alkstore/tasks/mem-doc-growth-outbox-notes.md

id, name, status, depends_on, scope, risk, impact, level, tags

id	name	status	depends_on	scope	risk	impact	level	tags
mem-doc-growth-outbox-notes	Pin mem's growth postures and outbox semantics in the spec (review 004 items 10+11)	pending		narrow	trivial	isolated	implementation	review-004-fixes mem-engine docs

Description

Two recorded mem postures get their doc pins, per docs/reviews/004-pre-release-general-review.md §"Findings recorded, not fixed" items 10 and 11 (the review's "carry into the mem spec's growth section when next touched" — this is that touch).

(a) Growth postures (item 10) — two honest sentences in engine-mem.md's growth section:

• The subscribe path drains the full backlog into the receiver's pending deque before the first yield, and pending grows at publish rate for a stalled consumer (stream.rs:314-331 — the documented "drains to the tail then parks" shape, unbounded on the consumer side).
• The claim path is an O(total-live-rows) scan with full-row clones per claim (queue.rs:122-181) — blessed economics for the ephemeral tier.

(b) Outbox outcome swallow (item 11) — outbox run_once drops the ack/retry row-refs' booleans and returns Ok(true) even when delivery outlived the visibility window and nothing landed (outbox.rs:104-122). Inherent to the no-heartbeat outbox design (at-least-once reclaim is the recovery). Pin the "processed means delivered-or-reclaimable" semantic with a doc sentence in engine-mem.md's outbox section; add the debug_assert! too if it adds value without noise — the review offered either, implementer's call (record which and why).

Doc-only plus at most one debug_assert! — no behavioral change.

Acceptance Criteria

• engine-mem.md carries the two growth-posture sentences, anchored to the code sites
• The outbox "processed means delivered-or-reclaimable" semantic is pinned (doc sentence; debug_assert! per the recorded call)
• Doc gate green (RUSTDOCFLAGS="-D warnings" cargo doc --no-deps); mem tests green (the debug_assert! arm, if added, exercised by an existing outbox test)

References

• docs/reviews/004-pre-release-general-review.md §"Findings recorded, not fixed" items 10–11 (the findings, the blessed-economics framing)
• docs/architecture/engine-mem.md (the growth section, the outbox section)
• alkstore-mem/src/stream.rs:314-331, queue.rs:122-181, outbox.rs:104-122 (the anchored sites)

Notes

To be filled by implementation agent

Summary

To be filled on completion