Diagnose

Choose the branch before selecting a model. Coordinator work and deterministic commands proceed within invocation authority. Apply this method in the current role. It does not dispatch a worker. For a worker dispatch, use shared/references/model-preview.md and its one approved route snapshot. Nested skills and runners consume it without another selection or worker.

Find the cause from observed failure evidence and the relevant code. Pattern-match is not diagnosis: a familiar symptom gives a hypothesis. An artifact of proof connects symptom → mechanism → cause.

A diagnosis is complete when that chain is supported. If the investigation cannot establish it, report the remaining uncertainty and the evidence needed to resolve it. Apply a fix when the request authorizes it.

Establish the evidence

Read the supplied error, logs, traces, values, failing test results, and the code path they identify. Check that the evidence applies to the affected version and conditions. Reuse sufficient evidence from the current task.

Existing evidence can prove the cause without a new local reproduction. State the connection, for example: “The trace is the artifact of proof: the retry leaves the connection open, which exhausts the pool.”

Resolve open questions

Use only the techniques that can resolve a remaining uncertainty: