diu: one negative per sentence, rewritten as the positive action

[EdbertChan]

Summary

The always-on writing rule now bans stacked negatives. "No longer queues a check it can never deliver" hides what happens behind two negatives.

The rule says one negative per sentence, rewritten as the positive action: "skips the check once the helper stops." It bites hardest in pull request titles and summaries.

Review Claim

Replies, titles, and summaries carry at most one negative per sentence; stacked "no longer / never" chains are rewritten as the positive action before sending.

Review Lane

behavior

Review Unit

product-skill

Safety Invariant

This slice changes only markdown rule text and a scenario fixture inside one skill, plus a unit test that pins the rule's presence. No hook, script, or gate executes the new sentences; the installed checkers (trigger mechanism, test coverage, three-harness, ecosystem boundaries) all pass against the edited text as it stands.

Slice Rationale

One skill, one new shape rule plus its pre-send check line and a scenario fixture — a single writing-rule change, so it ships alone rather than riding on an unrelated skill edit.

Non-goals

• A mechanical checker that scans prose for stacked negatives — the reply checker's wording judge picks that up in the slice below this one.
• Rewriting existing skill text that already contains stacked negatives.

Test Plan

Test Plan

• python3 scripts/ci/check_skill_trigger_mechanism.py → ok skill trigger mechanism
• python3 scripts/ci/check_skill_test_coverage.py → ok skill test coverage
• python3 scripts/ci/check_skills_three_harnesses.py → ok skills three-harness check
• python3 scripts/ci/check_ecosystem_boundaries.py → ok ecosystem boundaries
• python3 scripts/ci/check_skill_trigger_policy.py → ok skill trigger policy
• python3 scripts/ci/check_no_dated_provenance.py → ok no dated provenance
• python3 -m unittest product.skills.diu.tests.test_stacked_negatives_rule -v → Ran 5 tests / OK
• python3 engine/skills/make-pr/scripts/preflight.py --base origin/main --body-file /tmp/diu-pr-body.md → ok preflight passed

Revert Plan

Revert Plan

• Safe to revert? Yes
• Revert command: git revert <sha>
• Post-revert steps: None — the rule is advisory prose; nothing executes it.
• Data migration? No

---

Note

Low Risk
Markdown-only skill guidance and unittest assertions; nothing executes the new wording at runtime.

Overview
The diu always-on shape rules now require one negative per sentence, rewriting stacked chains like "no longer … never" into the positive action (especially for PR titles and summaries).

SKILL.md updates the front-matter description, adds Part 2 rule #9 with an example, and extends the pre-send checklist with item #6 for multi-negative sentences. A shape_example.md scenario fixture documents a bad PR title and the preferred rewrite. test_stacked_negatives_rule.py pins that the rule, positive-action wording, pre-send check, and fixture are present, and that the skill does not instruct retired escape-hatch markers.

^{Reviewed by Cursor Bugbot for commit c85151e. Bugbot is set up for automated code reviews on this repo. Configure here.}

[EdbertChan]

This pull request is part of a Mergify stack:

#	Pull Request	Link
1	diu-stop: judge flags a reply that stacks two negatives in one sentence	#997
2	diu: one negative per sentence, rewritten as the positive action	#998	👈

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[mergify]

Queued — the merge queue status continues in this comment ↓.

[EdbertChan]

Mergify repair stopped: required check failed: validate. The retry cap was reached for current head 01693ce.

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[EdbertChan]

@Mergifyio queue

[mergify]

Merge Queue Status

• ✅ Entered queue — 2026-09-25 04:01 UTC · Rule: admin-bypass · triggered by @EdbertChan with the @mergifyio queue command
• ✅ Checks passed · on draft merge queue: checking #998 on main (aa1b584), stacked on 4 pull requests ahead #1097
• ✅ Merged — 2026-09-25 04:20 UTC · at 3b0c4d94c1722a13877e875efd35fd58144d1738 · squash

This pull request spent 19 minutes 28 seconds in the queue, including 18 minutes running CI.

Required conditions to merge

• check-success = lint
• check-success = test
• check-success = validate