diff --git a/apps/web/src/components/ComposerPromptEditor.tsx b/apps/web/src/components/ComposerPromptEditor.tsx
index 3ba086e0e981..8cd441db8ae6 100644
--- a/apps/web/src/components/ComposerPromptEditor.tsx
+++ b/apps/web/src/components/ComposerPromptEditor.tsx
@@ -892,6 +892,15 @@ interface ComposerPromptEditorProps {
   onCitationSubmitAndSend?: () => void;
   onPaste: React.ClipboardEventHandler<HTMLElement>;
   editorRef: React.RefObject<ComposerPromptEditorHandle | null>;
+  /**
+   * Trigger-menu wiring for screen readers. `menuListboxId` is the listbox the
+   * menus render into and, when present, advertises list autocomplete.
+   * `menuActiveOptionId` is the highlighted option while that listbox is
+   * rendered; it drives aria-activedescendant so the reader follows the menu
+   * without focus ever leaving the editor.
+   */
+  menuListboxId?: string | undefined;
+  menuActiveOptionId?: string | undefined;
 }
 
 /**
@@ -1638,6 +1647,8 @@ function ComposerPromptEditorInner({
   onCitationSubmitAndSend,
   onPaste,
   editorRef,
+  menuListboxId,
+  menuActiveOptionId,
 }: ComposerPromptEditorProps) {
   const [editor] = useLexicalComposerContext();
   const onChangeRef = useRef(onChange);
@@ -1985,6 +1996,9 @@ function ComposerPromptEditorInner({
                 )}
                 data-testid="composer-editor"
                 aria-placeholder={placeholder}
+                ariaAutoComplete={menuListboxId ? "list" : undefined}
+                ariaControls={menuActiveOptionId ? menuListboxId : undefined}
+                ariaActiveDescendant={menuActiveOptionId}
                 placeholder={<span />}
                 onKeyDown={(event) => {
                   if (
@@ -2083,6 +2097,8 @@ export function ComposerPromptEditor({
   onCitationSubmitAndSend,
   onPaste,
   editorRef,
+  menuListboxId,
+  menuActiveOptionId,
 }: ComposerPromptEditorProps) {
   const initialValueRef = useRef(value);
   const initialSkillMetadataRef = useRef(skillMetadataByName(skills));
@@ -2124,6 +2140,8 @@ export function ComposerPromptEditor({
           onPaste={onPaste}
           {...(onCitationSubmitAndSend ? { onCitationSubmitAndSend } : {})}
           editorRef={editorRef}
+          menuListboxId={menuListboxId}
+          menuActiveOptionId={menuActiveOptionId}
           {...(onCommandKeyDown ? { onCommandKeyDown } : {})}
           {...(onPageScrollKeyDown ? { onPageScrollKeyDown } : {})}
           {...(onPageScrollKeyUp ? { onPageScrollKeyUp } : {})}
diff --git a/apps/web/src/components/chat/ChatComposer.tsx b/apps/web/src/components/chat/ChatComposer.tsx
index e3ae13911036..4a8b0f38f7a7 100644
--- a/apps/web/src/components/chat/ChatComposer.tsx
+++ b/apps/web/src/components/chat/ChatComposer.tsx
@@ -55,6 +55,7 @@ import {
   type ReactNode,
   useCallback,
   useEffect,
+  useId,
   useImperativeHandle,
   useLayoutEffect,
   useMemo,
@@ -239,7 +240,11 @@ import {
 import { useEnvironmentQuery } from "~/state/query";
 import { useDebouncedValue } from "~/state/queries";
 import { ProviderModelPicker } from "./ProviderModelPicker";
-import { type ComposerCommandItem, ComposerCommandMenu } from "./ComposerCommandMenu";
+import {
+  type ComposerCommandItem,
+  ComposerCommandMenu,
+  composerCommandOptionDomId,
+} from "./ComposerCommandMenu";
 import { ComposerPendingApprovalActions } from "./ComposerPendingApprovalActions";
 import { CompactComposerControlsMenu } from "./CompactComposerControlsMenu";
 import { ComposerPrimaryActions } from "./ComposerPrimaryActions";
@@ -2461,6 +2466,18 @@ export const ChatComposer = memo(function ChatComposer(props: ChatComposerProps)
   );
 
   const isComposerApprovalState = activePendingApproval !== null;
+
+  // The editor only references an option while the listbox is actually
+  // rendered, so aria-activedescendant never points at a missing node.
+  const composerMenuListboxId = useId();
+  const composerMenuActiveOptionDomId =
+    composerMenuOpen &&
+    !isComposerApprovalState &&
+    composerMenuItems.length > 0 &&
+    activeComposerMenuItem
+      ? composerCommandOptionDomId(composerMenuListboxId, activeComposerMenuItem.id)
+      : undefined;
+
   const activePendingUserInput = pendingUserInputs[0] ?? null;
   const isChoiceOnlyPendingQuestion =
     activePendingProgress?.activeQuestion?.allowCustomAnswer === false;
@@ -6216,6 +6233,7 @@ export const ChatComposer = memo(function ChatComposer(props: ChatComposerProps)
                 <ComposerCommandMenuLayer anchor={composerMenuAnchor}>
                   <ComposerCommandMenu
                     items={composerMenuItems}
+                    listboxId={composerMenuListboxId}
                     resolvedTheme={resolvedTheme}
                     isLoading={isComposerMenuLoading}
                     triggerKind={composerTriggerKind}
@@ -6638,6 +6656,8 @@ export const ChatComposer = memo(function ChatComposer(props: ChatComposerProps)
                     onChange={onPromptChange}
                     onVisibleSelectionChange={expandComposerForEditorChange}
                     onCommandKeyDown={onComposerCommandKey}
+                    menuListboxId={composerMenuListboxId}
+                    menuActiveOptionId={composerMenuActiveOptionDomId}
                     onPageScrollKeyDown={onPageScrollKeyDown}
                     onPageScrollKeyUp={onPageScrollKeyUp}
                     onPageScrollRelease={onPageScrollRelease}
diff --git a/apps/web/src/components/chat/ComposerCommandMenu.test.tsx b/apps/web/src/components/chat/ComposerCommandMenu.test.tsx
index 7a59d9054631..844c3949c32f 100644
--- a/apps/web/src/components/chat/ComposerCommandMenu.test.tsx
+++ b/apps/web/src/components/chat/ComposerCommandMenu.test.tsx
@@ -2,7 +2,19 @@ import { renderToStaticMarkup } from "react-dom/server";
 import { ProviderDriverKind } from "@t3tools/contracts";
 import { describe, expect, it } from "vite-plus/test";
 
-import { ComposerCommandMenu } from "./ComposerCommandMenu";
+import { ComposerCommandMenu, composerCommandOptionDomId } from "./ComposerCommandMenu";
+
+describe("composerCommandOptionDomId", () => {
+  it("produces a whitespace-free id that stays distinct across near-identical paths", () => {
+    const spaced = composerCommandOptionDomId("menu", "path:file:docs/my file.md");
+    const underscored = composerCommandOptionDomId("menu", "path:file:docs/my_file.md");
+    const escaped = composerCommandOptionDomId("menu", "path:file:docs/my%0020file.md");
+
+    expect(spaced).not.toMatch(/\s/);
+    expect(new Set([spaced, underscored, escaped]).size).toBe(3);
+    expect(composerCommandOptionDomId("menu", "slash:model")).toBe("menu-slash:model");
+  });
+});
 
 describe("ComposerCommandMenu", () => {
   it("renders slash commands with their descriptions", () => {
@@ -17,6 +29,7 @@ describe("ComposerCommandMenu", () => {
             description: "Switch response model for this thread",
           },
         ]}
+        listboxId="composer-menu"
         resolvedTheme="dark"
         isLoading={false}
         triggerKind="slash-command"
@@ -48,6 +61,7 @@ describe("ComposerCommandMenu", () => {
             description: "Open and control the in-app browser",
           },
         ]}
+        listboxId="composer-menu"
         resolvedTheme="dark"
         isLoading={false}
         triggerKind="skill"
@@ -83,6 +97,7 @@ describe("ComposerCommandMenu", () => {
             description: "Find the right skill or workflow",
           },
         ]}
+        listboxId="composer-menu"
         resolvedTheme="dark"
         isLoading={false}
         triggerKind="slash-command"
diff --git a/apps/web/src/components/chat/ComposerCommandMenu.tsx b/apps/web/src/components/chat/ComposerCommandMenu.tsx
index 9cdfc37a329f..bfc5c583762d 100644
--- a/apps/web/src/components/chat/ComposerCommandMenu.tsx
+++ b/apps/web/src/components/chat/ComposerCommandMenu.tsx
@@ -68,8 +68,30 @@ export type ComposerCommandItem =
       description: string;
     };
 
+/**
+ * DOM id of a menu option, so the editor's aria-activedescendant can point at
+ * it. Item ids embed paths and may contain whitespace, which an IDREF cannot;
+ * the fixed-width escape keeps ids that differ only there distinct.
+ */
+export function composerCommandOptionDomId(listboxId: string, itemId: string): string {
+  const escaped = itemId.replace(
+    /[\s%]/g,
+    (char) => `%${char.charCodeAt(0).toString(16).padStart(4, "0")}`,
+  );
+  return `${listboxId}-${escaped}`;
+}
+
+const LISTBOX_LABEL_BY_TRIGGER: Record<ComposerTriggerKind, string> = {
+  path: "Files and folders",
+  "pull-request": "Pull requests",
+  "slash-command": "Commands",
+  skill: "Skills",
+};
+
 export const ComposerCommandMenu = memo(function ComposerCommandMenu(props: {
   items: ComposerCommandItem[];
+  /** Id the editor references via aria-controls while the menu is open. */
+  listboxId: string;
   resolvedTheme: "light" | "dark";
   isLoading: boolean;
   triggerKind: ComposerTriggerKind | null;
@@ -104,12 +126,17 @@ export const ComposerCommandMenu = memo(function ComposerCommandMenu(props: {
         data-composer-command-drawer="true"
       >
         {props.items.length > 0 ? (
-          <CommandList className="max-h-72 min-h-0 scroll-pb-6">
+          <CommandList
+            id={props.listboxId}
+            aria-label={props.triggerKind ? LISTBOX_LABEL_BY_TRIGGER[props.triggerKind] : undefined}
+            className="max-h-72 min-h-0 scroll-pb-6"
+          >
             <CommandGroup>
               {props.items.map((item) => (
                 <ComposerCommandMenuItem
                   key={item.id}
                   item={item}
+                  domId={composerCommandOptionDomId(props.listboxId, item.id)}
                   triggerKind={props.triggerKind}
                   resolvedTheme={props.resolvedTheme}
                   isActive={props.activeItemId === item.id}
@@ -121,7 +148,7 @@ export const ComposerCommandMenu = memo(function ComposerCommandMenu(props: {
           </CommandList>
         ) : (
           <div className="px-5 pt-3.5 pb-7">
-            <p className="text-secondary-label text-xs">
+            <p role="status" className="text-secondary-label text-xs">
               {props.isLoading
                 ? props.triggerKind === "skill"
                   ? "Searching workspace skills..."
@@ -144,6 +171,7 @@ export const ComposerCommandMenu = memo(function ComposerCommandMenu(props: {
 
 const ComposerCommandMenuItem = memo(function ComposerCommandMenuItem(props: {
   item: ComposerCommandItem;
+  domId: string;
   triggerKind: ComposerTriggerKind | null;
   resolvedTheme: "light" | "dark";
   isActive: boolean;
@@ -159,7 +187,10 @@ const ComposerCommandMenuItem = memo(function ComposerCommandMenuItem(props: {
 
   return (
     <CommandItem
+      // Item owns `id` in its prop types; the render element carries ours.
+      render={<div id={props.domId} />}
       value={props.item.id}
+      aria-selected={props.isActive}
       data-composer-item-id={props.item.id}
       className={cn(
         "cursor-pointer select-none gap-3 rounded-lg px-3 py-2! hover:bg-transparent hover:text-inherit data-highlighted:bg-transparent data-highlighted:text-inherit",