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+# Subagent Delivery Watchdog State Shape
+
+This directory is reserved for file-backed state used by the subagent delivery watchdog.
+
+## Purpose
+
+The watchdog tracks whether a subagent dispatch has a matching completion receipt and whether the main thread has enough evidence to classify the run state without guessing.
+
+This task defines the **state JSON shape only**. It does **not** implement receipt write logic, status recomputation, recovery behavior, or live integration.
+
+## Suggested file model
+
+One JSON document per dispatched subagent run.
+
+Example path pattern:
+
+- `state/subagent-delivery-watchdog/<runId>.json`
+
+## State JSON shape
+
+```json
+{
+  "runId": "run_2026_04_24_abc123",
+  "childSessionKey": "agent:engineering:subagent:cd236af1-7d4a-4f4e-bccd-04e4f9a96c02",
+  "dispatchAt": "2026-04-24T10:40:00+08:00",
+  "expectedBy": "2026-04-24T10:50:00+08:00",
+  "completionReceivedAt": null,
+  "forwardedToMain": false,
+  "resultSource": null,
+  "status": "active",
+  "statusUpdatedAt": "2026-04-24T10:40:00+08:00",
+  "statusReason": "Dispatch receipt exists and SLA has not been crossed.",
+  "recoveryAction": null,
+  "recoveryAttemptCount": 0,
+  "lastRecoveryAt": null,
+  "notes": []
+}
+```
+
+## Receipt fields
+
+### Dispatch receipt fields
+
+- `runId`: unique identifier for the dispatched subagent run.
+- `childSessionKey`: session key or stable child-session identifier used to correlate the run.
+- `dispatchAt`: ISO-8601 timestamp for when the subagent was dispatched.
+- `expectedBy`: ISO-8601 timestamp for the watchdog SLA / expected completion deadline.
+
+### Completion receipt fields
+
+- `completionReceivedAt`: ISO-8601 timestamp for when a completion receipt was observed by the owner thread; `null` if not yet observed.
+- `forwardedToMain`: boolean indicating whether the completion/result was confirmed forwarded back to the main thread.
+- `resultSource`: source label for the result evidence, for example `completion_event`, `history_fetch`, or `manual_recovery`; `null` if no completion evidence exists yet.
+
+## Status fields
+
+- `status`: current watchdog classification. Expected values include:
+  - `active`
+  - `suspect_delivery_failure`
+  - `done_but_not_forwarded`
+  - `completed`
+  - `recovered`
+  - `blocked`
+- `statusUpdatedAt`: ISO-8601 timestamp of the latest status evaluation/update.
+- `statusReason`: short human-readable explanation for why the current status was assigned.
+
+## Optional supporting fields
+
+These fields are not a substitute for the required receipt/status fields, but they can support later tasks safely.
+
+- `recoveryAction`: pending or last recovery decision, if any.
+- `recoveryAttemptCount`: number of recovery attempts already made.
+- `lastRecoveryAt`: ISO-8601 timestamp of the last recovery attempt.
+- `notes`: append-only diagnostic notes.
+
+## Constraints
+
+- Receipt fields and status fields must remain explicit in stored state.
+- `completionReceivedAt`, `resultSource`, and recovery-related fields may be `null` before any completion signal exists.
+- `forwardedToMain` should remain `false` until the return path to the main thread is actually confirmed.
+- Status must be derived from evidence; later implementation should not infer success without a receipt or equivalent recovery proof.