Paths: File paths (shared/, references/, ../ln-*) are relative to skills repo root. If not found at CWD, locate this SKILL.md directory and go up one level for repo root.

Tech Debt Cleaner (L3 Worker)

Automated cleanup of safe, low-risk tech debt findings from codebase audits.

Purpose & Scope

• Consume audit findings from docs/project/codebase_audit.md (ln-620 output) or ln-511 code quality output
• Filter to auto-fixable findings with confidence >=90%
• Apply safe fixes: remove unused imports, delete dead code, clean commented-out blocks, remove deprecated aliases
• Never touch business logic, complex refactoring, or architectural changes
• Create single commit with structured summary of all changes
• Invocable from ln-510 quality coordinator pipeline or standalone

Auto-Fixable Categories

Category	Source Prefix	Risk	Auto-Fix Action
Unused imports	MNT-DC-	LOW	Delete import line
Unused variables	MNT-DC-	LOW	Delete declaration
Unused functions (unexported)	MNT-DC-	LOW	Delete function block
Commented-out code (>5 lines)	MNT-DC-	LOW	Delete comment block
Backward-compat shims (>6 months)	MNT-DC-	MEDIUM	Delete shim + update re-exports
Deprecated aliases	MNT-DC-	LOW	Delete alias line
Trailing whitespace / empty lines	MNT-	LOW	Trim / collapse

NOT Auto-Fixable (skip always)

Category	Reason
DRY violations (MNT-DRY-)	Requires architectural decision on where to extract
God classes (MNT-GOD-)	Requires domain knowledge for splitting
Security issues (SEC-)	Requires context-specific fix
Architecture violations (ARCH-*)	Requires design decision
Performance issues (PERF-*)	Requires benchmarking
Any finding with effort M or L	Too complex for auto-fix

When to Use

• Invoked by ln-510-quality-coordinator Phase 3 (after ln-511 code quality check)
• Standalone: After ln-620 codebase audit completes (user triggers manually)
• Scheduled: As periodic "garbage collection" for codebase hygiene

Inputs

• Pipeline mode (ln-510): findings from ln-511 code quality output (passed via coordinator context)
• Standalone mode: docs/project/codebase_audit.md (ln-620 output)

Workflow

1. Load findings: Read docs/project/codebase_audit.md. Parse findings from Dead Code section (ln-626 results) and Code Quality section (ln-624 results).

2. Filter to auto-fixable:

   • Category must be in Auto-Fixable table above
   • Severity must be LOW or MEDIUM (no HIGH/CRITICAL)
   • Effort must be S (small)
   • Skip files in: node_modules/, vendor/, dist/, build/, *.min.*, generated code, test fixtures

3. Verify each finding (confidence check): MANDATORY READ: shared/references/clean_code_checklist.md For each candidate fix: a) Read the target file at specified location b) Confirm the finding still exists (file may have changed since audit) c) Confirm removal is safe:

   • For unused imports: grep codebase for usage (must have 0 references)
   • For unused functions: grep for function name (must have 0 call sites)
   • For commented-out code: verify block is code, not documentation
   • For deprecated aliases: verify no consumers remain d) Assign confidence score (0-100). Only proceed if confidence >=90

4. Apply fixes (bottom-up within each file):

   • Sort fixes by line number descending (bottom-up prevents line shift issues)
   • Apply each fix using Edit tool
   • Track: file, lines removed, category, original finding ID

5. Verify build integrity: Per shared/references/ci_tool_detection.md discovery hierarchy: detect and run lint + typecheck commands.

   • If ANY check fails: revert ALL changes (git checkout .), report failure
   • If no lint/type commands detected: skip verification with warning

6. Create commit:

   • Stage only modified files (explicit git add per file, not git add .)
   • Commit message format:

     chore: automated tech debt cleanup
     
     Removed {N} auto-fixable findings from codebase audit:
     - {count} unused imports
     - {count} dead functions
     - {count} commented-out code blocks
     - {count} deprecated aliases
     
     Source: docs/project/codebase_audit.md
     Confidence threshold: >=90%
     

7. Update audit report:

   • Add "Last Cleanup" section to docs/project/codebase_audit.md:

     ## Last Automated Cleanup
     **Date:** YYYY-MM-DD
     **Findings fixed:** N of M auto-fixable
     **Skipped:** K (confidence <90% or verification failed)
     **Build check:** PASSED / SKIPPED
     

Output Format

verdict: CLEANED | NOTHING_TO_CLEAN | BUILD_FAILED
stats:
  total_findings: {from audit}
  auto_fixable: {filtered count}
  applied: {actually fixed}
  skipped: {confidence <90 or stale}
  reverted: {if build failed, all}
fixes:
  - file: "src/utils/helpers.ts"
    line: 45
    category: "unused_function"
    removed: "formatDate()"
    finding_id: "MNT-DC-003"
  - file: "src/api/v1/auth.ts"
    line: 12
    category: "deprecated_alias"
    removed: "export { newAuth as oldAuth }"
    finding_id: "MNT-DC-007"
build_check: PASSED | SKIPPED | FAILED
commit_sha: "abc1234" | null

Critical Rules

• Safety first: Never fix if confidence <90%. When in doubt, skip.
• Bottom-up editing: Always apply fixes from bottom to top of file to avoid line number shifts.
• Build verification: If linter/type-checker fails after fixes, revert ALL changes immediately.
• No business logic: Never modify function bodies, conditionals, or control flow.
• Explicit staging: Stage files by name, never git add . or git add -A.
• Idempotent: Running twice produces no changes if audit report unchanged.
• Git-aware: Only operate on tracked files. Skip untracked or ignored files.
• Exclusions: Skip generated code, vendor directories, minified files, test fixtures.

Definition of Done

• Audit report loaded and parsed
• Findings filtered to auto-fixable categories
• Each finding verified with confidence >=90%
• Fixes applied bottom-up per file
• Build integrity verified (lint + type check) or skipped with warning
• Single commit created with structured message (or all reverted on build failure)
• Audit report updated with "Last Automated Cleanup" section
• Output YAML returned to caller

Reference Files

• Clean code checklist: shared/references/clean_code_checklist.md
• Audit output schema: shared/references/audit_output_schema.md
• Audit report template: shared/templates/codebase_audit_template.md

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Version: 1.0.0 Last Updated: 2026-02-15