bug(testing): imageAttachment corpus test fails locally once a cited Claude session is rotated #684

Found while working on #681. Unrelated to that change — reproduces on a clean main.

Expected

npm test passes on the author's machine, and core-tier *.test.ts files do not depend on the developer's home directory.

Actual

FAIL |unit| src/providers/shared/renderer/protocols/media/imageAttachment.test.ts
  > corpus-wide invariants > every fixture is traceable to a census row and a real session

AssertionError: atp-codex-image-inside-claude-transcript cites a missing session:
/Users/<user>/.claude/projects/-Users-<user>-Desktop-Development-klay/c0c60d3d-….jsonl

The project directory still exists; that individual session JSONL does not. Claude Code rotates and removes session transcripts as a matter of course, so this is expected local behavior, not corruption.

Mechanism

imageAttachment.test.ts:296-301 resolves CORPUS_ROOTS from homedir() and asserts existsSync on the absolute source path each fixture records:

const CORPUS_ROOTS = {
  claude: join(homedir(), '.claude', 'projects'),
  codex: join(homedir(), '.codex', 'sessions'),
}
…
if (existsSync(CORPUS_ROOTS.claude) || existsSync(CORPUS_ROOTS.codex)) {
  const rooted = path.startsWith(CORPUS_ROOTS.claude) || path.startsWith(CORPUS_ROOTS.codex)
  if (rooted) {
    expect(existsSync(path), `${f.$fixture.id} cites a missing session: ${path}`).toBe(true)
  }
}

The outer guard means CI never runs the assertion — no corpus roots there, and the baked-in absolute paths would not match a CI homedir anyway. The failure is therefore invisible in CI and permanent on the machine the fixtures were recorded on, which is the worst distribution: the person most likely to run the suite is the only one who sees it, and it never blocks a merge.

Why this is worth an issue rather than a quick patch

docs/testing/standard.md is explicit:

npm test MUST be safe on a clean machine with no credentials, no personal configuration, and no network access. Loading an ambient .env, reading a developer's home directory, or launching an installed provider is live behavior and requires an explicit opt-in variable in addition to the test:live command.

This assertion is live behavior inside a deterministic-tier file. The intent behind it is good — the comment says it wants to "give an opinion where the evidence is available, and say nothing where it is not" — but the evidence it reaches for is mutable state outside the repository, so "available" is not a stable property.

Impact

Low severity, ongoing friction: a permanently red suite on the author's machine trains people to ignore a red suite, which is the expensive part.

Suggested direction

Either move the traceability assertion behind the test:live opt-in, or drop the existsSync check and keep verifying only what the fixture itself carries (census row, fingerprint, recorded payload size) — which is self-contained and cannot rot.