diff --git a/extensions/codex/src/app-server/thread-lifecycle.test.ts b/extensions/codex/src/app-server/thread-lifecycle.test.ts
index 2a2255551b0c..81f9f80721d5 100644
--- a/extensions/codex/src/app-server/thread-lifecycle.test.ts
+++ b/extensions/codex/src/app-server/thread-lifecycle.test.ts
@@ -3465,8 +3465,7 @@ describe("Codex app-server supervised branch lifecycle", () => {
           "native-provider",
           typeof reasoningEffort === "string" ? reasoningEffort : null,
         );
-        const { reasoningEffort: _reasoningEffort, ...withoutReasoningEffort } = response;
-        return withoutReasoningEffort;
+        return response;
       }
       if (method === "thread/resume") {
         const config = (requestParams as { config?: Record<string, unknown> }).config;
diff --git a/extensions/codex/src/app-server/thread-supervision.ts b/extensions/codex/src/app-server/thread-supervision.ts
index ee7823394560..726ff5bc76f8 100644
--- a/extensions/codex/src/app-server/thread-supervision.ts
+++ b/extensions/codex/src/app-server/thread-supervision.ts
@@ -29,12 +29,11 @@ import type {
   CodexTurnEnvironmentParams,
   JsonObject,
 } from "./protocol.js";
-import {
-  resolveCodexBindingReasoningEffort,
-  type CodexAppServerBindingIdentity,
-  type CodexAppServerBindingStore,
-  type CodexAppServerPendingSupervisionBranch,
-  type CodexAppServerThreadBinding,
+import type {
+  CodexAppServerBindingIdentity,
+  CodexAppServerBindingStore,
+  CodexAppServerPendingSupervisionBranch,
+  CodexAppServerThreadBinding,
 } from "./session-binding.js";
 import {
   CodexThreadBindingConflictAfterCleanupError,
@@ -236,10 +235,6 @@ export async function materializePendingSupervisionBranch(
       modelProvider: nativeModelProvider,
       operation: "thread/start response",
     });
-    const nativeReasoningEffort = resolveCodexBindingReasoningEffort(
-      startResponse.reasoningEffort,
-      probeResponse.reasoningEffort,
-    );
     if (params.restrictedToolSurface) {
       await params.lifecycleTiming.measure("restricted-tool-surface-mcp-attestation", () =>
         attestCodexRestrictedToolSurfaceMcpServersDisabled(
@@ -312,7 +307,7 @@ export async function materializePendingSupervisionBranch(
           ...params.bindingPatch,
           model: nativeModel,
           modelProvider: bindingModelProvider,
-          reasoningEffort: nativeReasoningEffort,
+          reasoningEffort: startResponse.reasoningEffort,
           historyCoveredThrough,
         },
       });
@@ -373,7 +368,7 @@ export async function materializePendingSupervisionBranch(
       pendingSupervisionBranch: undefined,
       model: nativeModel,
       modelProvider: bindingModelProvider,
-      reasoningEffort: nativeReasoningEffort,
+      reasoningEffort: startResponse.reasoningEffort,
       historyCoveredThrough,
       lifecycle: { action: "forked" },
     };