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SKILL verified MIT Self-run

Diagnose

skill-mblauberg-provenant-diagnose · by mblauberg

Use to reproduce and find the root cause of broken behaviour, crashes, test failures, flakes, or performance regressions. Not for a known-cause repair or change review; use implement or code-review.

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Install

$ agentstack add skill-mblauberg-provenant-diagnose

✓ scanned · ✓ verified — works with Claude Code, Cursor, and more.

Security review

✓ Passed

No issues found. Passed automated security review. · v0.1.0 How review works →

  • ✓ Prompt-injection patterns
  • ✓ Secret / credential exfiltration
  • ✓ Dangerous shell & filesystem operations
  • ✓ Untrusted network calls
  • ✓ Known-malicious package signatures

What it can access

  • ✓ Network access No
  • ✓ Filesystem access No
  • ✓ Shell / process execution No
  • ✓ Environment & secrets No
  • ✓ Dynamic code execution No

From automated source analysis of v0.1.0. “Used” means the capability is present in the source — more access means more to trust, not that it’s unsafe.

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About

Diagnose

Build a mental model and check recorded constraints before probing. Work in order; record why any phase is skipped.

Iron law

NO FIX WITHOUT A REPRODUCTION AND A ROOT CAUSE FIRST

Diagnosis is read-only except temporary instrumentation. Permanent repair requires an explicit user request or an authorised implement scope.

Workflow

  1. Feedback loop. Create the fastest sharp signal that reaches the reported

failure: failing test, CLI/HTTP/browser fixture, replay, property loop, bisection, differential harness or structured user loop. Pin time/randomness and isolate mutable dependencies. For flakes, raise the reproduction rate. If no useful loop is possible, stop and request the missing environment or artifact; do not guess.

  1. Reproduce. Confirm repeated runs show the user's exact symptom, not a

nearby failure. Capture the observation needed to prove later repair.

  1. Hypothesise. Rank 3–5 falsifiable causes before testing. Each needs a

distinct prediction; inspect recent diffs, deploys and dependency changes.

  1. Instrument. Map one probe to one prediction and vary one thing at a

time. Prefer debugger/breakpoints; tag targeted temporary logs uniquely. Performance work starts with baseline, profile and bisect.

  1. Handoff or fix. Without repair authority, stop with root cause,

confidence, affected paths and the proposed regression seam. With authority, first turn the repro into a failing test at the real call-site seam, then make one root-cause fix and rerun the regression, original loop and suite. An absent correct seam is an architectural finding, not permission for a shallow test.

  1. Clean up. Remove only instrumentation/harnesses proven run-owned and

covered by authority; preserve unknown, pre-existing and user-authored work. Record the winning hypothesis and prevention opportunity. Never bundle unrelated refactoring.

After three failed fix attempts, stop and question the architecture with the user. An enclosing lifecycle's stricter repair-cycle cap always wins. Detailed loop choices and cleanup checks: [references/method.md](references/method.md).

Source & license

This open-source skill is cataloged on AgentStack and links to its original source — we do not rehost the code.

Install and usage instructions live in the source repository linked above.

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Versions

  • v0.1.0 Imported from the upstream source.

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