fix: defer session-lock release on dispose/abort inside active write

Kun.Long · Kun.Long · commit 881a33b32706 · 2026-06-05T01:17:38.000+08:00
When disposeHeldLockAfterRetainedIdle or releaseHeldLockWithFence
are called from within the active retained-write context
(waitForRetainedLockIdle returns false), register a deferred
release callback on retainedLockIdleWaiters instead of silently
returning.

This preserves write serialization (no concurrent writes from
force-release) while ensuring the lock is eventually released
when the retained-use counter drains to zero.

Previously the early return leaked the lock in memory and on disk,
causing subsequent sub-agents to time out with "session file locked"
errors when the web GUI rapidly switches sessions.
diff --git a/src/agents/embedded-agent-runner/run/attempt.session-lock.ts b/src/agents/embedded-agent-runner/run/attempt.session-lock.ts
@@ -797,6 +797,15 @@ export async function createEmbeddedAttemptSessionLockController(params: {
     const drainOwner = await beginHeldLockDrain();
     try {
       if (!(await waitForRetainedLockIdle())) {
+        // Inside the active retained-write context: releasing synchronously
+        // would deadlock, and force-releasing would let another attempt
+        // overlap writes and stale the session fence.  Defer release to
+        // when the retained-use counter drains to zero.
+        const pending = heldLock;
+        retainedLockIdleWaiters.add(() => {
+          if (heldLock === pending) heldLock = undefined;
+          pending?.release().catch(() => {});
+        });
         return;
       }
       if (!heldLock) {
@@ -854,6 +863,14 @@ export async function createEmbeddedAttemptSessionLockController(params: {
     const drainOwner = await beginHeldLockDrain();
     try {
       if (!(await waitForRetainedLockIdle())) {
+        // Inside the active retained-write context during teardown.
+        // Defer release to after the in-flight write completes so we
+        // preserve write serialization and release the lock reliably.
+        const pending = heldLock;
+        retainedLockIdleWaiters.add(() => {
+          if (heldLock === pending) heldLock = undefined;
+          pending?.release().catch(() => {});
+        });
         return;
       }
       if (!heldLock) {
