fix(artifact-store): keep recovery hints identical across requests so the prompt cache holds - #90

Summary

When an adapter shortens a large tool output, it saves the original to an archive file and adds a recovery hint with an Archive: <path> line. That file name contained the current time (Date.now()).

The adapters re-shorten the whole conversation on every request, so the same tool output got a different Archive: line each time. Any change there breaks the provider's prompt cache from that point onwards, on every request.

This PR names archive files after their content instead of the time. The same output now produces exactly the same text on every request.

What was going wrong

I ran each adapter's real per-request code twice on the same conversation, 10 ms apart:

Two side effects of the timestamped name are fixed too:

• Duplicate files: a new archive file was written on every request, even for content already archived.
• Wrong path in the hint: tool_payload_trim builds the hint's path and the path it writes with two separate Date.now() calls. When the clock ticked in between, the hint named a file that doesn't exist. Recovery still worked, because it looks archives up by dataKey, but the path shown to the model was wrong.

The fix

• artifact-store: buildArchiveLocation takes an optional originalText.
  • When given, the file name is <segment>-<sha256(sessionId + text)[:16]>.json, so the same content in the same session always maps to the same path.
  • Without it, the old timestamped name is kept, so existing callers are unaffected.
• reduction: tool_payload_trim now passes the text when building the hint's path.
  • The other passes, eviction and the adapters' own archive calls already go through archiveContent, which passes the text, so they pick this up with no changes.

Recovery is unaffected: archives are still found by dataKey.

Tests

• artifact-store, new file tests/archive-location-stability.test.ts:
  • A1: same content gives the same path.
  • A2: different content, segment or session gives a different path.
  • A3: without the text, the timestamped name is kept.
  • A4: unsafe segment ids are sanitized.
  • A5: archiving the same content twice writes one file, and the lookup still resolves.
• reduction, new file tests/archive-path-stability.test.ts:
  • T1: tool_payload_trim output is byte-identical across requests.
  • T2: the hint names the file actually written.
  • T3: different content gets a different path.
  • T4: the same holds for exec_output_truncation.
• Mutation checks:
  • Restoring the timestamped names makes A1, A2, A5, T1 and T4 fail.
  • Removing the one-line tool_payload_trim change makes T1 and T2 fail.
• pnpm build, pnpm typecheck and check:boundaries pass, and every suite CI runs passes (openclaw, claude-code, codex, host-adapter, history, preset, runtime-core, product-surface, eviction, deepseek-harness, mcp, cli, artifact-store, reduction).

Prepared with help from Claude Code; the commit is marked Co-Authored-By: Claude.