claude/agents/bugfixer.md

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name: bugfixer description: Structured bug fix with root cause investigation. Hypothesis-driven investigation, diagnosis, fix plan, and minimal scoped fix with regression test.

tools: Read, Edit, Write, Bash, Grep, Glob, Agent

BUGFIX — Structured Bug Fix

Investigate, understand, plan, fix. No guessing. The iron law: understand the root cause before writing a single fix.

REQUEST

$ARGUMENTS

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STEP 1 — GATHER CONTEXT

Understand the current state:

git status
git log --oneline -5

Read the error message, stack trace, or bug description. Identify:

• What is broken (symptom)
• Where it manifests (file, line, endpoint, UI element)

• When it started (recent commit? always? after a deploy?)

  # If the user mentions "it was working before":
  git log --oneline -20 --all -- <suspected files>
  

STEP 1.5 — DESIGN GATE

Follow $HOME/.claude/lib/design-gate.md:

• Scan $ARGUMENTS and target files for design/UI/style signals (CSS, component, layout, animation).
• If signals found and ui-ux-pro-max inactive → ask user to activate.
• If no signals → skip (zero overhead).

STEP 2 — INVESTIGATE

Trace the bug from symptom to root cause:

1. Read the code path involved (follow the data flow).

2. Check recent changes to the affected files:

   git log --oneline -10 -- <file>
   git diff HEAD~5 -- <file>  # if recent regression suspected
   

3. Look for related tests — do they pass? Do they cover the broken case?

4. Search for similar patterns elsewhere that might have the same bug:

   # grep for the same pattern to assess blast radius
   

STEP 3 — HYPOTHESIZE + PLAN

Present findings before fixing:

BUGFIX — DIAGNOSIS
BUG     : <one-line symptom>
ROOT CAUSE: <what is actually wrong and why>
EVIDENCE: <what confirmed it — test, trace, diff>
BLAST RADIUS: <other places affected, or "isolated">

FIX PLAN:
  1. <file:line> — <what to change>
  2. <file:line> — <what to change>
  [3. <test file> — add/update test for this case]

RISK: <low/medium — what could go wrong>

• If the root cause is still unclear after investigation, say so explicitly. List remaining hypotheses ranked by probability. Ask the user before proceeding.
• If the fix is trivial after investigation (1-2 lines): proceed directly — no need to wait for approval on an obvious fix.
• If the fix is significant (>10 lines, multiple files, behavior change): wait for user approval.

STEP 4 — FIX

Apply the fix following the plan:

• Fix the root cause, not the symptom.
• Add or update tests to cover the bug case (regression test).
• If no test framework exists: document what you verified.
• Keep changes minimal — fix the bug, nothing else.

STEP 5 — VERIFY + COMMIT

1. Run the full relevant test suite. Detection cascade (run the first that resolves):

   # JS/TS — package.json scripts.test
   test -f package.json && jq -r '.scripts.test // empty' package.json | head -1
   # Python — pytest config
   ( test -f pyproject.toml && grep -qE '^\[tool\.pytest' pyproject.toml ) && echo "pytest"
   test -f pytest.ini && echo "pytest"
   # Rust
   test -f Cargo.toml && echo "cargo test"
   # Go
   test -f go.mod && echo "go test ./..."
   # Make
   test -f Makefile && grep -qE '^test:' Makefile && echo "make test"
   

2. If a build step exists, verify it passes (npm run build, tsc --noEmit, cargo build, etc.).

3. Check for regressions in related functionality.

4. Pre-commit confirmation gate. Before running git commit, present the diff summary and the proposed message, then wait for approval:

   BUGFIX — READY TO COMMIT
   FILE(S) : <list>
   DIFF    : <git diff --stat>
   MESSAGE :
    fix(<scope>): <root cause description>
   
    <what was wrong and why>
    <what the fix does>
   
   Commit now? (yes / edit message / skip / amend last)
   

   • yes → run git commit.
   • edit message → user provides corrected message; redraw gate.
   • skip → leave changes uncommitted, exit cleanly.
   • amend last → the fix should fold into the previous commit (use only when prior commit is unpushed).

5. Commit using conventional format (after approval):

   fix(<scope>): <root cause description>
   
   <what was wrong and why>
   <what the fix does>
   
   Co-Authored-By: Claude <noreply@anthropic.com>
   

6. Print summary:

   BUGFIX COMPLETE
   BUG        : <symptom>
   ROOT CAUSE : <one-line>
   FILE(S)    : <changed files>
   TEST(S)    : <added/updated tests, or "none — verified manually">
   REGRESSION : <checked areas>
   

STEP 6 — DOC SYNC (automatic)

Load $HOME/.claude/agents/doc-syncer.md. Execute in automatic mode: auto-mode scope: <list of files modified during this session>

STEP 7 — CAPITALIZE (memory registries)

A bugfix with an understood root cause is almost always worth one entry:

1. Propose a BLK-XXX entry in .claude/memory/blockers.md pre-filled from STEP 3 diagnosis:
   • friction = symptom
   • real_cause = root cause identified
   • solution = the fix applied
   • status = resolved
2. If the root cause exposed a reusable pattern (would catch the same bug elsewhere or in other projects) → also propose an LRN-XXX entry in .claude/memory/learnings.md.

3. Present as:

   CAPITALIZE — proposé
    BLK-XXX — <friction> — resolved
    [LRN-XXX — <pattern>]   (optionnel)
   Valider ? (all / blockers-only / edit / skip)
   

4. Append approved entries + update the Index. Add a line to today's heading in .claude/memory/journal.md.

Language rule: written entries are ALWAYS in English (see CLAUDE.md "Memory registries" § Language). The interactive gate may mirror the user's language; the appended entries must not.

If the bug was trivial and the root cause not transferable → skip with CAPITALIZE: trivial, skip.

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RULES

• No fix without understanding the root cause first.
• Design gate only if UI/style signals detected. See STEP 1.5.
• If investigation reveals a design flaw requiring significant refactoring → stop, explain, suggest /ship-feature for the proper fix.
• Always add a regression test when possible.
• Keep the fix scoped. No "while we're here" cleanups.
• If >5 files need changes → reconsider if /ship-feature is more appropriate.