Conciseness

The core workflow is command-driven and efficient, but several sections pad the document: "Best Practices" recites generic advice Claude already knows, "Comparison Strategies" includes trivial snippets like `old_output == new_output`, and the "Helper Script" section repeats the exact three `compare_results.py` invocations already shown in step 4. Not verbose enough overall for a 2 (mostly efficient core workflow), but more trimming needed than a 4 allows.

Actionability

Mostly executable, copy-paste-ready commands (`pytest --json-report --json-report-file=old_results.json`, `git bisect run pytest path/to/failing_test.py`, `python scripts/compare_results.py old_results.json new_results.json --tolerance 0.001`) backed by a real bundled script, with both pytest and Jest covered. Minor gaps keep it below 5: `compare_ignoring_fields(old, new, ['timestamp', 'id'])` is pseudocode for a nonexistent function, and the `pytest-json-report` plugin dependency is never noted.

Workflow Clarity

A clear 8-step sequence (prepare versions → baseline → new run → compare → analyze → investigate → document → fix/accept) with explicit validation ("Verify baseline stability", "Run multiple times to check stability", compare via script) and feedback loops for error recovery (git bisect for root cause; fix → re-run tests → re-compare in step 8). Every risky step has a corresponding checkpoint, matching the top anchor.

Progressive Disclosure

Good structure with both bundle files real, one level deep, and clearly linked ("Review strategies in [detection_strategies.md](references/detection_strategies.md)"; `scripts/compare_results.py` used throughout). Below 5 because the body's "Regression Types" Quick Reference duplicates content that already lives in detection_strategies.md, and the ~54-line sample report template is inline content that would fit better in a reference file.

Specificity

"Checks whether a new version of a repository preserves the behavior observed by tests on the old version", "Detects differences in function outputs, exceptions, observable states, and performance between versions", "Generates reports highlighting potential regressions (critical, high, medium, low severity), improvements" — multiple specific concrete actions (four detection categories plus severity-graded reporting) with comprehensive coverage of the skill's behavior, matching the top anchor rather than the 'several actions, minor gaps' anchor below it.

Completeness

Explicitly answers both questions with concrete trigger phrases: the 'what' ("Detects differences in function outputs, exceptions, observable states, and performance... Generates reports...") and the 'when' twice over ("Use this skill when comparing two versions of code to detect regressions, verify refactoring safety..." and "Triggers when users ask to check for regressions between versions..."). This is the anchor-5 pattern, well above anchor 4's 'when could be more explicit'.

Trigger Term Quality

"Check for regressions between versions, compare test behavior across versions, verify behavior preservation, verify refactoring safety, ensure backward compatibility, validate that changes don't break existing tests" — comprehensive natural-phrase coverage with the synonyms and phrasings a user would actually say (regressions, refactoring, backward compatibility, behavior preservation).

Distinctiveness Conflict Risk

The cross-version regression niche is clear with distinct triggers ("regressions between versions", "behavior preservation"), but broad phrases like "validate that changes don't break existing functionality" carry minor overlap risk with general test-running or code-review skills. Mostly distinct with minor overlap risk (anchor 4) rather than the minimal-conflict anchor 5.