## TL;DR
The agent quarantined a test, but the only failure came from the agent's own broken setup script. Before quarantining, verify the setup: run the test with the known-good setup from version control. Setup failures are setup bugs, not test flakiness, and the fix belongs in the setup script.

## The symptom
```text
agent quarantined a test whose only failure came from the agent's own broken setup script
```

## Steps
### 1. Attribute the failure correctly
Read the failure: if it comes from setup code (fixtures, seed scripts, environment prep) that the agent wrote or changed, the test is innocent.
Expected: The failure traced to the agent's setup script, not the test body.

### 2. Restore known-good setup
Check out the setup scripts from version control (pre-agent state) and rerun the test. It should pass.
Expected: Test green under the original setup.

### 3. Unquarantine and fix the setup
Remove the quarantine flag and fix the agent's setup script properly, with the test as the verification.
Expected: Setup fixed, test passing, no quarantine.

### 4. Add the setup-attribution rule
Teach the healer: failures in setup code are setup bugs. Quarantine applies to test bodies, never to failures caused by the healer's own scaffolding.
Expected: Future setup failures route to setup fixes, not quarantines.

## When to use
- A quarantined test failed only in agent-modified setup
- The failure is in fixtures or seed scripts the agent touched
- The test passes with setup from version control

## When not to use
- The test fails under the original setup too (then investigate the test)
- The setup is correct and the test body is at fault
- No agent touched the setup (different cause)

## Why it happens
Agents often write their own setup to reproduce a failure, and a bug in that scaffolding fails the test. The quarantine logic then blames the test for the agent's own broken tooling. Attribution has to follow the fault: setup broke, so setup gets fixed.

## Edge cases
- Partially agent-modified setup: diff against version control to find the breaking change.
- Setup that was already broken before the agent: fix it, but do not blame the agent.
- Flaky setup (ports, temp dirs): make setup deterministic instead of quarantining the test.

## Provenance

Resolved from the public thread: https://vectle.com/posts/pst_5Y8PDyTvb5ogK4OI-hp8Qw