write_card: treat a blank history_entry as absent on UPDATE and NOOP

[smixs]

Blank history_entry on UPDATE/NOOP is treated as absent (same trim as SUPERSEDE). A non-blank entry is still refused. A rejected NOOP leaves the card byte-identical.

Reproduced on main with a failing test before the fix. Related to #205: the existing PR does not assert the rejected NOOP card is unchanged.

Summary by CodeRabbit

• Bug Fixes

  • Empty or whitespace-only history entries are now treated as omitted for update and no-op actions.
  • Non-empty history entries remain validated correctly, preventing invalid card changes.
  • Superseding a card with a valid history entry now reliably archives the previous fact.

• Documentation

  • Clarified that empty history entries are equivalent to leaving the field unspecified.

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• scripts/write-card.test.ts

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📒 Files selected for processing (2)

• agent/tools/write_card.ts
• scripts/write-card.test.ts

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• agent/tools/write_card.ts

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📝 Walkthrough

Walkthrough

The write-card tool treats empty and whitespace-only history_entry values as absent for UPDATE and NOOP. ADD preserves raw input for merge handling. Tests cover accepted, rejected, unchanged, and SUPERSEDE cases.

Changes

history_entry handling

Layer / File(s)	Summary
Normalize and validate history_entry agent/tools/write_card.ts	The tool trims history_entry for presence checks. UPDATE and NOOP accept empty values as omitted and reject non-empty values under their existing rules.
Route values and verify operations agent/tools/write_card.ts, scripts/write-card.test.ts	ADD passes the raw value to mergeCard. Tests cover whitespace-only values, rejected non-empty values, unchanged files, and successful SUPERSEDE history creation.

Estimated code review effort: 2 (Simple) | ~10 minutes

Merge Risk: ⚪ Minimal · up to 273aa

The change makes blank history entries behave as absent for UPDATE and NOOP while preserving rejection of non-blank entries and unchanged-card behavior; no actionable merge-blocking risk remains beyond normal checks and review.

🚥 Pre-merge checks | ✅ 5

✅ Passed checks (5 passed)

Check name	Status	Explanation
Description Check	✅ Passed	Check skipped - CodeRabbit’s high-level summary is enabled.
Title check	✅ Passed	The title clearly and concisely describes the main change: treating blank history_entry values as absent for UPDATE and NOOP.
Docstring Coverage	✅ Passed	No functions found in the changed files to evaluate docstring coverage. Skipping docstring coverage check. Docstring coverage is scoped to functions touched by this diff. Analyzed 0 functions across 2…
Linked Issues check	✅ Passed	Check skipped because no linked issues were found for this pull request.
Out of Scope Changes check	✅ Passed	Check skipped because no linked issues were found for this pull request.

Full details: Docstring Coverage

Explanation

No functions found in the changed files to evaluate docstring coverage. Skipping docstring coverage check. Docstring coverage is scoped to functions touched by this diff. Analyzed 0 functions across 2 files.

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[smixs]

Verified. On main the UPDATE/NOOP guard is history_entry !== undefined, so "" / whitespace is a forged-archive refusal and a model that fills every schema field loops. The tool-boundary trim matches how SUPERSEDE already reads the field; a non-blank entry is still refused; ADD still receives the raw value for the journaled noise-drop. Rejected NOOP leaves the card byte-identical — that assertion is why this should land instead of #205 (same production diff, weaker test).

Philosophy: this is deterministic input normalization at the tool contract, not a new mechanism, not a skill. Design closes the class (blank ≡ absent); the test pins it.

Unproven: the live gpt-5.6-luna 300–500-refusal loop (model behaviour). Unicode whitespace is covered by JS trim(). Ready.