diff --git a/apps/server/src/orchestration-v2/Adapters/CodexAdapterV2.test.ts b/apps/server/src/orchestration-v2/Adapters/CodexAdapterV2.test.ts
index 85748fa056e7..78015dac1d89 100644
--- a/apps/server/src/orchestration-v2/Adapters/CodexAdapterV2.test.ts
+++ b/apps/server/src/orchestration-v2/Adapters/CodexAdapterV2.test.ts
@@ -3869,7 +3869,9 @@ describe("CodexAdapterV2 post-settle continuation", () => {
       ),
   );
 
-  const backgroundStopCases = [true, false, "still_running"] as const;
+  // "thread_unloaded": the thread was settled, so T3 unsubscribed and Codex
+  // unloaded it (killing its terminals) before Stop arrived.
+  const backgroundStopCases = [true, false, "still_running", "thread_unloaded"] as const;
   const makeBackgroundStopTranscript = (terminated: (typeof backgroundStopCases)[number]) => {
     const stillRunning = terminated === "still_running";
     return makeCodexReplayTranscript({
@@ -3888,9 +3890,15 @@ describe("CodexAdapterV2 post-settle continuation", () => {
         {
           type: "emit_inbound",
           label: "terminate-background-command",
-          frame: { id: 4, result: { terminated: terminated === true } },
+          frame:
+            terminated === "thread_unloaded"
+              ? {
+                  id: 4,
+                  error: { code: -32600, message: `thread not found: ${BG_NATIVE_THREAD}` },
+                }
+              : { id: 4, result: { terminated: terminated === true } },
         },
-        ...(terminated !== true
+        ...(terminated === false || stillRunning
           ? [
               {
                 type: "expect_outbound" as const,
diff --git a/apps/server/src/orchestration-v2/Adapters/CodexAdapterV2.ts b/apps/server/src/orchestration-v2/Adapters/CodexAdapterV2.ts
index 8da6ffe4357d..f00dba6d4a62 100644
--- a/apps/server/src/orchestration-v2/Adapters/CodexAdapterV2.ts
+++ b/apps/server/src/orchestration-v2/Adapters/CodexAdapterV2.ts
@@ -2053,6 +2053,13 @@ export function makeCodexAdapterV2(adapterOptions: CodexAdapterV2Options): Provi
                 Effect.catchTags({
                   CodexAppServerProcessExitedError: () => Effect.succeed({ terminated: true }),
                   CodexAppServerInputStreamEndedError: () => Effect.succeed({ terminated: true }),
+                  // The thread is unloaded, as Codex does a minute after a
+                  // settle or archive unsubscribes it. Unloading kills the
+                  // thread's terminals, so nothing is left to stop.
+                  CodexAppServerRequestError: (error) =>
+                    error.code === -32600 && error.errorMessage.startsWith("thread not found:")
+                      ? Effect.succeed({ terminated: true })
+                      : Effect.fail(error),
                 }),
               );
             const result = yield* decodeCodexBackgroundTerminalTerminateResponse(response);