trellis-break-loop

name	trellis-break-loop
description	Deep bug analysis to break the fix-forget-repeat cycle. Analyzes root cause category, why fixes failed, prevention mechanisms, and captures knowledge into specs. Use after fixing a bug to prevent the same class of bugs.

Break the Loop - Deep Bug Analysis

When debug is complete, use this for deep analysis to break the "fix bug -> forget -> repeat" cycle.

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Analysis Framework

Analyze the bug you just fixed from these 5 dimensions:

1. Root Cause Category

Which category does this bug belong to?

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	Strict type checking, no escape hatches	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 relevant .trellis/spec/ docs
• Create issue record (if applicable)
• Create feature ticket for root fix
• Update check guidelines if needed

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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]

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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:

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

30 minutes of analysis saves 30 hours of future debugging.

Thinking Framework: Bayesian Reasoning

When multiple root causes are plausible and evidence is incomplete, update your beliefs proportionally to new evidence rather than clinging to initial assumptions.

Step 1: Establish Priors

Before investigating, state what you believe and why:

Hypothesis	Prior	Reasoning
H1: [cause A]	40%	Most common for this pattern
H2: [cause B]	30%	Plausible given environment
H3: [other]	30%	Catch-all

Priors must sum to 100%. If you can't assign probabilities, investigate first.

Step 2: Observe Evidence

Document what you found — be specific about reliability:

• What exactly did you observe?
• How reliable? (test output > log message > user report > hunch)
• Could multiple hypotheses explain this?

Step 3: Update Beliefs

For each hypothesis, ask: How likely is this evidence if this hypothesis were true?

Direction of update matters more than calculation:

• Evidence strongly predicted by H1 → H1 probability increases
• Evidence contradicts H2 → H2 probability decreases
• Evidence equally likely under all → no update

Step 4: Seek Discriminating Evidence

Don't gather more of the same. Find evidence that differs strongly between top hypotheses.

If H1 and H3 are close: "What would I see if H1 is true but not if H3 is true?" Then check for that.

Step 5: State Confidence

Confidence	Action
90%+	Proceed with fix, monitor
70-90%	Proceed, add fallback check
50-70%	Test hypothesis before committing
<50%	Need more evidence, don't guess

Never express binary certainty when evidence is incomplete. Use "most likely", "plausible but unlikely", "worth investigating".

Common Fallacies

Fallacy	Example	Correction
Base rate neglect	"Test failed → code is broken"	How often do tests fail for other reasons?
Confirmation bias	"Must be a race condition, let me find race evidence"	Actively seek evidence AGAINST your top hypothesis
Anchoring	"Last time it was caching, probably caching again"	Establish priors from current context, not yesterday's bug

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After Analysis: Immediate Actions

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

1. 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

2. Sync templates - After updating .trellis/spec/, sync to src/templates/markdown/spec/

3. 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.