[wusijian007]

…6 / §3)

The final v3.1 item: resource control for background tasks. Two mechanisms, the task-dependency DAG explicitly NOT built (Claude Code has no DAG scheduler; it would be a parallel workflow engine against the repo's "extend primitives, no control plane" spirit — see docs/v3-kernel-roadmap.md §3 M3.6).

Concurrency cap — createTaskScheduler({ store, maxConcurrent }) is a FIFO admission semaphore: tasks beyond the cap stay "pending" (queued) until a running one reaches a terminal state and frees a slot. maxConcurrent 0 (default) = unlimited, so this is non-breaking and opt-in. The run+terminal-state logic is extracted into a shared runManagedTaskBody used by both startManagedTask (unbounded, unchanged) and the scheduler. The cap is a strong guarantee only for in-process managed tasks the scheduler admits; detached out-of-process workers are not gated across processes (known v1 limit, documented).

Graceful kill — markTaskKilled now terminates gracefully: in-process tasks cancel cooperatively via their AbortSignal (no signal sent), and a detached worker's pid gets SIGTERM -> graceMs grace -> SIGKILL only if still alive. The signal sender is injectable (signalProcess) so the escalation sequence is asserted offline without real processes. Windows has no real SIGTERM (process.kill -> TerminateProcess) so the first signal already terminates and the escalation is a documented no-op.

• core: createTaskScheduler + TaskScheduler, runManagedTaskBody refactor, graceful markTaskKilled (KillOptions/ProcessSignaler), ToolContext.taskScheduler.
• tools: runBackgroundSubAgent routes through context.taskScheduler when present, else startManagedTask (unchanged).
• cli: MYAGENT_MAX_BACKGROUND_TASKS env builds the scheduler in the agent path.
• tests: 6 new — cap+queue (deterministic via started barriers), queue-cancel, unbounded default, SIGTERM->SIGKILL escalation, SIGTERM honored (no escalation), in-process pid not signaled.
• docs: CLAUDE.md background-tasks + env; roadmap M3.6 marked delivered.

220 tests pass (+6).