[BUG] Scheduled task dispatch acknowledged by renderer but no session starts; 'Cleared stale pending dispatch' after 12 min, lastRunAt stamped anyway (3 of 18 tasks lost overnight)

Thank you for the desktop scheduler — running ~60 unattended tasks a day on it has genuinely changed how I work, and the recent lastRunAt/nextRunAt visibility in the task list is appreciated.

What happened

A scheduled task is dispatched, the renderer acknowledges it, no session is ever started, and ~12 minutes later the main process logs Cleared stale pending dispatch. lastRunAt is stamped anyway, so the task list shows the task as having run. On one night this hit 4 of 18 dispatches; 3 of them never ran at all.

~/Library/Logs/Claude/main.log, 2026-09-08 (local time), redacted only to task names:

03:12:59 [info] [CCDScheduledTasks] Spawning new session for scheduled task voc-weekly-incremental {...}
03:12:59 [info] [CCDScheduledTasks] Dispatch acknowledged by renderer: voc-weekly-incremental
03:21:00 [warn] [CCDScheduledTasks] Cleared stale pending dispatch for: voc-weekly-incremental
   (no "Starting local session" for that task's folder all night; lastRunAt now shows 2026-09-08T09:21:00Z)

03:36:05 ... Spawning new session for scheduled task daily-reading
03:36:05 ... Dispatch acknowledged by renderer: daily-reading
03:51:00 [warn] Cleared stale pending dispatch for: daily-reading        (never ran)

04:28:23 ... Spawning new session for scheduled task singularity-research-weekly
04:28:23 ... Dispatch acknowledged by renderer: singularity-research-weekly
04:40:00 [warn] Cleared stale pending dispatch for: singularity-research-weekly   (never ran)

08:35:27 [info] Delaying dispatch for morning-checkin-daily by 265s (jitter)
08:39:52 ... Spawning new session for scheduled task morning-checkin-daily
08:39:52 ... Dispatch acknowledged by renderer: morning-checkin-daily
08:51:27 [warn] Cleared stale pending dispatch for: morning-checkin-daily
09:51:41 [info] Confirmed task run for: morning-checkin-daily          (started 72 min late, on its own)

A healthy dispatch on the same night is the triple Spawning new session → Dispatch acknowledged by renderer → Confirmed task run within ~1 s (14 of 18 did this).

The same Cleared stale pending dispatch warning also appears in this log on 2026-08-29 (ig-publish-daily and a one-time task, 3×) and 2026-08-31 (early-run-sunday-weekly, which likewise stamped lastRunAt with no session created).

Environment

• Claude desktop app 1.46388.4 (Code tab), Claude Code 2.1.260, macOS 26.x (Darwin 25.6.0), Apple silicon
• Laptop awake, on AC power the whole time; app running since the previous evening; no sleep/wake events near the 03:xx or 08:3x dispatches (checked pmset -g log)
• Interactive sessions were open in other folders at 08:39 (one actively running)
• Also visible the same night: Skipping dispatch for <task>: global_limit (active=3, limit=3) for ~9 consecutive minutes — the concurrency cap in #91387. The lost dispatches above were not skipped by that cap; they were acknowledged and then went nowhere.

Expected

Either the acknowledged dispatch starts a session, or the stale-clear re-dispatches it promptly (the 08:39 one eventually did, 60 min after the clear; the three overnight ones never did). lastRunAt should not advance for a run that never created a session — for a daily task that makes a lost run invisible until someone reads the log.

Impact / workaround

Three daily/weekly tasks silently produced nothing, and the task list reported them as run. I now grep the log every morning for Cleared stale pending dispatch and re-fire any lost task as a one-time task.

Happy to share the full log excerpt or run a debug build if that helps.