Wave-6 decomposition (mem engine): eleven tasks per the pg-wave rhythm — foundations (crate scaffold, MemStore::new isolation, guarded state core, wake routing, wasm32 gate from birth), seam-tx (the load-bearing tx overlay: eleven staged _tx methods, commit-merge + wake-at-commit — pg-fix-tx-wake's discipline structural from the start, drop = discard trivial, with_tx panic posture), mechanisms mutually parallel (notify-listen close-at-engine-drop/no-replay/never-coalesced; queues = ADR-010 machine driver-free with the equal-jitter curve and opts resolution as ADR-012 §2's third owner; streams log+offsets+trim; locks TTL registry, no busy-path analog), scheduler-outbox (tick/catch-up-64/leadership through the __alkstore_scheduler lock, engine-uniform per ADR-009 §4; outbox over queues with the 60/5/5 seam stamp), integration (suite third StoreFactory column green on host under a current-thread flavor, wasm32 acceptance items, engine-mem.md to implementation-complete), and the review-wave-6 gate (born-pinned audit: conformance read, discharge-map wiring, wasm items, three-way equivalence green, class-1 window discipline). Window riders: suite-harness-current-thread — the wave's one suite-side pre-task, past_stamp_sleep's blocking sleep goes async per review 003's properties.rs:1683 posture note, enabling the current-thread flavor; pg-fix-scheduler-tick-seam — review 003 Finding 1, the cfg(test) transient-fault seam driving the real tick_with_retries through retry-then-success and exhaustion arms (the last uncovered wave-4 hardening arm, sqlite-commit-error-arm pattern). Task hygiene: pg-fix-open-path frontmatter fixed (unquoted 'max_size: 0' colon-space inside the name scalar broke YAML parsing — taskgraph validate had been red one-error since the wave-4 fix-batch decomposition; also restores review-wave-4-fixes' dependency resolution). implementation.md: wave-6 table row → decomposed, task-set listing with the parallelism note (rider + pre-task independent of the mem chain; rider closes before the gate), wave-6 decomposition bullet in the review-rounds record. Docs-only change; verified taskgraph validate (60 tasks, no cycles), cargo fmt --check, cross-reference read

tasks/mem-engine-queues.md

@@ -0,0 +1,86 @@
+---
+id: mem-engine-queues
+name: Mem engine — queues (in-memory job table, ADR-010 state machine, engine-owned backoff curve)
+status: pending
+depends_on: [mem-engine-seam-tx, mem-engine-notify-listen]
+scope: moderate
+risk: medium
+impact: component
+level: implementation
+tags: [wave-6, mem-engine, queues]
+---
+
+## Description
+
+The queue mechanism: the
+[ADR-010](../architecture/decisions/010-queue-semantics-depth.md) state
+machine realized over an in-memory job table — all driver-free.
+
+- **`Queue` handle surface** ([ADR-019](../architecture/decisions/019-mechanism-handle-surfaces.md)
+  §1): `enqueue` (auto-commit, resolving over the handle's opts),
+  `claim_one`/`claim_batch` (extents: `n <= 0` claims nothing),
+  `ack_batch` (per-id uniform predicate, lapsed/non-claimed silently
+  not counted), `cancel` (unconditional delete), `get_job`, and the
+  queue-scoped `sweep_expired` (no-stranded-rows: *every* past-expiry
+  row in any state moves to dead + retention enforcement).
+- **Claim discipline**: exactly-once handout, `worker_id` claimant
+  identity (non-empty), claim ordering priority DESC → ready-time →
+  enqueue FIFO. Visibility expiry and reclaim — **reclaim consumes an
+  attempt**; the dual-execution window is contract-honest (a worker
+  past its deadline may complete its work but its ack will not land).
+  Under a single engine instance the claim race is in-process — the
+  guarded merge discipline must still make claim-vs-claim atomic and
+  claim-vs-expiry deterministic at the row level.
+- **JobHandle ops** ([ADR-019](../architecture/decisions/019-mechanism-handle-surfaces.md)
+  §3): `ack`/`retry`/`fail` one-shot terminal, `heartbeat(&self)`
+  repeatable absolute-reset renewal; the uniform validity predicate
+  (processing + unexpired deadline); deadline lapse refuses all ops,
+  false not error. `retry(err, None)` computes the queue's
+  **equal-jitter exponential delay — mem's own implementation**
+  ([ADR-012](../architecture/decisions/012-forked-substrate-design.md)
+  §2's one-owner rule, third owner; the SQLite engine's `resolution.rs`
+  is reference, not a dependency); `retry(err, Some(d))` overrides
+  verbatim; `fail` = immediate dead-letter with the engine-default
+  strings (`"failed"` / `"max attempts exceeded"`).
+- **Opts stamping** ([ADR-020](../architecture/decisions/020-enqueue-opt-semantics-and-bridges.md)):
+  resolution rules (delay-over-`run_at`, relative `expires`) are
+  mem-owned (third copy); handle-enqueue stamps the handle's opts;
+  the tx/no-handle shapes stamped plain 300/3/5/none in
+  `mem-engine-seam-tx`. `get_job` shows resolved values.
+- **Dead letters**: move-to-dead storage, `get_job` sees dead rows
+  (`last_error`/`died_at`), `dead_letter_retention_s` (None = forever)
+  enforced by `sweep_expired`. No redrive API.
+- Timestamps and expiry checks are tokio-time/clock reads against the
+  state core's clock accessor; expiry is *checked* at claim/renew
+  boundaries (no ambient sweeper — `sweep_expired` is caller-driven,
+  cadence recipe unchanged).
+
+## Acceptance Criteria
+
+- [ ] Full `Queue`/`JobHandle` surfaces over the in-memory job table
+- [ ] The ADR-010 state machine properties unit-pinned: visibility
+      reclaim consumes an attempt, dead-letter moves, no-stranded-rows
+      sweep, handle-op validity predicate, late-heartbeat boundary
+- [ ] Equal-jitter curve + opts resolution pinned to the identical
+      numeric behavior the suite's equivalence rows assert (per the
+      engine-side pin posture used for the cap legs)
+- [ ] Numeric-domain guards (extents) at entry — pinned
+- [ ] `cargo check --target wasm32-unknown-unknown -p alkstore-mem`
+      clean; workspace gates green
+
+## References
+
+- docs/architecture/queues.md; core-contract.md §queues
+- docs/architecture/decisions/010-queue-semantics-depth.md;
+  019-mechanism-handle-surfaces.md §1/§3; 020 §1–§3; 023 §2
+- docs/architecture/engine-mem.md §Mapping the contract (queues row)
+- tasks/pg-engine-queues.md (the structural twin's task of record —
+  the wave-4 rhythm and the resolution rule set)
+
+## Notes
+
+> To be filled by implementation agent
+
+## Summary
+
+> To be filled on completion