Teach Agent to Fix Bugs by Root Cause, Not Guesswork

Where this fits

Your CI just turned red after a dependency bump. The test failure is cryptic, and the agent starts patching the first suspicious line. That is exactly when fix-bug earns its place. It turns a vague “make tests pass” instruction into a disciplined debugging workflow: pin the root cause from logs, form at least three hypotheses, instrument the hot path, and only then change code. It is for bugs in play, not greenfield features or type-only edits.

Why agents benefit

• Enforces a hard gate: no code changes before the agent can explain the cause from evidence. This stops “try a few things” loops.
• Requires three hypotheses across different layers: our function, caller, dependency. Covers real bugs instead of symptom patches.
• Adds and removes debug instrumentation deliberately, and turns on debug modes for third-party packages, leaving no log noise behind.
• Loads prove-it only after a green fix and only if asked, so the agent does not overdo verification by default.
• Respects existing CopilotKit debug skills rather than overwriting them, making it easier to adopt incrementally.

Practical scenarios

Flaky API response in a service layer

A service returns an unexpected payload only in production. The agent uses fix-bug to add debug logging at the client boundary, in the caller, and inside the dependency call. It quickly isolates the cause to a missing timeout configuration, removes the logs, and writes a regression test.

Red CI after a dependency upgrade

A Rails upgrade breaks one feature test. Instead of pinning the gem version or tweaking code blindly, the agent forms three hypotheses: upgraded gem changed behavior, test setup is stale, or our code relied on removed APIs. It enables the gem's debug logger, pins the breaking API change, and fixes the calling code.

User reports “it's broken” with no details

A user says “the export button is broken.” With no stack trace, the agent instruments the export path, generates three plausible causes from code inspection, and uses debug logs to confirm cache invalidation never fires. The fix is surgical and no feature creep sneaks in.

Add it to your agent workflow

Install the skill with:

npx skills add AlemTuzlak/skills --skill fix-bug

Then reference it in your agent's system prompt or project instructions:

When a test fails, CI is red, an API returns an unexpected result, or the user says 'fix this', load and follow fix-bug before editing any code.

The skill itself decides when not to load, so it won't slow down feature work or docs-only changes.

Compare before adopting

Before making it default, compare it with your current debugging prompts. Look for quality signals: does the skill actually enforce root-cause before edits, clean up debug output, and ask for a regression test? Check maintenance freshness: when was the repo last updated, and are issues/PRs active? Also compare alternatives: a generic “be careful” instruction costs nothing, but gives no protocol; a homegrown skill can be tailored but takes time. Finally, see if it fits your workflow: it says it does not overwrite CopilotKit debug skills, so verify integration with your existing agent runtime.

Why it is worth tracking

With 39 stars and a focused category (coding-agents), fix-bug is small but opinionated, and that is valuable: it encodes a debugging discipline most agents lack. The skill listing on OpenAgentSkill — https://www.openagentskill.com/skills/alemtuzlak-fix-bug — is a useful place to revisit as the repo evolves and community signals, like stars and forks, grow. Track it now, evaluate it on your next red CI, and adopt it when you need agents to fix bugs instead of guessing.