fix: address review round four

- the cached-identity rung gains a finality gate: the identity value
  carries its descriptor seq and a cached row is served only when that
  seq lands in the child's own suffix, so a fork seed's replayed
  ancestor identity can never outrank the authoritative refold
  (stateVersion bumped for the state-shape change)
- the cold preparation validates the inspected header against the
  enumerated candidate's lifecycle witness; a republished id degrades to
  that child's corrupt diagnostic instead of leaking the new owner's log
- the new projection registration proves HMR disposal; companion notes
  qualify the superseded decision text and record the deliberate
  error-face asymmetry

.agents/notes/implemented/architecture/2026-08-06-subagent-list-identity-projection.md

@@ -14,14 +14,14 @@ The root cause is that the [durable-subagent-catalog decision](../feature/2026-0
 
 ## Decision
 
-mode and label are folded by the new `subagent` projection unit (pure identity, two arms), and the unit is the sole authority over the fold rules; `listChildren` no longer depends on session-query — enumeration is a subagent-owned live-preferred merge, and value retrieval walks a three-rung compute-and-discard ladder: a live child synchronously reads the registry's existing watermark cache (zero log reads); a cold child first asks the optional `sessionProjectionCache` checkpoint, and a served value is final; otherwise it pays one full `persistence.inspect` read plus one `registry.restore` fold. No index, no cache of its own, no write-back.
+mode and label are folded by the new `subagent` projection unit (pure identity, two arms), and the unit is the sole authority over the fold rules; `listChildren` no longer depends on session-query — enumeration is a subagent-owned live-preferred merge, and value retrieval walks a three-rung compute-and-discard ladder: a live child synchronously reads the registry's existing watermark cache (zero log reads); a cold child first asks the optional `sessionProjectionCache` checkpoint, and a served identity that passes the seq gate is final; otherwise it pays one full `persistence.inspect` read plus one `registry.restore` fold. No index, no cache of its own, no write-back.
 
 There are three families of escape from the per-child scan: promote mode/label into the header (the write path pays); build a durable derivation for the projection (a checkpoint ladder, or values landed during query-index rebuild with read-side reconciliation); or compute at read time (live from the watermark cache, cold from one full read). This note takes the third. "Values landed with the query index" was once this note's settled direction and was under construction for a time, then retired wholesale: query infrastructure was forced to learn domain vocabulary while the sole consumer is satisfied by read-time computation — the live child's zero reads come for free from session-projection's existing watermark cache, and the cold child's single full read is explicitly accepted as compute-and-discard. The first two routes and the retirement rationale are detailed under Alternatives considered.
 
 Key points:
 
 - **The subagent list does not depend on session-query**: enumeration is completed by a subagent-owned live-preferred merge, and mode/label is retrieved through `ctx.sessionProjections`; deployments without a query backend list as usual.
-- **Value retrieval is a three-rung compute-and-discard ladder**: a live child reads `sessionProjections.snapshot()` (the registry's existing watermark cache, zero log reads); a cold child first reads the optional `sessionProjectionCache.cachedSnapshot(header)`, using the value directly when a non-null `subagent` identity is among its values; otherwise it pays one full `persistence.inspect` read plus one `registry.restore({}, events, 0)` fold; beyond that, absent is absent — no cache of its own, no write-back, no index.
+- **Value retrieval is a three-rung compute-and-discard ladder**: a live child reads `sessionProjections.snapshot()` (the registry's existing watermark cache, zero log reads); a cold child first reads the optional `sessionProjectionCache.cachedSnapshot(header)`, using the value directly when a non-null `subagent` identity passing the seq gate (`seq >= seedLength ?? 0`) is among its values; otherwise it pays one full `persistence.inspect` read plus one `registry.restore({}, events, 0)` fold; beyond that, absent is absent — no cache of its own, no write-back, no index.
 - **The `subagent` projection unit is the sole authority over the fold rules**: the live snapshot, the cold restore, and GUI history's detached fold all compute through the registry; no second copy of descriptor-interpretation logic exists.
 - **The header, the descriptor (v2), session-persistence, session-projection(-cache), and session-query(-sqlite) are all untouched**; pre-existing data acquires exact values through one `inspect` computation the first time it is listed — no degraded unknown state, no migration.
 
@@ -36,8 +36,8 @@ It hangs beside the existing `subagentTiming` ([projection.ts](../../../../packa
 
 ```ts ignore-check
 export type SubagentIdentityProjection =
-  | { mode: 'one-shot'; label?: string }
-  | { mode: 'continuable'; label: string }
+  | { mode: 'one-shot'; label?: string; seq: number }
+  | { mode: 'continuable'; label: string; seq: number }
 
 declare module '@deepseek-ai/dsh-session-projection/types' {
   interface SessionProjectionMap {
@@ -47,7 +47,8 @@ declare module '@deepseek-ai/dsh-session-projection/types' {
 ```
 
 - The projection is pure identity, and **the projection system has no failure channel**: a unit never throws; a corrupt payload or an unrecognized version folds exactly like a log with no descriptor at all — the result is a **serializable null sentinel**: the map entry is `SubagentIdentityProjection | null`, non-optional, never undefined or an absent key. The reason: the registry's onChanged push goes through JSON serialization, where an undefined field is dropped by stringify, the client's frame validation rejects the frame, and a consumer's stored old identity would never update; null passes frames intact, and consumers replace the old identity with the sentinel. The judging discipline: consuming surfaces treat null and undefined (which only a JSON boundary dropping the key can produce) alike as no value. How "computed to nothing" is presented is the consumer's own business (see the `listChildren` four-state mapping below).
-- Label strength is decided by the descriptor schema: a continuable's label is mandatory at parse, a one-shot's was always optional; this discriminant matches the child row's strong mode/label contract below exactly.
+- Label strength is decided by the descriptor schema: a continuable's label is mandatory at parse, a one-shot's was always optional; the mode/label discriminant matches the child row's strong contract below exactly (the row carries no `seq` — it is the projection's internal own-suffix proof).
+- The identity carries `seq`: the seq of the `subagent/descriptor` event it was folded from, mandatory on both arms and absent on the null sentinel — `seq >= header.seedLength ?? 0` proves the identity was folded from the child's own suffix rather than a fork seed's replayed ancestor descriptor. The state gaining `seq` bumps the unit's `stateVersion` to 2, and existing checkpoint rows are invalidated by version mismatch per the registry contract, falling to the authoritative refold.
 - Fold rule: `subagent/descriptor` is last-wins, under the same descriptor-reset discipline as `subagentTiming` — ancestor descriptors in the fork prefix are overridden by the session's own descriptor. A corrupt or unrecognized-version payload is last-wins all the same: it resets to the null sentinel rather than keeping the prior identity, so a fork of a healthy ancestor does not inherit an identity its own descriptor cannot stand up.
 
 ### Enumeration: subagent-owned live-preferred merge
@@ -68,19 +69,20 @@ For each enumerated child, mode/label retrieval walks a three-rung ladder — co
 | Rung | Read | Cost |
 | --- | --- | --- |
 | 1: live child | `ctx.sessionProjections.snapshot(session).values.subagent` | Zero log reads — the registry's existing watermark cache, synchronous retrieval |
-| 2: cold child, cache hit | The optional `sessionProjectionCache.cachedSnapshot(header)`, used directly when a non-null `subagent` identity is among its values — identity is immutable once appended, so a served value is final regardless of the row's watermark | Zero log reads |
+| 2: cold child, cache hit | The optional `sessionProjectionCache.cachedSnapshot(header)`, used directly only when a non-null `subagent` identity satisfies `identity.seq >= header.seedLength ?? 0` — an own descriptor is immutable once appended, and the seq gate proves the value was folded from the child's own suffix, regardless of the row's watermark | Zero log reads |
 | 3: cold child, fallback | One full `persistence.inspect(id)` read + `registry.restore({}, events, 0).snapshot.values.subagent` | One full read computed per listing |
 
-- Error contract: an unmounted `ctx.sessionProjections` is a configuration error; `listChildren` checks unconditionally before enumerating and fails loudly with `SUBAGENT_CONTROL_PROJECTIONS_UNAVAILABLE` — a deployment with zero children fails just as deterministically, so an empty listing cannot mask the misconfiguration. The session store gets the same posture: an absent `ctx.get('sessions')` (a strict global read, never the caller-scope-bound property proxy) fails with `SUBAGENT_CONTROL_SESSION_STORE_UNAVAILABLE`. `SUBAGENT_CONTROL_SESSION_QUERY_UNAVAILABLE` is deleted along with the session-query dependency.
-- The cache is a purely optional acceleration layer: an absent service is skipped on a null check — no error code, no part in configuration validation (in contrast to `sessionProjections`' loud contract). Anything the second rung throws (including a poisoned unit row in the cache detonating `viewCheckpoint`) silently falls to the third rung — the cache is derived data, so its faults never produce a `corrupt` verdict; the final judgment belongs to the authoritative refold. A row whose checkpoint cut predates the descriptor naturally lacks the `subagent` key and falls through automatically, with no special-casing; a null sentinel in the row does not count either — it falls to the third rung for the authoritative refold's verdict.
+- Error contract: an unmounted `ctx.sessionProjections` is a configuration error; `listChildren` checks unconditionally before enumerating and fails loudly with `SUBAGENT_CONTROL_PROJECTIONS_UNAVAILABLE` — a deployment with zero children fails just as deterministically, so an empty listing cannot mask the misconfiguration. The session store gets the same posture: an absent `ctx.get('sessions')` (a strict global read, never the caller-scope-bound property proxy) fails with `SUBAGENT_CONTROL_SESSION_STORE_UNAVAILABLE`. The two codes map differently on the wire: apiproxy gives only `PROJECTIONS_UNAVAILABLE` a dedicated wire face, and `SESSION_STORE_UNAVAILABLE` goes through the generic internal fallback — the apiproxy composition injects `sessions` itself, so that error is unreachable in its deployment, and a dedicated mapping would violate the need principle. `SUBAGENT_CONTROL_SESSION_QUERY_UNAVAILABLE` is deleted along with the session-query dependency.
+- The cache is a purely optional acceleration layer: an absent service is skipped on a null check — no error code, no part in configuration validation (in contrast to `sessionProjections`' loud contract). Anything the second rung throws (including a poisoned unit row in the cache detonating `viewCheckpoint`) silently falls to the third rung — the cache is derived data, so its faults never produce a `corrupt` verdict; the final judgment belongs to the authoritative refold. A row whose checkpoint cut predates the descriptor naturally lacks the `subagent` key and falls through automatically, with no special-casing; a null sentinel in the row does not count either — it falls to the third rung for the authoritative refold's verdict. A count/interval checkpoint inside the creation window can land a fork seed's replayed ancestor identity in the row — the ancestor's seq falls inside the seed range, the seq gate rejects it, and it likewise falls to the third rung's verdict.
 - Per-child isolation: a single child's failed cold full read only turns that row into an `unavailable` diagnostic, naturally retried on the next listing, without affecting siblings (see the four-state mapping).
+- The cold path's lifecycle witness: preparation's result must still point at the lifecycle that was enumerated — the witness field set is the same seven fields as the old SOURCE_CONFLICT check (version, id, createdAt, cwd, parentSession, seedLength, delegationDepth); a session deleted and republished under the same id degrades to a `corrupt` row in the old parent's catalog, leaking nothing of the new owner's child.
 - Cold-read concurrency is bounded by the constant 4 — it constrains a read-only scan of local media, not deployment behavior; when a networked persistence backend appears, it is promoted to a validated `Config` field.
 - The cold-read cost, recorded honestly: only with the cache unmounted or missed does a cold child pay one full read per listing, at a cost proportional to its transcript size; the settled stance is compute-and-discard, and no cache of its own is built. The full read goes through `inspect()` into the [Session preparation](2026-08-05-session-preparation.md) cold read, so short-term repeated reads of the same id can hit its LRU for reuse, but listing does not depend on this. A live child reads zero log throughout.
 - Cancellation: the caller's signal is checked before and after each persistence read, and a read that settles only after abort is rejected, normalized to the stable error code `CANCELLED`.
 
 ### Authority model
 
-- The session log is the sole authority; this design adds no derived persistence of any kind — no index values, no checkpoints of its own, no in-process memo; the `sessionProjectionCache` checkpoint the second rung reads is an existing composition item's derived data, which this design only reads and never writes. Values are computed on read and discarded, and a value's freshness is exactly the live state or persisted revision at the moment of the read (identity is immutable, so a cached value has no staleness problem).
+- The session log is the sole authority; this design adds no derived persistence of any kind — no index values, no checkpoints of its own, no in-process memo; the `sessionProjectionCache` checkpoint the second rung reads is an existing composition item's derived data, which this design only reads and never writes. Values are computed on read and discarded, and a value's freshness is exactly the live state or persisted revision at the moment of the read (an own descriptor is immutable once appended — a cached identity past the seq gate has no staleness problem; the gate guards against seed-replayed ancestor identities).
 - The Session and persistence write paths are entirely unaware of listing and projection consumption: no event-listener write-back, no fold-on-write.
 - Enumeration and value retrieval constitute no second authorization source and make no unpublished child visible — the two sources see only published live records and durably written persisted records, consistent with the rule the durable-subagent-catalog note laid down for derived read surfaces.
 
@@ -162,7 +164,7 @@ Consuming surfaces: diagnostic handling across wire, tool, and GUI **stays entir
 
 ## Verification
 
-`packages/subagent/subagent/tests/list-children.spec.ts` is rewritten to this contract: live-only listing without persistence, query services, or the continuation runtime; with the registry absent, even zero children loudly report `SUBAGENT_CONTROL_PROJECTIONS_UNAVAILABLE`; a live child incurs zero `inspect` throughout while a cold child incurs exactly one per listing; multiple descriptors resolve last-wins to the final one; corrupt payloads and unknown versions fold to `corrupt`; a cold-read failure maps to `unavailable` and retries on the next listing; the ancestor descriptor in a fork seed forms a row under that identity (pinning deviation one); ordinary forks and descendants without a subagent origin neither enter the list nor count toward `hasChildren`; `createdAt`-then-id ordering; an unmounted provider does not affect listing; compacted and uncompacted twins list identically; the three cases of pre-abort, persistence listing, and cold-read cancellation all normalize to `CANCELLED`; the empty list and stable error codes. A hostile-unit dual-path probe (`apply` lazily poisons, `view` detonates) proves that any registered unit's fold/schema throw on this child's log is contained as that child's `corrupt` row on both the live and the cold retrieval paths, with siblings and the listing itself unaffected. Four second-rung cases: a real-composition cache hit with zero `inspect`, an in-row identity absence (null sentinel or absent key) falling through, an absent cache service falling through, and a poisoned cache row silently falling through to the refold. The `tool-subagent-control` list-agents tests are updated for the narrowed load requirement; `optional-session-query.spec.ts` is deleted with the dependency it guarded; the existing keyless snapshots (`subagent-list-agents` among others) are unchanged, pinning that the healthy path's wire and model-visible surfaces did not move; a new keyless snapshot, `subagent-diagnostic` (examples/headless-agent), pins the four-state mapping's diagnostic classification — the model-visible changes such as descriptor-less settled debris becoming a `corrupt` row.
+`packages/subagent/subagent/tests/list-children.spec.ts` is rewritten to this contract: live-only listing without persistence, query services, or the continuation runtime; with the registry absent, even zero children loudly report `SUBAGENT_CONTROL_PROJECTIONS_UNAVAILABLE`; a live child incurs zero `inspect` throughout while a cold child incurs exactly one per listing; multiple descriptors resolve last-wins to the final one; corrupt payloads and unknown versions fold to `corrupt`; a cold-read failure maps to `unavailable` and retries on the next listing; the ancestor descriptor in a fork seed forms a row under that identity (pinning deviation one); ordinary forks and descendants without a subagent origin neither enter the list nor count toward `hasChildren`; `createdAt`-then-id ordering; an unmounted provider does not affect listing; compacted and uncompacted twins list identically; the three cases of pre-abort, persistence listing, and cold-read cancellation all normalize to `CANCELLED`; the empty list and stable error codes. A hostile-unit dual-path probe (`apply` lazily poisons, `view` detonates) proves that any registered unit's fold/schema throw on this child's log is contained as that child's `corrupt` row on both the live and the cold retrieval paths, with siblings and the listing itself unaffected. Second-rung cases: an own-seq identity used directly with zero `inspect`, a fork seed's ancestor identity (seq inside the seed range) rejected by the gate and falling through, an in-row identity absence (null sentinel or absent key) falling through, an absent cache service falling through, and a poisoned cache row silently falling through to the refold; cold-path lifecycle tampering degrades to `corrupt` field by witness field (`it.each` over the seven). The `tool-subagent-control` list-agents tests are updated for the narrowed load requirement; `optional-session-query.spec.ts` is deleted with the dependency it guarded; the existing keyless snapshots (`subagent-list-agents` among others) are unchanged, pinning that the healthy path's wire and model-visible surfaces did not move; a new keyless snapshot, `subagent-diagnostic` (examples/headless-agent), pins the four-state mapping's diagnostic classification — the model-visible changes such as descriptor-less settled debris becoming a `corrupt` row.
 
 ## Consequences