• Test failures
• Bugs in production
• Unexpected behavior
• Performance problems
• Build failures
• Integration issues

• 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

• 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)

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
2. 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
3. Check Recent Changes
   • What changed that could cause this?
   • Git diff, recent commits
   • New dependencies, config changes
   • Environmental differences
4. 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 OK, workflow - build FAIL)
5. Trace Data Flow
   WHEN error is deep in call stack:
   See

   root-cause-tracing.md

   in this directory for the complete 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

1. Find Working Examples
   • Locate similar working code in same codebase
   • What works that's similar to what's broken?
2. Compare Against References
   • If implementing pattern, read 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?

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 hypothesis
   • One variable at a time
   • Don't fix multiple things at once
3. Verify Before Continuing
   • Did it work? Yes - Phase 4
   • 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
   • Research more

1. Create Failing Test Case
   • Simplest possible reproduction
   • Automated test if possible
   • One-off test script if no framework
   • MUST have before fixing
   • Use the

     tdd

     skill 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?
4. 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
5. 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.

• "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

• "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

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

• root-cause-tracing.md

  - Trace bugs backward through call stack to find original trigger

• defense-in-depth.md

  - Add validation at multiple layers after finding root cause

• condition-based-waiting.md

  - Replace arbitrary timeouts with condition polling
• find-polluter - For test pollution bisection (flaky tests due to shared state): run

  .claude/tools/analysis/find-polluter/find-polluter.sh

  (or

  find-polluter.ps1

  on Windows) from the project root to isolate which test pollutes the suite.

• tdd - For creating failing test case (Phase 4, Step 1)
• verification-before-completion - Verify fix worked before claiming success

• 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

.claude/context/memory/learnings.md

• New pattern ->

  .claude/context/memory/learnings.md

• Issue found ->

  .claude/context/memory/issues.md

• Decision made ->

  .claude/context/memory/decisions.md

ASSUME INTERRUPTION: If it's not in memory, it didn't happen.