debug

name	debug
description	Reproduce, diagnose, and fix bugs, CI failures, and test failures. Use when the user wants the failure resolved; use diagnose for a read-only durable root-cause report.
allowed-tools	Bash, Read, Glob, Grep, Edit, Write
argument-hint	[error-description|blueprint-slug-or-path]

Debug

Resolve a failure from reproducible evidence without creating a tracker.

@rules/context-budget.md and @rules/harness-compat.md apply.

Workflow

1. Resolve the failure description and read any explicitly named proposal, review, report, or legacy blueprint as optional context. Do not search for an artifact when none was named.
2. Read applicable repository instructions, inspect the working tree, and preserve unrelated changes.
3. Reproduce the failure with the narrowest known command. Bound logs at their source and capture the exact expected behavior, actual behavior, and baseline failures before editing.
4. Trace the relevant control/data flow and recent changes. Form competing root-cause hypotheses and falsify them with source evidence or focused probes; do not patch a merely correlated symptom.
5. Make the smallest complete root-cause fix. Add or strengthen a regression test when it would catch the reported bug, and avoid adjacent refactors.
6. Re-run the original reproducer, the focused regression checks, and broader checks warranted by the change's risk.
7. Report the root cause, files changed, commands and results, and any remaining uncertainty or risk.

If the failure cannot be reproduced or the cause remains unproven, report the evidence and the next discriminating check instead of making a speculative edit. Do not create a blueprint. If the user explicitly requests a durable diagnosis, use the diagnose artifact skill and do not edit source files.