fix: replace stale codex threads

src/backend/codex-stdio.ts

@@ -453,7 +453,8 @@ async function runCodexStdioTurnWithSession(options: CodexStdioTurnOptions, sess
       } catch (error) {
         const failure = normalizeFailure(error);
         if (!isMissingRolloutThreadResumeFailure(failure)) throw error;
-        throw threadResumeFailure(options.threadId, failure);
+        emitEvent({ type: "backend_status", payload: threadResumeNonResumablePayload(options.threadId, failure) });
+        threadId = await startThread("thread/replacement-start");
       }
     } else {
       threadId = await startThread();
@@ -930,6 +931,18 @@ function threadResumeFailure(threadId: string, error: CodexStdioFailure): CodexS
   );
 }
 
+function threadResumeNonResumablePayload(threadId: string, error: CodexStdioFailure): JsonRecord {
+  return {
+    phase: "thread/resume:non-resumable",
+    requestedThreadId: threadId,
+    originalFailureKind: error.failureKind,
+    originalPhase: error.phase,
+    originalDetails: redactJson(error.details),
+    replacement: "thread/start",
+    valuesPrinted: false,
+  };
+}
+
 function classifyCodexErrorRecord(error: JsonRecord, fallback: FailureKind): FailureKind {
   const parts: string[] = [];
   if (typeof error.message === "string") parts.push(error.message);