Structured root-cause debugging loop — reproduce, isolate, form a hypothesis, verify the fix. Use whenever a bug, crash, test failure, or unexpected behavior is reported.
Collected from public GitHub. Every version is saved exactly as it was and never changes. Install it at an exact version with the mdr tool, and every file is checked before it reaches your agent. The main file is checked against the SHA-256 fingerprint recorded here, and the others against the fingerprints GitHub keeps for its source commit. The automatic checks below grade the latest version, and the same checks always give the same file the same grade.
What the file says
# Systematic Debugging
A disciplined loop that finds the true root cause before changing code. Skipping it is the #1 cause of "fixes" that regress or don't hold.
## The loop
1. **Reproduce reliably.** Get a minimal, repeatable repro (command, input, test). If you can't reproduce it, say so and gather more info before touching code.
2. **Read the error fully.** Capture the exact message, stack trace, and the line it points to. Don't guess from a summary.
3. **Isolate.** Narrow the trigger: which input, which code path, which environment/version? Binary-search with logs or by disabling code.
4. **Form ONE hypothesis** about the root cause. State it explicitly: "I think X happens because Y."
5. **Verify the hypothesis** with the cheapest probe: a log, a print, a test, a debugger breakpoint (`lsp_diagnostics`, `exec` with a tiny script). Confirm before fixing.
6. **Fix the root cause**, not the symptom. The fix should make the repro pass AND not break related cases.
7. **Add a regression test** that captures the repro, so it can't come back.
8. **Re-run the full affected test suite**, not just the one case.
## Anti-patterns to avoid
…
The line at the top of this page pins the label git:20260624.52cbbd6, which is what most people want. This one pins the sha256 fingerprint of the contents instead, so it survives a label being moved. Either way the exact version is written to mdr.lock, and mdr install downloads and checks those contents again, so it installs them exactly or stops with an error.
A 17 of 17 checks passed. Fixed automatic checks with no AI involved, so the same checks give the same answer every run.
pass: Frontmatter block present
pass: Frontmatter declares a name
pass: Frontmatter declares a description
pass: Size between 200 bytes and 200 KB (1879 bytes)
pass: No zero-width or bidi control characters
pass: No instruction hidden inside an HTML comment
pass: No link to an exfiltration or paste host
pass: No credential-shaped string
pass: No instruction to send local credentials anywhere
pass: No text hidden with inline styles
pass: No prompt-injection phrasing
pass: No curl or wget piped into a shell
pass: No recursive delete of root, home or parent
pass: No instruction to read or print local credentials
pass: No base64 blob over 200 characters
pass: No link to a raw IP address
pass: No script tag
Source
GitHub
metaspartan/cybara · 32 stars · license MIT · pushed 2026-10-20 · branch main
API
GET https://markdownregistry.com/api/v1/artifacts/art_lvtye75znkgam5p6
GET https://markdownregistry.com/api/v1/resolve?ref=metaspartan/cybara/systematic-debugging
GET https://markdownregistry.com/api/v1/blob/7e2468e80cc478fbc836fcb58da45d89239d1e58e71f5129457840a8341ec118
Your AI assistant does the legwork. You hear about the deals worth your word. Hand yours the standing instructions at modelranch.com and it joins the network that reads files like this one.
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