boo-diagnose

name	boo-diagnose
description	Performs root-cause diagnosis for Ruby on Rails issues across performance, correctness, architecture, security, and reliability. Use when requests involve bugs, regressions, N+1 queries, slow endpoints, flaky tests, unexpected behavior, or unclear failures. Triggers on words like diagnose, debug, investigate, root cause, slowdown, flaky, regression, N+1, timeout.

Rails Diagnose

Overview

Use this skill to move from symptom to root cause with evidence, not guesses.

LSP Recommendation

Strongly recommend enabling LSP before running this skill:

1. ENABLE_LSP_TOOL=1 in the shell running Claude/Codex.
2. Run from the Rails app root directory.
3. Ensure a Ruby LSP backend is available in the app bundle (ruby-lsp and/or solargraph).

If LSP is not enabled, continue execution but mark reduced confidence for symbol-resolution findings.

Diagnostic Workflow

1. Reproduce: Confirm the problem and capture exact failure signal.
2. Scope: Identify impacted code paths, models, endpoints, and environments.
3. Observe: Inspect logs, queries, stack traces, and recent changes.
4. Hypothesize: List candidate causes and rank by probability.
5. Prove: Validate or invalidate each hypothesis with targeted checks.
6. Conclude: Report root cause, fix plan, and prevention step.

Investigation Matrix

1. Performance: query count, N+1 patterns, missing indexes, cache misses.
2. Correctness: wrong assumptions, nil handling, callback side effects.
3. Security: unsafe params, interpolation in SQL, authorization gaps.
4. Reliability: flaky specs, race conditions, background retry behavior.

Evidence Requirements

Never close diagnosis without at least one direct evidence source:

1. Repro steps.
2. Log/trace evidence.
3. Query or timing evidence.
4. Test demonstrating failure and/or fix.

Scripted Execution

Use the bundled diagnostic runner for repeatable investigation:

1. scripts/run_diagnose.sh
2. scripts/run_diagnose.sh --project-dir /path/to/rails-app
3. scripts/run_diagnose.sh --mode advisory --output-file tmp/diagnose-report.md
4. scripts/run_diagnose.sh --require-lsp (hard fail if ENABLE_LSP_TOOL!=1)

Default behavior:

1. Scans for likely N+1 hotspots, broad rescue patterns, callback overload, oversized controllers, flaky test hints, and job idempotency risk.
2. Categorizes findings into HIGH, MEDIUM, and LOW.
3. Persists logs in tmp/rails-diagnose-<timestamp>/.

In strict mode, HIGH findings return exit code 1.

Output Contract

1. Symptom.
2. Root Cause.
3. Evidence.
4. Primary Fix.
5. Alternative Fix.
6. Guardrail to prevent recurrence.

Final Summary (Required)

Always end execution with:

1. Diagnostic outcome: confirmed root cause or pending unknown.
2. Top findings by severity.
3. Recommended fix and one alternative.
4. Evidence references used.
5. Immediate next step.

References

Load references/external-resources.md for canonical debugging and Active Record references.