Follow-up task from a reloaded page occasionally never runs (202 accepted, no execution)

[hiyouga]

Surfaced and root-isolated while stabilizing PR #78's e2e (see its final comment for the distilled repro): a follow-up task sent from a reloaded page intermittently goes dead under load (~1 in 4–6):

• POST /tasks answers 202, but the task never runs — trace-verified: no LLM call, no task_state change, no messages; or
• the input area is left in a stale running/steer state (a steer attempt 409s and the fallback detour strands the composer).

Reproduced with a Playwright script that never touches the subagents panel, and identically with #78's core input-forwarding change reverted — pre-existing session-runtime/stream behavior, independent of that PR. Suspect area: the post-reload stream/runtime handshake (steer-vs-new-task routing against a stale runtime entry).

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https://claude.ai/code/session_01XQX3ye1wELm1SRMku5cdni

[hiyouga]

Reopening: #227 (merged as ce44efb) fixes one of the two symptoms recorded here, not both.

Fixed — the second bullet: after a reload the composer could hold a stale running state, /steer would answer 409 not_running, and the fallback's plain POST /tasks could race the manager's idle flip, take a 409 task_in_progress, and strand the draft. The fallback now goes through the queueIfBusy task path, which is safe on both sides of that seam. Covered by packages/web/e2e/reloaded-followup.spec.mjs (verified to fail with 409 without the fix).

Still open — the first bullet, and the title of this issue: POST /tasks answers 202 but the task never runs, trace-verified with no LLM call, no task_state change and no messages. That is a server/runtime-side behavior, matching the suspicion already noted here (the post-reload stream/runtime handshake); #227 is a client-side routing change and cannot account for it. Note that a plain POST /tasks only returns 202 once startTask has launched, so the 202-without-execution path is not explained by the old fallback either.

Suggest keeping this open, scoped to the 202-accepted-no-execution case.