diff --git a/apps/server/src/provider/Layers/CodexProvider.ts b/apps/server/src/provider/Layers/CodexProvider.ts
index 31d02f42c5f4..a0e2b744c2a7 100644
--- a/apps/server/src/provider/Layers/CodexProvider.ts
+++ b/apps/server/src/provider/Layers/CodexProvider.ts
@@ -146,7 +146,8 @@ export function mapCodexModelCapabilities(
   model: CodexSchema.V2ModelListResponse__Model,
 ): ModelCapabilities {
   const reasoningOptions = model.supportedReasoningEfforts.map(({ reasoningEffort }) =>
-    reasoningEffort === model.defaultReasoningEffort
+    reasoningEffort ===
+    (codexModelFamily(model.model) === "gpt-6-astra" ? "medium" : model.defaultReasoningEffort)
       ? {
           id: reasoningEffort,
           label: reasoningEffortLabel(reasoningEffort),
diff --git a/apps/server/src/provider/model-manifest.json b/apps/server/src/provider/model-manifest.json
index bca9f09eee8c..9ea0c0063eb5 100644
--- a/apps/server/src/provider/model-manifest.json
+++ b/apps/server/src/provider/model-manifest.json
@@ -1,6 +1,6 @@
 {
   "version": 1,
-  "updatedAt": "2026-09-04T19:10:48Z",
+  "updatedAt": "2026-09-12T00:41:55Z",
   "currentModels": {
     "codex": [
       "gpt-6-astra",
@@ -16,7 +16,7 @@
   "providers": {
     "claudeAgent": {
       "defaults": {
-        "chat": "claude-sonnet-5"
+        "chat": "claude-fable-5-1"
       },
       "profiles": {
         "fable-5": {
@@ -33,12 +33,12 @@
                   },
                   {
                     "id": "medium",
-                    "label": "Medium"
+                    "label": "Medium",
+                    "isDefault": true
                   },
                   {
                     "id": "high",
-                    "label": "High",
-                    "isDefault": true
+                    "label": "High"
                   },
                   {
                     "id": "xhigh",
diff --git a/packages/contracts/src/model.ts b/packages/contracts/src/model.ts
index bce1a766bc9b..0882aef51d05 100644
--- a/packages/contracts/src/model.ts
+++ b/packages/contracts/src/model.ts
@@ -149,7 +149,7 @@ const CURSOR_DRIVER_KIND = ProviderDriverKind.make("cursor");
 const GROK_DRIVER_KIND = ProviderDriverKind.make("grok");
 const OPENCODE_DRIVER_KIND = ProviderDriverKind.make("opencode");
 
-export const DEFAULT_MODEL = "gpt-5.6-sol";
+export const DEFAULT_MODEL = "gpt-6-astra";
 
 /**
  * Codex default-model preference, most preferred first. The provider snapshot
@@ -157,6 +157,7 @@ export const DEFAULT_MODEL = "gpt-5.6-sol";
  * default; when none are available, Codex's own `isDefault` flag wins.
  */
 export const PREFERRED_DEFAULT_CODEX_MODELS: ReadonlyArray<string> = [
+  DEFAULT_MODEL,
   "gpt-5.6-sol",
   "gpt-5.6-terra",
 ];
@@ -167,7 +168,7 @@ export const DEFAULT_TEXT_GENERATION_REASONING_EFFORT = "low";
 
 export const DEFAULT_MODEL_BY_PROVIDER: Partial<Record<ProviderDriverKind, string>> = {
   [CODEX_DRIVER_KIND]: DEFAULT_MODEL,
-  [CLAUDE_DRIVER_KIND]: "claude-sonnet-5",
+  [CLAUDE_DRIVER_KIND]: "claude-fable-5-1",
   [CURSOR_DRIVER_KIND]: "auto",
   // Product slug, not an ACP model id. The Grok adapter treats it as "the session's current model".
   [GROK_DRIVER_KIND]: "grok-build",