Real Codex sessions emit records like
`{"type":"event_msg","payload":{"type":"error",...}}` and
`{"type":"event_msg","payload":{"type":"approval_request",...}}`.
readLastJsonlEntry only exposed the top-level `type`, so the codex
plugin's activity switch matched `event_msg` and decayed to ready/idle,
never surfacing `blocked` or `waiting_input`. The approval_request/error
branches were dead code for payload-wrapped sessions, which is the exact
format this PR series is migrating to.
- readLastJsonlEntry now returns payloadType alongside lastType.
- Codex getActivityState prefers payloadType when present and classifies
task_started/agent_reasoning as active, task_complete as ready, and
the approval/error variants as waiting_input/blocked.
- New tests cover the payload-wrapped approval_request, exec_approval_request,
error, task_started, and task_complete cases end-to-end.
- Core utils gains coverage for payloadType extraction and null fallbacks.
Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>
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