Mk Investigate

---
name: "mk-investigate"
description: "Systematic root-cause debugging that produces a diagnostic report (mk:fix applies the fix; mk:build-fix owns compile failures). Use for 'debug this', 'why is this broken', 'root cause'."
---

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<!-- References loaded just-in-time, not all upfront -->

# Systematic Investigation

> **Path convention:** Commands below assume cwd is `$(git rev-parse --show-toplevel)` (project root). Prefix paths with `"$(git rev-parse --show-toplevel)/"` when invoking from subdirectories.

**Iron Law: NO FIXES WITHOUT ROOT CAUSE INVESTIGATION FIRST.**

## Skill wiring

- **Reads memory:** canonical `.meowkit/memory/fixes.json` and `architecture-decisions.json`; fall back to matching generated Markdown views only when JSON is absent. See `AGENTS.md` (Memory).
- **Writes:** a diagnostic report only, under `tasks/reports/**`; the hook enforces this path. `mk:fix` owns remediation and any memory capture after a fix.

## Plan-First Gate

Investigation precedes planning for bug fixes:

1. Confirm root cause FIRST (Iron Law)
2. After root cause confirmed, hand off to `mk:fix`. If the remedy affects more than two files, `mk:fix` requests an approved bug-fix plan using supported plan-creator syntax.

Skip: Investigation itself doesn't need a plan — it produces the input for planning.

## When to Use

- User reports errors, bugs, unexpected behavior
- "debug this", "fix this bug", "why is this broken"
- "investigate this error", "root cause analysis"
- Troubleshooting why something stopped working

## Process

1. **Run preamble** — load `references/preamble.md` and execute the startup bash block
2. **Collect symptoms** — read error messages, stack traces, reproduction steps
3. **Investigate root cause** — load `references/debugging-methodology.md` and follow Phase 1-3. For recurring patterns or complex failures, load `references/rca-method-selection.md` for methodology selection. Load `references/rca-anti-patterns.md` to avoid common RCA mistakes.
4. **Check alternatives** — test the strongest competing explanation before declaring a root cause.
5. **Write diagnostic report** — save only to `tasks/reports/{timestamp}-investigation-{slug}.md`; include the required output contract below.
6. **Hand off** — route confirmed defects to `mk:fix`, compile/build failures to `mk:build-fix`, and unresolved causes back to the user with explicit uncertainty.
7. **Run shared protocols** — load `references/shared-protocols.md` for completion status + telemetry

## References

Load **only when executing** the corresponding step — not upfront.

| Reference                                                             | When to load                    | Content                                                                     |
| --------------------------------------------------------------------- | ------------------------------- | --------------------------------------------------------------------------- |
| **[preamble.md](./references/preamble.md)**                           | Step 1 — skill startup          | Session init, env detection, upgrade check                                  |
| **[debugging-methodology.md](./references/debugging-methodology.md)** | Steps 2-4 — investigation | Evidence collection and hypothesis testing |
| **[shared-protocols.md](./references/shared-protocols.md)**           | Step 7 — completion             | stop and ask the user in chat format, completion status, telemetry, contributor mode      |

### Specialized Techniques (load based on bug type)

| Bug type | Load reference | What it adds |
|----------|---------------|-------------|
| Deep stack trace errors | `references/root-cause-tracing.md` | Backward trace: symptom → cause → ROOT CAUSE |
| Server/CI/DB incidents | `references/system-investigation.md` | 5-step system investigation methodology |
| CI/CD failures, log correlation | `references/log-analysis.md` | Filter → timeline → pattern → cross-source |
| Performance issues | `references/performance-diagnostics.md` | Quantify → layer isolation → bottleneck |
| Post-fix validation | `references/reporting-standards.md` | Enhanced DEBUG REPORT with timeline + recommendations |
| Test pollution | Run `scripts/find-polluter.sh <file> <test-pattern>` | Bisection to find which test creates unwanted state |
| Defense-in-depth | See `mk:fix/references/prevention-gate.md` | 4-layer validation (DRY — shared with mk:fix) |

## Constraints

- **Diagnostic only** — never edit source, tests, configuration, plans, or memory stores
- **Report-only writes** — `Write` is allowed solely for `tasks/reports/**` and is hook-enforced
- **3-strike rule** — if 3 hypotheses fail, STOP and escalate
- **Evidence boundary** — label each claimed cause as confirmed or uncertain; do not imply remediation completed

## Diagnostic Output Contract

Every report includes: symptom, reproduction status, expected versus actual behavior, ranked causes,
confirmed root cause or explicit uncertainty, evidence, and blast radius. Recommendations may name a
next owner but must not implement a fix.

## Hooks

- **Iron Law enforcement**: No fixes without confirmed root cause; `mk:fix` is the only remediation owner.
- **Report-path hook**: a pre-write hook, enforced by this project's configured hooks when present, fails closed unless the destination is under `tasks/reports/**`.
- If root cause cannot be confirmed after 3 hypotheses, escalate to human
- **Interaction with mk:careful**: If mk:careful is active, debugging commands that touch state will still prompt for confirmation. This is expected — do not bypass.

## Gotchas

- **Confirming hypothesis without disproving alternatives**: Finding evidence FOR a theory doesn't mean it's correct → Actively test at least one alternative hypothesis before concluding
- **Log timestamps in wrong timezone**: Server logs in UTC, local comparison in local time → Normalize all timestamps to UTC before correlation

## Delegation: `mk:web-to-markdown`

When investigation requires fetching an arbitrary external URL (e.g. a vendor error page,
a remote log endpoint, a referenced issue URL), this skill delegates to
`mk:web-to-markdown` via the `--wtm-accept-risk` flag.

- **Without `--wtm-accept-risk`:** `mk:web-to-markdown` refuses cross-skill delegation.
  External URL resolution falls back to Context7 / chub / WebSearch only.
- **With `--wtm-accept-risk`:** delegation proceeds through all security layers
  (SSRF guard, injection scanner, DATA boundary, secret scrub). The flag is a conscious
  trust-boundary crossing — the caller acknowledges the target URL may contain prompt
  injection and that the skill's defenses are best-effort.
- Delegation example: `.cursor/skills/.venv/bin/python3 .cursor/skills/web-to-markdown/scripts/fetch_as_markdown.py "<url>" --wtm-accept-risk --caller mk:investigate`