Debug to Fix

Prerequisites

This elixir works best with these skills installed:

Skill	Purpose	If Missing
rubber-duck	Structured problem clarification	Falls back to built-in questions
prove-it	Verification enforcement	Falls back to built-in verification
retrospective	Document learnings	Skipped (optional phase)

The elixir degrades gracefully - it will use built-in fallbacks for missing skills.

When To Activate

Instructions

Phase 1: Clarify

<phase_clarify> If rubber-duck skill installed: Invoke it now.

If not installed, ask:

Before we debug, let me understand the problem:

1. Expected: What should happen?
2. Actual: What actually happens?
3. Tried: What have you already attempted?
4. Changed: What changed before this broke?

GATE: Do not proceed until you can state the problem in one sentence: "When I [action], I expect [expected], but instead [actual]."

Write this sentence before continuing. </phase_clarify>

Phase 2: Investigate

<phase_investigate> Objective: Find the root cause, not just symptoms.

Investigation checklist:

1. Reproduce: Can you trigger the bug reliably?

   • Yes, every time
   • Sometimes (note conditions)
   • Haven't tried yet → Try now

2. Isolate: Where does the bug live?

   • Identified the file(s)
   • Identified the function(s)
   • Narrowed to specific lines

3. Understand: Why does it fail?

   • Read the actual error (not just the message)
   • Checked the data/state at failure point
   • Understood the expected flow vs actual flow

Investigation techniques (try in order):

1. Read the error message completely - what does it actually say?
2. Add logging/print at the failure point - what are the actual values?
3. Trace backwards - where do the bad values come from?
4. Check recent changes - git diff, git log
5. Rubber duck the code flow aloud

GATE: Do not proceed until you can answer:

• "The bug happens because [specific cause]"
• "I know this because [evidence]"

Write both sentences before continuing. </phase_investigate>

Phase 3: Fix

<phase_fix> Now implement the fix.

Before writing code, state:

1. What you're changing
2. Why this fixes the root cause (not just symptoms)
3. Risk of this change breaking something else

Implement the minimal fix. Resist the urge to refactor nearby code. </phase_fix>

Phase 4: Verify

<phase_verify> If prove-it skill installed: Invoke it now.

If not installed:

Verification checklist:

• Original bug no longer reproduces
• Tested the exact scenario from Phase 1
• Checked for regressions in related functionality
• Tests pass (if applicable)

GATE: Do not declare victory until verification complete.

Show the evidence:

VERIFIED:
- [What you tested]
- [What you observed]
- [Why this confirms the fix]

</phase_verify>

Phase 5: Document (Optional)

<phase_document> If retrospective skill installed: Invoke it for significant bugs.

If not installed or bug was minor: Skip this phase.

For significant debugging sessions (>15 min), capture:

• What the bug was
• Why it was hard to find
• What you'd do differently </phase_document>

Output Format

## Debug Session: [Brief description]

### Problem Statement
When I [action], I expect [expected], but instead [actual].

### Root Cause
The bug happens because [cause].
Evidence: [how you know]

### Fix
[What you changed and why]

### Verification
- [x] Original bug fixed
- [x] [Other checks performed]

### Learnings (if significant)
[What you'd do differently]

NEVER

• Jump to fixes before completing Phase 1 (clarify)
• Guess at root cause without evidence (Phase 2)
• Declare "fixed" without verification (Phase 4)
• Skip gates because "I already know the answer"
• Refactor unrelated code while fixing a bug

ALWAYS

• Write the problem statement sentence before investigating
• State root cause with evidence before fixing
• Verify the exact original scenario after fixing
• Keep fixes minimal and focused

Example

User: "The login is broken, I don't know why"

Phase 1 - Clarify:

Before we debug, help me understand:

1. What should happen when you log in?
2. What actually happens?
3. What have you tried?
4. Did anything change recently?

[User answers]

Problem statement: "When I submit the login form, I expect to be redirected to /dashboard, but instead I see a blank page with no errors."

Phase 2 - Investigate:

Let me investigate...

• Checked network tab: POST /api/login returns 200 ✓
• Checked console: No errors ✓
• Checked redirect logic: router.push('/dashboard') is called
• Added logging: redirect fires but page doesn't change
• Checked recent commits: Found change to middleware yesterday

Root cause: "The bug happens because new auth middleware redirects /dashboard back to /login for users without 'verified' flag, creating a loop that results in blank page." Evidence: "Middleware logs show redirect loop, user object missing 'verified' field."

Phase 3 - Fix:

Fixing: Add 'verified: true' to user object after successful login Why: Root cause is missing field, not redirect logic Risk: Low - only affects login success path

Phase 4 - Verify:

VERIFIED:

• Logged in with test user → redirected to /dashboard ✓
• No redirect loop in network tab ✓
• Middleware logs show single redirect ✓
• Existing tests pass ✓