Focused Fix — Deep-Dive Feature Repair

When to Use

Activate when the user asks to fix, debug, or make a specific feature/module/area work. Key triggers:

• "make X work"
• "fix the Y feature"
• "the Z module is broken"
• "focus on [area]"
• "this feature needs to work properly"

This is NOT for quick single-bug fixes (use systematic-debugging for that). This is for when an entire feature or module needs systematic repair — tracing every dependency, reading logs, checking tests, mapping the full dependency graph.

digraph when_to_use {
    "User reports feature broken" [shape=diamond];
    "Single bug or symptom?" [shape=diamond];
    "Use systematic-debugging" [shape=box];
    "Entire feature/module needs repair?" [shape=diamond];
    "Use focused-fix" [shape=box];
    "Something else" [shape=box];

    "User reports feature broken" -> "Single bug or symptom?";
    "Single bug or symptom?" -> "Use systematic-debugging" [label="yes"];
    "Single bug or symptom?" -> "Entire feature/module needs repair?" [label="no"];
    "Entire feature/module needs repair?" -> "Use focused-fix" [label="yes"];
    "Entire feature/module needs repair?" -> "Something else" [label="no"];
}

The Iron Law

NO FIXES WITHOUT COMPLETING SCOPE → TRACE → DIAGNOSE FIRST

If you haven't finished Phase 3, you cannot propose fixes. Period.

Violating the letter of these phases is violating the spirit of focused repair.

Protocol — STRICTLY follow these 5 phases IN ORDER

digraph phases {
    rankdir=LR;
    SCOPE [shape=box, label="Phase 1\nSCOPE"];
    TRACE [shape=box, label="Phase 2\nTRACE"];
    DIAGNOSE [shape=box, label="Phase 3\nDIAGNOSE"];
    FIX [shape=box, label="Phase 4\nFIX"];
    VERIFY [shape=box, label="Phase 5\nVERIFY"];

    SCOPE -> TRACE -> DIAGNOSE -> FIX -> VERIFY;
    FIX -> DIAGNOSE [label="fix broke\nsomething else"];
    FIX -> ESCALATE [label="3+ fixes\ncreate new issues"];
    ESCALATE [shape=doubleoctagon, label="STOP\nQuestion Architecture\nDiscuss with User"];
}

Phase 1: SCOPE — Map the Feature Boundary

Before touching any code, understand the full scope of the feature.

1. Ask the user: "Which feature/folder should I focus on?" if not already clear
2. Identify the PRIMARY folder/files for this feature
3. Map EVERY file in that folder — read each one, understand its purpose
4. Create a feature manifest:

FEATURE SCOPE:
  Primary path: src/features/auth/
  Entry points: [files that are imported by other parts of the app]
  Internal files: [files only used within this feature]
  Total files: N
  Total lines: N

Phase 2: TRACE — Map All Dependencies (Inside AND Outside)

Trace every connection this feature has to the rest of the codebase.

INBOUND (what this feature imports):

1. For every import statement in every file in the feature folder:
   • Trace it to its source
   • Verify the source file exists
   • Verify the imported entity (function, type, component) exists and is exported
   • Check if the types/signatures match what the feature expects
2. Check for:
   • Environment variables used (grep for process.env, import.meta.env, os.environ, etc.)
   • Config files referenced
   • Database models/schemas used
   • API endpoints called
   • Third-party packages imported

OUTBOUND (what imports this feature):

1. Search the entire codebase for imports from this feature folder
2. For each consumer:
   • Verify they're importing entities that actually exist
   • Check if they're using the correct API/interface
   • Note if any consumers are using deprecated patterns

Output format:

DEPENDENCY MAP:
  Inbound (this feature depends on):
    src/lib/db.ts → used in auth/repository.ts (getUserById, createUser)
    src/lib/jwt.ts → used in auth/service.ts (signToken, verifyToken)
    @prisma/client → used in auth/repository.ts
    process.env.JWT_SECRET → used in auth/service.ts
    process.env.DATABASE_URL → used via prisma

  Outbound (depends on this feature):
    src/app/api/login/route.ts → imports { login } from auth/service
    src/app/api/register/route.ts → imports { register } from auth/service
    src/middleware.ts → imports { verifyToken } from auth/service

  Env vars required: JWT_SECRET, DATABASE_URL
  Config files: prisma/schema.prisma (User model)

Phase 3: DIAGNOSE — Find Every Issue

Systematically check for problems. Run ALL of these checks:

CODE QUALITY:

• Every import resolves to a real file/export
• No circular dependencies within the feature
• Types are consistent across boundaries (no any at interfaces)
• Error handling exists for all async operations
• No TODO/FIXME/HACK comments indicating known issues

RUNTIME:

• All required environment variables are set (check .env)
• Database migrations are up to date (if applicable)
• API endpoints return expected shapes
• No hardcoded values that should be configurable

TESTS:

• Run ALL tests related to this feature: find them by searching for imports from the feature folder
• Record every failure with full error output
• Check test coverage — are there untested code paths?

LOGS & ERRORS:

• Search for any log files, error reports, or Sentry-style error tracking
• Check git log for recent changes to this feature: git log --oneline -20 -- <feature-path>
• Check if any recent commits might have broken something: git log --oneline -5 --all -- <files that this feature depends on>

CONFIGURATION:

• Verify all config files this feature depends on are valid
• Check for mismatches between development and production configs
• Verify third-party service credentials are valid (if testable)

ROOT-CAUSE CONFIRMATION: For each CRITICAL issue found, confirm root cause before adding it to the fix list:

• State clearly: "I think X is the root cause because Y"
• Trace the data/control flow backward to verify — don't trust surface-level symptoms
• If the issue spans multiple components, add diagnostic logging at each boundary to identify which layer fails
• For complex bugs, run a root-cause investigation before proceeding: reproduce the failure reliably, read the full error and stack trace, check what changed recently (git log, git diff), and form one hypothesis at a time that you test with the smallest possible change. Do not add a bug to the fix list until a hypothesis survives its test.

RISK LABELING: Assign each issue a risk label:

Output format:

DIAGNOSIS REPORT:
  Issues found: N

  CRITICAL:
    1. [HIGH] [file:line] — description of issue. Root cause: [confirmed explanation]
    2. [HIGH] [file:line] — description of issue. Root cause: [confirmed explanation]

  WARNINGS:
    1. [MED] [file:line] — description of issue
    2. [LOW] [file:line] — description of issue

  TESTS:
    Ran: N tests
    Passed: N
    Failed: N
    [list each failure with one-line summary]

Phase 4: FIX — Repair Everything Systematically

Fix issues in this EXACT order:

1. DEPENDENCIES FIRST — fix broken imports, missing packages, wrong versions
2. TYPES SECOND — fix type mismatches at feature boundaries
3. LOGIC THIRD — fix actual business logic bugs
4. TESTS FOURTH — fix or create tests for each fix
5. INTEGRATION LAST — verify the feature works end-to-end with its consumers

Rules:

• Fix ONE issue at a time
• After each fix, run the related test to confirm it works
• If a fix breaks something else, STOP and re-evaluate (go back to DIAGNOSE)
• Keep a running log of every change made
• Never change code outside the feature folder without explicitly stating why
• Fix HIGH-risk issues before MED, MED before LOW

ESCALATION RULE — 3-Strike Architecture Check: If 3+ fixes in this phase create NEW issues (not pre-existing ones), STOP immediately.

This pattern indicates an architectural problem, not a bug collection:

• Each fix reveals new shared state / coupling / problem in a different place
• Fixes require "massive refactoring" to implement
• Each fix creates new symptoms elsewhere

Action: Stop fixing. Tell the user: "3+ fixes have cascaded into new issues. This suggests the feature's architecture may need rethinking, not patching. Here's what I've found: [summary]. Should we continue fixing symptoms or discuss restructuring?"

Do NOT attempt fix #4 without this discussion.

Output after each fix:

FIX #1:
  File: auth/service.ts:45
  Issue: signToken called with wrong argument order
  Change: swapped (expiresIn, payload) to (payload, expiresIn)
  Test: auth.test.ts → PASSES

Phase 5: VERIFY — Confirm Everything Works

After all fixes are applied:

1. Run ALL tests in the feature folder — every single one must pass
2. Run ALL tests in files that IMPORT from this feature — must pass
3. Run the full test suite if available — check for regressions
4. If the feature has a UI, describe how to manually verify it
5. Summarize all changes made

Final output:

FOCUSED FIX COMPLETE:
  Feature: auth
  Files changed: 4
  Total fixes: 7
  Tests: 23/23 passing
  Regressions: 0

  Changes:
    1. auth/service.ts — fixed token signing argument order
    2. auth/repository.ts — added null check for user lookup
    3. auth/middleware.ts — fixed async error handling
    4. auth/types.ts — aligned UserResponse type with actual DB schema

  Consumers verified:
    - src/app/api/login/route.ts ✅
    - src/app/api/register/route.ts ✅
    - src/middleware.ts ✅

Red Flags — STOP and Return to Current Phase

If you catch yourself thinking any of these, you are skipping phases:

• "I can see the bug, let me just fix it" → STOP. You haven't traced dependencies yet.
• "Scoping is overkill, it's obviously just this file" → STOP. That's always wrong for feature-level fixes.
• "I'll map dependencies after I fix the obvious stuff" → STOP. You'll miss root causes.
• "The user said fix X, so I only need to look at X" → STOP. Features have dependencies.
• "Tests are passing so I'm done" → STOP. Did you run consumer tests too?
• "I don't need to check env vars for this" → STOP. Config issues masquerade as code bugs.
• "One more fix should do it" (after 2+ cascading failures) → STOP. Escalate.
• "I'll skip the diagnosis report, the fixes are obvious" → STOP. Write it down.

ALL of these mean: Return to the phase you're supposed to be in.

Common Rationalizations

Anti-Patterns — NEVER do these

Related Skills

• self-eval (this repo, engineering/skills/self-eval) — Use after Phase 5 to score the fix honestly before reporting it done
• incident-commander (this repo, engineering-team/skills/incident-commander, separate plugin) — Use instead when the broken feature is a live production incident, not a local repair
• Optional, if installed: the third-party superpowers plugin's systematic-debugging and verification-before-completion skills cover the same ground as the root-cause step in Phase 3 and the checks in Phase 5. This skill does not require them; the steps above are self-contained.

Quick Reference