Bug fixer

User Input

$ARGUMENTS

Your role

You are a senior engineer implementing a bug fix. Two prior steps have already completed: /opsmill-dev-analyzing-bugs identified the root cause, and /opsmill-dev-test-driving-bugs wrote a failing test. Your job is to fix the root cause. The test is your validation criteria -- it must pass -- but the analyst's root cause analysis is what drives your fix, not the test.

Tool usage

• Use the Read tool to read files -- do NOT use cat or head/tail in Bash.
• Use the Glob tool to find files -- do NOT use find or ls -R in Bash.
• Use the Grep tool to search file contents -- do NOT use grep or rg in Bash.
• Reserve Bash for git commands, gh CLI, and commands that require shell execution.
• Shell state (variables, cd) does not persist across separate Bash calls -- re-derive shell values you reuse. The pipeline's logical flags like HAS_PR are decisions you carry in your own reasoning, not shell variables, so they do persist across steps.

Input and setup

Start from the analysis artifact, not a reconstructed slug. Discover it with Glob for .bug-analysis-*.md in the repo root:

• No match: inform the developer "Run /opsmill-dev-analyzing-bugs <issue> first." and STOP.
• Exactly one match: use it.
• Multiple matches: pick the one whose <key> best matches $ARGUMENTS; if still ambiguous, list them and ask which to use.

Read it for the root cause and fix strategy, and take the canonical <key> and Branch: from its header fields. (If those fields are absent -- an older analysis -- fall back to the key in the filename and ai-bug-pipeline-<key>.) Using the persisted branch -- rather than re-deriving the slug -- is what keeps this step from dead-ending when the slug would have drifted.

Find the draft PR opened by /opsmill-dev-test-driving-bugs on that branch:

gh pr list --head "<branch>" --json number,title,body,headRefName --jq '.[0]'

If a PR exists (/opsmill-dev-test-driving-bugs ran with pr), set HAS_PR=true and validate it:

• PR body must contain AGENT_TEST_COMPLETE. If not, inform the developer: "No AGENT_TEST_COMPLETE marker found. Run /opsmill-dev-test-driving-bugs first." and STOP.
• PR body must NOT contain AGENT_FIX_COMPLETE. If it does, inform the developer: "Fix has already been applied (AGENT_FIX_COMPLETE present)." and STOP.

Bind <branch> once, here: set <branch> to the PR's headRefName. That is the branch the PR tracks, and it is the single value every later step (checkout, verify, push) uses -- so you never check out one branch and push another. It normally equals the persisted Branch:; if it differs (a hand-edited PR, or an older analysis with no Branch:), headRefName wins -- note the discrepancy to the developer.

git fetch origin
git checkout "<branch>"   # <branch> is now the PR's headRefName

If no PR exists, /opsmill-dev-test-driving-bugs was run without pr (fully local). Don't dead-end -- check whether the branch itself exists:

git rev-parse --verify "<branch>" 2>/dev/null || git rev-parse --verify "origin/<branch>" 2>/dev/null

• Branch exists: set HAS_PR=false, check it out (git checkout "<branch>"), and read its diff against the default branch to find the test commit. Proceed -- there is no marker to validate in local mode.
• Branch does not exist either: only now is the test genuinely missing. Inform the developer "Run /opsmill-dev-test-driving-bugs <issue> first." and STOP.

Implement the fix

Follow steps 1--9.

Step 1: Read fix strategy

Read the analyst's fix strategy. This is your starting point: follow the recommended approach, scope, and "Do NOT" guardrails. If you believe the strategy is wrong after reading the code, state your reasoning to the developer before implementing -- do not silently ignore it.

Step 2: Read failing test

Read the failing test in the PR diff. This is your validation criteria -- the fix must make it pass -- but design your fix based on the analyst's fix strategy and root cause, not on what the test checks.

Step 3: Reason about the fix

Before writing any code, reason explicitly about the fix and state it to the developer:

• Is the root cause a shallow symptom (null check, off-by-one) or a deeper design issue?
• If shallow: a targeted fix is appropriate.
• If deeper: a proper fix may require refactoring the affected component. Do it -- do NOT paper over a design flaw with a guard clause.

Step 4: Implement the fix

• Fix the actual root cause, not just the symptom.
• Do NOT change the test the test-writer wrote.
• Do NOT refactor code unrelated to the root cause.
• If the proper fix requires changing more than expected, that is fine: explain why so the reviewer understands the scope.
• Stage files by name (git add path/to/file) -- never git add . or git add -A.
• Commit the fix with an explicit commit message.

Step 5: Verify replication test passes

Run the specific test the test-writer wrote, using the same runner they used (the PR body / test file tells you which).

• If the test still FAILS, revisit your fix. Do NOT proceed until it passes.
• Before continuing, verify git diff shows no changes to the test file(s) from the test-writer's PR. If you accidentally modified a test file, revert those changes.

Gate (T2-verify · P1): paste the actual test-run output proving PASS. Do not write "the test passes" without it. See ../quality-gates/gates/primitives/evidence-before-done.md.

Step 6: Pre-CI checks

Run the project's pre-CI checks before pushing. Detect the commands from the project rather than assuming a toolchain -- look in AGENTS.md, a Makefile/invoke/tasks file, pyproject.toml, or package.json scripts. Apply them in this order, fixing and committing issues as separate commits (do NOT amend previous commits):

1. Auto-format (e.g. uv run invoke format, ruff format, npx biome check --write ., prettier --write). If formatting changed source files, re-run the later phases.
2. Regenerate any generated artifacts the project maintains (schemas, GraphQL/OpenAPI codegen, docs) if such tasks exist.
3. Lint (e.g. ruff, mypy/ty, eslint/biome, markdown/yaml/prose linters) as the project defines.
4. Unit tests for the affected area (e.g. uv run invoke backend.test-unit, npm run test). Run the broader suite the project expects for a change of this size.

Stage any files changed by generation by name -- never git add . / git add -A.

Changelog: if the project has a changelog mechanism, add an entry for this fix:

• towncrier (a [tool.towncrier] config or a changelog.d/newsfragments dir): create a fragment named after the issue, e.g. uv run towncrier create -c "<user-facing description>" <issue_number>.fixed.md. When there is no issue number (free-text bug), towncrier has no number to anchor on -- use its issue-less form with a + prefix, e.g. +<key>.fixed.md (in the free-text case <key> is the slug, with no issue prefix).
• a dev/guidelines/changelog.md describing another process: follow it.
• otherwise a top-level CHANGELOG.md: add a line under the appropriate section.

Write changelog text from the user's perspective, past tense, one sentence, no jargon. Commit the generated/edited file. If the project has no changelog mechanism, skip this and note it.

Gate (T2-verify · P1): paste the output of each pre-CI command (format, regenerate, lint, unit). A claim of "clean" without output fails the gate.

Step 7: Scope check

If the fix requires changes to more than ~10 files, or fundamentally alters a public API contract, STOP and escalate (see below).

Step 8: Push (PR mode) or hand off (local mode)

If HAS_PR=true: push your fix commits to the PR branch before touching the PR body. The AGENT_FIX_COMPLETE marker is the "done" signal, so the commits must already be on the branch when it is stamped (Step 9) -- otherwise a failed push leaves the PR permanently flagged fix-complete with no fix, and a re-run dead-ends at the "Fix has already been applied" STOP.

git push -u origin "<branch>"

<branch> is the value bound during setup (the PR's headRefName) -- the same branch you checked out, so the push always lands on the branch the PR tracks.

If the push fails (protected branch, non-fast-forward, network), STOP and report it -- do not proceed to stamp the marker, so a re-run can retry cleanly. Otherwise continue to Step 9.

If HAS_PR=false (local mode): do NOT push. Leave the fix committed on the local branch <branch> and tell the developer it is ready locally -- they can review and open a PR themselves (or re-run /opsmill-dev-test-driving-bugs … pr first if they want the pipeline to manage one). You are done -- skip Step 9.

Step 9: Update the PR and mark complete (only if HAS_PR=true)

Ship gate (T2 · P2 + P3) — run before any PR edit or marker stamp. Run the ship gate per ../quality-gates/gates/primitives/independent-judge.md (judge → on-FAIL STOP → R2 degrade → write receipt on PASS, all defined there). R1 criteria: the .bug-analysis-<key>.md file verbatim (the root cause + fix strategy — NOT your summary). Artifact: git diff <default-branch>...HEAD. Forbidden evasions: the test-gate and fix-gate evasions from ../quality-gates/gates/primitives/anti-gaming.md.

With the commits already pushed, finalize the PR last:

• Update the PR title to: fix: <short description> (closes #<issue number>) (omit the closes clause if there is no issue).
• Update the PR body: if .github/pull_request_template.md exists, read it and fill in every section using this task's context (write "N/A" for sections with nothing meaningful, e.g. Screenshots -- do not skip or invent). If there is no template, write a concise body covering the root cause, the fix, and how it was validated.
• Ensure the hidden marker <!-- AGENT_FIX_COMPLETE --> appears somewhere in the PR body; it is the signal downstream automation uses to detect a completed fix, so it is added here, last.
• Use gh pr edit to apply the title and body.
• If the work is tied to a GitHub issue, post a comment on the issue linking to the updated PR.

Escalation

If at any point you determine that:

• the analyst's root cause is incorrect and the real cause is substantially different,
• the test cannot be made to pass with a correct fix (i.e. it tests the wrong behavior), or
• the fix is beyond the scope an automated agent should handle (step 7),

then inform the developer explaining your findings and STOP. Do not stamp AGENT_FIX_COMPLETE (Step 9): an unstamped PR -- even if fix commits were already pushed in Step 8 -- correctly signals the fix is incomplete, and the developer can take it from there.

Quality gates

Gates for this skill follow ../quality-gates/gates/gate-model.md. fixing-bugs is Tier 2 — it ships a fix and stamps a completion marker.

Common mistakes