Category	Characteristics	Example
A. Missing Spec	No documentation on how to do it	New feature without checklist
B. Cross-Layer Contract	Interface between layers unclear	API returns different format than expected
C. Change Propagation Failure	Changed one place, missed others	Changed function signature, missed call sites
D. Test Coverage Gap	Unit test passes, integration fails	Works alone, breaks when combined
E. Implicit Assumption	Code relies on undocumented assumption	Timestamp seconds vs milliseconds

2. Why Fixes Failed (if applicable)

If you tried multiple fixes before succeeding, analyze each failure:

Surface Fix: Fixed symptom, not root cause
Incomplete Scope: Found root cause, didn't cover all cases
Tool Limitation: grep missed it, type check wasn't strict
Mental Model: Kept looking in same layer, didn't think cross-layer

3. Prevention Mechanisms

What mechanisms would prevent this from happening again?

Type	Description	Example
Documentation	Write it down so people know	Update thinking guide
Architecture	Make the error impossible structurally	Type-safe wrappers
Compile-time	TypeScript strict, no any	Signature change causes compile error
Runtime	Monitoring, alerts, scans	Detect orphan entities
Test Coverage	E2E tests, integration tests	Verify full flow
Code Review	Checklist, PR template	"Did you check X?"

4. Systematic Expansion

What broader problems does this bug reveal?

Similar Issues: Where else might this problem exist?
Design Flaw: Is there a fundamental architecture issue?
Process Flaw: Is there a development process improvement?
Knowledge Gap: Is the team missing some understanding?

5. Knowledge Capture

Solidify insights into the system:

Update .trellis/spec/guides/ thinking guides
Update .trellis/spec/backend/ or frontend/ docs
Create issue record (if applicable)
Create feature ticket for root fix
Update check skills if needed

Output Format

Please output analysis in this format:

## Bug Analysis: [Short Description]

### 1. Root Cause Category
- **Category**: [A/B/C/D/E] - [Category Name]
- **Specific Cause**: [Detailed description]

### 2. Why Fixes Failed (if applicable)
1. [First attempt]: [Why it failed]
2. [Second attempt]: [Why it failed]
...

### 3. Prevention Mechanisms
| Priority | Mechanism | Specific Action | Status |
|----------|-----------|-----------------|--------|
| P0 | ... | ... | TODO/DONE |

### 4. Systematic Expansion
- **Similar Issues**: [List places with similar problems]
- **Design Improvement**: [Architecture-level suggestions]
- **Process Improvement**: [Development process suggestions]

### 5. Knowledge Capture
- [ ] [Documents to update / tickets to create]

Core Philosophy

The value of debugging is not in fixing the bug, but in making this class of bugs never happen again.

Three levels of insight:

Tactical: How to fix THIS bug
Strategic: How to prevent THIS CLASS of bugs
Philosophical: How to expand thinking patterns

30 minutes of analysis saves 30 hours of future debugging.

After Analysis: Immediate Actions

IMPORTANT: After completing the analysis above, you MUST immediately:

Update spec/guides - Don't just list TODOs, actually update the relevant files:
- If it's a cross-platform issue → update cross-platform-thinking-guide.md
- If it's a cross-layer issue → update cross-layer-thinking-guide.md
- If it's a code reuse issue → update code-reuse-thinking-guide.md
- If it's domain-specific → update backend/*.md or frontend/*.md
Sync templates - After updating .trellis/spec/, sync to src/templates/markdown/spec/
Commit the spec updates - This is the primary output, not just the analysis text

The analysis is worthless if it stays in chat. The value is in the updated specs.