor runtime restoration, and unknown future state fields survive.
+    pub(crate) async fn save_session_model_selection(
+        &self,
+        workspace_path: &Path,
+        session: &Session,
+    ) -> OpenBitFunResult<()> {
+        let session_id = &session.session_id;
+        Self::validate_session_id(session_id)?;
+        let _writer = self.lock_session_write_operation(workspace_path, session_id)?;
+        self.ensure_runtime_for_write(workspace_path).await?;
+        let lock = self
+            .get_session_persistence_lock(workspace_path, session_id)
+            .await;
+        let _guard = lock.lock().await;
+        let original_metadata = self
+            .load_session_metadata(workspace_path, session_id)
+            .await?
+            .ok_or_else(|| OpenBitFunError::NotFound(format!("Session not found: {session_id}")))?;
+        let state_path = self.state_path(workspace_path, session_id);
+        let original_state = self
+            .read_json_optional::<serde_json::Value>(&state_path)
+            .await?;
+        let mut state = match original_state.as_ref() {
+            Some(value) => value.clone(),
+            None => serde_json::to_value(StoredSessionStateFile {
+                schema_version: SESSION_STORAGE_SCHEMA_VERSION,
+                config: session.config.clone(),
+                snapshot_session_id: session.snapshot_session_id.clone(),
+                last_user_dialog_agent_type: session.last_user_dialog_agent_type.clone(),
+                last_submitted_agent_type: session.last_submitted_agent_type.clone(),
+                compression_state: session.compression_state.clone(),
+                runtime_state: sanitize_persisted_session_state(&session.state),
+            })?,
+        };
+        let object = state
+            .as_object_mut()
+            .ok_or_else(|| OpenBitFunError::session("Invalid session state object"))?;
+        let config = object
+            .entry("config")
+            .or_insert_with(|| serde_json::json!({}))
+            .as_object_mut()
+            .ok_or_else(|| OpenBitFunError::session("Invalid session config object"))?;
+        config.insert(
+            "model_id".into(),
+            serde_json::to_value(&session.config.model_id)?,
+        );
+        config.insert(
+            "reasoning_preset".into(),
+            serde_json::to_value(&session.config.reasoning_preset)?,
+        );
+        config.insert(
+            "max_context_tokens".into(),
+            serde_json::to_value(session.config.max_context_tokens)?,
+        );
+        let mut metadata = original_metadata.clone();
+        metadata.model_name = session.config.model_id.clone().unwrap_or_default();
+        metadata.last_active_at = Self::system_time_to_unix_ms(session.last_activity_at);
+        if original_state.as_ref() == Some(&state)
+            && original_metadata.model_name == metadata.model_name
+            && original_metadata.last_active_at == metadata.last_active_at
+        {
+            return Ok(());
+        }
+        let write_result = async {
+            self.save_stored_session_state(workspace_path, session_id, &state)
+                .await?;
+            self.save_session_metadata_locked(workspace_path, &metadata)
+                .await
+        }
+        .await;
+        if let Err(error) = write_result {
+            // An IO error can be reported before or after an atomic rename.
+            // Avoid unnecessary rollback writes when the original is intact.
+            if self
+                .read_json_optional::<serde_json::Value>(&state_path)
+                .await
+                .is_ok_and(|state| state == original_state)
+                && self
+                    .load_session_metadata(workspace_path, session_id)
+                    .await
+                    .is_ok_and(|value| {
+                        value.is_some_and(|value| {
+                            value.model_name == original_metadata.model_name
+                                && value.last_active_at == original_metadata.last_active_at
+                        })
+                    })
+            {
+                return Err(error);
+            }
+            let state_rollback = match original_state {
+                Some(state) => {
+                    self.save_stored_session_state(workspace_path, session_id, &state)
+                        .await
+                }
+                None => tokio::fs::remove_file(&state_path)
+                    .await
+                    .map_err(Into::into),
+            };
+            let metadata_rollback = self
+                .save_session_metadata_locked(workspace_path, &original_metadata)
+                .await;
+            if state_rollback.is_err() || metadata_rollback.is_err() {
+                return Err(OpenBitFunError::OutcomeUnknown(format!(
+                    "Session model update rollback failed: session_id={session_id}, error={error}, state={state_rollback:?}, metadata={metadata_rollback:?}"
+                )));
+            }
+            return Err(error);
+        }
+        Ok(())
+    }
+
     /// Save session
     pub async fn save_session(
         &self,
diff --git a/src/crates/assembly/core/src/agentic/session/session_manager.rs b/src/crates/assembly/core/src/agentic/session/session_manager.rs
index 579fc76641..c8d98a3fd5 100644
--- a/src/crates/assembly/core/src/agentic/session/session_manager.rs
+++ b/src/crates/assembly/core/src/agentic/session/session_manager.rs
@@ -2555,6 +2555,9 @@ impl SessionManager {
                 config: manager_config,
             };
 
+            let mut model_inputs = Self::load_ai_config_for_model_resolution()
+                .await
+                .and_then(|ai| serde_json::to_value((&ai.models, &ai.default_models)).ok());
             loop {
                 match receiver.recv().await {
                     Ok(ConfigUpdateEvent::ModelsReconciled {
@@ -2575,6 +2578,15 @@ impl SessionManager {
                         | ConfigUpdateEvent::DefaultAIModelUpdated { .. }
                         | ConfigUpdateEvent::ConfigReloaded,
                     ) => {
+                        let next_inputs = Self::load_ai_config_for_model_resolution()
+                            .await
+                            .and_then(|ai| {
+                                serde_json::to_value((&ai.models, &ai.default_models)).ok()
+                            });
+                        if next_inputs.is_some() && next_inputs == model_inputs {
+                            continue;
+                        }
+                        model_inputs = next_inputs;
                         manager
                             .reconcile_loaded_session_reasoning_presets(
                                 "model_configuration_updated",
@@ -4213,39 +4225,71 @@ impl SessionManager {
         model_id: &str,
         reasoning_preset: Option<&str>,
     ) -> OpenBitFunResult<()> {
+        self.update_session_model_selection_in_storage(
+            None,
+            session_id,
+            model_id,
+            reasoning_preset,
+            true,
+            |_| Ok(()),
+        )
+        .await
+        .map(|_| ())
+    }
+
+    pub(crate) async fn update_session_model_selection_in_storage(
+        &self,
+        storage_path: Option<&Path>,
+        session_id: &str,
+        model_id: &str,
+        reasoning_preset: Option<&str>,
+        include_internal: bool,
+        validate_binding: impl FnOnce(&Session) -> OpenBitFunResult<()>,
+    ) -> OpenBitFunResult<Session> {
+        let _mutation_guard = self.acquire_session_mutation(session_id).await?;
+        let storage_path = storage_path.map(Path::to_path_buf).or_else(|| {
+            Self::committed_session_storage_path(&self.session_storage_path_index, session_id)
+        });
+        if let Some(path) = storage_path.as_deref() {
+            self.validate_session_storage_path_binding(session_id, path)?;
+        }
+        let loaded = self.sessions.get(session_id).map(|session| session.clone());
+        // Keep the cross-process lease until the complete read/modify/write has
+        // finished. A cold selector update never reserves active-session capacity.
+        let _writer = if loaded.is_none() {
+            storage_path
+                .as_deref()
+                .map(|path| {
+                    self.persistence_manager
+                        .lock_session_writes(path, session_id)
+                })
+                .transpose()?
+        } else {
+            None
+        };
+        let was_loaded = loaded.is_some();
+        let original_session = match loaded {
+            Some(session) => session,
+            None => {
+                let path = storage_path.as_deref().ok_or_else(|| {
+                    OpenBitFunError::NotFound(format!("Session not found: {session_id}"))
+                })?;
+                let session = self
+                    .persistence_manager
+                    .load_session_header(path, session_id)
+                    .await?;
+                if !include_internal && session.kind != SessionKind::Standard {
+                    return Err(OpenBitFunError::NotFound(format!(
+                        "Session not found: {session_id}"
+                    )));
+                }
+                session
+            }
+        };
+        validate_binding(&original_session)?;
         let ai_config = Self::load_ai_config_for_model_resolution().await;
         let mut resolved_context_window = None;
         let mut auto_cleared_reasoning_preset = None;
-
-        // If the session was evicted from memory (idle > 1h), try to restore it
-        // using the storage path recorded when it was first created/restored.
-        if !self.sessions.contains_key(session_id) && self.config.enable_persistence {
-            let session_storage_path =
-                Self::committed_session_storage_path(&self.session_storage_path_index, session_id);
-            if let Some(session_storage_path) = session_storage_path {
-                debug!(
-                    "Session evicted from memory, restoring for model update: session_id={}",
-                    session_id
-                );
-                let _ = self
-                    .restore_session_from_storage_path(&session_storage_path, session_id)
-                    .await;
-            }
-        }
-
-        // Restore owns the same keyed lock internally, so acquire the mutation
-        // permit only after the optional restore completes. From here through
-        // persistence, explicit deletion cannot remove and then be recreated by
-        // a late model update.
-        let _mutation_guard = self.acquire_session_mutation(session_id).await?;
-
-        let original_session = self
-            .sessions
-            .get(session_id)
-            .map(|session| session.clone())
-            .ok_or_else(|| {
-                OpenBitFunError::NotFound(format!("Session not found: {}", session_id))
-            })?;
         let mut updated_session = original_session.clone();
         updated_session.config.model_id = Some(model_id.to_string());
         updated_session.config.reasoning_preset = reasoning_preset
@@ -4270,43 +4314,44 @@ impl SessionManager {
             resolved_context_window =
                 Self::sync_session_context_window_from_ai_config(&mut updated_session, ai_config);
         }
+        if original_session.config.model_id == updated_session.config.model_id
+            && original_session.config.reasoning_preset == updated_session.config.reasoning_preset
+            && original_session.config.max_context_tokens
+                == updated_session.config.max_context_tokens
+        {
+            if !was_loaded && self.should_persist_session_id(session_id) {
+                if let Some(path) = storage_path.as_deref() {
+                    // Repair a metadata projection left behind by an interrupted
+                    // two-file commit; an aligned snapshot performs no write.
+                    self.persistence_manager
+                        .save_session_model_selection(path, &original_session)
+                        .await?;
+                }
+            }
+            return Ok(original_session);
+        }
         let now = SystemTime::now();
         updated_session.updated_at = now;
         updated_session.last_activity_at = now;
 
         if self.should_persist_session_id(session_id) {
-            let effective_path = self.effective_session_storage_path(session_id).await;
-            if let Some(workspace_path) = effective_path {
-                if let Err(error) = self
-                    .persistence_manager
-                    .save_session(&workspace_path, &updated_session)
-                    .await
-                {
-                    if let Err(rollback_error) = self
-                        .persistence_manager
-                        .save_session(&workspace_path, &original_session)
-                        .await
-                    {
-                        return Err(OpenBitFunError::session(format!(
-                            "Session model persistence failed and rollback did not complete: session_id={session_id}, error={error}, rollback_error={rollback_error}"
-                        )));
-                    }
-                    return Err(error);
-                }
+            let effective_path = match storage_path {
+                Some(path) => Some(path),
+                None => self.effective_session_storage_path(session_id).await,
+            };
+            if let Some(path) = effective_path {
+                self.persistence_manager
+                    .save_session_model_selection(&path, &updated_session)
+                    .await?;
             }
         }
 
         if let Some(mut session) = self.sessions.get_mut(session_id) {
-            session.config.model_id = updated_session.config.model_id;
+            session.config.model_id = updated_session.config.model_id.clone();
             session.config.reasoning_preset = updated_session.config.reasoning_preset.clone();
             session.config.max_context_tokens = updated_session.config.max_context_tokens;
             session.updated_at = now;
             session.last_activity_at = now;
-        } else {
-            return Err(OpenBitFunError::NotFound(format!(
-                "Session not found: {}",
-                session_id
-            )));
         }
 
         debug!(
@@ -4329,7 +4374,7 @@ impl SessionManager {
             }
         }
 
-        Ok(())
+        Ok(updated_session)
     }
 
     /// Sets the session's own tool permission mode (in-memory + persistence).
@@ -4343,7 +4388,7 @@ impl SessionManager {
         session_id: &str,
         permission_mode: Option<PermissionMode>,
     ) -> OpenBitFunResult<()> {
-        // Match the model-selection path: an evicted session is restored before
+        // Permission updates still restore an evicted session before
         // the mutation permit is taken, because restore owns the same keyed lock.
         if !self.sessions.contains_key(session_id) && self.config.enable_persistence {
             let session_storage_path =
@@ -12831,6 +12876,289 @@ mod tests {
         assert!(!manager.context_store.has_session(&session_id));
     }
 
+    #[tokio::test]
+    async fn cold_session_model_update_preserves_history_and_unknown_state_without_restore() {
+        let workspace = TestWorkspace::new();
+        let paths = workspace.path_manager();
+        let persistence = Arc::new(PersistenceManager::new(paths.clone()).unwrap());
+        let manager = test_manager(persistence.clone());
+        let id = Uuid::new_v4().to_string();
+        let session = Session::new_with_id(
+            id.clone(),
+            "Cold selector".into(),
+            "Standard".into(),
+            SessionConfig {
+                workspace_path: Some(workspace.path().to_string_lossy().into_owned()),
+                model_id: Some("primary".into()),
+                ..Default::default()
+            },
+        );
+        persistence
+            .save_session(workspace.path(), &session)
+            .await
+            .unwrap();
+        let directory = paths.project_sessions_dir(workspace.path()).join(&id);
+        let state_path = directory.join("state.json");
+        let mut state: serde_json::Value =
+            serde_json::from_slice(&std::fs::read(&state_path).unwrap()).unwrap();
+        state["future_state"] = serde_json::json!({"preserve": true});
+        state["config"]["future_config"] = serde_json::json!(42);
+        std::fs::write(&state_path, serde_json::to_vec(&state).unwrap()).unwrap();
+        // A corrupt turn body would make a full restore fail. Selector writes
+        // must leave transcript bytes alone, including unknown legacy content.
+        std::fs::create_dir_all(directory.join("turns")).unwrap();
+        let turn_path = directory.join("turns").join("untouched.json");
+        std::fs::write(&turn_path, b"unreadable historical turn").unwrap();
+        let update = manager
+            .update_session_model_selection_in_storage(
+                Some(workspace.path()),
+                &id,
+                "fast",
+                Some("high"),
+                false,
+                |_| Ok(()),
+            )
+            .await
+            .unwrap();
+        assert_eq!(update.config.reasoning_preset.as_deref(), Some("high"));
+        assert!(manager.get_session(&id).is_none());
+        assert!(manager.active_session_permits.is_empty());
+        assert!(!manager.context_store.has_session(&id));
+        let updated: serde_json::Value =
+            serde_json::from_slice(&std::fs::read(&state_path).unwrap()).unwrap();
+        assert_eq!(updated["future_state"], state["future_state"]);
+        assert_eq!(updated["config"]["future_config"], 42);
+        assert_eq!(updated["config"]["model_id"], "fast");
+        assert_eq!(
+            persistence
+                .load_session_metadata(workspace.path(), &id)
+                .await
+                .unwrap()
+                .unwrap()
+                .model_name,
+            "fast"
+        );
+        assert_eq!(
+            std::fs::read(&turn_path).unwrap(),
+            b"unreadable historical turn"
+        );
+        let bytes = std::fs::read(&state_path).unwrap();
+        manager
+            .update_session_model_selection_in_storage(
+                Some(workspace.path()),
+                &id,
+                "fast",
+                Some("high"),
+                false,
+                |_| Ok(()),
+            )
+            .await
+            .unwrap();
+        assert_eq!(std::fs::read(&state_path).unwrap(), bytes);
+        // Clearing a preset on the same model is a real mutation.
+        manager
+            .update_session_model_selection_in_storage(
+                Some(workspace.path()),
+                &id,
+                "fast",
+                None,
+                false,
+                |_| Ok(()),
+            )
+            .await
+            .unwrap();
+        assert!(persistence
+            .load_session_header(workspace.path(), &id)
+            .await
+            .unwrap()
+            .config
+            .reasoning_preset
+            .is_none());
+        persistence.fail_next_session_state_write_for_test(&id);
+        manager
+            .update_session_model_selection_in_storage(
+                Some(workspace.path()),
+                &id,
+                "primary",
+                None,
+                false,
+                |_| Ok(()),
+            )
+            .await
+            .unwrap_err();
+        assert_eq!(
+            persistence
+                .load_session_header(workspace.path(), &id)
+                .await
+                .unwrap()
+                .config
+                .model_id
+                .as_deref(),
+            Some("fast")
+        );
+        let state_before_failure = std::fs::read(&state_path).unwrap();
+        persistence.fail_next_session_metadata_write_for_test(&id);
+        assert!(manager
+            .update_session_model_selection_in_storage(
+                Some(workspace.path()),
+                &id,
+                "primary",
+                None,
+                false,
+                |_| Ok(())
+            )
+            .await
+            .is_err());
+        assert_eq!(std::fs::read(&state_path).unwrap(), state_before_failure);
+        assert_eq!(
+            persistence
+                .load_session_metadata(workspace.path(), &id)
+                .await
+                .unwrap()
+                .unwrap()
+                .model_name,
+            "fast"
+        );
+        assert!(manager
+            .update_session_model_selection_in_storage(
+                Some(workspace.path()),
+                &id,
+                "primary",
+                None,
+                false,
+                |_| Err(OpenBitFunError::Validation("binding denied".into()))
+            )
+            .await
+            .is_err());
+        let writer = persistence
+            .lock_session_writes(workspace.path(), &id)
+            .unwrap();
+        assert!(manager
+            .update_session_model_selection_in_storage(
+                Some(workspace.path()),
+                &id,
+                "primary",
+                None,
+                false,
+                |_| Ok(())
+            )
+            .await
+            .is_err());
+        drop(writer);
+        assert_eq!(std::fs::read(&state_path).unwrap(), state_before_failure);
+        // A restart may encounter a metadata projection from before a commit.
+        persistence
+            .update_session_metadata(workspace.path(), &id, |metadata| {
+                metadata.model_name = "primary".into()
+            })
+            .await
+            .unwrap();
+        manager
+            .update_session_model_selection_in_storage(
+                Some(workspace.path()),
+                &id,
+                "fast",
+                None,
+                false,
+                |_| Ok(()),
+            )
+            .await
+            .unwrap();
+        assert_eq!(
+            persistence
+                .load_session_metadata(workspace.path(), &id)
+                .await
+                .unwrap()
+                .unwrap()
+                .model_name,
+            "fast"
+        );
+    }
+
+    #[tokio::test]
+    async fn cold_session_model_update_upgrades_metadata_only_and_rejects_missing_or_internal_sessions(
+    ) {
+        let workspace = TestWorkspace::new();
+        let paths = workspace.path_manager();
+        let persistence = Arc::new(PersistenceManager::new(paths.clone()).unwrap());
+        let manager = test_manager(persistence.clone());
+        let id = Uuid::new_v4().to_string();
+        let mut session = Session::new_with_id(
+            id.clone(),
+            "Legacy".into(),
+            "Standard".into(),
+            SessionConfig {
+                workspace_path: Some(workspace.path().to_string_lossy().into_owned()),
+                model_id: Some("primary".into()),
+                ..Default::default()
+            },
+        );
+        persistence
+            .save_session(workspace.path(), &session)
+            .await
+            .unwrap();
+        std::fs::remove_file(
+            paths
+                .project_sessions_dir(workspace.path())
+                .join(&id)
+                .join("state.json"),
+        )
+        .unwrap();
+        manager
+            .update_session_model_selection_in_storage(
+                Some(workspace.path()),
+                &id,
+                "fast",
+                None,
+                false,
+                |_| Ok(()),
+            )
+            .await
+            .unwrap();
+        assert_eq!(
+            persistence
+                .load_session(workspace.path(), &id)
+                .await
+                .unwrap()
+                .config
+                .model_id
+                .as_deref(),
+            Some("fast")
+        );
+        session.kind = SessionKind::Subagent;
+        persistence
+            .save_session(workspace.path(), &session)
+            .await
+            .unwrap();
+        assert!(manager
+            .update_session_model_selection_in_storage(
+                Some(workspace.path()),
+                &id,
+                "fast",
+                None,
+                false,
+                |_| Ok(())
+            )
+            .await
+            .is_err());
+        assert!(manager
+            .update_session_model_selection_in_storage(
+                Some(workspace.path()),
+                "missing-session",
+                "fast",
+                None,
+                false,
+                |_| Ok(())
+            )
+            .await
+            .is_err());
+        assert!(!paths
+            .project_sessions_dir(workspace.path())
+            .join("missing-session")
+            .join("metadata.json")
+            .exists());
+    }
+
     #[tokio::test]
     async fn session_model_update_is_restored_from_persistence() {
         let workspace = TestWorkspace::new();
diff --git a/src/crates/assembly/core/src/agentic/tools/openbitfun_control_config.rs b/src/crates/assembly/core/src/agentic/tools/openbitfun_control_config.rs
index e6cd475393..3f6f31221c 100644
--- a/src/crates/assembly/core/src/agentic/tools/openbitfun_control_config.rs
+++ b/src/crates/assembly/core/src/agentic/tools/openbitfun_control_config.rs
@@ -222,12 +222,16 @@ impl SharedProductControlExecutor {
     pub async fn configure_legacy_path(&self, path: &str, value: Value) -> Result<Value, String> {
         let _mutation = self.mutation_lock.lock().await;
         let applied = apply_legacy_config_mutation(&self.config_service, path, value).await?;
-        let revision = self.revision.fetch_add(1, Ordering::AcqRel) + 1;
+        let revision = if applied.changed {
+            self.revision.fetch_add(1, Ordering::AcqRel) + 1
+        } else {
+            self.revision.load(Ordering::Acquire)
+        };
         Ok(json!({
             "catalogDigest": product_control_catalog()?.digest.clone(),
             "configured": true,
             "changedPath": applied.changed_path.clone(),
-            "changedPaths": [applied.changed_path],
+            "changedPaths": if applied.changed { vec![applied.changed_path] } else { vec![] },
             "controlledBindings": applied.controlled_bindings,
             "effectiveValue": applied.effective_value,
             "revision": revision,
@@ -266,6 +270,7 @@ pub struct ProductConfigBinding {
 
 #[derive(Debug, Clone, PartialEq)]
 pub struct AppliedLegacyProductConfig {
+    pub changed: bool,
     pub changed_path: String,
     pub effective_value: Value,
     pub controlled_bindings: Vec<ProductConfigBinding>,
@@ -454,8 +459,8 @@ pub async fn apply_legacy_config_mutation(
 ) -> Result<AppliedLegacyProductConfig, String> {
     let controlled_bindings = validate_legacy_config_mutation(path, &value)?;
     validate_config_semantics(path, &value)?;
-    config_service
-        .set_config(path, value)
+    let changed = config_service
+        .set_config_if_changed(path, value)
         .await
         .map_err(|error| error.to_string())?;
     let effective_value = config_service
@@ -463,6 +468,7 @@ pub async fn apply_legacy_config_mutation(
         .await
         .map_err(|error| error.to_string())?;
     Ok(AppliedLegacyProductConfig {
+        changed,
         changed_path: path.to_string(),
         effective_value,
         controlled_bindings,
diff --git a/src/crates/assembly/core/src/infrastructure/ai/reasoning_catalog.rs b/src/crates/assembly/core/src/infrastructure/ai/reasoning_catalog.rs
index ed6a1c4f63..6140dc2b08 100644
--- a/src/crates/assembly/core/src/infrastructure/ai/reasoning_catalog.rs
+++ b/src/crates/assembly/core/src/infrastructure/ai/reasoning_catalog.rs
@@ -1,6 +1,6 @@
 use std::sync::Arc;
 #[cfg(feature = "model-catalog")]
-use std::sync::{OnceLock, RwLock};
+use std::sync::{Mutex, OnceLock, RwLock};
 #[cfg(feature = "model-catalog")]
 use std::time::{Duration, Instant};
 
@@ -41,19 +41,110 @@ pub(crate) struct ModelsDevReasoningCatalogSnapshot {
     pub(crate) source: ModelsDevSnapshotSource,
 }
 
+// This is a background check interval, not a snapshot expiration time.
 #[cfg(feature = "model-catalog")]
-const CATALOG_RELOAD_INTERVAL: Duration = Duration::from_secs(60);
+const CATALOG_CHECK_INTERVAL: Duration = Duration::from_secs(60);
 
 #[cfg(feature = "model-catalog")]
 struct CachedReasoningCatalogSnapshot {
-    loaded_at: Instant,
     snapshot: ModelsDevReasoningCatalogSnapshot,
 }
 
 #[cfg(feature = "model-catalog")]
-fn parsed_catalog_cache() -> &'static RwLock<Option<CachedReasoningCatalogSnapshot>> {
-    static CACHE: OnceLock<RwLock<Option<CachedReasoningCatalogSnapshot>>> = OnceLock::new();
-    CACHE.get_or_init(|| RwLock::new(None))
+#[derive(Default)]
+struct ParsedCatalogCache {
+    snapshot: RwLock<Option<CachedReasoningCatalogSnapshot>>,
+    // Covers reading, parsing and publication, including manual refreshes.
+    update: tokio::sync::Mutex<()>,
+    last_check: Mutex<Option<Instant>>,
+}
+
+#[cfg(feature = "model-catalog")]
+impl ParsedCatalogCache {
+    fn current(&self) -> Option<ModelsDevReasoningCatalogSnapshot> {
+        self.snapshot
+            .read()
+            .unwrap_or_else(|error| error.into_inner())
+            .as_ref()
+            .map(|cached| cached.snapshot.clone())
+    }
+
+    async fn load(&self, service: &ModelsDevCatalogService) -> ModelsDevReasoningCatalogSnapshot {
+        if let Some(snapshot) = self.current() {
+            return snapshot;
+        }
+        let _update = self.update.lock().await;
+        if let Some(snapshot) = self.current() {
+            return snapshot;
+        }
+        let source = service.load_cached_or_bundled().await;
+        self.publish(source).await;
+        self.current().expect("initial catalog snapshot")
+    }
+
+    // Caller holds update so a cold read cannot publish over a newer refresh.
+    async fn publish(&self, source: ModelsDevSnapshot) -> bool {
+        let current = self.current();
+        if let Some(current) = current
+            .as_ref()
+            .filter(|current| current.sha256 == source.sha256)
+        {
+            if current.source == source.source {
+                return false;
+            }
+            let mut updated = current.clone();
+            updated.source = source.source;
+            return replace_cached_catalog(
+                &mut self
+                    .snapshot
+                    .write()
+                    .unwrap_or_else(|error| error.into_inner()),
+                updated,
+            );
+        }
+        let version = source.version;
+        let sha256 = source.sha256.clone();
+        let source_kind = source.source;
+        let parsed = tokio::task::spawn_blocking(move || parse_models_dev_snapshot(&source))
+            .await
+            .ok()
+            .flatten();
+        let updated = match parsed {
+            Some(updated) => updated,
+            None if current.is_some() => return false,
+            None => ModelsDevReasoningCatalogSnapshot {
+                catalog: None,
+                version,
+                sha256,
+                source: source_kind,
+            },
+        };
+        replace_cached_catalog(
+            &mut self
+                .snapshot
+                .write()
+                .unwrap_or_else(|error| error.into_inner()),
+            updated,
+        )
+    }
+
+    fn claim_background_check(&self) -> bool {
+        let mut last = self
+            .last_check
+            .lock()
+            .unwrap_or_else(|error| error.into_inner());
+        if last.is_some_and(|last| last.elapsed() < CATALOG_CHECK_INTERVAL) {
+            return false;
+        }
+        *last = Some(Instant::now());
+        true
+    }
+}
+
+#[cfg(feature = "model-catalog")]
+fn parsed_catalog_cache() -> &'static ParsedCatalogCache {
+    static CACHE: OnceLock<ParsedCatalogCache> = OnceLock::new();
+    CACHE.get_or_init(ParsedCatalogCache::default)
 }
 
 #[cfg(feature = "model-catalog")]
@@ -113,100 +204,89 @@ pub(crate) async fn get_models_dev_catalog_status() -> ModelsDevCatalogStatus {
 
 #[cfg(feature = "model-catalog")]
 pub(crate) async fn refresh_models_dev_catalog_now() -> Result<ModelsDevRefreshResult, String> {
+    let cache = parsed_catalog_cache();
     let service = models_dev_catalog_service();
-    let outcome = service.refresh_now().await;
-    match outcome {
-        ModelsDevRefreshOutcome::Updated(snapshot) => {
-            if let Some(updated) = parse_models_dev_snapshot(&snapshot) {
-                if replace_parsed_catalog_cache(updated) {
-                    emit_models_dev_catalog_updated(&snapshot).await;
-                }
+    // Ensure status reads never have to wait on an in-progress network refresh.
+    cache.load(service).await;
+    let outcome = if let Ok(_update) = cache.update.try_lock() {
+        let outcome = service.refresh_now().await;
+        match &outcome {
+            ModelsDevRefreshOutcome::Failed => {
+                return Err("Failed to refresh models.dev catalog".to_string())
             }
-            Ok(ModelsDevRefreshResult {
-                outcome: ModelsDevRefreshStatus::Updated,
-                status: models_dev_catalog_status().await,
-            })
+            ModelsDevRefreshOutcome::Throttled => {}
+            _ => publish_current_catalog(cache, service).await,
         }
-        ModelsDevRefreshOutcome::Unchanged { .. } => {
-            let snapshot = service.load_cached_or_bundled().await;
-            if let Some(updated) = parse_models_dev_snapshot(&snapshot) {
-                replace_parsed_catalog_cache(updated);
-            }
-            Ok(ModelsDevRefreshResult {
-                outcome: ModelsDevRefreshStatus::Unchanged,
-                status: models_dev_catalog_status().await,
-            })
-        }
-        ModelsDevRefreshOutcome::NotNeeded => Ok(ModelsDevRefreshResult {
-            outcome: ModelsDevRefreshStatus::Unchanged,
-            status: models_dev_catalog_status().await,
-        }),
-        ModelsDevRefreshOutcome::Throttled => Ok(ModelsDevRefreshResult {
-            outcome: ModelsDevRefreshStatus::Throttled,
-            status: models_dev_catalog_status().await,
-        }),
-        ModelsDevRefreshOutcome::Failed => Err("Failed to refresh models.dev catalog".to_string()),
-    }
+        outcome
+    } else {
+        ModelsDevRefreshOutcome::Throttled
+    };
+    Ok(ModelsDevRefreshResult {
+        outcome: match outcome {
+            ModelsDevRefreshOutcome::Updated(_) => ModelsDevRefreshStatus::Updated,
+            ModelsDevRefreshOutcome::Throttled => ModelsDevRefreshStatus::Throttled,
+            _ => ModelsDevRefreshStatus::Unchanged,
+        },
+        status: models_dev_catalog_status().await,
+    })
 }
 
 #[cfg(feature = "model-catalog")]
-pub(crate) async fn load_models_dev_reasoning_catalog_without_refresh(
-) -> ModelsDevReasoningCatalogSnapshot {
-    if let Ok(cache) = parsed_catalog_cache().read() {
-        if let Some(cached) = cache
-            .as_ref()
-            .filter(|cached| cached.loaded_at.elapsed() < CATALOG_RELOAD_INTERVAL)
-        {
-            return cached.snapshot.clone();
-        }
-    }
-
-    let service = models_dev_catalog_service();
-    let snapshot = service.load_cached_or_bundled().await;
-    let catalog = match ModelsDevCatalog::parse_str(&snapshot.body) {
-        Ok(catalog) => Some(Arc::new(catalog)),
-        Err(error) => {
-            debug!("Failed to parse models.dev catalog snapshot: {}", error);
-            None
-        }
+async fn publish_current_catalog(cache: &ParsedCatalogCache, service: &ModelsDevCatalogService) {
+    let source = service.load_cached_or_bundled().await;
+    let event = AIModelCatalogUpdatedEvent {
+        source_version: source.version.to_string(),
+        sha256: source.sha256.clone(),
     };
-
-    let loaded = ModelsDevReasoningCatalogSnapshot {
-        catalog,
-        #[cfg(feature = "model-catalog")]
-        version: snapshot.version,
-        sha256: snapshot.sha256,
-        source: snapshot.source,
-    };
-    if let Ok(mut cache) = parsed_catalog_cache().write() {
-        *cache = Some(CachedReasoningCatalogSnapshot {
-            loaded_at: Instant::now(),
-            snapshot: loaded.clone(),
-        });
+    if cache.publish(source).await {
+        emit_models_dev_catalog_updated(event).await;
     }
+}
 
-    loaded
+#[cfg(feature = "model-catalog")]
+pub(crate) async fn load_models_dev_reasoning_catalog_without_refresh(
+) -> ModelsDevReasoningCatalogSnapshot {
+    parsed_catalog_cache()
+        .load(models_dev_catalog_service())
+        .await
 }
 
 #[cfg(feature = "model-catalog")]
 pub(crate) async fn load_models_dev_reasoning_catalog() -> ModelsDevReasoningCatalogSnapshot {
     let loaded = load_models_dev_reasoning_catalog_without_refresh().await;
+    schedule_catalog_refresh();
+    loaded
+}
 
-    let refresh_service = models_dev_catalog_service().clone();
+#[cfg(feature = "model-catalog")]
+fn schedule_catalog_refresh() {
+    let cache = parsed_catalog_cache();
+    if !cache.claim_background_check() {
+        return;
+    }
     tokio::spawn(async move {
-        let ModelsDevRefreshOutcome::Updated(snapshot) = refresh_service.refresh_if_stale().await
-        else {
+        let Ok(_update) = cache.update.try_lock() else {
             return;
         };
-        let Some(updated) = parse_models_dev_snapshot(&snapshot) else {
-            return;
-        };
-        if !replace_parsed_catalog_cache(updated) {
-            return;
+        let service = models_dev_catalog_service();
+        // Observe changes written by another host process, then check the source.
+        publish_current_catalog(cache, service).await;
+        if !matches!(
+            service.refresh_if_stale().await,
+            ModelsDevRefreshOutcome::Failed | ModelsDevRefreshOutcome::Throttled
+        ) {
+            publish_current_catalog(cache, service).await;
         }
-        emit_models_dev_catalog_updated(&snapshot).await;
     });
-    loaded
+}
+
+/// Prepare local capabilities once the host configuration is available. Network
+/// freshness is optional; readers always retain the last valid local snapshot.
+#[cfg(feature = "model-catalog")]
+pub(crate) fn prepare_model_catalog() {
+    tokio::spawn(async {
+        load_models_dev_reasoning_catalog().await;
+    });
 }
 
 #[cfg(feature = "model-catalog")]
@@ -231,41 +311,27 @@ fn parse_models_dev_snapshot(
     })
 }
 
-#[cfg(feature = "model-catalog")]
-fn replace_parsed_catalog_cache(updated: ModelsDevReasoningCatalogSnapshot) -> bool {
-    let Ok(mut cache) = parsed_catalog_cache().write() else {
-        return false;
-    };
-    replace_cached_catalog(&mut cache, updated)
-}
-
 #[cfg(feature = "model-catalog")]
 fn replace_cached_catalog(
     cache: &mut Option<CachedReasoningCatalogSnapshot>,
     updated: ModelsDevReasoningCatalogSnapshot,
 ) -> bool {
     if cache.as_ref().is_some_and(|cached| {
-        cached.snapshot.version == updated.version && cached.snapshot.source == updated.source
+        cached.snapshot.sha256 == updated.sha256 && cached.snapshot.source == updated.source
     }) {
         return false;
     }
-    *cache = Some(CachedReasoningCatalogSnapshot {
-        loaded_at: Instant::now(),
-        snapshot: updated,
-    });
+    *cache = Some(CachedReasoningCatalogSnapshot { snapshot: updated });
     true
 }
 
 #[cfg(feature = "model-catalog")]
-async fn emit_models_dev_catalog_updated(snapshot: &ModelsDevSnapshot) {
+async fn emit_models_dev_catalog_updated(event: AIModelCatalogUpdatedEvent) {
     crate::service::config::GlobalConfigManager::broadcast_update(
         crate::service::config::ConfigUpdateEvent::ReasoningCatalogUpdated,
     )
     .await;
-    let payload = match serde_json::to_value(AIModelCatalogUpdatedEvent {
-        source_version: snapshot.version.to_string(),
-        sha256: snapshot.sha256.clone(),
-    }) {
+    let payload = match serde_json::to_value(event) {
         Ok(payload) => payload,
         Err(error) => {
             debug!(
@@ -847,7 +913,6 @@ mod tests {
     #[test]
     fn refreshed_catalog_replaces_projection_without_waiting_for_reload_interval() {
         let mut cache = Some(super::CachedReasoningCatalogSnapshot {
-            loaded_at: std::time::Instant::now(),
             snapshot: super::ModelsDevReasoningCatalogSnapshot {
                 catalog: None,
                 version: 1,
@@ -872,7 +937,6 @@ mod tests {
     fn cache_source_change_replaces_equal_bundled_snapshot() {
         let catalog = std::sync::Arc::new(catalog());
         let mut cache = Some(super::CachedReasoningCatalogSnapshot {
-            loaded_at: std::time::Instant::now(),
             snapshot: super::ModelsDevReasoningCatalogSnapshot {
                 catalog: Some(catalog.clone()),
                 version: 1,
@@ -894,4 +958,45 @@ mod tests {
             Some(openbitfun_services_integrations::models_dev::ModelsDevSnapshotSource::Cache)
         );
     }
+    #[cfg(feature = "model-catalog")]
+    #[tokio::test]
+    async fn catalog_readers_share_initial_parse_and_keep_snapshot_until_publication() {
+        let directory = tempfile::tempdir().unwrap();
+        let file = directory.path().join("catalog.json");
+        tokio::fs::write(&file, r#"{"openai":{"models":{"a":{"id":"a"}}}}"#)
+            .await
+            .unwrap();
+        let service =
+            openbitfun_services_integrations::models_dev::ModelsDevCatalogService::new(&file);
+        let cache = super::ParsedCatalogCache::default();
+        let (a, b) = tokio::join!(cache.load(&service), cache.load(&service));
+        assert!(std::sync::Arc::ptr_eq(
+            a.catalog.as_ref().unwrap(),
+            b.catalog.as_ref().unwrap()
+        ));
+        tokio::fs::write(
+            &file,
+            r#"{"openai":{"models":{"new-model":{"id":"new-model"}}}}"#,
+        )
+        .await
+        .unwrap();
+        // A read never revalidates the source, even after the background deadline.
+        *cache.last_check.lock().unwrap() =
+            Some(std::time::Instant::now() - std::time::Duration::from_secs(120));
+        assert_eq!(cache.load(&service).await.sha256, a.sha256);
+        assert!(cache.claim_background_check());
+        assert!(!cache.claim_background_check());
+        let _update = cache.update.lock().await;
+        assert!(cache.publish(service.load_cached_or_bundled().await).await);
+        let updated = cache.load(&service).await;
+        assert_ne!(updated.sha256, a.sha256);
+        assert!(!cache.publish(service.load_cached_or_bundled().await).await);
+        assert!(std::sync::Arc::ptr_eq(
+            updated.catalog.as_ref().unwrap(),
+            cache.current().unwrap().catalog.as_ref().unwrap()
+        ));
+        tokio::fs::write(&file, "corrupt").await.unwrap();
+        assert!(!cache.publish(service.load_cached_or_bundled().await).await);
+        assert_eq!(cache.load(&service).await.sha256, updated.sha256);
+    }
 }
diff --git a/src/crates/assembly/core/src/product_runtime.rs b/src/crates/assembly/core/src/product_runtime.rs
index 44af140a86..97a6346c2c 100644
--- a/src/crates/assembly/core/src/product_runtime.rs
+++ b/src/crates/assembly/core/src/product_runtime.rs
@@ -1633,6 +1633,25 @@ impl CoreAgentRuntimeCompatibility {
         Ok(())
     }
 
+    pub async fn update_session_model_selection_from_storage_path(
+        &self,
+        storage_path: &Path,
+        session_id: &str,
+        model_id: &str,
+        reasoning_preset: Option<&str>,
+        include_internal: bool,
+    ) -> OpenBitFunResult<Session> {
+        self.coordinator
+            .update_session_model_selection_from_storage_path(
+                storage_path,
+                session_id,
+                model_id,
+                reasoning_preset,
+                include_internal,
+            )
+            .await
+    }
+
     pub async fn begin_persisted_session_mutation(
         &self,
         storage_path: &Path,
diff --git a/src/crates/assembly/core/src/service/config/global.rs b/src/crates/assembly/core/src/service/config/global.rs
index e4c8d29188..412a4c6cd3 100644
--- a/src/crates/assembly/core/src/service/config/global.rs
+++ b/src/crates/assembly/core/src/service/config/global.rs
@@ -106,6 +106,9 @@ impl GlobalConfigManager {
             crate::service::web_search::refresh_global_web_search_runtime(&ai_config).await;
         }
 
+        #[cfg(feature = "model-catalog")]
+        crate::infrastructure::ai::reasoning_catalog::prepare_model_catalog();
+
         info!("Global config service initialized");
 
         Ok(())
diff --git a/src/crates/assembly/core/src/service/config/manager.rs b/src/crates/assembly/core/src/service/config/manager.rs
index 70bfd88bce..0cda3f06b1 100644
--- a/src/crates/assembly/core/src/service/config/manager.rs
+++ b/src/crates/assembly/core/src/service/config/manager.rs
@@ -647,7 +647,20 @@ impl ConfigManager {
         })?;
 
         reject_protected_metadata_path(path)?;
+        if self.get::<serde_json::Value>(path).ok().as_ref() == Some(&json_value) {
+            return Ok(());
+        }
         let mut config = self.config_with_value(path, json_value)?;
+        // Selecting a future-session default changes only a reference to an
+        // already validated model. Keep legacy alias/fallback normalization,
+        // without constructing clients or revalidating every provider.
+        if path == "ai.agent_model_defaults.mode" {
+            reconcile_model_references(&mut config);
+            if config.ai.agent_model_defaults.mode == self.config.ai.agent_model_defaults.mode {
+                return Ok(());
+            }
+            return self.commit_config(config, Some(path)).await;
+        }
         // Apply capability-driven canonicalization before validation and persistence.
         // Speech/embedding/image-only models must never carry text-generation sentinels.
         normalize_typed_config(&mut config);
diff --git a/src/crates/assembly/core/src/service/config/service.rs b/src/crates/assembly/core/src/service/config/service.rs
index fcf8208d65..78fb11346c 100644
--- a/src/crates/assembly/core/src/service/config/service.rs
+++ b/src/crates/assembly/core/src/service/config/service.rs
@@ -184,12 +184,26 @@ impl ConfigService {
     where
         T: serde::Serialize,
     {
+        self.set_config_if_changed(path, value).await.map(|_| ())
+    }
+
+    /// Compares and persists under the same lock; unchanged preferences do not
+    /// trigger validation, disk writes, account sync, or runtime notifications.
+    pub async fn set_config_if_changed<T>(&self, path: &str, value: T) -> OpenBitFunResult<bool>
+    where
+        T: serde::Serialize,
+    {
+        let value = serde_json::to_value(value)?;
         {
             let mut manager = self.manager.write().await;
+            let before = manager.get::<serde_json::Value>(path).ok();
             manager.set(path, value).await?;
+            if before == manager.get::<serde_json::Value>(path).ok() {
+                return Ok(false);
+            }
         }
         self.after_config_change(path).await;
-        Ok(())
+        Ok(true)
     }
 
     /// Reads, modifies, validates, and persists a section under one write lock.
@@ -225,11 +239,13 @@ impl ConfigService {
     async fn after_config_change(&self, path: &str) {
         let model_configuration_changed = Self::path_touches_models(path);
         if model_configuration_changed {
-            if let Err(e) = self.reconcile_models("set_config").await {
-                warn!(
-                    "Model reconcile after set_config failed: path={}, error={}",
-                    path, e
-                );
+            if path != "ai.agent_model_defaults.mode" {
+                if let Err(e) = self.reconcile_models("set_config").await {
+                    warn!(
+                        "Model reconcile after set_config failed: path={}, error={}",
+                        path, e
+                    );
+                }
             }
             super::global::GlobalConfigManager::broadcast_update(
                 super::global::ConfigUpdateEvent::ModelConfigurationUpdated,
@@ -803,6 +819,53 @@ mod tests {
         (service, dir)
     }
 
+    #[tokio::test]
+    async fn model_default_noop_does_not_persist_or_notify() {
+        let (service, dir) = test_service("model-default-noop").await;
+        service
+            .add_ai_model(runtime_model("chosen", "fixture-key"))
+            .await
+            .unwrap();
+        let mut changes = service.subscribe_local_changes();
+        assert!(service
+            .set_config_if_changed("ai.agent_model_defaults.mode", "chosen")
+            .await
+            .unwrap());
+        changes.borrow_and_update();
+        let before: GlobalConfig = service.get_config(None).await.unwrap();
+        assert!(!service
+            .set_config_if_changed("ai.agent_model_defaults.mode", "chosen")
+            .await
+            .unwrap());
+        assert!(!changes.has_changed().unwrap());
+        let after: GlobalConfig = service.get_config(None).await.unwrap();
+        assert_eq!(before.last_modified, after.last_modified);
+        let restarted = restart_test_service(&dir, "model-default-noop").await;
+        assert_eq!(
+            restarted
+                .get_config::<String>(Some("ai.agent_model_defaults.mode"))
+                .await
+                .unwrap(),
+            "chosen"
+        );
+        // Keep the legacy invalid-reference fallback and reject malformed types.
+        service
+            .set_config("ai.agent_model_defaults.mode", "removed-model")
+            .await
+            .unwrap();
+        assert_eq!(
+            service
+                .get_config::<String>(Some("ai.agent_model_defaults.mode"))
+                .await
+                .unwrap(),
+            "primary"
+        );
+        assert!(service
+            .set_config("ai.agent_model_defaults.mode", 123)
+            .await
+            .is_err());
+    }
+
     fn realtime_voice_fixture() -> VoiceCallConfig {
         VoiceCallConfig {
             api_key: "fixture-realtime-voice-key".to_string(),
@@ -1137,9 +1200,10 @@ mod tests {
             ),
         ];
         for (path, value) in &fixtures {
-            source.set_config(path, value).await.unwrap();
-            assert!(
+            let changed = source.set_config_if_changed(path, value).await.unwrap();
+            assert_eq!(
                 changes.has_changed().unwrap(),
+                changed,
                 "Missing configuration change signal: {path}"
             );
             changes.borrow_and_update();
diff --git a/src/crates/assembly/core/src/service_agent_runtime.rs b/src/crates/assembly/core/src/service_agent_runtime.rs
index 8baca8ac1e..8dfd43836e 100644
--- a/src/crates/assembly/core/src/service_agent_runtime.rs
+++ b/src/crates/assembly/core/src/service_agent_runtime.rs
@@ -2378,10 +2378,25 @@ impl CoreServiceAgentRuntime {
             .get_session(session_id)
             .is_none()
         {
-            coordinator
-                .restore_session_for_workspace_binding(&binding, session_id)
+            let session = coordinator
+                .update_session_model_selection_from_storage_path(
+                    &binding.session_storage_dir(),
+                    session_id,
+                    &normalized_model_id,
+                    normalized_reasoning_preset
+                        .as_ref()
+                        .and_then(|value| value.as_deref()),
+                    false,
+                )
                 .await
-                .map_err(|e| format!("Failed to restore session: {e}"))?;
+                .map_err(|error| format!("Failed to update session model: {error}"))?;
+            if session_uses_shared_mode_default(&session) {
+                Self::persist_mode_model(&normalized_model_id).await;
+            }
+            return Ok(RemoteSessionModelSelection {
+                model_id: session.config.model_id.unwrap_or(normalized_model_id),
+                reasoning_preset: session.config.reasoning_preset,
+            });
         }
 
         let previous_model_id = coordinator
@@ -4199,7 +4214,6 @@ mod tests {
         assert!(!open_workspace.contains("initialize_snapshot_manager_for_workspace"));
 
         for (start, end) in [
-            ("pub(crate) async fn update_remote_session_model", "/// Persist the shared selector"),
             ("async fn restore_remote_session(\n        &self,\n        session_id: &str,\n        workspace: RemoteDialogWorkspaceBinding", "fn prewarm_remote_terminal"),
             ("async fn ensure_session_loaded(&self, session_id: &str)", "async fn update_session_title"),
             ("async fn restore_remote_session(\n        &self,\n        session_id: &str,\n        _restore_path_hint: &str", "async fn cancel_remote_turn"),
@@ -4219,6 +4233,17 @@ mod tests {
             );
         }
 
+        let selector = source
+            .split("pub(crate) async fn update_remote_session_model")
+            .nth(1)
+            .and_then(|source| source.split("/// Persist the shared selector").next())
+            .unwrap();
+        assert!(selector.contains("ensure_remote_binding_runtime_ownership"));
+        assert!(selector.contains(
+            "coordinator\n                .update_session_model_selection_from_storage_path"
+        ));
+        assert!(!selector.contains("restore_session"));
+
         let remote_session_host = source
             .split("impl RemoteSessionRuntimeHost for CoreRemoteSessionRuntimeHost")
             .nth(1)
diff --git a/src/crates/services/services-integrations/AGENTS.md b/src/crates/services/services-integrations/AGENTS.md
index f57f00b4e4..70ae078199 100644
--- a/src/crates/services/services-integrations/AGENTS.md
+++ b/src/crates/services/services-integrations/AGENTS.md
@@ -187,3 +187,9 @@ cargo test --locked -p openbitfun-services-integrations --no-default-features --
 
 These loopback protocol fixtures exercise the serving host's HTTP and filesystem
 behavior; they do not establish real SSH, relay, peer or dispatch support.
+
+For models.dev snapshot reuse, last-valid recovery, and background refresh:
+
+```bash
+cargo test --locked -p openbitfun-services-integrations --no-default-features --features models-dev --lib models_dev::tests
+```
diff --git a/src/crates/services/services-integrations/Cargo.toml b/src/crates/services/services-integrations/Cargo.toml
index 4ceca79f62..40cc5d9b02 100644
--- a/src/crates/services/services-integrations/Cargo.toml
+++ b/src/crates/services/services-integrations/Cargo.toml
@@ -106,6 +106,7 @@ models-dev = [
     "reqwest/system-proxy",
     "sha2",
     "tokio/fs",
+    "tokio/rt",
     "tokio/sync",
     "tokio/time",
     "windows",
diff --git a/src/crates/services/services-integrations/src/miniapp/worker.rs b/src/crates/services/services-integrations/src/miniapp/worker.rs
index 3f24ed2078..a623663a44 100644
--- a/src/crates/services/services-integrations/src/miniapp/worker.rs
+++ b/src/crates/services/services-integrations/src/miniapp/worker.rs
@@ -84,15 +84,14 @@ impl JsWorker {
                 if line.is_empty() {
                     continue;
                 }
-                let _ =
-                    last_activity_clone.fetch_update(Ordering::SeqCst, Ordering::SeqCst, |_| {
-                        Some(
-                            std::time::SystemTime::now()
-                                .duration_since(std::time::UNIX_EPOCH)
-                                .unwrap_or_default()
-                                .as_millis() as i64,
-                        )
-                    });
+                let _ = last_activity_clone.try_update(Ordering::SeqCst, Ordering::SeqCst, |_| {
+                    Some(
+                        std::time::SystemTime::now()
+                            .duration_since(std::time::UNIX_EPOCH)
+                            .unwrap_or_default()
+                            .as_millis() as i64,
+                    )
+                });
                 let msg: Value = match serde_json::from_str(&line) {
                     Ok(v) => v,
                     Err(_) => continue,
diff --git a/src/crates/services/services-integrations/src/models_dev.rs b/src/crates/services/services-integrations/src/models_dev.rs
index 5158bc0589..eb4a65501c 100644
--- a/src/crates/services/services-integrations/src/models_dev.rs
+++ b/src/crates/services/services-integrations/src/models_dev.rs
@@ -29,6 +29,19 @@ struct RefreshState {
     last_attempt: Option<Instant>,
 }
 
+#[derive(Debug, Clone, PartialEq, Eq)]
+struct FileStamp {
+    length: u64,
+    modified: SystemTime,
+}
+
+#[derive(Debug)]
+struct ValidatedSnapshot {
+    stamp: Option<FileStamp>,
+    cache_valid: bool,
+    snapshot: ModelsDevSnapshot,
+}
+
 #[derive(Debug, Clone, Copy, PartialEq, Eq)]
 pub enum ModelsDevSnapshotSource {
     Cache,
@@ -74,6 +87,7 @@ pub struct ModelsDevCatalogService {
     cache_ttl: Duration,
     refresh_state: Arc<Mutex<RefreshState>>,
     refresh_in_progress: Arc<AtomicBool>,
+    validated_snapshot: Arc<Mutex<Option<ValidatedSnapshot>>>,
 }
 
 struct RefreshGuard(Arc<AtomicBool>);
@@ -93,6 +107,7 @@ impl ModelsDevCatalogService {
             cache_ttl: DEFAULT_CACHE_TTL,
             refresh_state: Arc::new(Mutex::new(RefreshState::default())),
             refresh_in_progress: Arc::new(AtomicBool::new(false)),
+            validated_snapshot: Arc::new(Mutex::new(None)),
         }
     }
 
@@ -122,9 +137,21 @@ impl ModelsDevCatalogService {
 
     /// Load the best immediately available source without contacting the network.
     pub async fn load_cached_or_bundled(&self) -> ModelsDevSnapshot {
+        // Share cold reads across consumers. A timestamp controls revalidation,
+        // never the lifetime of the last valid document.
+        let mut cached = self.validated_snapshot.lock().await;
+        let stamp = self.file_stamp().await;
+        if let Some(cached) = cached.as_ref().filter(|cached| cached.stamp == stamp) {
+            return cached.snapshot.clone();
+        }
         if let Ok(body) = fs::read_to_string(&self.cache_file).await {
-            if is_valid_catalog_document(&body) {
-                return snapshot(body, ModelsDevSnapshotSource::Cache);
+            if let Some(snapshot) = checked_snapshot(body, ModelsDevSnapshotSource::Cache).await {
+                *cached = Some(ValidatedSnapshot {
+                    stamp,
+                    cache_valid: true,
+                    snapshot: snapshot.clone(),
+                });
+                return snapshot;
             }
             debug!(
                 "Ignoring invalid models.dev cache at {}",
@@ -132,14 +159,29 @@ impl ModelsDevCatalogService {
             );
         }
 
-        if is_valid_catalog_document(&self.bundled_snapshot) {
-            return snapshot(
+        let snapshot = match cached.as_ref() {
+            Some(cached) => cached.snapshot.clone(),
+            None => checked_snapshot(
                 self.bundled_snapshot.to_string(),
                 ModelsDevSnapshotSource::Bundled,
-            );
-        }
+            )
+            .await
+            .unwrap_or_else(|| snapshot("{}".to_string(), ModelsDevSnapshotSource::Empty)),
+        };
+        *cached = Some(ValidatedSnapshot {
+            stamp,
+            cache_valid: false,
+            snapshot: snapshot.clone(),
+        });
+        snapshot
+    }
 
-        snapshot("{}".to_string(), ModelsDevSnapshotSource::Empty)
+    async fn file_stamp(&self) -> Option<FileStamp> {
+        let metadata = fs::metadata(&self.cache_file).await.ok()?;
+        Some(FileStamp {
+            length: metadata.len(),
+            modified: metadata.modified().ok()?,
+        })
     }
 
     pub async fn cache_metadata(&self) -> ModelsDevCacheMetadata {
@@ -181,17 +223,10 @@ impl ModelsDevCatalogService {
             return ModelsDevRefreshOutcome::Throttled;
         }
         let _refresh_guard = RefreshGuard(self.refresh_in_progress.clone());
-        let body = match &self.runtime_source {
+        let incoming = match &self.runtime_source {
             ModelsDevRuntimeSource::LocalFile(path) => {
                 let body = match fs::read_to_string(path).await {
-                    Ok(body) if is_valid_catalog_document(&body) => body,
-                    Ok(_) => {
-                        warn!(
-                            "Local models.dev catalog at {} failed schema validation",
-                            path.display()
-                        );
-                        return ModelsDevRefreshOutcome::Failed;
-                    }
+                    Ok(body) => body,
                     Err(error) => {
                         warn!(
                             "Failed to read local models.dev catalog at {}: {}",
@@ -201,10 +236,18 @@ impl ModelsDevCatalogService {
                         return ModelsDevRefreshOutcome::Failed;
                     }
                 };
-                if self.cache_matches(&body).await {
+                let Some(incoming) = checked_snapshot(body, ModelsDevSnapshotSource::Cache).await
+                else {
+                    warn!(
+                        "Local models.dev catalog at {} failed schema validation",
+                        path.display()
+                    );
+                    return ModelsDevRefreshOutcome::Failed;
+                };
+                if self.cache_matches(&incoming.body).await {
                     return ModelsDevRefreshOutcome::NotNeeded;
                 }
-                body
+                incoming
             }
             ModelsDevRuntimeSource::Http(endpoint_url) => {
                 if endpoint_url.trim().is_empty() {
@@ -272,14 +315,21 @@ impl ModelsDevCatalogService {
 
         let previous = self.load_cached_or_bundled().await;
 
-        match self.write_cache_atomically(&body).await {
-            Ok(()) if previous.sha256 == sha256_hex(body.as_bytes()) => {
-                ModelsDevRefreshOutcome::Unchanged {
-                    version: previous.version,
-                }
-            }
+        match self.write_cache_atomically(&incoming.body).await {
             Ok(()) => {
-                ModelsDevRefreshOutcome::Updated(snapshot(body, ModelsDevSnapshotSource::Cache))
+                let stamp = self.file_stamp().await;
+                *self.validated_snapshot.lock().await = Some(ValidatedSnapshot {
+                    stamp,
+                    cache_valid: true,
+                    snapshot: incoming.clone(),
+                });
+                if previous.sha256 == incoming.sha256 {
+                    ModelsDevRefreshOutcome::Unchanged {
+                        version: incoming.version,
+                    }
+                } else {
+                    ModelsDevRefreshOutcome::Updated(incoming)
+                }
             }
             Err(error) => {
                 warn!(
@@ -293,19 +343,22 @@ impl ModelsDevCatalogService {
     }
 
     async fn is_cache_fresh(&self) -> bool {
-        let Ok(metadata) = fs::metadata(&self.cache_file).await else {
-            return false;
-        };
-        let Ok(modified) = metadata.modified() else {
+        let Some(stamp) = self.file_stamp().await else {
             return false;
         };
         let age = SystemTime::now()
-            .duration_since(modified)
+            .duration_since(stamp.modified)
             .unwrap_or_default();
-        age < self.cache_ttl
-            && fs::read_to_string(&self.cache_file)
-                .await
-                .is_ok_and(|body| is_valid_catalog_document(&body))
+        if age >= self.cache_ttl {
+            return false;
+        }
+        // Only a document that was validated at this exact file revision is fresh.
+        self.load_cached_or_bundled().await;
+        self.validated_snapshot
+            .lock()
+            .await
+            .as_ref()
+            .is_some_and(|cached| cached.cache_valid && cached.stamp.as_ref() == Some(&stamp))
     }
 
     async fn cache_matches(&self, expected: &str) -> bool {
@@ -347,6 +400,18 @@ impl ModelsDevCatalogService {
     }
 }
 
+async fn checked_snapshot(
+    body: String,
+    source: ModelsDevSnapshotSource,
+) -> Option<ModelsDevSnapshot> {
+    tokio::task::spawn_blocking(move || {
+        is_valid_catalog_document(&body).then(|| snapshot(body, source))
+    })
+    .await
+    .ok()
+    .flatten()
+}
+
 fn runtime_source_from_environment() -> ModelsDevRuntimeSource {
     runtime_source_from_values(
         std::env::var(MODELS_DEV_PATH_ENV).ok(),
@@ -467,7 +532,7 @@ impl std::fmt::Display for RefreshError {
 async fn fetch_catalog_body(
     client: &reqwest::Client,
     endpoint_url: &str,
-) -> Result<String, RefreshError> {
+) -> Result<ModelsDevSnapshot, RefreshError> {
     let response = client
         .get(endpoint_url)
         .send()
@@ -478,10 +543,9 @@ async fn fetch_catalog_body(
         return Err(RefreshError::Status(status));
     }
     let body = response.text().await.map_err(RefreshError::ResponseBody)?;
-    if !is_valid_catalog_document(&body) {
-        return Err(RefreshError::InvalidDocument);
-    }
-    Ok(body)
+    checked_snapshot(body, ModelsDevSnapshotSource::Cache)
+        .await
+        .ok_or(RefreshError::InvalidDocument)
 }
 
 fn retry_backoff(attempt: usize) -> Duration {
@@ -565,6 +629,29 @@ mod tests {
         assert!(snapshot.body.contains("gpt-test"));
     }
 
+    #[tokio::test]
+    async fn loaded_snapshot_survives_corruption_and_observes_replacement() {
+        let directory = tempfile::tempdir().unwrap();
+        let file = directory.path().join("catalog.json");
+        tokio::fs::write(&file, VALID).await.unwrap();
+        let service = ModelsDevCatalogService::new(&file);
+        let first = service.load_cached_or_bundled().await;
+        assert!(service.is_cache_fresh().await);
+        tokio::fs::write(&file, "invalid").await.unwrap();
+        assert_eq!(service.load_cached_or_bundled().await, first);
+        assert!(!service.is_cache_fresh().await);
+        tokio::fs::remove_file(&file).await.unwrap();
+        assert_eq!(service.load_cached_or_bundled().await, first);
+        tokio::fs::write(
+            &file,
+            r#"{"provider":{"models":{"replacement":{"id":"replacement"}}}}"#,
+        )
+        .await
+        .unwrap();
+        assert_ne!(service.load_cached_or_bundled().await.sha256, first.sha256);
+        assert!(service.is_cache_fresh().await);
+    }
+
     #[tokio::test]
     async fn invalid_cache_falls_back_to_bundled_snapshot() {
         let directory = tempfile::tempdir().expect("temp directory");
diff --git a/src/crates/services/services-integrations/src/remote_ssh/port_forward.rs b/src/crates/services/services-integrations/src/remote_ssh/port_forward.rs
index 5b76fd6898..c5507288bd 100644
--- a/src/crates/services/services-integrations/src/remote_ssh/port_forward.rs
+++ b/src/crates/services/services-integrations/src/remote_ssh/port_forward.rs
@@ -83,11 +83,11 @@ impl ForwardRuntime {
         // Saturate rather than wrap. The counter should never reach zero with a
         // connection still open, but underflowing it would report four billion
         // active connections in the UI and there is no failure worth that.
-        let _ =
-            self.active_connections
-                .fetch_update(Ordering::SeqCst, Ordering::SeqCst, |active| {
-                    Some(active.saturating_sub(1))
-                });
+        let _ = self
+            .active_connections
+            .try_update(Ordering::SeqCst, Ordering::SeqCst, |active| {
+                Some(active.saturating_sub(1))
+            });
     }
 
     fn record_error(&self, message: String) {
diff --git a/src/web-ui/src/app/scenes/settings/pages/ai/ModelSettingsPage.loading.test.tsx b/src/web-ui/src/app/scenes/settings/pages/ai/ModelSettingsPage.loading.test.tsx
index 91b75b33aa..d209cd80c8 100644
--- a/src/web-ui/src/app/scenes/settings/pages/ai/ModelSettingsPage.loading.test.tsx
+++ b/src/web-ui/src/app/scenes/settings/pages/ai/ModelSettingsPage.loading.test.tsx
@@ -35,7 +35,7 @@ const model: AIModelConfig = {
 
 // Service reads are controlled to exercise pending, failed, and recovered states.
 // The actual settings and design-system components render; this is not visual QA.
-describe('ModelSettingsPage independent loading', () => {
+describe('ModelSettingsPage loading and provider actions', () => {
   let container: HTMLDivElement;
   let root: Root;
   let reads: Map<string, ReturnType<typeof deferred>>;
@@ -149,4 +149,60 @@ describe('ModelSettingsPage independent loading', () => {
     expect(container.querySelector('[data-testid="settings-model-pool"]')?.textContent).toContain(model.model_name);
     expect(button('actions.addModel').disabled).toBe(false);
   });
+
+  it.each(['api', 'subscription'] as const)(
+    'confirms %s capsule deletion before removing only that provider’s models',
+    async kind => {
+      const providerModels: AIModelConfig[] = [model, { ...model, id: 'second-model', model_name: 'second-model' }]
+        .map(entry => ({
+          ...entry,
+          metadata: { provider_instance_id: 'provider-to-delete' },
+          ...(kind === 'subscription' ? { auth: { type: 'subscription' as const, provider: 'codex' as const } } : {}),
+        }));
+      const otherModel: AIModelConfig = { ...model, id: 'other-model', name: 'Other provider' };
+      let savedModels = [...providerModels, otherModel];
+      const updateConfig = vi.spyOn(configManager, 'updateConfig').mockImplementation(async <T,>(_path: string, update: (current: T) => T) => {
+        const updated = update(savedModels as T);
+        savedModels = updated as AIModelConfig[];
+        return updated;
+      });
+      reads.set('ai.task_models', deferred());
+      reads.set('ai.agent_model_defaults', deferred());
+      await act(async () => root.render(<ModelSettingsPage />));
+      await act(async () => {
+        reads.get('ai.models')!.resolve(savedModels);
+        reads.get('ai.default_models')!.resolve({ primary: model.id });
+        reads.get('ai.task_models')!.resolve({});
+        reads.get('ai.agent_model_defaults')!.resolve({});
+      });
+
+      const deleteButton = [...container.querySelectorAll<HTMLButtonElement>('.openbitfun-model-settings__source-pill-delete')]
+        .find(element => element.getAttribute('aria-label')?.endsWith(`: ${model.name}`))!;
+      expect(deleteButton.getAttribute('aria-label')).toContain(model.name);
+      expect(deleteButton.parentElement?.closest('button')).toBeNull();
+      await act(async () => deleteButton.click());
+
+      const dialog = document.querySelector<HTMLElement>('[role="alertdialog"]')!;
+      expect(dialog.textContent).toContain(copy('providerDeleteConfirm.title'));
+      expect(dialog.textContent).toContain(String(i18nService.getI18nInstance().t('providerDeleteConfirm.message', {
+        ns: 'settings/models', name: model.name, modelCount: 2, referenceCount: 1,
+      })));
+      expect(document.querySelectorAll('[role="dialog"]')).toHaveLength(0);
+      expect(updateConfig).not.toHaveBeenCalled();
+
+      const cancel = dialog.querySelector<HTMLButtonElement>('button[data-openbitfun-variant="fill"]')!;
+      await act(async () => cancel.click());
+      expect(updateConfig).not.toHaveBeenCalled();
+      expect(savedModels).toHaveLength(3);
+
+      await act(async () => deleteButton.click());
+      const confirm = document.querySelector<HTMLButtonElement>('[role="alertdialog"] button[data-openbitfun-tone="danger"]')!;
+      await act(async () => confirm.click());
+      expect(updateConfig).toHaveBeenCalledTimes(1);
+      expect(updateConfig).toHaveBeenCalledWith('ai.models', expect.any(Function));
+      expect(savedModels).toEqual([otherModel]);
+      expect(container.querySelectorAll('.openbitfun-model-settings__source-pill')).toHaveLength(1);
+      expect(container.querySelector('.openbitfun-model-settings__source-pill')?.textContent).toBe(otherModel.name);
+    },
+  );
 });
diff --git a/src/web-ui/src/app/scenes/settings/pages/ai/ModelSettingsPage.scss b/src/web-ui/src/app/scenes/settings/pages/ai/ModelSettingsPage.scss
index b23adfbb4b..64bb24f828 100644
--- a/src/web-ui/src/app/scenes/settings/pages/ai/ModelSettingsPage.scss
+++ b/src/web-ui/src/app/scenes/settings/pages/ai/ModelSettingsPage.scss
@@ -51,6 +51,7 @@
   }
 
   &__import-item {
+    display: inline-flex;
     min-width: 0;
     max-inline-size: 100%;
   }
@@ -1597,25 +1598,7 @@
   }
 
   &__model-capsule {
-    position: relative;
-    display: inline-flex;
-    flex: 0 1 auto;
-    align-items: center;
     width: auto;
-    min-width: 0;
-    max-width: 100%;
-
-    &:hover,
-    &:focus-within {
-      .openbitfun-model-settings__model-capsule-dismiss {
-        opacity: 1;
-        pointer-events: auto;
-      }
-
-      .openbitfun-model-settings__model-capsule-edit > [data-openbitfun-part='content'] {
-        clip-path: inset(0 calc(var(--openbitfun-control-icon-button-xs-size) - var(--openbitfun-control-button-xs-padding-inline)) 0 0);
-      }
-    }
   }
 
   &__model-capsule-edit {
@@ -1623,16 +1606,6 @@
     min-width: 0;
   }
 
-  &__model-capsule-dismiss {
-    position: absolute;
-    inset-block-start: 50%;
-    inset-inline-end: var(--openbitfun-border-width-default);
-    transform: translateY(-50%);
-    opacity: 0;
-    pointer-events: none;
-    transition: opacity var(--openbitfun-motion-duration-fast) var(--openbitfun-motion-easing-standard);
-  }
-
   &__selected-model-tags {
     display: grid;
     grid-column: 1 / -1;
@@ -2556,7 +2529,6 @@
   }
 
   .openbitfun-model-settings__model-actions,
-  .openbitfun-model-settings__tag-editor .openbitfun-model-settings__model-capsule-dismiss,
   .openbitfun-model-settings__pool-card-controls,
   .openbitfun-model-settings__provider-group-list .openbitfun-collection-item__details-toggle {
     transition: none;
@@ -2564,17 +2536,6 @@
 }
 
 @media (hover: none), (pointer: coarse) {
-  .openbitfun-model-settings__tag-editor .openbitfun-model-settings__model-capsule-dismiss {
-    position: static;
-    transform: none;
-    opacity: 1;
-    pointer-events: auto;
-  }
-
-  .openbitfun-model-settings__tag-editor .openbitfun-model-settings__model-capsule-edit > [data-openbitfun-part='content'] {
-    clip-path: none;
-  }
-
   .openbitfun-model-settings__pool-card-controls {
     opacity: 1;
     pointer-events: auto;
diff --git a/src/web-ui/src/app/scenes/settings/pages/ai/ModelSettingsPage.tsx b/src/web-ui/src/app/scenes/settings/pages/ai/ModelSettingsPage.tsx
index ce816ccf69..c997f1412b 100644
--- a/src/web-ui/src/app/scenes/settings/pages/ai/ModelSettingsPage.tsx
+++ b/src/web-ui/src/app/scenes/settings/pages/ai/ModelSettingsPage.tsx
@@ -88,6 +88,7 @@ import { translateConnectionTestMessage } from '@/shared/utils/aiConnectionTestM
 import { createLogger } from '@/shared/utils/logger';
 import {
   Button,
+  Capsule,
   Card,
   CardFooter,
   CardHeader,
@@ -2878,7 +2879,8 @@ const ModelSettingsPage: React.FC = () => {
             </small>
           )}
           {selectedModelDrafts.map(draft => (
-            <div
+            <Capsule
+              size="xs"
               key={draft.key}
               className="openbitfun-model-settings__model-capsule"
               data-testid="settings-model-selected-row"
@@ -2886,6 +2888,23 @@ const ModelSettingsPage: React.FC = () => {
               data-model-name={draft.modelName}
               data-selected="true"
               data-unsaved={modelDraftHasUnsavedChanges(draft, aiModels) ? 'true' : 'false'}
+              action={(
+                <Tooltip content={t('providerSelection.removeModel')}>
+                  <IconButton
+                    className="openbitfun-model-settings__model-capsule-dismiss"
+                    aria-label={t('providerSelection.removeModelByName', { name: draft.modelName })}
+                    data-testid="settings-model-selected-remove-btn"
+                    data-model-id={draft.modelName}
+                    data-model-name={draft.modelName}
+                    size="xs"
+                    shape="circle"
+                    variant="quiet"
+                    onClick={() => removeSelectedModelDraft(draft.modelName)}
+                    disabled={isEditorSaving}
+                    icon={<Icon name="xmark" size="xs" />}
+                  />
+                </Tooltip>
+              )}
             >
               <Button
                 ref={element => {
@@ -2902,22 +2921,7 @@ const ModelSettingsPage: React.FC = () => {
               >
                 {draft.modelName}
               </Button>
-              <Tooltip content={t('providerSelection.removeModel')}>
-                <IconButton
-                  className="openbitfun-model-settings__model-capsule-dismiss"
-                  aria-label={t('providerSelection.removeModelByName', { name: draft.modelName })}
-                  data-testid="settings-model-selected-remove-btn"
-                  data-model-id={draft.modelName}
-                  data-model-name={draft.modelName}
-                  size="xs"
-                  shape="circle"
-                  variant="quiet"
-                  onClick={() => removeSelectedModelDraft(draft.modelName)}
-                  disabled={isEditorSaving}
-                  icon={<Icon name="xmark" size="xs" />}
-                />
-              </Tooltip>
-            </div>
+            </Capsule>
           ))}
           {isAddingCustomModel && (
             <Input
@@ -4066,13 +4070,28 @@ const ModelSettingsPage: React.FC = () => {
               <ul className="openbitfun-model-settings__import-summary" aria-label={t('acquisition.api')}>
                 {apiProviderGroups.map(group => (
                   <li key={group.key} className="openbitfun-model-settings__import-item">
-                    <Tooltip content={group.models[0].base_url} trigger="hover-focus">
-                      <Button size="sm" variant="outline" className="openbitfun-model-settings__source-pill"
-                        aria-label={t('acquisition.configureProvider', { provider: group.providerName })}
-                        onClick={() => handleEditProvider(group.models[0])}>
-                        {group.providerName}
-                      </Button>
-                    </Tooltip>
+                    <Capsule size="sm" action={(
+                      <Tooltip content={t('actions.deleteProvider')} trigger="hover-focus">
+                        <IconButton
+                          className="openbitfun-model-settings__source-pill-delete"
+                          aria-label={`${t('actions.deleteProvider')}: ${group.providerName}`}
+                          size="xs"
+                          shape="circle"
+                          variant="quiet"
+                          tone="danger"
+                          onClick={() => void requestProviderDelete(group)}
+                          icon={<Icon name="delete" size="xs" />}
+                        />
+                      </Tooltip>
+                    )}>
+                      <Tooltip content={group.models[0].base_url} trigger="hover-focus">
+                        <Button size="sm" variant="outline" className="openbitfun-model-settings__source-pill"
+                          aria-label={t('acquisition.configureProvider', { provider: group.providerName })}
+                          onClick={() => handleEditProvider(group.models[0])}>
+                          {group.providerName}
+                        </Button>
+                      </Tooltip>
+                    </Capsule>
                   </li>
                 ))}
               </ul>
@@ -4102,11 +4121,26 @@ const ModelSettingsPage: React.FC = () => {
               <ul className="openbitfun-model-settings__import-summary" aria-label={t('acquisition.subscriptions')}>
                 {subscriptionProviderGroups.map(group => (
                   <li key={group.key} className="openbitfun-model-settings__import-item">
-                    <Button size="sm" variant="outline" className="openbitfun-model-settings__source-pill"
-                      aria-label={t('acquisition.configureProvider', { provider: group.providerName })}
-                      onClick={() => handleEditProvider(group.models[0])}>
-                      {group.providerName}
-                    </Button>
+                    <Capsule size="sm" action={(
+                      <Tooltip content={t('actions.deleteProvider')} trigger="hover-focus">
+                        <IconButton
+                          className="openbitfun-model-settings__source-pill-delete"
+                          aria-label={`${t('actions.deleteProvider')}: ${group.providerName}`}
+                          size="xs"
+                          shape="circle"
+                          variant="quiet"
+                          tone="danger"
+                          onClick={() => void requestProviderDelete(group)}
+                          icon={<Icon name="delete" size="xs" />}
+                        />
+                      </Tooltip>
+                    )}>
+                      <Button size="sm" variant="outline" className="openbitfun-model-settings__source-pill"
+                        aria-label={t('acquisition.configureProvider', { provider: group.providerName })}
+                        onClick={() => handleEditProvider(group.models[0])}>
+                        {group.providerName}
+                      </Button>
+                    </Capsule>
                   </li>
                 ))}
               </ul>
diff --git a/src/web-ui/src/flow_chat/components/HostPendingQueuePanel.tsx b/src/web-ui/src/flow_chat/components/HostPendingQueuePanel.tsx
index 5fcbc7475f..fb1c7e28d3 100644
--- a/src/web-ui/src/flow_chat/components/HostPendingQueuePanel.tsx
+++ b/src/web-ui/src/flow_chat/components/HostPendingQueuePanel.tsx
@@ -2,8 +2,8 @@ import { pendingQueueManager } from '../services/flow-chat-manager/PendingQueueM
 import type { QueuedMessage } from '../types/flow-chat';
 import { useEffect, useId, useState, useSyncExternalStore } from 'react';
 import { useI18n } from '@/infrastructure/i18n';
-import { Button, IconButton, OverflowText, Tooltip } from '@openbitfun/ui';
-import { ArrowUp, ChevronDown, ChevronUp, Copy, Info, Pencil, RotateCw, X } from 'lucide-react';
+import { Button, Icon, IconButton, OverflowText, Tooltip } from '@openbitfun/ui';
+import { RotateCw } from 'lucide-react';
 import './HostPendingQueuePanel.scss';
 import { HostDialogQueue, observeHostQueue, type QueueOutboxRecord, type QueueItem } from '../../../../shared/dialog-queue/HostDialogQueue';
 import {
@@ -55,11 +55,11 @@ export function HostPendingQueuePanel({ queue, onRestore }: { queue: HostDialogQ
   return <ChatComposerQueue data-openbitfun-product-component="pending-queue-panel" data-openbitfun-product-part="root" className="host-pending-queue" aria-label={t('hostQueue.title')}>
     <ChatComposerQueueHeader data-openbitfun-product-component="pending-queue-panel" data-openbitfun-product-part="header">
       <Button variant="text" size="xs" className="host-pending-queue__toggle" aria-expanded={expanded} aria-controls={listId}
-        onClick={() => setExpanded(value => !value)} trailingIcon={expanded ? <ChevronDown size={14} /> : <ChevronUp size={14} />}>
+        onClick={() => setExpanded(value => !value)} trailingIcon={<Icon name={expanded ? 'chevron-down' : 'chevron-up'} />}>
         <ChatComposerQueueTitle data-openbitfun-product-component="pending-queue-panel" data-openbitfun-product-part="title" count={items.length + view.pending.length}>{t('hostQueue.title')}</ChatComposerQueueTitle>
       </Button>
       <Tooltip content={t('hostQueue.about')}><IconButton size="xs" aria-label={t('hostQueue.about')} aria-expanded={showHelp}
-        icon={<Info size={14} />} onClick={() => setShowHelp(value => !value)} /></Tooltip>
+        icon={<Icon name="info" />} onClick={() => setShowHelp(value => !value)} /></Tooltip>
     </ChatComposerQueueHeader>
     {showHelp && <p data-openbitfun-product-component="pending-queue-panel" data-openbitfun-product-part="status" className="host-pending-queue__note">{t('hostQueue.memoryNotice')}</p>}
     {visibleError && <div data-openbitfun-product-component="pending-queue-panel" data-openbitfun-product-part="status" role="alert" className="host-pending-queue__error">{visibleError}<Button size="xs" variant="text" disabled={busy} onClick={() => void run(() => queue.refresh())}>{t('hostQueue.refresh')}</Button></div>}
@@ -72,13 +72,13 @@ export function HostPendingQueuePanel({ queue, onRestore }: { queue: HostDialogQ
           {item.reason && <OverflowText className="host-pending-queue__status" title={item.reason}>{item.reason}</OverflowText>}
         </ChatComposerQueueItemContent>
         <ChatComposerQueueItemActions data-openbitfun-product-component="pending-queue-panel" data-openbitfun-product-part="actions">
-          <Tooltip content={t('hostQueue.edit')}><IconButton size="xs" aria-label={t('hostQueue.edit')} icon={<Pencil size={14} />} disabled={busy || !!view.error || item.status === 'steering_pending'} onClick={() => void run(async () => {
+          <Tooltip content={t('hostQueue.edit')}><IconButton size="xs" aria-label={t('hostQueue.edit')} icon={<Icon name="edit" />} disabled={busy || !!view.error || item.status === 'steering_pending'} onClick={() => void run(async () => {
             const saved = await queue.savedDraft(item.turnId);
             if (!saved || saved.request.action !== 'submit') throw new Error(t('hostQueue.noDraft'));
             await restoreDraft(saved, item);
           })} /></Tooltip>
-          <Tooltip content={t('hostQueue.sendNow')}><IconButton size="xs" aria-label={t('hostQueue.sendNow')} icon={<ArrowUp size={14} />} disabled={busy || !!view.error || item.status === 'steering_pending'} onClick={() => void run(() => queue.act(item, 'promote'))} /></Tooltip>
-          <Tooltip content={t('hostQueue.cancel')}><IconButton size="xs" aria-label={t('hostQueue.cancel')} icon={<X size={14} />} disabled={busy || !!view.error || item.status === 'steering_pending'} onClick={() => void run(() => queue.act(item, 'cancel'))} /></Tooltip>
+          <Tooltip content={t('hostQueue.sendNow')}><IconButton size="xs" aria-label={t('hostQueue.sendNow')} icon={<Icon name="arrow-up" />} disabled={busy || !!view.error || item.status === 'steering_pending'} onClick={() => void run(() => queue.act(item, 'promote'))} /></Tooltip>
+          <Tooltip content={t('hostQueue.cancel')}><IconButton size="xs" aria-label={t('hostQueue.cancel')} icon={<Icon name="xmark" />} disabled={busy || !!view.error || item.status === 'steering_pending'} onClick={() => void run(() => queue.act(item, 'cancel'))} /></Tooltip>
         </ChatComposerQueueItemActions>
       </ChatComposerQueueItem>)}
       {view.pending.map(record => <ChatComposerQueueItem data-openbitfun-product-component="pending-queue-panel" data-openbitfun-product-part="item" key={record.key} state="failed">
@@ -87,9 +87,9 @@ export function HostPendingQueuePanel({ queue, onRestore }: { queue: HostDialogQ
         </ChatComposerQueueItemContent>
         <ChatComposerQueueItemActions data-openbitfun-product-component="pending-queue-panel" data-openbitfun-product-part="actions">
           {record.restoreIntent && record.request.action === 'submit'
-            ? <IconButton size="xs" aria-label={t('hostQueue.edit')} title={t('hostQueue.edit')} icon={<Pencil size={14} />} disabled={busy} onClick={() => void run(() => restoreDraft(record))} />
-            : <IconButton size="xs" aria-label={t('hostQueue.checkRetry')} title={t('hostQueue.checkRetry')} icon={<RotateCw size={14} />} disabled={busy} onClick={() => void run(() => queue.retry(record))} />}
-          {record.request.action === 'submit' && <IconButton size="xs" aria-label={t('hostQueue.copyDraft')} title={t('hostQueue.copyDraft')} icon={<Copy size={14} />} disabled={busy} onClick={() => {
+            ? <IconButton size="xs" aria-label={t('hostQueue.edit')} title={t('hostQueue.edit')} icon={<Icon name="edit" />} disabled={busy} onClick={() => void run(() => restoreDraft(record))} />
+            : <IconButton size="xs" aria-label={t('hostQueue.checkRetry')} title={t('hostQueue.checkRetry')} icon={<Icon glyph={RotateCw} />} disabled={busy} onClick={() => void run(() => queue.retry(record))} />}
+          {record.request.action === 'submit' && <IconButton size="xs" aria-label={t('hostQueue.copyDraft')} title={t('hostQueue.copyDraft')} icon={<Icon name="duplicate" />} disabled={busy} onClick={() => {
             if (record.request.action !== 'submit') return;
             const message = record.request.message;
             const cache = record.draft as Partial<QueuedMessage> | undefined;
@@ -101,7 +101,7 @@ export function HostPendingQueuePanel({ queue, onRestore }: { queue: HostDialogQ
               status: 'queued', retryCount: cache?.retryCount ?? 0,
               userMessageMetadata: message.metadata });
           }} />}
-          <IconButton size="xs" aria-label={t('hostQueue.dismiss')} title={t('hostQueue.dismiss')} icon={<X size={14} />} disabled={busy} onClick={() => void run(() => queue.dismiss(record))} />
+          <IconButton size="xs" aria-label={t('hostQueue.dismiss')} title={t('hostQueue.dismiss')} icon={<Icon name="xmark" />} disabled={busy} onClick={() => void run(() => queue.dismiss(record))} />
         </ChatComposerQueueItemActions>
       </ChatComposerQueueItem>)}
     </ChatComposerQueueList>
diff --git a/src/web-ui/src/flow_chat/components/ModelSelector.tsx b/src/web-ui/src/flow_chat/components/ModelSelector.tsx
index e6e15a706b..89ff84fd42 100644
--- a/src/web-ui/src/flow_chat/components/ModelSelector.tsx
+++ b/src/web-ui/src/flow_chat/components/ModelSelector.tsx
@@ -17,19 +17,17 @@ import { useI18n } from '@/infrastructure/i18n';
 import { configManager } from '@/infrastructure/config/services/ConfigManager';
 import { agentAPI } from '@/infrastructure/api/service-api/AgentAPI';
 import {
-  aiApi,
   type AIModelCatalog,
   type ReasoningCatalogProjection,
 } from '@/infrastructure/api/service-api/AIApi';
 import { ACPClientAPI, type AcpSessionOptions } from '@/infrastructure/api/service-api/ACPClientAPI';
 import { getProviderDisplayName, getProviderGroupKey } from '@/infrastructure/config/services/modelConfigs';
-import { globalEventBus } from '@/infrastructure/event-bus';
 import type { AIModelConfig, AgentModelDefaultsConfig, DefaultModelsConfig } from '@/infrastructure/config/types';
 import { Tooltip, Icon } from '@openbitfun/ui';
 import { RetainedMountBoundary } from '@/shared/presence';
 import { notificationService } from '@/shared/notification-system';
 import { FlowChatStore } from '../store/FlowChatStore';
-import { getModelMaxTokens } from '../services/flow-chat-manager/SessionModule';
+import { modelCatalogStore } from '@/infrastructure/config/services/ModelCatalogStore';
 import { acpClientIdFromAgentType } from '../utils/acpSession';
 import {
   buildAcpFastModeValue,
@@ -67,6 +65,7 @@ import {
 import {
   resolveModelReference,
   resolveModelSelection,
+  resolveModelMaxTokens,
   type ModelAvailabilityStatus,
 } from '../utils/modelResolution';
 import { getRecentManualModel, setRecentManualModel } from '../utils/manualModelSelection';
@@ -75,6 +74,8 @@ import './ModelSelector.scss';
 const log = createLogger('ModelSelector');
 const ACP_SESSION_OPTIONS_TIMEOUT_MS = 65_000;
 const MODEL_SELECTOR_EXIT_DURATION_MS = 100;
+const EMPTY_MODELS: AIModelConfig[] = [];
+const EMPTY_DEFAULT_MODELS: DefaultModelsConfig = {};
 
 export interface ExternalModelSelection {
   models: string[];
@@ -161,7 +162,7 @@ interface ProviderGroupInfo {
   models: ModelInfo[];
 }
 
-type ModelSelectorPanel = 'modes' | 'models';
+type ModelSelectorPanel = 'modes' | 'models' | 'providers';
 type UpcomingModelMode = 'smart' | 'pool';
 type ModelSelectorLevelDirection = 'none' | 'forward' | 'back';
 
@@ -337,23 +338,29 @@ export const ModelSelector: React.FC<ModelSelectorProps> = ({
   const modelSelectionScopeRef = useRef(modelSelectionScopeKey);
   modelSelectionScopeRef.current = modelSelectionScopeKey;
   const manualModelRef = useRef<{ scopeKey: string; modelId: string } | null>(null);
-  const [allModels, setAllModels] = useState<AIModelConfig[]>([]);
-  const [modelCatalog, setModelCatalog] = useState<AIModelCatalog | null>(null);
-  const [defaultModels, setDefaultModels] = useState<DefaultModelsConfig>({});
-  const [modeModel, setModeModel] = useState('primary');
-  const [configLoadState, setConfigLoadState] = useState<'loading' | 'ready' | 'error'>('loading');
-  const [catalogLoadState, setCatalogLoadState] = useState<'loading' | 'ready' | 'error'>('loading');
+  const [configEpoch, setConfigEpoch] = useState(deviceSurfaceScope.epoch);
+  const [loadedModels, setAllModels] = useState<AIModelConfig[]>([]);
+  const allModels = configEpoch === deviceSurfaceScope.epoch ? loadedModels : EMPTY_MODELS;
+  const { catalog: modelCatalog, status: catalogLoadState } = useSyncExternalStore(
+    modelCatalogStore.subscribe, modelCatalogStore.getSnapshot, modelCatalogStore.getSnapshot,
+  );
+  const [loadedDefaults, setDefaultModels] = useState<DefaultModelsConfig>({});
+  const defaultModels = configEpoch === deviceSurfaceScope.epoch ? loadedDefaults : EMPTY_DEFAULT_MODELS;
+  const [loadedModeModel, setModeModel] = useState('primary');
+  const modeModel = configEpoch === deviceSurfaceScope.epoch ? loadedModeModel : 'primary';
+  const [configState, setConfigLoadState] = useState<'loading' | 'ready' | 'error'>('loading');
+  const configLoadState = configEpoch === deviceSurfaceScope.epoch ? configState : 'loading';
   const [acpOptions, setAcpOptions] = useState<AcpSessionOptions | null>(null);
   const [acpOptionsLoadState, setAcpOptionsLoadState] = useState<'loading' | 'ready' | 'error'>('loading');
   const [dropdownOpen, setDropdownOpen] = useState(false);
   const [keyboardNavigationOpen, setKeyboardNavigationOpen] = useState(false);
   /** Provider whose models the menu is currently showing; null is the provider level. */
   const [activeProviderKey, setActiveProviderKey] = useState<string | null>(null);
-  /** Models use a detail view; modes expand horizontally inside the summary card. */
+  /** Providers and models use detail views; modes expand inside the summary card. */
   const [activePanel, setActivePanel] = useState<ModelSelectorPanel | null>(null);
   const [modeSelectionPending, setModeSelectionPending] = useState(false);
   const [modeFocusRevision, setModeFocusRevision] = useState(0);
-  const [providerFromSummary, setProviderFromSummary] = useState(false);
+  const [modelsFromSummary, setModelsFromSummary] = useState(false);
   // Upcoming modes execute through primary until the runtime supports routing.
   const [upcomingMode, setUpcomingMode] = useState<{
     id: UpcomingModelMode;
@@ -369,8 +376,9 @@ export const ModelSelector: React.FC<ModelSelectorProps> = ({
   } | null>(null);
   const acpRestoreToastShownRef = useRef<string | null>(null);
   const acpOptionsRef = useRef<AcpSessionOptions | null>(null);
+  const configEpochRef = useRef(configEpoch);
+  configEpochRef.current = configEpoch;
   const configLoadRequestRef = useRef(0);
-  const catalogLoadRequestRef = useRef(0);
   const acpOptionsLoadRequestRef = useRef(0);
 
   const dropdownRef = useRef<HTMLDivElement>(null);
@@ -382,10 +390,19 @@ export const ModelSelector: React.FC<ModelSelectorProps> = ({
   const modeRetryFocusRef = useRef<string | undefined>(undefined);
   const providerFieldRef = useRef<HTMLButtonElement>(null);
   const focusPanelOnOpenRef = useRef(false);
-  const focusSummaryOnReturnRef = useRef<ModelSelectorPanel | 'provider' | null>(null);
+  const focusSummaryOnReturnRef = useRef<ModelSelectorPanel | null>(null);
   const triggerRef = useRef<HTMLButtonElement>(null);
   const menuId = useId();
 
+  useEffect(() => {
+    setLoading(false);
+    setReasoningLoading(false);
+    setUpcomingMode(null);
+    setPreSessionReasoningSelection(null);
+    setDropdownOpen(false);
+    setActivePanel(null);
+  }, [deviceSurfaceScope.epoch]);
+
   useEffect(() => {
     onLoadingChange?.(loading || reasoningLoading);
   }, [loading, onLoadingChange, reasoningLoading]);
@@ -432,28 +449,10 @@ export const ModelSelector: React.FC<ModelSelectorProps> = ({
   const isAcpSession = Boolean(acpClientId && sessionId);
   const targetIsSubagent = isSubagentSession || activeSession?.sessionKind === 'subagent';
 
-  const loadModelCatalog = useCallback(async () => {
-    const requestId = ++catalogLoadRequestRef.current;
-    setCatalogLoadState('loading');
-    try {
-      const catalog = await aiApi.getModelCatalog();
-      if (requestId !== catalogLoadRequestRef.current) return false;
-      setModelCatalog(catalog);
-      setCatalogLoadState('ready');
-      return true;
-    } catch (error) {
-      if (requestId !== catalogLoadRequestRef.current) return false;
-      setModelCatalog(null);
-      setCatalogLoadState('error');
-      log.warn('Failed to load AI model catalog', { error });
-      return false;
-    }
-  }, []);
-
   // Load configuration data.
   const loadConfigData = useCallback(async () => {
     const requestId = ++configLoadRequestRef.current;
-    setConfigLoadState('loading');
+    const scope = getActiveSurfaceScope();
     try {
       const configData = await configManager.getConfigs([
         'ai.models',
@@ -466,53 +465,40 @@ export const ModelSelector: React.FC<ModelSelectorProps> = ({
       const defaultModelsData = (configData['ai.default_models'] as DefaultModelsConfig | undefined) || {};
       const agentModelDefaults = configData['ai.agent_model_defaults'] as AgentModelDefaultsConfig | undefined;
 
-      if (requestId !== configLoadRequestRef.current) return false;
+      if (requestId !== configLoadRequestRef.current || !scope.isCurrent()) return false;
+      setConfigEpoch(scope.epoch);
       setAllModels(models);
       setDefaultModels(defaultModelsData);
       setModeModel(agentModelDefaults?.mode?.trim() || 'primary');
       setConfigLoadState('ready');
-      await loadModelCatalog();
 
-      if (requestId !== configLoadRequestRef.current) return false;
+      if (requestId !== configLoadRequestRef.current || !scope.isCurrent()) return false;
 
       log.debug('Configuration loaded', {
         modelsCount: models.length
       });
       return true;
     } catch (error) {
-      if (requestId !== configLoadRequestRef.current) return false;
+      if (requestId !== configLoadRequestRef.current || !scope.isCurrent()) return false;
+      if (configEpochRef.current !== scope.epoch) {
+        setAllModels([]); setDefaultModels({}); setModeModel('primary');
+      }
+      setConfigEpoch(scope.epoch);
       setConfigLoadState('error');
       log.error('Failed to load configuration', error);
       return false;
     }
-  }, [loadModelCatalog]);
+  }, []);
   
   useEffect(() => {
-    const unsubscribeCatalog = aiApi.onModelCatalogUpdated(() => {
-      void loadModelCatalog();
-    });
     void loadConfigData();
-    
-    const handleConfigUpdate = () => {
-      log.debug('Configuration update detected, reloading');
-      void loadConfigData();
-    };
-    
-    globalEventBus.on('mode:config:updated', handleConfigUpdate);
-    
     const unsubscribe = configManager.onConfigChange((path) => {
-      if (path === 'ai' || path.startsWith('ai.')) {
-        log.debug('AI configuration changed', { path });
-        void loadConfigData();
-      }
+      if (!path || path === 'ai' || ['ai.models', 'ai.default_models', 'ai.agent_model_defaults'].some(
+        owned => path === owned || path.startsWith(`${owned}.`),
+      )) void loadConfigData();
     });
-    
-    return () => {
-      globalEventBus.off('mode:config:updated', handleConfigUpdate);
-      unsubscribe();
-      unsubscribeCatalog();
-    };
-  }, [loadConfigData, loadModelCatalog]);
+    return () => { configLoadRequestRef.current += 1; unsubscribe(); };
+  }, [loadConfigData, deviceSurfaceScope.epoch]);
 
   const loadAcpOptions = useCallback(async () => {
     const requestId = ++acpOptionsLoadRequestRef.current;
@@ -1009,7 +995,7 @@ export const ModelSelector: React.FC<ModelSelectorProps> = ({
     focusSummaryOnReturnRef.current = null;
     focusPanelOnOpenRef.current = false;
     setActiveProviderKey(null);
-    setProviderFromSummary(false);
+    setModelsFromSummary(false);
     setActivePanel(null);
     setLevelDirection('none');
   }, []);
@@ -1019,7 +1005,7 @@ export const ModelSelector: React.FC<ModelSelectorProps> = ({
     focusPanelOnOpenRef.current = moveFocus;
     focusSummaryOnReturnRef.current = null;
     setActiveProviderKey(null);
-    setProviderFromSummary(false);
+    setModelsFromSummary(false);
     setLevelDirection('forward');
     if (activePanel === kind && moveFocus && !activeProviderKey) {
       focusPanelOnOpenRef.current = false;
@@ -1032,7 +1018,7 @@ export const ModelSelector: React.FC<ModelSelectorProps> = ({
     focusSummaryOnReturnRef.current = restoreFocus ? activePanel : null;
     focusPanelOnOpenRef.current = false;
     setActiveProviderKey(null);
-    setProviderFromSummary(false);
+    setModelsFromSummary(false);
     setActivePanel(null);
     setLevelDirection('back');
   }, [activePanel]);
@@ -1043,25 +1029,24 @@ export const ModelSelector: React.FC<ModelSelectorProps> = ({
 
   const openProviderLevel = useCallback((providerKey: string, fromSummary = false) => {
     setActiveProviderKey(providerKey);
-    setProviderFromSummary(fromSummary);
+    setModelsFromSummary(fromSummary);
     setLevelDirection('forward');
   }, []);
 
   const closeProviderLevel = useCallback(() => {
-    if (providerFromSummary) {
+    if (modelsFromSummary) {
       closePanel(true);
-      focusSummaryOnReturnRef.current = 'provider';
       return;
     }
     setActiveProviderKey(null);
     setLevelDirection('back');
-  }, [closePanel, providerFromSummary]);
+  }, [closePanel, modelsFromSummary]);
 
   // Keep the last view intact during exit; trigger handlers reset it on reopening.
   // Catalog refreshes must not leave an open menu on a missing provider view.
   useEffect(() => {
     if (!dropdownOpen) return;
-    if (activePanel !== 'models' && activeProviderKey) {
+    if (activePanel !== 'models' && activePanel !== 'providers' && activeProviderKey) {
       setActiveProviderKey(null);
       return;
     }
@@ -1072,13 +1057,16 @@ export const ModelSelector: React.FC<ModelSelectorProps> = ({
 
   const currentNativeModelId = getCurrentModelId();
   const concreteModelId = resolveConcreteModelId(currentNativeModelId, defaultModels);
-  /** Provider that owns the pinned model, so the provider level can mark it. */
+  const currentModelId = externalSelection ? externalCurrentModelId
+    : isAcpSession ? acpOptions?.currentModelId || acpAvailableModels[0]?.id || ''
+      : currentNativeModelId;
+  /** Resolve symbolic defaults and target-owned models to their provider. */
   const selectedProviderKey = useMemo((): string | null => {
-    if (isSpecialModel(currentNativeModelId)) return null;
+    const modelId = externalSelection || isAcpSession ? currentModelId : concreteModelId;
     return providerGroups.find(
-      group => group.models.some(model => model.id === currentNativeModelId),
+      group => group.models.some(model => model.id === modelId),
     )?.key ?? null;
-  }, [currentNativeModelId, providerGroups]);
+  }, [concreteModelId, currentModelId, externalSelection, isAcpSession, providerGroups]);
   const currentReasoningProjection = useMemo((): ReasoningCatalogProjection | null => {
     if (!concreteModelId) return null;
     return modelCatalog?.models.find(model => model.id === concreteModelId)?.reasoning ?? null;
@@ -1245,12 +1233,14 @@ export const ModelSelector: React.FC<ModelSelectorProps> = ({
     const previousReasoningPreset = sessionId
       ? store.getState().sessions.get(sessionId)?.config.reasoningPreset
       : undefined;
+    const previousMaxContextTokens = sessionId ? store.getState().sessions.get(sessionId)?.maxContextTokens : undefined;
     const nextReasoningPreset = mode ? undefined : recentPresetForModel(modelId);
     let sessionModelWrittenOptimistically = false;
 
     try {
       if (externalSelection) {
         await externalSelection.onSelect(modelId);
+        selectionScope.assertCurrent('select external model');
         return true;
       }
       if (isAcpSession && acpClientId && sessionId) {
@@ -1263,6 +1253,7 @@ export const ModelSelector: React.FC<ModelSelectorProps> = ({
           remoteSshHost: activeSession?.remoteSshHost,
           modelId,
         });
+        selectionScope.assertCurrent('select ACP model');
         setAcpOptions(options);
         syncAcpContextUsageToStore(sessionId, options);
         store.updateSessionModelName(sessionId, modelId);
@@ -1272,13 +1263,14 @@ export const ModelSelector: React.FC<ModelSelectorProps> = ({
 
       const updateTargetSessionModel = async () => {
         if (!sessionId) return;
+        if (previousSessionModelName === modelId && previousReasoningPreset === nextReasoningPreset) return;
 
         // Update the frontend session model immediately so the UI reflects the
         // switch without waiting for the backend IPC round-trip.
         store.updateSessionModelName(sessionId, modelId);
         store.updateSessionReasoningPreset(sessionId, nextReasoningPreset);
         sessionModelWrittenOptimistically = true;
-        const maxContextTokens = await getModelMaxTokens(modelId, currentMode);
+        const maxContextTokens = resolveModelMaxTokens(modelId, allModels, defaultModels);
         selectionScope.assertCurrent('select model');
         store.updateSessionMaxContextTokens(sessionId, maxContextTokens);
         const session = store.getState().sessions.get(sessionId);
@@ -1305,13 +1297,26 @@ export const ModelSelector: React.FC<ModelSelectorProps> = ({
         return true;
       }
 
-      if (persistSharedModeDefault) {
-        await configManager.setConfig('ai.agent_model_defaults.mode', modelId);
-        selectionScope.assertCurrent('select model');
+      await updateTargetSessionModel();
+      if (persistSharedModeDefault && modeModel !== modelId) {
+        const saveDefault = configManager.setConfig('ai.agent_model_defaults.mode', modelId);
+        if (!sessionId) {
+          // A selector without a draft/session has no other owner for the next
+          // submission. Its preference is the selection commit itself.
+          await saveDefault;
+          selectionScope.assertCurrent('select initial model');
+        } else {
+          // ConfigManager captures the device and serializes related writes.
+          // Remembering a future default must not hold the current session UI.
+          void saveDefault.catch(error => {
+            if (!selectionScope.isCurrent()) return;
+            log.warn('Session model selected but default preference was not saved', { error });
+            notificationService.warning(t('modelSelector.defaultSaveFailed'));
+            void loadConfigData();
+          });
+        }
         setModeModel(modelId);
-        globalEventBus.emit('mode:config:updated');
       }
-      await updateTargetSessionModel();
       rememberManualModel();
       setUpcomingMode(mode ? { id: mode, scopeKey: modelSelectionScopeKey } : null);
       setPreSessionReasoningSelection({
@@ -1327,20 +1332,22 @@ export const ModelSelector: React.FC<ModelSelectorProps> = ({
     } catch (error) {
       if (!selectionScope.isCurrent()) return false;
       log.error('Failed to switch model', error);
-      // Only a previously pinned selection can be restored: the store has no
-      // way to express "never pinned" without claiming a session binding.
-      if (sessionId && sessionModelWrittenOptimistically && previousSessionModelName) {
+      if (sessionId && sessionModelWrittenOptimistically) {
         store.updateSessionModelName(sessionId, previousSessionModelName);
       }
       if (sessionId && sessionModelWrittenOptimistically) {
         store.updateSessionReasoningPreset(sessionId, previousReasoningPreset);
+        store.updateSessionMaxContextTokens(sessionId, previousMaxContextTokens);
       }
       notificationService.error(t('modelSelector.switchFailed'));
       return false;
     } finally {
-      setLoading(false);
+      if (selectionScope.isCurrent()) setLoading(false);
     }
   }, [
+    allModels,
+    modeModel,
+    loadConfigData,
     activeSession?.config.workspacePath,
     activeSession?.remoteConnectionId,
     activeSession?.remoteSshHost,
@@ -1411,6 +1418,7 @@ export const ModelSelector: React.FC<ModelSelectorProps> = ({
     const previousPreset = session.config.reasoningPreset;
     if (previousPreset === normalizedPreset) return true;
 
+    const selectionScope = getActiveSurfaceScope();
     setReasoningLoading(true);
     store.updateSessionReasoningPreset(sessionId, normalizedPreset);
     try {
@@ -1426,6 +1434,7 @@ export const ModelSelector: React.FC<ModelSelectorProps> = ({
           includeInternal: shouldIncludeInternalModelSession(session),
         });
       }
+      selectionScope.assertCurrent('select reasoning preset');
       if (!targetIsSubagent) {
         setRecentReasoningPreset(concreteModelId, normalizedPreset);
         setPreSessionReasoningSelection({
@@ -1440,12 +1449,13 @@ export const ModelSelector: React.FC<ModelSelectorProps> = ({
       });
       return true;
     } catch (error) {
+      if (!selectionScope.isCurrent()) return false;
       store.updateSessionReasoningPreset(sessionId, previousPreset);
       log.error('Failed to update session reasoning preset', error);
       notificationService.error(t('reasoningSelector.updateFailed'));
       return false;
     } finally {
-      setReasoningLoading(false);
+      if (selectionScope.isCurrent()) setReasoningLoading(false);
     }
   }, [
     concreteModelId,
@@ -1727,7 +1737,7 @@ export const ModelSelector: React.FC<ModelSelectorProps> = ({
     if (event.key === 'ArrowRight') {
       const focusedElement = document.activeElement as HTMLElement | null;
       const focusedTarget = focusedElement?.dataset?.modelMenuTarget;
-      if (focusedTarget === 'modes' || focusedTarget === 'models') {
+      if (focusedTarget === 'modes' || focusedTarget === 'models' || focusedTarget === 'providers') {
         event.preventDefault();
         openPanel(focusedTarget, true);
       }
@@ -1752,7 +1762,7 @@ export const ModelSelector: React.FC<ModelSelectorProps> = ({
       return;
     }
 
-    if (event.key === 'ArrowRight' && activePanel === 'models' && !activeProviderKey) {
+    if (event.key === 'ArrowRight' && !activeProviderKey) {
       const focusedElement = document.activeElement as HTMLElement | null;
       const focusedProviderKey = focusedElement?.dataset?.providerKey;
       if (focusedProviderKey) {
@@ -1801,14 +1811,14 @@ export const ModelSelector: React.FC<ModelSelectorProps> = ({
       const returnTarget = focusSummaryOnReturnRef.current;
       focusSummaryOnReturnRef.current = null;
       if (returnTarget) {
-        const field = returnTarget === 'provider' ? providerFieldRef.current
+        const field = returnTarget === 'providers' ? providerFieldRef.current
           : returnTarget === 'modes' ? modeFieldRef.current : modelFieldRef.current;
         (field ?? modeFieldRef.current ?? modelFieldRef.current)?.focus({ preventScroll: true });
       }
       return;
     }
     if (activePanel === 'modes' && (modeSelectionPending || loading || reasoningLoading)) return;
-    const providerLevelChanged = activePanel === 'models'
+    const providerLevelChanged = (activePanel === 'models' || activePanel === 'providers')
       && previousProviderKey !== activeProviderKey;
     if (!focusPanelOnOpenRef.current && !providerLevelChanged) return;
     focusPanelOnOpenRef.current = false;
@@ -1827,7 +1837,7 @@ export const ModelSelector: React.FC<ModelSelectorProps> = ({
       return;
     }
 
-    if (activePanel === 'models' && previousProviderKey) {
+    if (previousProviderKey) {
       const providerRows = Array.from(
         menu.querySelectorAll<HTMLButtonElement>('button[data-provider-key]'),
       );
@@ -1858,9 +1868,6 @@ export const ModelSelector: React.FC<ModelSelectorProps> = ({
   
   const resolvedContextUsageSource: ContextUsageSource =
     contextUsageSource ?? (isAcpSession ? 'acp_context' : 'agent_prompt');
-  const currentModelId = externalSelection ? externalCurrentModelId
-    : isAcpSession ? acpOptions?.currentModelId || acpAvailableModels[0]?.id || ''
-      : currentNativeModelId;
   const displayedModel = externalSelection ? externalCurrentModel
     : isAcpSession ? acpCurrentModel ?? acpAvailableModels[0] ?? null : currentModel;
   const isAcpSelection = isAcpSession && !externalSelection;
@@ -1871,7 +1878,7 @@ export const ModelSelector: React.FC<ModelSelectorProps> = ({
   const displayedAvailability = externalSelection ? externalAvailability
     : isAcpSession ? acpAvailability : nativeAvailability;
   const showModelLoadingState = modelInformationLoading && (
-    isNativeModelSelection ? !modelCatalog : isAcpSelection ? !acpOptions : !displayedModel
+    isNativeModelSelection ? configLoadState === 'loading' || !modelCatalog : isAcpSelection ? !acpOptions : !displayedModel
   );
   useEffect(() => {
     // An ACP response may hand model ownership entirely to its separate mode control.
@@ -1890,14 +1897,13 @@ export const ModelSelector: React.FC<ModelSelectorProps> = ({
   ));
   const manualModelLabel = manualModelConfig?.model_name
     || getAvailabilityLabel(rememberedManualModelId ? 'target-model-unavailable' : nativeAvailability.status, t);
-  const displayedProviderGroup = providerGroups.find(group => group.models.some(model => (
-    model.id === (isNativeModelSelection ? concreteModelId : currentModelId)
-  )));
-  const openCurrentProvider = () => {
-    if (!displayedProviderGroup || disabled || loading || externalSelection?.disabled) return;
+  const displayedProviderGroup = providerGroups.find(group => group.key === selectedProviderKey);
+  const openCurrentProviderModels = () => {
+    if (disabled || loading || externalSelection?.disabled) return;
     openPanel('models', true);
-    openProviderLevel(displayedProviderGroup.key, true);
+    if (displayedProviderGroup) openProviderLevel(displayedProviderGroup.key, true);
   };
+  const isSelectionPanel = activePanel === 'models' || activePanel === 'providers';
   const acpModeLabel = acpMode?.option.options.find(option => option.value === acpMode.currentValue)?.name
     ?? acpMode?.currentValue ?? '';
   const targetTooltip = buildContextUsageTooltip({
@@ -2055,16 +2061,16 @@ export const ModelSelector: React.FC<ModelSelectorProps> = ({
             data-keyboard-open={keyboardNavigationOpen ? 'true' : 'false'}
             data-placement={resolvedDropdownPlacement}
             data-open={dropdownOpen ? 'true' : 'false'}
-            data-menu-level={activeProviderGroup ? 'provider' : activePanel === 'models' ? 'models' : 'settings'}
+            data-menu-level={activeProviderGroup ? 'provider' : isSelectionPanel ? activePanel : 'settings'}
             data-model-mode={currentModelMode ?? 'manual'}
             aria-busy={modelInformationLoading || undefined}
             aria-hidden={!dropdownOpen}
             {...(!dropdownOpen ? { inert: '' } : {})}
             aria-label={activeProviderGroup?.providerName ?? (activePanel === 'modes'
                 ? t('modelSelector.modes.selection') : t('modelSelector.modelSettings'))}
-            onKeyDown={activePanel === 'models' ? handlePanelKeyDown : handleDropdownKeyDown}
+            onKeyDown={isSelectionPanel ? handlePanelKeyDown : handleDropdownKeyDown}
           >
-            {!showModelLoadingState && activePanel !== 'models' && !activeProviderGroup
+            {!showModelLoadingState && !isSelectionPanel && !activeProviderGroup
               && (currentModelMode === 'smart' || currentModelMode === 'pool') && (
                 <ModelModeAnimation mode={currentModelMode} />
               )}
@@ -2078,7 +2084,7 @@ export const ModelSelector: React.FC<ModelSelectorProps> = ({
               >
                 <LoadingState size="sm">{t('modelSelector.status.loading')}</LoadingState>
               </div>
-            ) : activePanel === 'models' ? (
+            ) : isSelectionPanel ? (
               <div data-testid="chat-model-selector-options" data-panel-kind={activePanel}>
                 <ModelSelectorMenuLevel
                   key={activeProviderGroup ? `provider:${activeProviderGroup.key}` : activePanel}
@@ -2090,9 +2096,9 @@ export const ModelSelector: React.FC<ModelSelectorProps> = ({
                         className="openbitfun-model-selector__selection-back"
                         data-testid="chat-model-selector-summary-back"
                         aria-label={t('modelSelector.backToSettings')}
-                        aria-describedby={activePanel === 'models' ? `${menuId}-current-selection` : undefined}
+                        aria-describedby={`${menuId}-current-selection`}
                         leading={<Icon name="chevron-left" size="xs" aria-hidden />}
-                        metadata={activePanel === 'models' ? (
+                        metadata={(
                           <Tooltip
                             content={currentModelMode ? undefined : displayedModel?.providerName}
                             disabled={Boolean(currentModelMode) || !displayedModel?.providerName}
@@ -2102,15 +2108,17 @@ export const ModelSelector: React.FC<ModelSelectorProps> = ({
                               {settingsModelLabel}
                             </OverflowText>
                           </Tooltip>
-                        ) : undefined}
+                        )}
                         onClick={() => closePanel(true)}
                       >
-                        {t('modelSelector.model')}
+                        {activePanel === 'providers'
+                          ? displayedModel?.providerName || t('modelSelector.modelSettings')
+                          : t('modelSelector.model')}
                       </MenuItem>
                       <MenuSeparator />
                     </>
                   )}
-                  {(externalSelection || isAcpSession) && !activeProviderGroup ? (
+                  {(externalSelection || isAcpSession) && activePanel === 'models' && !activeProviderGroup ? (
                     <>
                       {showModelChoices && (
                         <MenuSection title={externalSelection
@@ -2148,7 +2156,7 @@ export const ModelSelector: React.FC<ModelSelectorProps> = ({
                         data-testid="chat-model-selector-back"
                         data-openbitfun-component="model-selector"
                         data-openbitfun-part="back"
-                        aria-label={t(providerFromSummary ? 'modelSelector.backToSettings' : 'modelSelector.backToProviders')}
+                        aria-label={t(modelsFromSummary ? 'modelSelector.backToSettings' : 'modelSelector.backToProviders')}
                         leading={<Icon name="chevron-left" size="xs" aria-hidden />}
                         onClick={closeProviderLevel}
                       >
@@ -2179,77 +2187,10 @@ export const ModelSelector: React.FC<ModelSelectorProps> = ({
                         );
                       })}
                     </>
-                  ) : availableModels.length === 0 ? (
-                    <>{renderUnavailableModelMenu(nativeAvailability, true)}</>
+                  ) : providerGroups.length === 0 ? (
+                    <>{renderUnavailableModelMenu(displayedAvailability, isNativeModelSelection)}</>
                   ) : (
                     <>
-                      {(() => {
-                        const primaryModel = allModels.find(
-                          m => m.id === defaultModels.primary && isSelectableTextChatModel(m),
-                        );
-                        const primaryTooltip = primaryModel
-                          ? buildResolvedModelTooltipText(primaryModel.model_name, {
-                            providerName: getProviderDisplayName(primaryModel),
-                            contextWindow: primaryModel.context_window
-                          }, t('modelSelector.primaryModelDesc'))
-                          : t('modelSelector.primaryModelDesc');
-                        return (
-                          <Tooltip content={primaryTooltip} placement="right">
-                            <MenuItem
-                              role="menuitemradio"
-                              checked={currentModelId === 'primary' && !currentModelMode}
-                              data-testid="chat-model-selector-option"
-                              data-model-id="primary"
-                              data-model-name={primaryModel?.model_name || 'primary'}
-                              data-selected={currentModelId === 'primary' && !currentModelMode ? 'true' : 'false'}
-                              data-openbitfun-component="model-selector"
-                              data-openbitfun-part="option"
-                              data-openbitfun-state={currentModelId === 'primary' && !currentModelMode ? 'selected' : undefined}
-                              metadata={currentModelId === 'primary' && !currentModelMode ? <Icon name="check-line" size="sm" aria-hidden /> : null}
-                               disabled={!primaryModel}
-                               onClick={() => handleSelectModelFromMenu('primary')}
-                            >
-                              {t('modelSelector.primaryModel')}
-                            </MenuItem>
-                          </Tooltip>
-                        );
-                      })()}
-
-                      {(() => {
-                        const fastModel = allModels.find(
-                          m => m.id === defaultModels.fast && isSelectableTextChatModel(m),
-                        ) ?? allModels.find(
-                          m => m.id === defaultModels.primary && isSelectableTextChatModel(m),
-                        );
-                        const fastTooltip = fastModel
-                          ? buildResolvedModelTooltipText(fastModel.model_name, {
-                            providerName: getProviderDisplayName(fastModel),
-                            contextWindow: fastModel.context_window
-                          }, t('modelSelector.fastModelDesc'))
-                          : t('modelSelector.fastModelDesc');
-                        return (
-                          <Tooltip content={fastTooltip} placement="right">
-                            <MenuItem
-                              role="menuitemradio"
-                              checked={currentModelId === 'fast'}
-                              data-testid="chat-model-selector-option"
-                              data-model-id="fast"
-                              data-model-name={fastModel?.model_name || 'fast'}
-                              data-selected={currentModelId === 'fast' ? 'true' : 'false'}
-                              data-openbitfun-component="model-selector"
-                              data-openbitfun-part="option"
-                              data-openbitfun-state={currentModelId === 'fast' ? 'selected' : undefined}
-                              metadata={currentModelId === 'fast' ? <Icon name="check-line" size="sm" aria-hidden /> : null}
-                              onClick={() => handleSelectModelFromMenu('fast')}
-                            >
-                              {t('modelSelector.fastModel')}
-                            </MenuItem>
-                          </Tooltip>
-                        );
-                      })()}
-
-                      <MenuSeparator />
-
                       {providerGroups.map(group => {
                         const isSelected = selectedProviderKey === group.key;
 
@@ -2355,8 +2296,13 @@ export const ModelSelector: React.FC<ModelSelectorProps> = ({
                             data-testid="chat-model-selector-settings-model"
                             data-model-menu-target="models"
                             aria-label={`${t('modelSelector.model')}: ${settingsModelLabel}`}
-                            onClick={() => openPanelFromClick('models')}
-                            onKeyDown={(event) => handlePanelTriggerKeyDown('models', event)}
+                            onClick={openCurrentProviderModels}
+                            onKeyDown={event => {
+                              if (event.key !== 'ArrowRight') return;
+                              event.preventDefault();
+                              event.stopPropagation();
+                              openCurrentProviderModels();
+                            }}
                             disabled={disabled || loading || externalSelection?.disabled}
                           >
                             <OverflowText className="openbitfun-model-selector__model-name">
@@ -2397,15 +2343,11 @@ export const ModelSelector: React.FC<ModelSelectorProps> = ({
                           className="openbitfun-model-selector__provider-control"
                           labelBehavior="static"
                           data-testid="chat-model-selector-settings-provider"
+                          data-model-menu-target="providers"
                           data-provider-key={displayedProviderGroup?.key}
-                          disabled={disabled || loading || externalSelection?.disabled || !displayedProviderGroup}
-                          onClick={openCurrentProvider}
-                          onKeyDown={event => {
-                            if (event.key !== 'ArrowRight') return;
-                            event.preventDefault();
-                            event.stopPropagation();
-                            openCurrentProvider();
-                          }}
+                          disabled={disabled || loading || externalSelection?.disabled || providerGroups.length === 0}
+                          onClick={() => openPanelFromClick('providers')}
+                          onKeyDown={event => handlePanelTriggerKeyDown('providers', event)}
                         >
                           <OverflowText className="openbitfun-model-selector__model-provider">
                             {displayedModel.providerName}
diff --git a/src/web-ui/src/flow_chat/components/ModelSelectorAcpMode.test.tsx b/src/web-ui/src/flow_chat/components/ModelSelectorAcpMode.test.tsx
index 1f1ecd0d4e..625c8aa7fe 100644
--- a/src/web-ui/src/flow_chat/components/ModelSelectorAcpMode.test.tsx
+++ b/src/web-ui/src/flow_chat/components/ModelSelectorAcpMode.test.tsx
@@ -8,6 +8,7 @@
  * both, and the agent that has fixed the mode and left exactly one choice.
  */
 
+import { activateSurface } from '@/infrastructure/peer-device/deviceSurface';
 import { act } from 'react';
 import { createRoot, type Root } from 'react-dom/client';
 import { afterEach, beforeEach, describe, expect, it, vi } from 'vitest';
@@ -108,6 +109,7 @@ describe('ModelSelector ACP mode picker', () => {
   let root: Root;
 
   beforeEach(() => {
+    activateSurface('local');
     flowChatStoreMocks.sessions.clear();
     flowChatStoreMocks.sessions.set('acp-session', {
       workspacePath: '/tmp/project',
@@ -375,7 +377,7 @@ describe('ModelSelector ACP mode picker', () => {
     await act(async () => { button?.click(); });
   };
 
-  it('opens only the current ACP provider and switches models through the remote adapter', async () => {
+  it.each(['model', 'provider'])('selects ACP models through the %s entry and its transport', async entry => {
     Object.assign(flowChatStoreMocks.sessions.get('acp-session')!, {
       remoteConnectionId: 'ssh-connection', remoteSshHost: 'a100',
     });
@@ -389,7 +391,17 @@ describe('ModelSelector ACP mode picker', () => {
     };
     await renderWithOptions([reasoningOption], sessionOptions);
     await click('chat-model-selector-btn');
-    await click('chat-model-selector-settings-provider');
+    await click(`chat-model-selector-settings-${entry}`);
+    if (entry === 'provider') {
+      const providers = document.body.querySelectorAll('[data-testid="chat-model-selector-provider"]');
+      expect(providers).toHaveLength(2);
+      expect(document.body.querySelector('[data-testid="chat-model-selector-option"]')).toBeNull();
+      const currentProvider = document.body.querySelector<HTMLButtonElement>(
+        '[data-testid="chat-model-selector-provider"][data-provider-key="acp:Acme"]',
+      )!;
+      expect(currentProvider.getAttribute('data-selected')).toBe('true');
+      await act(async () => currentProvider.click());
+    }
 
     expect(document.body.querySelector('[data-testid="chat-model-selector-provider"]')).toBeNull();
     expect(document.body.querySelector('[data-model-id="other-model"]')).toBeNull();
@@ -420,7 +432,7 @@ describe('ModelSelector ACP mode picker', () => {
     expect(document.body.querySelector('[data-testid="chat-model-selector-settings-model"]')).not.toBeNull();
     await click('chat-model-selector-settings-model');
     expect(document.body.querySelectorAll('[data-testid="chat-model-selector-option"]')).toHaveLength(1);
-    await click('chat-model-selector-summary-back');
+    await click('chat-model-selector-back');
     await click('chat-model-selector-settings-reasoning');
     expect(document.body.querySelector('[data-openbitfun-value="preset:auto"]')).toBeNull();
     vi.mocked(ACPClientAPI.setSessionConfigOption).mockResolvedValue({
diff --git a/src/web-ui/src/flow_chat/components/ModelSelectorExternal.test.tsx b/src/web-ui/src/flow_chat/components/ModelSelectorExternal.test.tsx
index 056259ddec..19b1769c4b 100644
--- a/src/web-ui/src/flow_chat/components/ModelSelectorExternal.test.tsx
+++ b/src/web-ui/src/flow_chat/components/ModelSelectorExternal.test.tsx
@@ -2,6 +2,7 @@
  * @vitest-environment jsdom
  */
 
+import { activateSurface } from '@/infrastructure/peer-device/deviceSurface';
 import { act } from 'react';
 import { createRoot, type Root } from 'react-dom/client';
 import { afterEach, beforeEach, describe, expect, it, vi } from 'vitest';
@@ -143,6 +144,7 @@ describe('ModelSelector external transport reuse', () => {
   let catalogUpdated: (() => void) | undefined;
 
   beforeEach(() => {
+    activateSurface('local');
     catalogUpdated = undefined;
     flowChatStoreMocks.sessions.clear();
     flowChatStoreMocks.subscribers.clear();
@@ -311,11 +313,6 @@ describe('ModelSelector external transport reuse', () => {
         '[data-testid="chat-model-selector-settings-model"]',
       )?.click();
     });
-    await act(async () => {
-      document.body.querySelector<HTMLButtonElement>(
-        '[data-testid="chat-model-selector-provider"][data-provider-key="provider-shared"]',
-      )?.click();
-    });
     await act(async () => {
       document.body.querySelector<HTMLButtonElement>(
         '[data-testid="chat-model-selector-option"][data-model-id="model-b"]',
@@ -739,11 +736,21 @@ describe('ModelSelector external transport reuse', () => {
     await act(async () => { control?.click(); });
   };
 
-  it('opens only the current target provider and applies choices through its transport', async () => {
+  it.each(['model', 'provider'])('selects target models through the %s entry and its transport', async entry => {
     const selection = targetSelection({ models: ['model-a', 'remote-model', 'remote-plain'] });
     await renderTarget(selection);
     await clickControl('chat-model-selector-btn');
-    await clickControl('chat-model-selector-settings-provider');
+    await clickControl(`chat-model-selector-settings-${entry}`);
+    if (entry === 'provider') {
+      const providers = document.body.querySelectorAll('[data-testid="chat-model-selector-provider"]');
+      expect(providers).toHaveLength(2);
+      expect(document.body.querySelector('[data-testid="chat-model-selector-option"]')).toBeNull();
+      const currentProvider = document.body.querySelector<HTMLButtonElement>(
+        '[data-testid="chat-model-selector-provider"][data-provider-key="external:a100"]',
+      )!;
+      expect(currentProvider.getAttribute('data-selected')).toBe('true');
+      await act(async () => currentProvider.click());
+    }
 
     expect(document.body.querySelector('[data-testid="chat-model-selector-provider"]')).toBeNull();
     expect(document.body.querySelector('[data-model-id="model-a"]')).toBeNull();
diff --git a/src/web-ui/src/flow_chat/components/ModelSelectorProviderLevels.test.tsx b/src/web-ui/src/flow_chat/components/ModelSelectorProviderLevels.test.tsx
index 68f72bdad1..d08cbfff74 100644
--- a/src/web-ui/src/flow_chat/components/ModelSelectorProviderLevels.test.tsx
+++ b/src/web-ui/src/flow_chat/components/ModelSelectorProviderLevels.test.tsx
@@ -2,6 +2,7 @@
  * @vitest-environment jsdom
  */
 
+import { activateSurface } from '@/infrastructure/peer-device/deviceSurface';
 import { act, cloneElement } from 'react';
 import { createRoot, type Root } from 'react-dom/client';
 import { afterEach, beforeEach, describe, expect, it, vi } from 'vitest';
@@ -147,11 +148,13 @@ describe('ModelSelector provider levels', () => {
 
   const openMenu = async () => {
     await openSettingsMenu();
-    const settingsModel = document.body.querySelector<HTMLButtonElement>(
+    const entry = document.body.querySelector<HTMLButtonElement>(
+      '[data-testid="chat-model-selector-settings-provider"]:not(:disabled)',
+    ) ?? document.body.querySelector<HTMLButtonElement>(
       '[data-testid="chat-model-selector-settings-model"]',
     );
-    if (settingsModel) {
-      await act(async () => settingsModel.click());
+    if (entry) {
+      await act(async () => entry.click());
     }
   };
 
@@ -210,6 +213,11 @@ describe('ModelSelector provider levels', () => {
   };
 
   beforeEach(() => {
+    activateSurface('local');
+    vi.mocked(configManager.getConfigs).mockReset();
+    vi.mocked(configManager.setConfig).mockReset().mockResolvedValue(undefined);
+    aiApiMocks.getModelCatalog.mockReset();
+    vi.mocked(agentAPI.updateSessionModel).mockReset().mockResolvedValue(undefined);
     notificationStore.clearActiveNotifications();
     notificationStore.clearHistory();
     flowChatStoreMocks.sessions.clear();
@@ -338,7 +346,7 @@ describe('ModelSelector provider levels', () => {
     }));
     await act(async () => { aiApiMocks.onModelCatalogUpdated.mock.calls[0][0](); });
 
-    expect(container.querySelector('[data-testid="chat-model-selector-btn"]')?.getAttribute('aria-busy')).toBe('true');
+    expect(container.querySelector('[data-testid="chat-model-selector-btn"]')?.hasAttribute('aria-busy')).toBe(false);
     expect(document.body.querySelector('[data-testid="chat-model-selector-loading"]')).toBeNull();
     expect(document.body.querySelector('[data-testid="chat-model-selector-settings-model"]')).toBe(modelField);
     expect(modelField?.textContent).toContain('acme-fast-native');
@@ -418,40 +426,41 @@ describe('ModelSelector provider levels', () => {
 
   });
 
-  it('opens the resolved primary provider directly and returns focus to its shortcut', async () => {
-    await renderSelector();
+  it.each(['primary', 'fast', 'acme-deep'])('opens the current provider models from the model entry for %s', async modelId => {
+    await renderSelector(CATALOG_MODELS, modelId);
     await openSettingsMenu();
 
-    const providerControl = () => document.body.querySelector<HTMLButtonElement>(
-      '[data-testid="chat-model-selector-settings-provider"]',
+    const modelControl = () => document.body.querySelector<HTMLButtonElement>(
+      '[data-testid="chat-model-selector-settings-model"]',
     )!;
-    expect(providerControl().textContent).toBe('Acme');
-    await act(async () => providerControl().click());
+    const isUmbra = modelId === 'fast';
+    const selectedModelId = modelId === 'primary' ? 'acme-fast' : isUmbra ? 'umbra-main' : modelId;
+    await act(async () => modelControl().click());
 
     expect(document.body.querySelector('[data-testid="chat-model-selector-menu"]')
       ?.getAttribute('data-menu-level')).toBe('provider');
     expect(providerRows()).toHaveLength(0);
-    expect(modelOption('acme-fast')?.getAttribute('aria-checked')).toBe('true');
-    expect(document.activeElement).toBe(modelOption('acme-fast'));
-    expect(modelOption('acme-deep')).not.toBeNull();
-    expect(modelOption('umbra-main')).toBeNull();
+    expect(modelOption(selectedModelId)?.getAttribute('aria-checked')).toBe('true');
+    expect(document.activeElement).toBe(modelOption(selectedModelId));
+    expect(Boolean(modelOption('acme-deep'))).toBe(!isUmbra);
+    expect(Boolean(modelOption('umbra-main'))).toBe(isUmbra);
     expect(modelOption('primary')).toBeNull();
 
     await act(async () => document.body.querySelector<HTMLButtonElement>(
       '[data-testid="chat-model-selector-back"]',
     )!.click());
     expect(optionsPanel()).toBeNull();
-    expect(document.activeElement).toBe(providerControl());
+    expect(document.activeElement).toBe(modelControl());
 
-    await act(async () => providerControl().dispatchEvent(
+    await act(async () => modelControl().dispatchEvent(
       new KeyboardEvent('keydown', { key: 'ArrowRight', bubbles: true }),
     ));
-    expect(modelOption('acme-deep')).not.toBeNull();
+    expect(Boolean(modelOption('acme-deep'))).toBe(!isUmbra);
     await act(async () => optionsPanel()!.dispatchEvent(
       new KeyboardEvent('keydown', { key: 'Escape', bubbles: true }),
     ));
     expect(optionsPanel()).toBeNull();
-    expect(document.activeElement).toBe(providerControl());
+    expect(document.activeElement).toBe(modelControl());
     expect(configManager.setConfig).not.toHaveBeenCalled();
   });
 
@@ -766,7 +775,7 @@ describe('ModelSelector provider levels', () => {
         { id: 'high', label: 'High', order: 1, source: 'models_dev', actions: [{ type: 'effort', value: 'high' }] },
       ] } }],
     });
-    await renderSelector();
+    await renderSelector(CATALOG_MODELS, 'acme-fast');
     await openSettingsMenu();
     const sky = document.body.querySelector('[data-openbitfun-part="reasoningSliderSky"]');
     expect(sky).not.toBeNull();
@@ -854,7 +863,7 @@ describe('ModelSelector provider levels', () => {
     expect(document.activeElement).toBe(autoChoice);
   });
 
-  it('offers providers first and keeps the symbolic selectors on that level', async () => {
+  it('opens only providers from the provider entry and marks the resolved default provider', async () => {
     await renderSelector();
     await openMenu();
 
@@ -867,32 +876,111 @@ describe('ModelSelector provider levels', () => {
     expect(document.body.querySelector(
       '[data-testid="chat-model-selector-settings"]',
     )).toBeNull();
-    expect(optionsPanel()?.dataset.panelKind).toBe('models');
+    expect(optionsPanel()?.dataset.panelKind).toBe('providers');
     expect(sharedPanelItems()).not.toBeNull();
     expect(providerRows().every(row => sharedPanelItems()?.contains(row))).toBe(true);
-    expect(sharedPanelItems()?.contains(modelOption('primary'))).toBe(true);
-    expect(sharedPanelItems()?.contains(modelOption('fast'))).toBe(true);
     expect(providerRows().map(row => row.dataset.providerKey))
       .toEqual(['provider-acme', 'provider-umbra']);
-    expect(modelOption('primary')).not.toBeNull();
-    expect(modelOption('fast')).not.toBeNull();
-    const submenuButtons = Array.from(
-      sharedPanelItems()?.querySelectorAll<HTMLButtonElement>('button') ?? [],
-    );
-    expect(submenuButtons.indexOf(modelOption('primary')!))
-      .toBeLessThan(submenuButtons.indexOf(modelOption('fast')!));
-    expect(submenuButtons.indexOf(modelOption('fast')!))
-      .toBeLessThan(submenuButtons.indexOf(providerRows()[0]));
+    expect(modelOption('primary')).toBeNull();
+    expect(modelOption('fast')).toBeNull();
+    expect(document.body.querySelectorAll('[data-testid="chat-model-selector-option"]')).toHaveLength(0);
+    expect(providerRows().find(row => row.dataset.selected === 'true')?.dataset.providerKey)
+      .toBe('provider-acme');
     expect(document.body.querySelector(
       '[data-testid="chat-model-selector-provider-selected-model"]',
     )).toBeNull();
     // A concrete model is only reachable through its provider now.
     expect(modelOption('acme-deep')).toBeNull();
     expect(modelOption('umbra-main')).toBeNull();
+    await act(async () => document.body.querySelector<HTMLButtonElement>(
+      '[data-testid="chat-model-selector-summary-back"]',
+    )!.click());
+    const providerControl = document.body.querySelector<HTMLButtonElement>(
+      '[data-testid="chat-model-selector-settings-provider"]',
+    )!;
+    expect(document.activeElement).toBe(providerControl);
+    await act(async () => providerControl.dispatchEvent(
+      new KeyboardEvent('keydown', { key: 'ArrowRight', bubbles: true }),
+    ));
+    expect(document.activeElement).toBe(providerRows()[0]);
+    await act(async () => {
+      providerRows()[1].focus();
+      providerRows()[1].dispatchEvent(new KeyboardEvent('keydown', { key: 'ArrowRight', bubbles: true }));
+    });
+    expect(modelOption('umbra-main')).not.toBeNull();
+    expect(modelOption('acme-fast')).toBeNull();
+    await act(async () => optionsPanel()!.dispatchEvent(
+      new KeyboardEvent('keydown', { key: 'ArrowLeft', bubbles: true }),
+    ));
+    expect(document.activeElement).toBe(providerRows()[1]);
+    expect(configManager.setConfig).not.toHaveBeenCalled();
+  });
+
+  it('commits the session before remembering defaults and leaves the selector usable during that save', async () => {
+    flowChatStoreMocks.sessions.set('session-a', { config: { modelName: 'umbra-main' } });
+    let commitSession!: () => void;
+    let saveDefault!: () => void;
+    vi.mocked(agentAPI.updateSessionModel).mockReturnValueOnce(new Promise(resolve => { commitSession = resolve; }));
+    vi.mocked(configManager.setConfig).mockReturnValueOnce(new Promise(resolve => { saveDefault = resolve; }));
+    await renderSelector(CATALOG_MODELS, 'umbra-main', 'session-a');
+    await openMenu();
+    await openProvider('provider-acme');
+    await act(async () => modelOption('acme-deep')!.click());
+    expect(agentAPI.updateSessionModel).toHaveBeenCalledTimes(1);
+    expect(configManager.setConfig).not.toHaveBeenCalled();
+    await act(async () => commitSession());
+    expect(configManager.setConfig).toHaveBeenCalledWith('ai.agent_model_defaults.mode', 'acme-deep');
+    expect(optionsPanel()).toBeNull();
+    expect(container.querySelector<HTMLButtonElement>('[data-testid="chat-model-selector-btn"]')!.disabled).toBe(false);
+    expect(flowChatStoreMocks.sessions.get('session-a')?.config.modelName).toBe('acme-deep');
+    await act(async () => saveDefault());
+  });
+
+  it('preserves a committed session selection when remembering the default fails', async () => {
+    flowChatStoreMocks.sessions.set('session-a', { config: { modelName: 'umbra-main' } });
+    vi.mocked(configManager.setConfig).mockRejectedValueOnce(new Error('default save failed'));
+    await renderSelector(CATALOG_MODELS, 'umbra-main', 'session-a');
+    await openMenu();
+    await openProvider('provider-acme');
+    await act(async () => modelOption('acme-deep')!.click());
+    expect(flowChatStoreMocks.sessions.get('session-a')?.config.modelName).toBe('acme-deep');
+    expect(notificationStore.getState().activeNotifications.some(item => item.message === 'modelSelector.defaultSaveFailed')).toBe(true);
+    expect(optionsPanel()).toBeNull();
+  });
+
+  it('skips an identical model and preset but clears a preset when entering an automatic selection mode', async () => {
+    flowChatStoreMocks.sessions.set('session-a', { config: { modelName: 'acme-fast' } });
+    await renderSelector(CATALOG_MODELS, 'acme-fast', 'session-a');
+    await openMenu();
+    await openProvider('provider-acme');
+    await act(async () => modelOption('acme-fast')!.click());
+    expect(agentAPI.updateSessionModel).not.toHaveBeenCalled();
+    expect(configManager.setConfig).not.toHaveBeenCalled();
+    flowChatStoreMocks.sessions.get('session-a')!.config.modelName = 'primary';
+    flowChatStoreMocks.sessions.get('session-a')!.config.reasoningPreset = 'high';
+    await act(async () => flowChatStoreMocks.subscribers.forEach(callback => callback()));
+    await act(async () => modeTrigger().click());
+    await act(async () => modeOption('smart')!.click());
+    expect(agentAPI.updateSessionModel).toHaveBeenCalledWith(expect.objectContaining({ modelName: 'primary', reasoningPreset: null }));
+    await act(async () => modeTrigger().click());
+    await act(async () => modeOption('pool')!.click());
+    expect(agentAPI.updateSessionModel).toHaveBeenCalledTimes(1);
+  });
+
+  it('rolls back an unpinned selection and context limit when the session update fails', async () => {
+    flowChatStoreMocks.sessions.set('session-a', { config: {} });
+    vi.mocked(agentAPI.updateSessionModel).mockRejectedValueOnce(new Error('session write failed'));
+    await renderSelector(CATALOG_MODELS, 'umbra-main', 'session-a');
+    await openMenu();
+    await openProvider('provider-acme');
+    await act(async () => modelOption('acme-deep')!.click());
+    expect(flowChatStoreMocks.store.updateSessionModelName).toHaveBeenLastCalledWith('session-a', undefined);
+    expect(flowChatStoreMocks.store.updateSessionMaxContextTokens).toHaveBeenLastCalledWith('session-a', undefined);
+    expect(configManager.setConfig).not.toHaveBeenCalled();
   });
 
   it('shows only the chosen provider\'s models and applies a selection', async () => {
-    await renderSelector();
+    await renderSelector(CATALOG_MODELS, 'umbra-main');
     await openMenu();
     await openProvider('provider-acme');
 
@@ -904,7 +992,7 @@ describe('ModelSelector provider levels', () => {
     expect(sharedPanelItems()).not.toBeNull();
     expect(sharedPanelItems()?.contains(modelOption('acme-fast'))).toBe(true);
     expect(sharedPanelItems()?.contains(modelOption('acme-deep'))).toBe(true);
-    // The symbolic selectors belong to the provider level and are not repeated.
+    // Model choices are concrete models owned by this provider.
     expect(modelOption('primary')).toBeNull();
 
     const card = document.body.querySelector('[data-testid="chat-model-selector-menu"]');
@@ -925,12 +1013,12 @@ describe('ModelSelector provider levels', () => {
     expect(container.querySelector('[data-testid="chat-model-selector-btn"]')?.getAttribute('aria-expanded')).toBe('true');
     expect(document.body.querySelector('[data-testid="chat-model-selector-menu"]')).toBe(card);
     expect(optionsPanel()).toBeNull();
-    expect(document.activeElement).toBe(document.body.querySelector('[data-testid="chat-model-selector-settings-model"]'));
+    expect(document.activeElement).toBe(document.body.querySelector('[data-testid="chat-model-selector-settings-provider"]'));
     await act(async () => document.body.querySelector<HTMLButtonElement>(
       '[data-testid="chat-model-selector-settings-model"]',
     )!.click());
-    expect(document.body.querySelector('[data-testid="chat-model-selector-current-selection"]')?.textContent)
-      .toBe('acme-deep-native');
+    expect(modelOption('acme-deep')?.getAttribute('aria-checked')).toBe('true');
+    expect(modelOption('umbra-main')).toBeNull();
   });
 
   it('marks the provider that owns the pinned model without repeating the model beneath it', async () => {
@@ -975,7 +1063,7 @@ describe('ModelSelector provider levels', () => {
     await openProvider('provider-acme');
     expect(modelOption('acme-deep')).not.toBeNull();
 
-    // Reopening starts at the summary; opening models resets the provider level.
+    // Reopening starts at the summary; opening models goes straight to the current provider.
     await act(async () => {
       container.querySelector<HTMLButtonElement>(
         '[data-testid="chat-model-selector-btn"]',
@@ -990,8 +1078,8 @@ describe('ModelSelector provider levels', () => {
       '[data-testid="chat-model-selector-settings-model"]',
     )!.click());
     expect(optionsPanel()?.dataset.panelKind).toBe('models');
-    expect(providerRows()).toHaveLength(2);
-    expect(modelOption('acme-deep')).toBeNull();
+    expect(providerRows()).toHaveLength(0);
+    expect(modelOption('acme-deep')).not.toBeNull();
   });
 
   it('keeps the selector visible and actionable when no model is configured', async () => {
@@ -1177,11 +1265,11 @@ describe('ModelSelector provider levels', () => {
       .toContain('first-model-native');
 
     const listeners = [...flowChatStoreMocks.configChangeListeners];
-    expect(listeners).toHaveLength(1);
+    expect(listeners).toHaveLength(2);
     await act(async () => {
       // ModelSettingsPage writes ai.models through ConfigManager's ai-scoped
       // mutation notification, so this is the post-save event to handle.
-      listeners[0]?.('ai');
+      listeners.forEach(listener => listener('ai'));
       await Promise.resolve();
       await Promise.resolve();
       await Promise.resolve();
@@ -1195,7 +1283,7 @@ describe('ModelSelector provider levels', () => {
     });
   });
 
-  it('lets Escape step from a provider to the model list, then the summary, then close', async () => {
+  it('lets Escape step from provider models to the provider list, then the summary, then close', async () => {
     await renderSelector();
     await openMenu();
     await openProvider('provider-acme');
@@ -1215,16 +1303,16 @@ describe('ModelSelector provider levels', () => {
     expect(document.body.querySelector(
       '[data-testid="chat-model-selector-settings"]',
     )).not.toBeNull();
-    const modelField = document.body.querySelector<HTMLButtonElement>(
-      '[data-testid="chat-model-selector-settings-model"]',
+    const providerField = document.body.querySelector<HTMLButtonElement>(
+      '[data-testid="chat-model-selector-settings-provider"]',
     )!;
-    expect(document.activeElement).toBe(modelField);
+    expect(document.activeElement).toBe(providerField);
     const trigger = container.querySelector<HTMLButtonElement>(
       '[data-testid="chat-model-selector-btn"]',
     )!;
     expect(trigger.getAttribute('aria-expanded')).toBe('true');
 
-    await act(async () => modelField.dispatchEvent(
+    await act(async () => providerField.dispatchEvent(
       new KeyboardEvent('keydown', { key: 'Escape', bubbles: true }),
     ));
     expect(trigger.getAttribute('aria-expanded')).toBe('false');
@@ -1316,7 +1404,7 @@ describe('ModelSelector provider levels', () => {
     expect(document.body.querySelectorAll('[role="menu"]')).toHaveLength(1);
 
     await act(async () => document.body.querySelector<HTMLButtonElement>(
-      '[data-testid="chat-model-selector-summary-back"]',
+      '[data-testid="chat-model-selector-back"]',
     )!.click());
     const reasoningRow = document.body.querySelector<HTMLButtonElement>(
       '[data-testid="chat-model-selector-settings-reasoning"]',
diff --git a/src/web-ui/src/flow_chat/services/flow-chat-manager/MessageModule.test.ts b/src/web-ui/src/flow_chat/services/flow-chat-manager/MessageModule.test.ts
index d472c39507..5ffa44f48b 100644
--- a/src/web-ui/src/flow_chat/services/flow-chat-manager/MessageModule.test.ts
+++ b/src/web-ui/src/flow_chat/services/flow-chat-manager/MessageModule.test.ts
@@ -1241,6 +1241,8 @@ describe('MessageModule model synchronization', () => {
     });
     const { context, session } = modelSyncContext('asdf');
     await syncSessionModelSelection(context, session.sessionId, 'Standard');
+    expect(mockGetConfigs).toHaveBeenCalledTimes(1);
+    expect(mockGetConfigs).toHaveBeenCalledWith(['ai.models', 'ai.default_models']);
     expect(context.flowChatStore.updateSessionModelName).not.toHaveBeenCalled();
     expect(context.flowChatStore.updateSessionMaxContextTokens).toHaveBeenCalledWith(session.sessionId, 64000);
     expect(mockUpdateSessionModel).toHaveBeenCalledWith(expect.objectContaining({
diff --git a/src/web-ui/src/flow_chat/store/FlowChatStore.ts b/src/web-ui/src/flow_chat/store/FlowChatStore.ts
index 893a382bd2..2fbe6ac04a 100644
--- a/src/web-ui/src/flow_chat/store/FlowChatStore.ts
+++ b/src/web-ui/src/flow_chat/store/FlowChatStore.ts
@@ -4669,12 +4669,12 @@ export class FlowChatStore {
     });
   }
 
-  public updateSessionModelName(sessionId: string, modelName: string): void {
+  public updateSessionModelName(sessionId: string, modelName: string | undefined): void {
     this.setState(prev => {
       const session = prev.sessions.get(sessionId);
       if (!session) return prev;
 
-      const normalizedModelName = modelName.trim() || 'primary';
+      const normalizedModelName = modelName === undefined ? undefined : modelName.trim() || 'primary';
       if (session.config.modelName?.trim() === normalizedModelName) {
         return prev;
       }
@@ -6788,7 +6788,7 @@ export class FlowChatStore {
   public rollbackTokenUsage(): void {
   }
 
-  public updateSessionMaxContextTokens(sessionId: string, maxContextTokens: number): void {
+  public updateSessionMaxContextTokens(sessionId: string, maxContextTokens: number | undefined): void {
     this.setState(prev => {
       const session = prev.sessions.get(sessionId);
       if (!session) return prev;
diff --git a/src/web-ui/src/flow_chat/utils/modelResolution.test.ts b/src/web-ui/src/flow_chat/utils/modelResolution.test.ts
index 4576deaf39..4bc8fb1fbd 100644
--- a/src/web-ui/src/flow_chat/utils/modelResolution.test.ts
+++ b/src/web-ui/src/flow_chat/utils/modelResolution.test.ts
@@ -75,6 +75,7 @@ describe('configured model identity', () => {
       'ai.models': models, 'ai.default_models': { primary: 'model-first' },
     });
     await expect(getModelMaxTokens('asdf')).resolves.toBe(64000);
+    expect(configManager.getConfigs).toHaveBeenLastCalledWith(['ai.models', 'ai.default_models']);
   });
 });
 
diff --git a/src/web-ui/src/flow_chat/utils/modelResolution.ts b/src/web-ui/src/flow_chat/utils/modelResolution.ts
index 4ffe050eab..b80d8599b0 100644
--- a/src/web-ui/src/flow_chat/utils/modelResolution.ts
+++ b/src/web-ui/src/flow_chat/utils/modelResolution.ts
@@ -162,44 +162,33 @@ export function resolveModelSelection({
   };
 }
 
+/** Resolve from already loaded facts so selection and send do not read settings twice. */
+export function resolveModelMaxTokens(
+  modelName: string | undefined,
+  models: readonly AIModelConfig[],
+  defaultModels: DefaultModelsConfig,
+  modeDefaultModel?: string,
+): number {
+  const selection = modelName?.trim() || modeDefaultModel;
+  return resolveModelForContextWindow(selection, models, defaultModels)?.context_window
+    || resolveModelForContextWindow('primary', models, defaultModels)?.context_window
+    || 128128;
+}
+
 export async function getModelMaxTokens(modelName?: string, agentType?: string): Promise<number> {
   try {
     const configManager = await import('@/infrastructure/config/services/ConfigManager').then(m => m.configManager);
     const configData = await configManager.getConfigs([
       'ai.models',
       'ai.default_models',
-      'ai.agent_model_defaults',
+      ...(!modelName?.trim() ? ['ai.agent_model_defaults'] : []),
     ]);
-    const models = (configData['ai.models'] as AIModelConfig[] | undefined) || [];
-    const defaultModels = (configData['ai.default_models'] as DefaultModelsConfig | undefined) || {};
-    const agentModelDefaults = configData['ai.agent_model_defaults'] as AgentModelDefaultsConfig | undefined;
-
-    const normalizedModelName = modelName?.trim();
-    const explicitModel = resolveModelForContextWindow(modelName, models, defaultModels);
-    if (explicitModel?.context_window) {
-      return explicitModel.context_window;
-    }
-
-    // Only legacy sessions without a model selector inherit the current mode
-    // default. Session-owned selectors are resolved above.
-    if (!normalizedModelName) {
-      const modeModel = resolveModelForContextWindow(
-        agentModelDefaults?.mode,
-        models,
-        defaultModels,
-      );
-      if (modeModel?.context_window) {
-        return modeModel.context_window;
-      }
-    }
-
-    const primaryModel = resolveModelForContextWindow('primary', models, defaultModels);
-    if (primaryModel?.context_window) {
-      return primaryModel.context_window;
-    }
-
-    log.debug('Model context_window config not found, using default', { modelName, agentType });
-    return 128128;
+    return resolveModelMaxTokens(
+      modelName,
+      (configData['ai.models'] as AIModelConfig[] | undefined) || [],
+      (configData['ai.default_models'] as DefaultModelsConfig | undefined) || {},
+      (configData['ai.agent_model_defaults'] as AgentModelDefaultsConfig | undefined)?.mode,
+    );
   } catch (error) {
     log.warn('Failed to get model max tokens', { modelName, agentType, error });
     return 128128;
@@ -214,7 +203,7 @@ export async function resolveReasoningPresetForSessionCreation(
     const configData = await configManager.getConfigs([
       'ai.models',
       'ai.default_models',
-      'ai.agent_model_defaults',
+      ...(!modelName?.trim() ? ['ai.agent_model_defaults'] : []),
     ]);
     const models = (configData['ai.models'] as AIModelConfig[] | undefined) || [];
     const defaultModels = (configData['ai.default_models'] as DefaultModelsConfig | undefined) || {};
diff --git a/src/web-ui/src/flow_chat/utils/modelSync.ts b/src/web-ui/src/flow_chat/utils/modelSync.ts
index 639120a43f..4bf1a8bf06 100644
--- a/src/web-ui/src/flow_chat/utils/modelSync.ts
+++ b/src/web-ui/src/flow_chat/utils/modelSync.ts
@@ -10,7 +10,7 @@ import { configManager } from '@/infrastructure/config/services/ConfigManager';
 import type { AIModelConfig, AgentModelDefaultsConfig, DefaultModelsConfig } from '@/infrastructure/config/types';
 import { createLogger } from '@/shared/utils/logger';
 import type { FlowChatContext } from '../services/flow-chat-manager/types';
-import { getModelMaxTokens, resolveModelReference } from './modelResolution';
+import { resolveModelMaxTokens, resolveModelReference } from './modelResolution';
 import { sessionProjectWorkspacePath, sessionWorkspaceId } from './sessionWorkspace';
 import {
   getActiveSurfaceScope,
@@ -52,8 +52,9 @@ export async function syncSessionModelSelection(
     throw new Error(`Session does not exist: ${sessionId}`);
   }
 
+  const sessionModelId = session.config.modelName?.trim();
   const configData = (await configManager.getConfigs([
-    'ai.agent_model_defaults',
+    ...(!sessionModelId ? ['ai.agent_model_defaults'] : []),
     'ai.models',
     'ai.default_models',
   ])) ?? {};
@@ -62,10 +63,9 @@ export async function syncSessionModelSelection(
   const allModels = (configData['ai.models'] as AIModelConfig[] | undefined) || [];
   const defaultModels = (configData['ai.default_models'] as DefaultModelsConfig | undefined) || {};
 
-  const sessionModelId = session.config.modelName?.trim();
   const requestedModelId = sessionModelId || agentModelDefaults?.mode;
   const desiredModelId = normalizeModelSelection(requestedModelId, allModels, defaultModels);
-  const desiredMaxContextTokens = await getModelMaxTokens(desiredModelId, agentType);
+  const desiredMaxContextTokens = resolveModelMaxTokens(desiredModelId, allModels, defaultModels);
   surfaceScope.assertCurrent('resolve session model context window');
   const shouldSyncContextWindow = session.maxContextTokens !== desiredMaxContextTokens;
 
diff --git a/src/web-ui/src/infrastructure/config/AGENTS.md b/src/web-ui/src/infrastructure/config/AGENTS.md
index f78ad52237..8ec95b019f 100644
--- a/src/web-ui/src/infrastructure/config/AGENTS.md
+++ b/src/web-ui/src/infrastructure/config/AGENTS.md
@@ -52,3 +52,14 @@ pnpm --dir src/web-ui run test:run src/infrastructure/config/components/modelEdi
 
 These checks cover draft isolation and source contracts, not rendered visuals
 or remote runtime behavior.
+
+For the device-scoped model catalog and non-blocking session/default selection:
+
+```bash
+pnpm --dir src/web-ui run test:run src/infrastructure/config/services/ModelCatalogStore.test.ts src/infrastructure/config/services/ConfigManager.test.ts src/flow_chat/components/ModelSelectorProviderLevels.test.tsx src/flow_chat/components/ModelSelectorExternal.test.tsx src/flow_chat/components/ModelSelectorAcpMode.test.tsx src/flow_chat/utils/modelResolution.test.ts src/flow_chat/services/flow-chat-manager/MessageModule.test.ts src/flow_chat/services/flow-chat-manager/SessionModule.test.ts
+```
+
+Keep warm catalogs while refreshing, invalidate them only for catalog/model
+facts, and isolate all snapshots and pending work by surface activation. An
+existing session commits its selection before remembering future defaults;
+explicit model reads before send must not await the future-default write.
diff --git a/src/web-ui/src/infrastructure/config/components/ModelTagsField.tsx b/src/web-ui/src/infrastructure/config/components/ModelTagsField.tsx
index cd7339c9a7..1051f95178 100644
--- a/src/web-ui/src/infrastructure/config/components/ModelTagsField.tsx
+++ b/src/web-ui/src/infrastructure/config/components/ModelTagsField.tsx
@@ -1,4 +1,4 @@
-import { Button, Field, Icon, IconButton, Input, StatusPill, Tooltip } from '@openbitfun/ui';
+import { Button, Capsule, Field, Icon, IconButton, Input, StatusPill, Tooltip } from '@openbitfun/ui';
 import { useRef, useState } from 'react';
 import { useI18n } from '@/infrastructure/i18n';
 import { MAX_MODEL_USER_TAGS, normalizeModelTags } from '../services/modelTags';
@@ -90,46 +90,46 @@ export default function ModelTagsField({ tags, recommendedTags, disabled, layout
     <div className="openbitfun-model-settings__tag-editor" role="group" aria-label={t('pool.tagsLabel')}>
       <div className="openbitfun-model-settings__tag-list">
         {tags.map(tag => (
-          <div className="openbitfun-model-settings__model-capsule" key={tag}>
-            {tagDraft?.originalTag === tag ? tagInput : (
-              <>
-                <Button
-                  ref={element => {
-                    if (element) tagButtonRefs.current.set(tag, element);
-                    else tagButtonRefs.current.delete(tag);
-                  }}
-                  variant="outline"
+          <Capsule size="xs" className="openbitfun-model-settings__model-capsule" key={tag}
+            action={tagDraft?.originalTag === tag ? undefined : (
+              <Tooltip content={t('pool.removeTag', { tag })}>
+                <IconButton
+                  className="openbitfun-model-settings__model-capsule-dismiss"
                   size="xs"
-                  className="openbitfun-model-settings__model-capsule-edit"
-                  aria-label={t('pool.editTag', { tag })}
-                  disabled={disabled || tags.length > MAX_MODEL_USER_TAGS}
-                  onClick={() => updateTagDraft({ originalTag: tag, value: tag })}
-                >
-                  {tag}
-                </Button>
-                <Tooltip content={t('pool.removeTag', { tag })}>
-                  <IconButton
-                    className="openbitfun-model-settings__model-capsule-dismiss"
-                    size="xs"
-                    shape="circle"
-                    variant="quiet"
-                    aria-label={t('pool.removeTag', { tag })}
-                    disabled={disabled}
-                    onClick={() => {
-                      onChange(tags.filter(value => value !== tag));
-                      restoreTagFocus(tags.find(value => value !== tag));
-                    }}
-                    icon={<Icon name="xmark" size="sm" />}
-                  />
-                </Tooltip>
-              </>
+                  shape="circle"
+                  variant="quiet"
+                  aria-label={t('pool.removeTag', { tag })}
+                  disabled={disabled}
+                  onClick={() => {
+                    onChange(tags.filter(value => value !== tag));
+                    restoreTagFocus(tags.find(value => value !== tag));
+                  }}
+                  icon={<Icon name="xmark" size="sm" />}
+                />
+              </Tooltip>
+            )}>
+            {tagDraft?.originalTag === tag ? tagInput : (
+              <Button
+                ref={element => {
+                  if (element) tagButtonRefs.current.set(tag, element);
+                  else tagButtonRefs.current.delete(tag);
+                }}
+                variant="outline"
+                size="xs"
+                className="openbitfun-model-settings__model-capsule-edit"
+                aria-label={t('pool.editTag', { tag })}
+                disabled={disabled || tags.length > MAX_MODEL_USER_TAGS}
+                onClick={() => updateTagDraft({ originalTag: tag, value: tag })}
+              >
+                {tag}
+              </Button>
             )}
-          </div>
+          </Capsule>
         ))}
         {tagDraft?.originalTag === null && (
-          <div className="openbitfun-model-settings__model-capsule">
+          <Capsule size="xs" className="openbitfun-model-settings__model-capsule">
             {tagInput}
-          </div>
+          </Capsule>
         )}
       </div>
       <Tooltip content={atTagLimit ? t('pool.tagsLimitReached', { max: MAX_MODEL_USER_TAGS }) : t('pool.addTags')}>
diff --git a/src/web-ui/src/infrastructure/config/services/ModelCatalogStore.test.ts b/src/web-ui/src/infrastructure/config/services/ModelCatalogStore.test.ts
new file mode 100644
index 0000000000..19a435883b
--- /dev/null
+++ b/src/web-ui/src/infrastructure/config/services/ModelCatalogStore.test.ts
@@ -0,0 +1,64 @@
+import { beforeEach, describe, expect, it, vi } from 'vitest';
+import { activateSurface } from '@/infrastructure/peer-device/deviceSurface';
+import { aiApi, type AIModelCatalog } from '@/infrastructure/api/service-api/AIApi';
+import { configManager } from './ConfigManager';
+import { createModelCatalogStore } from './ModelCatalogStore';
+
+vi.mock('@/infrastructure/api/service-api/AIApi', () => ({ aiApi: {
+  getModelCatalog: vi.fn(), onModelCatalogUpdated: vi.fn(() => () => {}),
+} }));
+vi.mock('./ConfigManager', () => ({ configManager: {
+  onConfigChange: vi.fn(() => () => {}),
+} }));
+const catalog = (version: number): AIModelCatalog => ({ version, models: [] });
+const deferred = () => {
+  let resolve!: (value: AIModelCatalog) => void;
+  const promise = new Promise<AIModelCatalog>(done => { resolve = done; });
+  return { promise, resolve };
+};
+describe('shared model catalog', () => {
+  beforeEach(() => { activateSurface('local'); vi.clearAllMocks(); });
+
+  it('shares concurrent selectors, retains warm data on errors, and ignores preference writes', async () => {
+    vi.mocked(aiApi.getModelCatalog).mockResolvedValue(catalog(1));
+    const store = createModelCatalogStore();
+    const offA = store.subscribe(vi.fn());
+    const offB = store.subscribe(vi.fn());
+    await vi.waitFor(() => expect(store.getSnapshot().status).toBe('ready'));
+    expect(aiApi.getModelCatalog).toHaveBeenCalledTimes(1);
+    vi.mocked(configManager.onConfigChange).mock.calls[0][0]('ai.agent_model_defaults.mode');
+    expect(aiApi.getModelCatalog).toHaveBeenCalledTimes(1);
+    vi.mocked(aiApi.getModelCatalog).mockRejectedValueOnce(new Error('offline'));
+    await store.refresh();
+    expect(store.getSnapshot()).toEqual({ catalog: catalog(1), status: 'ready' });
+    offA(); offB();
+  });
+
+  it('replays an invalidation arriving during a read and discards the superseded result', async () => {
+    const first = deferred();
+    vi.mocked(aiApi.getModelCatalog).mockReturnValueOnce(first.promise).mockResolvedValue(catalog(2));
+    const store = createModelCatalogStore();
+    const off = store.subscribe(vi.fn());
+    await Promise.resolve();
+    vi.mocked(configManager.onConfigChange).mock.calls[0][0]('ai.models');
+    first.resolve(catalog(1));
+    await vi.waitFor(() => expect(store.getSnapshot().catalog?.version).toBe(2));
+    expect(aiApi.getModelCatalog).toHaveBeenCalledTimes(2);
+    off();
+  });
+
+  it('never publishes an old host response on a new activation', async () => {
+    const old = deferred();
+    vi.mocked(aiApi.getModelCatalog).mockReturnValueOnce(old.promise).mockResolvedValue(catalog(2));
+    const store = createModelCatalogStore();
+    const off = store.subscribe(vi.fn());
+    await Promise.resolve();
+    activateSurface('peer');
+    expect(store.getSnapshot().catalog).toBeNull();
+    await vi.waitFor(() => expect(store.getSnapshot().catalog?.version).toBe(2));
+    old.resolve(catalog(1));
+    await Promise.resolve();
+    expect(store.getSnapshot().catalog?.version).toBe(2);
+    off();
+  });
+});
diff --git a/src/web-ui/src/infrastructure/config/services/ModelCatalogStore.ts b/src/web-ui/src/infrastructure/config/services/ModelCatalogStore.ts
new file mode 100644
index 0000000000..2f023b5153
--- /dev/null
+++ b/src/web-ui/src/infrastructure/config/services/ModelCatalogStore.ts
@@ -0,0 +1,84 @@
+import { aiApi, type AIModelCatalog } from '@/infrastructure/api/service-api/AIApi';
+import { getActiveSurfaceScope, onSurfaceActivated } from '@/infrastructure/peer-device/deviceSurface';
+import { createLogger } from '@/shared/utils/logger';
+import { configManager } from './ConfigManager';
+
+const log = createLogger('ModelCatalogStore');
+type Snapshot = { catalog: AIModelCatalog | null; status: 'loading' | 'ready' | 'error' };
+const EMPTY: Snapshot = { catalog: null, status: 'loading' };
+
+/** One catalog projection per device activation. Refreshes keep the last good
+ * projection usable; a config/catalog event during a read schedules another
+ * read so an older response cannot consume a newer invalidation.
+ */
+export function createModelCatalogStore() {
+  let epoch = -1;
+  let snapshot = EMPTY;
+  let revision = 0;
+  let pending: Promise<void> | undefined;
+  let stop: (() => void) | undefined;
+  const listeners = new Set<() => void>();
+  const notify = () => listeners.forEach(listener => listener());
+  const getSnapshot = () => epoch === getActiveSurfaceScope().epoch ? snapshot : EMPTY;
+
+  const refresh = (): Promise<void> => {
+    const scope = getActiveSurfaceScope();
+    if (epoch !== scope.epoch) {
+      epoch = scope.epoch;
+      snapshot = EMPTY;
+      pending = undefined;
+    }
+    revision += 1;
+    if (pending) return pending;
+    const read = async () => {
+      do {
+        const requestedRevision = revision;
+        try {
+          scope.assertCurrent('load model catalog');
+          const catalog = await aiApi.getModelCatalog();
+          if (!scope.isCurrent()) return;
+          if (requestedRevision !== revision) continue;
+          snapshot = { catalog, status: 'ready' };
+        } catch (error) {
+          if (!scope.isCurrent()) return;
+          if (requestedRevision !== revision) continue;
+          snapshot = { catalog: snapshot.catalog, status: snapshot.catalog ? 'ready' : 'error' };
+          log.warn('Failed to refresh model catalog', { error });
+        }
+        notify();
+        return;
+      } while (scope.isCurrent());
+    };
+    // Publish the promise before calling any loader that can emit events.
+    const promise = Promise.resolve().then(read).finally(() => {
+      if (pending === promise) pending = undefined;
+    });
+    pending = promise;
+    return promise;
+  };
+
+  const subscribe = (listener: () => void) => {
+    listeners.add(listener);
+    if (!stop) {
+      const offCatalog = aiApi.onModelCatalogUpdated(() => { void refresh(); });
+      const offConfig = configManager.onConfigChange(path => {
+        if (!path || path === 'ai' || ['ai.models', 'ai.default_models'].some(
+          owned => path === owned || path.startsWith(`${owned}.`),
+        )) void refresh();
+      });
+      const offSurface = onSurfaceActivated(() => {
+        void refresh();
+        notify();
+      });
+      stop = () => { offCatalog(); offConfig(); offSurface(); };
+      void refresh();
+    }
+    return () => {
+      listeners.delete(listener);
+      if (!listeners.size) { stop?.(); stop = undefined; }
+    };
+  };
+  return { subscribe, getSnapshot, refresh };
+}
+
+export const modelCatalogStore = createModelCatalogStore();
diff --git a/src/web-ui/src/locales/en-US/flow-chat.json b/src/web-ui/src/locales/en-US/flow-chat.json
index be4f9094c3..43ea76a65d 100644
--- a/src/web-ui/src/locales/en-US/flow-chat.json
+++ b/src/web-ui/src/locales/en-US/flow-chat.json
@@ -3331,6 +3331,7 @@
     "acpMode": "Mode",
     "acpModeLocked": "This conversation has already started, so its mode is fixed.",
     "acpModeFailed": "Failed to switch mode",
+    "defaultSaveFailed": "Model selected, but the default for future chats could not be saved.",
     "switchFailed": "Failed to switch model",
     "modelNotConfigured": "Not Configured",
     "openModelSettings": "Open model settings",
diff --git a/src/web-ui/src/locales/zh-CN/flow-chat.json b/src/web-ui/src/locales/zh-CN/flow-chat.json
index 335c390e4b..d6b0c1bb44 100644
--- a/src/web-ui/src/locales/zh-CN/flow-chat.json
+++ b/src/web-ui/src/locales/zh-CN/flow-chat.json
@@ -3331,6 +3331,7 @@
     "acpMode": "模式",
     "acpModeLocked": "会话已经开始，模式不能再改。",
     "acpModeFailed": "切换模式失败",
+    "defaultSaveFailed": "模型已切换，但未能保存后续会话的默认选择。",
     "switchFailed": "切换模型失败",
     "modelNotConfigured": "未配置",
     "openModelSettings": "前往模型设置",
diff --git a/src/web-ui/src/locales/zh-TW/flow-chat.json b/src/web-ui/src/locales/zh-TW/flow-chat.json
index 23f90ac627..0da8ccc993 100644
--- a/src/web-ui/src/locales/zh-TW/flow-chat.json
+++ b/src/web-ui/src/locales/zh-TW/flow-chat.json
@@ -3331,6 +3331,7 @@
     "acpMode": "模式",
     "acpModeLocked": "對話已經開始，模式不能再改。",
     "acpModeFailed": "切換模式失敗",
+    "defaultSaveFailed": "模型已切換，但未能儲存後續對話的預設選擇。",
     "switchFailed": "切換模型失敗",
     "modelNotConfigured": "未設定",
     "openModelSettings": "前往模型設定",
diff --git a/third_party/tao/OPENBITFUN-PATCH.md b/third_party/tao/OPENBITFUN-PATCH.md
index 9b7bb1d442..0ca53d76d2 100644
--- a/third_party/tao/OPENBITFUN-PATCH.md
+++ b/third_party/tao/OPENBITFUN-PATCH.md
@@ -23,6 +23,14 @@ Untitled and fullscreen style masks are excluded from the layout override;
 windows without a custom inset retain upstream behavior. No notification retry,
 timer, new private API or product-specific geometry is added.
 
+The vendored macOS sources also receive compiler-warning maintenance: current
+event constants and ivar reads, removal of unused private state/helpers and
+redundant unsafe blocks, and explicit retention of validated per-window icon
+data. The obsolete fullscreen button lookup is omitted because AppKit always
+returns nil for it; the zoom button remains in the list. The legacy filename-list
+pasteboard format is retained at its three registration/read sites, with local
+deprecation annotations, so this cleanup does not change drag payload semantics.
+
 OpenBitFun keeps its original toolbar height and tab spacing. The desktop host
 derives the configured inset from the shared design height and native metrics;
 the framework owns applying that inset during its native window lifecycle.
diff --git a/third_party/tao/src/platform/macos.rs b/third_party/tao/src/platform/macos.rs
index 32b8cbbf3f..1e58321b6a 100644
--- a/third_party/tao/src/platform/macos.rs
+++ b/third_party/tao/src/platform/macos.rs
@@ -416,7 +416,7 @@ impl<T> EventLoopWindowTargetExtMacOS for EventLoopWindowTarget<T> {
   fn show_application(&self) {
     // TODO: Safety.
     let mtm = unsafe { objc2_foundation::MainThreadMarker::new_unchecked() };
-    unsafe { objc2_app_kit::NSApplication::sharedApplication(mtm).unhide(None) }
+    objc2_app_kit::NSApplication::sharedApplication(mtm).unhide(None)
   }
 
   fn hide_other_applications(&self) {
diff --git a/third_party/tao/src/platform_impl/macos/app.rs b/third_party/tao/src/platform_impl/macos/app.rs
index a83363eefe..ea218e5c59 100644
--- a/third_party/tao/src/platform_impl/macos/app.rs
+++ b/third_party/tao/src/platform_impl/macos/app.rs
@@ -35,7 +35,7 @@ extern "C" fn send_event(this: &NSApplication, _sel: Sel, event: &NSEvent) {
     // but that doesn't really matter here.
     let event_type = event.r#type();
     let modifier_flags = event.modifierFlags();
-    if event_type == appkit::NSKeyUp
+    if event_type == NSEventType::KeyUp
       && util::has_flag(modifier_flags, appkit::NSEventModifierFlags::Command)
     {
       if let Some(key_window) = this.keyWindow() {
diff --git a/third_party/tao/src/platform_impl/macos/app_delegate.rs b/third_party/tao/src/platform_impl/macos/app_delegate.rs
index 5107814c94..b2b92915da 100644
--- a/third_party/tao/src/platform_impl/macos/app_delegate.rs
+++ b/third_party/tao/src/platform_impl/macos/app_delegate.rs
@@ -137,11 +137,9 @@ extern "C" fn application_will_terminate(_: &Object, _: Sel, _: id) {
 extern "C" fn application_open_urls(_: &Object, _: Sel, _: id, urls: &NSArray<NSURL>) {
   trace!("Trigger `application:openURLs:`");
 
-  let urls = unsafe {
-    (0..urls.count())
-      .flat_map(|i| url::Url::parse(&urls.objectAtIndex(i).absoluteString().unwrap().to_string()))
-      .collect::<Vec<_>>()
-  };
+  let urls = (0..urls.count())
+    .flat_map(|i| url::Url::parse(&urls.objectAtIndex(i).absoluteString().unwrap().to_string()))
+    .collect::<Vec<_>>();
   trace!("Get `application:openURLs:` URLs: {:?}", urls);
   AppState::open_urls(urls);
   trace!("Completed `application:openURLs:`");
diff --git a/third_party/tao/src/platform_impl/macos/event.rs b/third_party/tao/src/platform_impl/macos/event.rs
index 6b1ce97f52..6063bc5202 100644
--- a/third_party/tao/src/platform_impl/macos/event.rs
+++ b/third_party/tao/src/platform_impl/macos/event.rs
@@ -162,7 +162,7 @@ pub fn create_key_event(
     //#[cfg(debug_assertions)] println!("Couldn't get key from code: {:?}", physical_key);
     key_without_modifiers = get_modifierless_char(scancode);
 
-    let modifiers = unsafe { NSEvent::modifierFlags(ns_event) };
+    let modifiers = NSEvent::modifierFlags(ns_event);
     let has_alt = modifiers.contains(NSEventModifierFlags::Option);
     let has_ctrl = modifiers.contains(NSEventModifierFlags::Control);
     if has_alt || has_ctrl || text_with_all_modifiers.is_none() || !is_press {
@@ -304,7 +304,7 @@ pub fn extra_function_key_to_code(scancode: u16, string: &str) -> KeyCode {
 }
 
 pub fn event_mods(event: &NSEvent) -> ModifiersState {
-  let flags = unsafe { NSEvent::modifierFlags(event) };
+  let flags = NSEvent::modifierFlags(event);
   let mut m = ModifiersState::empty();
   m.set(
     ModifiersState::SHIFT,
diff --git a/third_party/tao/src/platform_impl/macos/event_loop.rs b/third_party/tao/src/platform_impl/macos/event_loop.rs
index 8179ea91fd..58644326dc 100644
--- a/third_party/tao/src/platform_impl/macos/event_loop.rs
+++ b/third_party/tao/src/platform_impl/macos/event_loop.rs
@@ -35,7 +35,7 @@ use crate::{
       observer::*,
       util::{self, IdRef},
     },
-    set_badge_label, set_progress_indicator,
+    set_progress_indicator,
   },
   window::{ProgressBarState, Theme},
 };
@@ -123,16 +123,6 @@ impl<T: 'static> EventLoopWindowTarget<T> {
     set_progress_indicator(progress);
   }
 
-  #[inline]
-  pub fn set_badge_count(&self, count: Option<i64>, _desktop_filename: Option<String>) {
-    set_badge_label(count.map(|c| c.to_string()));
-  }
-
-  #[inline]
-  pub fn set_badge_label(&self, label: Option<String>) {
-    set_badge_label(label);
-  }
-
   #[inline]
   pub fn set_theme(&self, theme: Option<Theme>) {
     set_ns_theme(theme)
diff --git a/third_party/tao/src/platform_impl/macos/icon.rs b/third_party/tao/src/platform_impl/macos/icon.rs
index c5c7439d06..edb4b37ac6 100644
--- a/third_party/tao/src/platform_impl/macos/icon.rs
+++ b/third_party/tao/src/platform_impl/macos/icon.rs
@@ -5,10 +5,15 @@
 use crate::icon::{BadIcon, RgbaIcon};
 
 #[derive(Debug, Clone)]
-pub struct PlatformIcon(RgbaIcon);
+pub struct PlatformIcon {
+  // macOS ignores per-window icons; retain validated pixels for the shared Icon API.
+  _rgba: RgbaIcon,
+}
 
 impl PlatformIcon {
   pub fn from_rgba(rgba: Vec<u8>, width: u32, height: u32) -> Result<Self, BadIcon> {
-    Ok(PlatformIcon(RgbaIcon::from_rgba(rgba, width, height)?))
+    Ok(PlatformIcon {
+      _rgba: RgbaIcon::from_rgba(rgba, width, height)?,
+    })
   }
 }
diff --git a/third_party/tao/src/platform_impl/macos/monitor.rs b/third_party/tao/src/platform_impl/macos/monitor.rs
index 7cdbd3986c..c9c60943c8 100644
--- a/third_party/tao/src/platform_impl/macos/monitor.rs
+++ b/third_party/tao/src/platform_impl/macos/monitor.rs
@@ -20,7 +20,7 @@ use core_graphics::{
 };
 use objc2::{msg_send, rc::Retained};
 use objc2_app_kit::NSScreen;
-use objc2_foundation::{ns_string, MainThreadMarker, NSString, NSUInteger};
+use objc2_foundation::{ns_string, MainThreadMarker, NSUInteger};
 
 #[derive(Clone)]
 pub struct VideoMode {
diff --git a/third_party/tao/src/platform_impl/macos/util/async.rs b/third_party/tao/src/platform_impl/macos/util/async.rs
index 4513b6bc7c..e584971554 100644
--- a/third_party/tao/src/platform_impl/macos/util/async.rs
+++ b/third_party/tao/src/platform_impl/macos/util/async.rs
@@ -8,7 +8,7 @@ use std::{
 };
 
 use core_graphics::base::CGFloat;
-use dispatch2::{DispatchQueue, DispatchQueueAttr};
+use dispatch2::DispatchQueue;
 use objc2::{rc::autoreleasepool, Message};
 use objc2_app_kit::{NSScreen, NSView, NSWindow, NSWindowStyleMask};
 use objc2_foundation::{MainThreadMarker, NSPoint, NSSize, NSString};
diff --git a/third_party/tao/src/platform_impl/macos/util/mod.rs b/third_party/tao/src/platform_impl/macos/util/mod.rs
index b9a39147e6..32714fbcf2 100644
--- a/third_party/tao/src/platform_impl/macos/util/mod.rs
+++ b/third_party/tao/src/platform_impl/macos/util/mod.rs
@@ -12,7 +12,7 @@ use std::ops::{BitAnd, Deref};
 use core_graphics::display::CGDisplay;
 use objc2::{
   class,
-  runtime::{AnyClass as Class, AnyObject as Object, Sel},
+  runtime::{AnyClass as Class, AnyObject as Object},
 };
 use objc2_app_kit::{NSApp, NSView, NSWindow, NSWindowStyleMask};
 use objc2_foundation::{MainThreadMarker, NSAutoreleasePool, NSPoint, NSRange, NSRect, NSUInteger};
@@ -20,7 +20,7 @@ use objc2_foundation::{MainThreadMarker, NSAutoreleasePool, NSPoint, NSRange, NS
 use crate::{
   dpi::{LogicalPosition, PhysicalPosition},
   error::ExternalError,
-  platform_impl::platform::ffi::{self, id, nil, BOOL, YES},
+  platform_impl::platform::ffi::{self, id, nil},
 };
 
 // Replace with `!` once stable
@@ -123,10 +123,6 @@ pub unsafe fn open_emoji_picker() {
   let () = msg_send![&NSApp(mtm), orderFrontCharacterPalette: nil];
 }
 
-pub extern "C" fn yes(_: &Object, _: Sel) -> BOOL {
-  YES
-}
-
 pub unsafe fn toggle_style_mask(
   window: &NSWindow,
   view: &NSView,
diff --git a/third_party/tao/src/platform_impl/macos/window.rs b/third_party/tao/src/platform_impl/macos/window.rs
index 06067e60d8..7f5d9a25e2 100644
--- a/third_party/tao/src/platform_impl/macos/window.rs
+++ b/third_party/tao/src/platform_impl/macos/window.rs
@@ -6,7 +6,6 @@
 use std::{
   collections::VecDeque,
   convert::TryInto,
-  f64,
   ffi::CStr,
   os::raw::c_void,
   sync::{
@@ -40,11 +39,7 @@ use crate::{
     WindowAttributes, WindowId as RootWindowId, WindowSizeConstraints,
   },
 };
-use core_graphics::{
-  base::CGFloat,
-  display::{CGDisplay, CGDisplayMode},
-  geometry::CGPoint,
-};
+use core_graphics::{base::CGFloat, display::CGDisplay, geometry::CGPoint};
 use objc2::{
   msg_send,
   rc::Retained,
@@ -53,8 +48,8 @@ use objc2::{
 use objc2_app_kit::{
   self as appkit, NSApp, NSApplicationPresentationOptions, NSBackingStoreType, NSColor, NSEvent,
   NSEventModifierFlags, NSEventSubtype, NSEventType, NSRequestUserAttentionType, NSScreen, NSView,
-  NSWindow, NSWindowButton, NSWindowCollectionBehavior, NSWindowFullScreenButton,
-  NSWindowOrderingMode, NSWindowSharingType, NSWindowStyleMask,
+  NSWindow, NSWindowButton, NSWindowCollectionBehavior, NSWindowOrderingMode, NSWindowSharingType,
+  NSWindowStyleMask,
 };
 use objc2_foundation::{
   ns_string, MainThreadMarker, NSArray, NSAutoreleasePool, NSDictionary, NSInteger, NSPoint,
@@ -266,7 +261,6 @@ fn create_window(
       }
       if pl_attrs.titlebar_buttons_hidden {
         for titlebar_button in &[
-          NSWindowFullScreenButton,
           NSWindowButton::MiniaturizeButton,
           NSWindowButton::CloseButton,
           NSWindowButton::ZoomButton,
@@ -435,9 +429,18 @@ extern "C" fn is_focusable(this: &Object, _: Sel) -> Bool {
 // Window chrome belongs to the window, not its replaceable content view.
 // Wry replaces TaoView with its WebView parent during window construction.
 pub(super) unsafe fn traffic_light_inset(window: &NSWindow) -> Option<LogicalPosition<f64>> {
-  let configured: Bool = *window.get_ivar("hasTrafficLightInset");
+  // These ivars are registered on TaoWindow above and accessed on the AppKit main thread.
+  let configured = window
+    .class()
+    .instance_variable(CStr::from_bytes_with_nul(b"hasTrafficLightInset\0").unwrap())
+    .unwrap();
+  let configured: Bool = *configured.load(window);
   if configured.as_bool() {
-    let position: NSPoint = *window.get_ivar("trafficLightInset");
+    let inset = window
+      .class()
+      .instance_variable(CStr::from_bytes_with_nul(b"trafficLightInset\0").unwrap())
+      .unwrap();
+    let position: NSPoint = *inset.load(window);
     Some(LogicalPosition::new(position.x, position.y))
   } else {
     None
@@ -511,7 +514,6 @@ pub struct SharedState {
   /// bar in exclusive fullscreen but want to restore the original options when
   /// transitioning back to borderless fullscreen.
   save_presentation_opts: Option<NSApplicationPresentationOptions>,
-  pub saved_desktop_display_mode: Option<(CGDisplay, CGDisplayMode)>,
   pub current_theme: Theme,
 }
 
@@ -548,7 +550,6 @@ pub struct UnownedWindow {
   decorations: AtomicBool,
   cursor_state: Weak<Mutex<CursorState>>,
   transparent: bool,
-  pub inner_rect: Option<PhysicalSize<u32>>,
 }
 
 unsafe impl Send for UnownedWindow {}
@@ -615,7 +616,10 @@ impl UnownedWindow {
       }
 
       // register for drag and drop operations.
-      ns_window.registerForDraggedTypes(&NSArray::arrayWithObject(appkit::NSFilenamesPboardType));
+      // Keep the filename-list format paired with the legacy drag delegates.
+      #[allow(deprecated)]
+      let filenames_type = appkit::NSFilenamesPboardType;
+      ns_window.registerForDraggedTypes(&NSArray::arrayWithObject(filenames_type));
     }
 
     // Since `win_attribs` is put into a mutex below, we'll just copy these
@@ -630,9 +634,6 @@ impl UnownedWindow {
     let focused = win_attribs.focused;
     let decorations = win_attribs.decorations;
     let visible_on_all_workspaces = win_attribs.visible_on_all_workspaces;
-    let inner_rect = win_attribs
-      .inner_size
-      .map(|size| size.to_physical(scale_factor));
 
     let cloned_preferred_theme = win_attribs.preferred_theme;
 
@@ -643,7 +644,6 @@ impl UnownedWindow {
       shared_state: Arc::new(Mutex::new(win_attribs.into())),
       decorations: AtomicBool::new(decorations),
       cursor_state,
-      inner_rect,
       transparent,
     });
 
diff --git a/third_party/tao/src/platform_impl/macos/window_delegate.rs b/third_party/tao/src/platform_impl/macos/window_delegate.rs
index fa6e63085d..001f2ad4da 100644
--- a/third_party/tao/src/platform_impl/macos/window_delegate.rs
+++ b/third_party/tao/src/platform_impl/macos/window_delegate.rs
@@ -3,7 +3,6 @@
 // SPDX-License-Identifier: Apache-2.0
 
 use std::{
-  f64,
   ffi::CStr,
   os::raw::c_void,
   sync::{Arc, Weak},
@@ -420,6 +419,8 @@ extern "C" fn dragging_entered(this: &Object, _: Sel, sender: id) -> BOOL {
   use std::path::PathBuf;
 
   let pb: Retained<NSPasteboard> = unsafe { msg_send![sender, draggingPasteboard] };
+  // Match the legacy filename-list format registered by UnownedWindow::new.
+  #[allow(deprecated)]
   let filenames =
     unsafe { NSPasteboard::propertyListForType(&pb, appkit::NSFilenamesPboardType) }.unwrap();
 
@@ -454,6 +455,8 @@ extern "C" fn perform_drag_operation(this: &Object, _: Sel, sender: id) -> BOOL
   use std::path::PathBuf;
 
   let pb: Retained<NSPasteboard> = unsafe { msg_send![sender, draggingPasteboard] };
+  // Match the legacy filename-list format registered by UnownedWindow::new.
+  #[allow(deprecated)]
   let filenames =
     unsafe { NSPasteboard::propertyListForType(&pb, appkit::NSFilenamesPboardType) }.unwrap();