diff --git a/open-sse/handlers/chatCore.ts b/open-sse/handlers/chatCore.ts
index b0d1406365..dd42cc0155 100644
--- a/open-sse/handlers/chatCore.ts
+++ b/open-sse/handlers/chatCore.ts
@@ -387,6 +387,12 @@ import {
   isRpmExhausted,
 } from "../services/geminiRateLimitTracker.ts";
 import { isSmallEnoughForSemanticCache } from "../utils/estimateSize.ts";
+
+type ChatCoreExecutorResult = ReturnType<typeof normalizeExecutorResult> & {
+  _executionCredentials?: Record<string, unknown>;
+  _accountSemaphoreRelease?: () => void;
+};
+
 /**
  * Core chat handler - shared between SSE and Worker
  * Returns { success, response, status, error } for caller to handle fallback
@@ -2731,7 +2737,7 @@ export async function handleChatCore({
 
       let releaseRawResultAccountSemaphore = () => {};
       try {
-        const rawResult = await (async () => {
+        const rawResult: ChatCoreExecutorResult = await (async () => {
           let attempts = 0;
           const isModelScopeForRequest = isModelScope();
           const maxAttempts = isModelScopeForRequest ? 3 : provider === "codex" ? 3 : 1;
@@ -3550,22 +3556,24 @@ export async function handleChatCore({
       // stay aligned if this block ever runs after a path that mutates body.model (e.g. fallback).
       try {
         const retryModelId = String(translatedBody.model || effectiveModel);
-        const retryResult = await runWithCapture(providerRequestCapture, () =>
-          executor.execute({
-            model: retryModelId,
-            body: translatedBody,
-            stream: upstreamStream,
-            credentials: getExecutionCredentials(),
-            signal: streamController.signal,
-            log,
-            extendedContext,
-            upstreamExtraHeaders: buildUpstreamHeadersForExecute(retryModelId),
-            clientHeaders: buildExecutorClientHeaders(clientRawRequest?.headers, userAgent),
-            clientResponseFormat,
-            onCredentialsRefreshed,
-            skipUpstreamRetry: isCombo,
-            contextEditing: { enabled: contextEditingEnabled },
-          })
+        const retryResult = normalizeExecutorResult(
+          await runWithCapture(providerRequestCapture, () =>
+            executor.execute({
+              model: retryModelId,
+              body: translatedBody,
+              stream: upstreamStream,
+              credentials: getExecutionCredentials(),
+              signal: streamController.signal,
+              log,
+              extendedContext,
+              upstreamExtraHeaders: buildUpstreamHeadersForExecute(retryModelId),
+              clientHeaders: buildExecutorClientHeaders(clientRawRequest?.headers, userAgent),
+              clientResponseFormat,
+              onCredentialsRefreshed,
+              skipUpstreamRetry: isCombo,
+              contextEditing: { enabled: contextEditingEnabled },
+            })
+          )
         );
 
         if (retryResult.response.ok) {
diff --git a/open-sse/handlers/chatCore/executionCredentials.ts b/open-sse/handlers/chatCore/executionCredentials.ts
index 1569b61178..8eb96ab14f 100644
--- a/open-sse/handlers/chatCore/executionCredentials.ts
+++ b/open-sse/handlers/chatCore/executionCredentials.ts
@@ -20,6 +20,10 @@ type CredentialsLike =
   | null
   | undefined;
 
+type ResolvedExecutionCredentials = Record<string, unknown> & {
+  providerSpecificData: Record<string, unknown>;
+};
+
 function buildKimiThinkingMetadata(
   modelInfo: Record<string, unknown> | null | undefined,
   staticThinkingPolicy: ReturnType<typeof getKimiCodeStaticThinkingPolicy>
@@ -79,7 +83,7 @@ export function resolveExecutionCredentials(opts: {
   provider: string | null | undefined;
   ccSessionId: string | null;
   modelInfo?: Record<string, unknown> | null;
-}) {
+}): ResolvedExecutionCredentials {
   const {
     credentials,
     nativeCodexPassthrough,
diff --git a/open-sse/handlers/chatCore/upstreamTimeouts.ts b/open-sse/handlers/chatCore/upstreamTimeouts.ts
index 551b952e2c..5de972dcae 100644
--- a/open-sse/handlers/chatCore/upstreamTimeouts.ts
+++ b/open-sse/handlers/chatCore/upstreamTimeouts.ts
@@ -98,17 +98,7 @@ export function getExecutorTimeoutMs(executor: unknown, provider?: string, model
   return resolveProviderTimeoutMs(executor);
 }
 
-export function normalizeExecutorResult(
-  result:
-    | Response
-    | {
-        response: Response;
-        url?: string;
-        headers?: Record<string, string>;
-        transformedBody?: unknown;
-        transport?: string;
-      }
-): {
+export function normalizeExecutorResult(result: unknown): {
   response: Response;
   url: string;
   headers: Record<string, string>;
@@ -118,12 +108,27 @@ export function normalizeExecutorResult(
   if (result instanceof Response) {
     return { response: result, url: "", headers: {}, transformedBody: null };
   }
+  if (
+    !result ||
+    typeof result !== "object" ||
+    !("response" in result) ||
+    !(result.response instanceof Response)
+  ) {
+    throw new TypeError("Executor result must contain a Response");
+  }
+  const normalized = result as {
+    response: Response;
+    url?: string;
+    headers?: Record<string, string>;
+    transformedBody?: unknown;
+    transport?: string;
+  };
   return {
-    response: result.response,
-    url: result.url || "",
-    headers: result.headers || {},
-    transformedBody: result.transformedBody ?? null,
-    transport: result.transport,
+    response: normalized.response,
+    url: normalized.url || "",
+    headers: normalized.headers || {},
+    transformedBody: normalized.transformedBody ?? null,
+    transport: normalized.transport,
   };
 }
 
diff --git a/tests/unit/chatcore-upstream-timeouts.test.ts b/tests/unit/chatcore-upstream-timeouts.test.ts
index 7fa90b3331..affad73611 100644
--- a/tests/unit/chatcore-upstream-timeouts.test.ts
+++ b/tests/unit/chatcore-upstream-timeouts.test.ts
@@ -49,3 +49,11 @@ test("normalizeExecutorResult wraps bare Response and passes through rich result
   assert.equal(rich.url, "u");
   assert.equal(rich.headers.a, "b");
 });
+
+test("normalizeExecutorResult rejects malformed executor output", () => {
+  assert.throws(() => normalizeExecutorResult({}), /must contain a Response/);
+  assert.throws(
+    () => normalizeExecutorResult({ response: "not-a-response" }),
+    /must contain a Response/
+  );
+});