Debug and Fix

Find the root cause of a failure, then, when the user chooses to, fix it with test-first discipline.

Done when: the causal chain from trigger to symptom is stated with no gaps and file:line evidence, and either a verified fix has been handed off (PR, commit, or the user's chosen stop) or a diagnosis-only summary has been delivered. Escalate rather than persist: 2-3 hypotheses exhausted without confirmation, or 3 failed fix attempts, means diagnose why instead of trying again, that is the smart escalation references/investigate.md describes. One hypothesis, one change at a time; changing several to see what helps is shotgun debugging.

<bug_description> is whatever this skill was invoked with, a failure description, a mode: token, or an issue reference (#123, org/repo#123, an issue URL), from the user or from a calling skill (ce-babysit-pr / lfg in mode:pipeline pass the failing jobs and log tails; lfg's defect route passes mode:return-to-caller and the user's own reference). Blank if nothing was provided.

Mode

Default is interactive: investigate, run the Phase 2 fix-choice gate, then the Phase 4 handoff.

mode:pipeline (set by an orchestrator such as ce-babysit-pr or lfg): run fully non-interactively and never call the blocking-question tool. Strip the token from <bug_description>, then read references/pipeline-mode.md and follow it, it overrides every "ask the user" point with a conservative default, replaces the Phase 2 fix-gate with "fix convergent bugs, defer divergent ones", and replaces the Phase 4 handoff with a structured return whose status is exactly one of fixed-and-pushed | fixed-not-pushed | diagnosed-no-fix | flaky-infra | needs-human. The caller branches on those exact spellings, so never rename, abbreviate, or add to them.