investigate

Core rule

No fix without understanding the root cause. Use verified evidence to explain how the cause produces the symptom. An apparently obvious cause still needs verification; an already established cause does not need a new round of hypotheses.

Step 1 — Understand the symptom

Gather the following from the report, available logs, project configuration, and prior attempts. Ask only for missing information that materially affects the investigation:

• Exact symptom: verbatim error, wrong output, crash, or silent failure.
• Reproduction: reliable trigger, frequency, and conditions for intermittent failures.
• Onset: when it started and potentially related changes.
• Environment: where it occurs and relevant differences from working environments.
• Prior attempts: what was tested or changed and the observed results.

Step 2 — Form hypotheses

Propose plausible causes supported by the available evidence. Rank them by evidential support and explain the uncertainty without inventing percentages or padding the list to a fixed count. For each hypothesis, identify a discriminating check: