The store's updateTask treats `undefined` as "no change" and `null` as "clear field". Six places in executor.ts passed `undefined` when intending to clear worktree/branch, leaving stale references that caused tasks to get stuck in in-progress with no active session after stuck-kills, pauses, and transient error retries. Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>