git:20260413.7bb5456 to git:20260419.30f5b92

---

name: interrogation-debugging

description: Use when encountering any bug, test failure, or unexpected behavior — finds the rat in the code through systematic root-cause interrogation before any fix attempts

---

# The Interrogation: Systematic Debugging

## Overview

Random fixes waste time and create new bugs. Quick patches let the real rat walk free.

**Violating the letter of this process is violating the spirit of debugging.**

## The Iron Law

```

NO FIXES WITHOUT ROOT CAUSE INVESTIGATION FIRST

```

If you haven't completed The Brief, you cannot propose fixes. This is Omerta.

## When to Use

Use for ANY technical issue:

- Test failures

- Bugs in production

- Unexpected behavior

- Performance problems

- Build failures

- Integration issues

**Use this ESPECIALLY when:**

- Under time pressure (emergencies make guessing tempting)

- "Just one quick fix" seems obvious

- You've already tried multiple fixes

- Previous fix didn't work

- You don't fully understand the issue

**Don't skip when:**

- Issue seems simple (simple bugs have root causes too)

- You're in a hurry (rushing guarantees rework)

- The Don wants it fixed NOW (systematic is faster than thrashing)

## The Four Phases

You MUST complete each phase before proceeding to the next.

### The Brief

**BEFORE attempting ANY fix:**

1. **Read the Evidence**

- Don't skip past errors or warnings

- They often contain the exact solution

- Read stack traces completely

- Note line numbers, file paths, error codes

2. **Reproduce the Crime**

- Can you trigger it reliably?

- What are the exact steps?

- Does it happen every time?

- If not reproducible → gather more data, don't guess

3. **Check Recent Activity**

- What changed that could cause this?

- Git diff, recent commits

- New dependencies, config changes

- Environmental differences

4. **Gather Evidence at Every Boundary**

**WHEN system has multiple components (CI → build → signing, API → service → database):**

**BEFORE proposing fixes, add diagnostic instrumentation:**

For EACH component boundary:

- Log what data enters the component

- Log what data exits the component

- Verify environment/config propagation

- Check state at each layer

Run once to gather evidence showing WHERE it breaks.

THEN analyze evidence to identify the failing component.

THEN investigate that specific component.

5. **Trace the Data Flow**

**WHEN error is deep in the call stack:**

- Where does the bad value originate?

- What called this with the bad value?

- Keep tracing backward until you find the source

- Fix at source, not at symptom

### Cross-Examination

**Find the pattern before fixing:**

1. **Find Working Examples**

- Locate similar working code in the same codebase

- What works that's similar to what's broken?

2. **Compare Against References**

- If implementing a pattern, read the reference implementation COMPLETELY

- Don't skim — read every line

- Understand the pattern fully before applying

3. **Identify Differences**

- What's different between working and broken?

- List every difference, however small

- Don't assume "that can't matter"

4. **Understand Dependencies**

- What other components does this need?

- What settings, config, environment?

- What assumptions does it make?

### The Theory

**Scientific method:**

1. **Form Single Hypothesis**

- State clearly: "I think X is the root cause because Y"

- Write it down

- Be specific, not vague

2. **Test Minimally**

- Make the SMALLEST possible change to test the hypothesis

- One variable at a time

- Don't fix multiple things at once

3. **Verify Before Continuing**

- Did it work? Yes → The Hit

- Didn't work? Form NEW hypothesis

- DON'T add more fixes on top

4. **When You Don't Know**

- Say "I don't understand X"

- Don't pretend to know

- Ask for help or research more

### The Hit

**Fix the root cause, not the symptom:**

1. **Create Failing Test Case**

- Simplest possible reproduction

- Automated test if possible

- One-off test script if no framework

- MUST have before fixing

- Use `gangsta:drill-tdd` for writing proper failing tests

2. **Implement Single Fix**

- Address the root cause identified

- ONE change at a time

- No "while I'm here" improvements

- No bundled refactoring

3. **Verify Fix**

- Test passes now?

- No other tests broken?

- Issue actually resolved?

- Use `gangsta:sweep-verification` to verify before claiming success

4. **If Fix Doesn't Work**

- STOP

- Count: How many fixes have you tried?

- If < 3: Return to The Brief, re-analyze with new information

- **If ≥ 3: STOP and escalate (Step 5 below)**

- DON'T attempt Fix #4 without architectural discussion

5. **If 3+ Fixes Failed: Escalate to the Don**

**Pattern indicating architectural rot:**

- Each fix reveals new shared state/coupling/problem in a different place

- Fixes require "massive refactoring" to implement

- Each fix creates new symptoms elsewhere

**STOP and question fundamentals:**

- Is this pattern fundamentally sound?

- Are we sticking with it through sheer inertia?

- Should we refactor architecture vs. continue fixing symptoms?

**Discuss with the Don before attempting more fixes.**

This is NOT a failed hypothesis — this is a wrong architecture.

## Red Flags — STOP and Follow Process

If you catch yourself thinking:

| Thought | Reality |

|---------|---------|

| "Quick fix for now, investigate later" | Investigate NOW. Quick fixes compound. |

| "Just try changing X and see" | That's guessing, not debugging. The Brief. |

| "Add multiple changes, run tests" | Can't isolate what worked. One at a time. |

| "Skip the test, I'll manually verify" | Manual verification is not evidence. |

| "It's probably X, let me fix that" | "Probably" means you haven't investigated. |

| "I don't fully understand but this might work" | Might = guessing. The Brief. |

| "One more fix attempt" (after 2+) | 3 failures = architectural problem. Escalate. |

| Proposing solutions before tracing data flow | STOP. Trace first, propose second. |

**ALL of these mean: STOP. Return to The Brief.**

## The Don's Signals You're Doing It Wrong

Watch for these redirections:

- "Is that not happening?" — You assumed without verifying

- "Will it show us...?" — You should have added evidence gathering

- "Stop guessing" — You're proposing fixes without understanding

- "Think harder" — Question fundamentals, not just symptoms

- "We're stuck?" (frustrated) — Your approach isn't working

**When you see these:** STOP. Return to The Brief.

## Common Rationalizations

| Excuse | Reality |

|--------|---------|

| "Issue is simple, don't need process" | Simple issues have root causes too. Process is fast for simple bugs. |

| "Emergency, no time for process" | Systematic debugging is FASTER than guess-and-check thrashing. |

| "Just try this first, then investigate" | First fix sets the pattern. Do it right from the start. |

| "I'll write test after confirming fix works" | Untested fixes don't stick. Test first proves it. |

| "Multiple fixes at once saves time" | Can't isolate what worked. Causes new bugs. |

| "Reference too long, I'll adapt the pattern" | Partial understanding guarantees bugs. Read it completely. |

| "I see the problem, let me fix it" | Seeing symptoms ≠ understanding root cause. |

| "One more fix attempt" (after 2+ failures) | 3+ failures = architectural problem. Escalate to the Don. |

## Quick Reference

| Phase | Key Activities | Success Criteria |

|-------|---------------|------------------|

| **The Brief** | Read errors, reproduce, check changes, gather evidence | Understand WHAT and WHY |

| **Cross-Examination** | Find working examples, compare | Identify differences |

| **The Theory** | Form hypothesis, test minimally | Confirmed or new hypothesis |

| **The Hit** | Create test, fix, verify | Bug resolved, tests pass |

## When Investigation Reveals No Root Cause

If systematic investigation reveals the issue is truly environmental, timing-dependent, or external:

1. You've completed the process

2. Document what you investigated

3. Implement appropriate handling (retry, timeout, error message)

4. Add monitoring/logging for future investigation

**But:** 95% of "no root cause" cases are incomplete investigation.

## Related Skills

- **gangsta:drill-tdd** — For creating failing test case (The Hit, Step 1)

- **gangsta:sweep-verification** — Verify fix worked before claiming success

## Omerta Compliance

- [ ] Rule of Truth: All findings cite specific code, error output, or evidence

- [ ] Spec is Law: Fixes trace to diagnosed root cause, not guesswork