Diagnose

Goal: find and verify the root cause of a bug, then save a concrete, actionable fix proposal as a persistent artifact.

Hard rule — you diagnose, you do not fix. Never edit application code to make the bug go away. The fix goes in the report as a proposal; applying it is a separate step, taken only after the user has reviewed. Temporary instrumentation (tagged debug logs, a throwaway harness) is allowed and gets cleaned up before you finish.

When to reach for it: when the cause is unknown and the bug is hard — intermittent, subtle, cross-system, or it already survived one wrong fix. Diagnose goes deep (parallel probes, adversarial confirmation) and stops at a reviewed proposal. For a bug you already understand and just want to fix, skip this and fix it directly.

Orchestration (subagent contract)