poimen-memory/tasks/M0.8-m0-gate.md

M0.8 — M0 composition gate

Field	Value
Phase	M0 — Read-only spine
Size	M — 1–3 days
Status	✅ Done
Flags	gate
Spec	inlined below
Blocks	all of M0

Goal

Prove the parts compose and that the swappable part is genuinely swappable — the properties no single M0 task owns.

Facts (inlined — no spec read needed)

The claim this phase makes: a new input kind is added by implementing RecordSource, and nothing downstream changes. If that is false, the crate split bought nothing and the streaming work later will be a rewrite.

The gate proves it by adding a third source that resembles nothing already supported, and asserting the rest of the pipeline is untouched.

Second claim: the whole phase is free. No model calls, so the gate is a CI job that runs on every push without a gateway or credentials.

Steps

1. Implement SyntheticSource in the test tree only — generates records from a seed, has no file format, and deliberately produces a record larger than the chunk budget and a run of empty-text records.
2. Assert chunks() handles it with no change to mem-chunk.
3. Assert dependency direction still holds (M0.1 assertion 3) after three sources exist — this is when someone is tempted to reach backwards.
4. Run mem ingest --dry-run over all three sources for one project and diff the summary against a committed expected file.
5. Wire the whole thing as a required CI job.

Acceptance

• Three sources, one RecordSource, zero source-specific branches in mem-chunk or mem-cli.
• Dry-run summary diffs empty against the committed expectation.
• CI job passes with no network and no credentials.

Verify

Harness: committed expected-output file, diffed. The script's output is the review artifact.

Integration test — tests/it_m0_gate.rs:

1. a1_third_source_needs_no_downstream_change — SyntheticSource flows through chunks(); assert git diff --stat crates/mem-chunk crates/mem-cli is empty for the commit that added it (enforced by a CI step, not by the test binary).
2. a2_no_source_specific_branches — grep crates/mem-chunk and crates/mem-cli for the strings pi:, claude:, sessionId, toolResult; assert none appear outside mem-ingest.
3. a3_dry_run_golden — run the dry run over all three sources, diff against expected/m0-gate.txt; empty diff is the only pass.
4. a4_offline — the entire gate runs with networking disabled.
5. a5_lossless_end_to_end — records in equals records out, across all three sources composed.

Command: cargo test --workspace m0_gate

False pass:

• Adding SyntheticSource in a way that mirrors the pi format. It then exercises the same code path and proves nothing about generality. It must have no file, no header line, and an oversized record.
• Assertion 3 passing because the expected file was regenerated in the same commit. A changed expected/ file in a diff is a claim that the contract changed, and must be reviewed as one.

Traps

• Skipping assertion 2 because "obviously there are no source-specific branches". There will be — the first if provenance.starts_with("pi:") gets added to fix a real bug and is entirely reasonable in isolation.
• Letting the gate need credentials. The value of an offline gate is that it runs on every push; the moment it needs a gateway key it becomes a nightly job that nobody watches.

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Background: DESIGN.md — mem-chunk, Verification