Stop the persisted state growing by megabytes per run

[christopherjnelson]

The state file grew by megabytes per run for three reasons:

• Every Worker result stored the complete repository tree (every file's bytes, base64) in workerEvidence.entries.
• Streamed progress events kept the raw provider event.
• Each 5 s poll of a running assignment appended an event and rewrote the whole state file.

On a 2.5 MB fixture repository the state grew 3.5 MB per run: 121 MB after 35 runs, with each state write taking about 950 ms and each run about 95 s.

Changes

• Compact Worker evidence.
  • New evidence stores only its exact changes, the complete snapshot's entry count, and a sha256 over the canonical tree (snapshotFormat: 'base_plus_changes').
  • fullSnapshotEntries() rebuilds the tree from the pinned Git base plus the changes. Every "before" must match the base, and a count or digest mismatch is rejected.
  • Validation and promotion use the rebuilt tree. Promotion's copy is transient and never written back.
• Legacy records are unchanged.
  • They keep their stored entries and are read exactly as before, so their approval and promotion digests do not change.
  • A recorded legacy state fixture (tests/fixtures/legacy-evidence-state.json) covers approve, promote, and tamper detection on old records.
• The approval digest still binds the whole result. It hashes the stored record, which now includes the snapshot digest.
• Bounded progress events.
  • They store the response id, model, status, assignment id, and activity kind and summary instead of the raw provider event. That is everything the Live Response panel reads.
  • assignment.progress and assignment.reconciled are capped at 500 in persisted state, and sequence numbers stay monotonic.
• No-op polls. A poll that finds a running assignment still running no longer appends an event or rewrites state.

Measured (same benchmark, before → after)

	before	after
State growth per run	3.5 MB	42–60 KB
State after 35 runs	121 MB	1.8 MB
State write (mutate) at run 20	~950 ms	~23 ms
Full run at run 35	~95 s	~7 s
200 polls of a running assignment	200 events, 200 rewrites	0 events, 0 rewrites

Verification

• Typecheck is clean.
• vitest: 559/559 passing. New tests: snapshot-evidence, event-volume and live-response, plus a compact-evidence approve → promote assertion in recorded-integration.
• pnpm test:bridge: 62/62 passing.
• Build succeeds.

The work was started by a sub-agent that was stopped partway through. I reviewed it, merged it onto current main, and updated its legacy test to send the evidence digest that approvals now require.

🤖 Generated with Claude Code

https://claude.ai/code/session_01DXCvrGWmmRNDLmy7nYS2QP

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