---
name: cratis-engineering-regression-cluster
description: Use when a third regression hits the same surface, a fix keeps being reapplied or recurring failures need a shared cause. Not for isolated bugs, consolidation loss checks or false-success effect boundaries.
license: LICENSE
---

# The third issue on one surface names a failure class

Each bug fixed alone adds one specification for one symptom. When the same
**surface** (one screen, endpoint, command, query, workflow, module or rule
area) breaks a third time, the instances share a cause that no specification
owns yet, and the fourth instance is already on its way. Stop fixing instances:
name the **failure class**, give it an **owning gate**, then fix the instance.

## Count first

Before fixing an issue, count the earlier ones on its surface:

```bash
gh issue list --state all --search "<surface> in:title,body" --limit 50
git log --oneline -- <paths of the surface>
```

Count bugs, regressions, reverts and review findings, open or closed. Fewer
than three: fix the instance with a regression specification. Three or more:
follow the steps below before writing the fix.

## Steps

1. **Name the failure class** in one sentence that states the property being
   violated, not the symptom. Each earlier issue must be an instance of it, and
   a reader must be able to recognize the next one by it. "Owner filter shows
   archived items" is a symptom; "list filters are not exercised through the
   rendered list by any test" is a class.
2. **Choose the owning gate by enforcement kind**, preferring the earliest that
   can catch the class: an analyzer (compile time), a lint rule, a CI check or
   verification script, or one specification suite that covers every member of
   the class (every filter, every endpoint), not one specification per bug. A
   class that only judgment can catch gets a review checklist entry, and the
   choice is stated as judgment-shaped; see the enforcement rule in
   [authoring-skills.md](../../rules/authoring-skills.md).
3. **Prove the gate fails** on the current broken instance, or on the earlier
   instances with their fixes reverted, before fixing anything. A gate that
   passes on the broken code owns nothing; follow
   [guards-and-fuses.md](../../rules/guards-and-fuses.md) so it cannot pass
   vacuously.
4. **Register the class.** When the repository keeps a failure-class table or
   gate inventory, add one row: class, owning gate, where it runs. Otherwise
   put the class name in the gate's failure message and the specification or
   check name, so the next failure names its class.
5. **Fix the instance**; the gate turns green. Run it with the repository's
   normal gates, and make it a required CI check when it lives in CI.
6. **Close the loop.** Link the earlier issues to the class in the pull request
   comment, and leave a prose rule only for the judgment-shaped part.

## Report

State the surface and the issues counted, the class sentence, the gate and
where it runs, that it failed before the fix and passes after, and anything
left judgment-shaped.

## Pitfalls

- **A fourth instance specification.** Copying the third fix's specification
  for the new symptom covers the symptom, not the class.
- **A prose rule instead of a gate.** Rules nobody enforces were already in
  place for the earlier instances; text costs context and catches nothing.
- **A class named after the symptom.** If the next instance would not be
  recognized by the sentence, the class is still too narrow.
- **A gate that never ran red.** Without the failing run, nothing shows it can
  catch the class.
- **A loose surface.** Three unrelated bugs in one large module are not a
  cluster; narrow the surface until the issues share a cause.