systematic-debugging

Random fixes waste time and create new bugs. Quick patches mask underlying issues.

Core principle: ALWAYS find root cause before attempting fixes. Symptom fixes are failure.

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

```

NO FIXES WITHOUT ROOT CAUSE INVESTIGATION FIRST

```

If you haven't completed Phase 1, you cannot propose fixes.

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)
• Manager wants it fixed NOW (systematic is faster than thrashing)

You MUST complete each phase before proceeding to the next.

Phase 1: Root Cause Investigation

BEFORE attempting ANY fix:

1. Read Error Messages Carefully

- Don't skip past errors or warnings

- They often contain the exact solution

- Read stack traces completely

- Note line numbers, file paths, error codes

1. Reproduce Consistently

- Can you trigger it reliably?

- What are the exact steps?

- Does it happen every time?

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

1. Check Recent Changes

- What changed that could cause this?

- Git diff, recent commits

- New dependencies, config changes

- Environmental differences

1. Gather Evidence in Multi-Component Systems

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 component

- Log what data exits component

- Verify environment/config propagation

- Check state at each layer

Run once to gather evidence showing WHERE it breaks

THEN analyze evidence to identify failing component

THEN investigate that specific component

```

Example (multi-layer system):

```bash

# Layer 1: Workflow

echo "=== Secrets available in workflow: ==="

echo "IDENTITY: ${IDENTITY:+SET}${IDENTITY:-UNSET}"

# Layer 2: Build script

echo "=== Env vars in build script: ==="

env | grep IDENTITY || echo "IDENTITY not in environment"

# Layer 3: Signing script

echo "=== Keychain state: ==="

security list-keychains

security find-identity -v

# Layer 4: Actual signing

codesign --sign "$IDENTITY" --verbose=4 "$APP"

```

This reveals: Which layer fails (secrets → workflow ✓, workflow → build ✗)

1. Trace Data Flow

WHEN error is deep in call stack:

REQUIRED SUB-SKILL: Use superpowers:root-cause-tracing for backward tracing technique

Quick version:

- Where does bad value originate?

- What called this with bad value?

- Keep tracing up until you find the source

- Fix at source, not at symptom

Phase 2: Pattern Analysis

Find the pattern before fixing:

1. Find Working Examples

- Locate similar working code in same codebase

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

1. Compare Against References

- If implementing pattern, read reference implementation COMPLETELY

- Don't skim - read every line

- Understand the pattern fully before applying

1. Identify Differences

- What's different between working and broken?

- List every difference, however small

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

1. Understand Dependencies

- What other components does this need?

- What settings, config, environment?

- What assumptions does it make?

Phase 3: Hypothesis and Testing

Scientific method:

1. Form Single Hypothesis

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

- Write it down

- Be specific, not vague

1. Test Minimally

- Make the SMALLEST possible change to test hypothesis

- One variable at a time

- Don't fix multiple things at once

1. Verify Before Continuing

- Did it work? Yes → Phase 4

- Didn't work? Form NEW hypothesis

- DON'T add more fixes on top

1. When You Don't Know

- Say "I don't understand X"

- Don't pretend to know

- Ask for help

- Research more

Phase 4: Implementation

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

- REQUIRED SUB-SKILL: Use superpowers:test-driven-development for writing proper failing tests

1. Implement Single Fix

- Address the root cause identified

- ONE change at a time

- No "while I'm here" improvements

- No bundled refactoring

1. Verify Fix

- Test passes now?

- No other tests broken?

- Issue actually resolved?

1. If Fix Doesn't Work

- STOP

- Count: How many fixes have you tried?

- If < 3: Return to Phase 1, re-analyze with new information

- If ≥ 3: STOP and question the architecture (step 5 below)

- DON'T attempt Fix #4 without architectural discussion

1. If 3+ Fixes Failed: Question Architecture

Pattern indicating architectural problem:

- Each fix reveals new shared state/coupling/problem in 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 your human partner before attempting more fixes

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

If you catch yourself thinking:

• "Quick fix for now, investigate later"
• "Just try changing X and see if it works"
• "Add multiple changes, run tests"
• "Skip the test, I'll manually verify"
• "It's probably X, let me fix that"
• "I don't fully understand but this might work"
• "Pattern says X but I'll adapt it differently"
• "Here are the main problems: [lists fixes without investigation]"
• Proposing solutions before tracing data flow
• "One more fix attempt" (when already tried 2+)
• Each fix reveals new problem in different place

ALL of these mean: STOP. Return to Phase 1.

If 3+ fixes failed: Question the architecture (see Phase 4.5)

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
• "Ultrathink this" - Question fundamentals, not just symptoms
• "We're stuck?" (frustrated) - Your approach isn't working

When you see these: STOP. Return to Phase 1.

| 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. Question pattern, don't fix again. |

| Phase | Key Activities | Success Criteria |

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

| 1. Root Cause | Read errors, reproduce, check changes, gather evidence | Understand WHAT and WHY |

| 2. Pattern | Find working examples, compare | Identify differences |

| 3. Hypothesis | Form theory, test minimally | Confirmed or new hypothesis |

| 4. Implementation | Create test, fix, verify | Bug resolved, tests pass |

If systematic investigation reveals 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.

This skill requires using:

• root-cause-tracing - REQUIRED when error is deep in call stack (see Phase 1, Step 5)
• test-driven-development - REQUIRED for creating failing test case (see Phase 4, Step 1)

Complementary skills:

• defense-in-depth - Add validation at multiple layers after finding root cause
• condition-based-waiting - Replace arbitrary timeouts identified in Phase 2
• verification-before-completion - Verify fix worked before claiming success

From debugging sessions:

• Systematic approach: 15-30 minutes to fix
• Random fixes approach: 2-3 hours of thrashing
• First-time fix rate: 95% vs 40%
• New bugs introduced: Near zero vs common