diff --git a/tests/broker-subscriptions.test.mjs b/tests/broker-subscriptions.test.mjs
index cd8eef5cb..db8c2f76c 100644
--- a/tests/broker-subscriptions.test.mjs
+++ b/tests/broker-subscriptions.test.mjs
@@ -741,7 +741,7 @@ test("broker rejects an explicit unsubscribe that would queue behind a hung clea
 });
 
 test("broker rolls back child threads inherited through a failed provisional claim", async (t) => {
-  const broker = startBroker("with-delayed-subagent");
+  const broker = startBroker("with-resume-inherited-subagent");
   t.after(() => broker.stop());
   assert.equal(await broker.listening(), true, `broker never listened: ${broker.stderr()}`);
 
@@ -754,8 +754,9 @@ test("broker rolls back child threads inherited through a failed provisional cla
   firstClient.destroy();
   await waitForUnsubscribes(broker.statePath, [threadId]);
 
-  // The resume fails after 250 ms; the delayed child arrives at 100 ms while the
-  // claim is still open, so the claiming socket inherits it.
+  // The child, and the grandchild under it, arrive while this resume's claim is open, and
+  // the resume fails only after both — a chain the fixture drives off the resume itself, so
+  // no part of it depends on how fast this client got here.
   const secondClient = await connectClient(broker.socketPath);
   await assert.rejects(
     secondClient.request("thread/resume", { threadId, persistFullHistory: true }),
diff --git a/tests/fake-codex-fixture.mjs b/tests/fake-codex-fixture.mjs
index 448adb8c9..24b155e93 100644
--- a/tests/fake-codex-fixture.mjs
+++ b/tests/fake-codex-fixture.mjs
@@ -372,6 +372,38 @@ rl.on("line", (line) => {
         if (BEHAVIOR === "permission-profiles-unsupported" && message.params.config) {
           throw new Error("unknown field config.default_permissions");
         }
+        if (BEHAVIOR === "with-resume-inherited-subagent" && message.params.persistFullHistory === true) {
+          // A causal chain, not a stopwatch: the child arrives while THIS resume's claim is
+          // open, the grandchild under it, and only then does the resume fail. Hanging any of
+          // it off turn/start instead made the test depend on the client getting from
+          // turn/start to resume inside 100ms, which a loaded runner does not promise.
+          const parentThread = ensureThread(state, message.params.threadId);
+          setTimeout(() => {
+            const childState = loadState();
+            const child = nextThread(childState, parentThread.cwd, true, parentThread.sandbox, { parentThreadId: parentThread.id });
+            const childRecord = ensureThread(childState, child.id);
+            childRecord.name = "delayed-design-challenger";
+            childState.subscriptions = [...new Set([...(childState.subscriptions || []), child.id])];
+            saveState(childState);
+            const childTurnId = nextTurnId(childState);
+            send({ method: "thread/started", params: { thread: { ...buildThread(childRecord), name: childRecord.name, agentNickname: childRecord.name } } });
+            send({ method: "turn/started", params: { threadId: child.id, turn: buildTurn(childTurnId) } });
+            send({ method: "turn/completed", params: { threadId: child.id, turn: buildTurn(childTurnId, "completed") } });
+            setTimeout(() => {
+              const nestedState = loadState();
+              const grandchild = nextThread(nestedState, parentThread.cwd, true, parentThread.sandbox, { parentThreadId: child.id });
+              const grandchildRecord = ensureThread(nestedState, grandchild.id);
+              grandchildRecord.name = "delayed-design-grandchild";
+              nestedState.subscriptions = [...new Set([...(nestedState.subscriptions || []), grandchild.id])];
+              saveState(nestedState);
+              send({ method: "thread/started", params: { thread: { ...buildThread(grandchildRecord), name: grandchildRecord.name, agentNickname: grandchildRecord.name } } });
+              setTimeout(() => {
+                send({ id: message.id, error: { code: -32000, message: "forced resume failure after child arrival" } });
+              }, 50);
+            }, 50);
+          }, 50);
+          break;
+        }
         if (BEHAVIOR === "with-delayed-subagent" && message.params.persistFullHistory === true) {
           state.nestedSubagentRequested = true;
           saveState(state);
diff --git a/tests/locking.test.mjs b/tests/locking.test.mjs
index eebc69559..a4761674e 100644
--- a/tests/locking.test.mjs
+++ b/tests/locking.test.mjs
@@ -142,8 +142,13 @@ test("stale legacy lock without process identity does not follow a reused PID fo
   const oldTime = new Date(Date.now() - 60000);
   fs.utimesSync(lockDir, oldTime, oldTime);
 
+  // Returning at all is the assertion, as above: with staleMs at 30s, a successor can only
+  // exist because the legacy lock was reclaimed on the spot. The budget is deliberately far
+  // wider than the work needs -- acquireLockSync() checks its deadline after a failed attempt,
+  // so under a loaded runner a single stalled attempt used to expire a 200ms budget in the
+  // moment between the reclaim and the retry that would have succeeded.
   const successor = acquireLockSync(lockDir, {
-    timeoutMs: 200,
+    timeoutMs: 5000,
     staleMs: 30000,
     retryDelayMs: 5,
     isProcessRunning: () => true