RLM Systematic Debugging (Phase 1.5)

Overview

When a requirement involves fixing a bug or investigating unexpected behavior, ad-hoc fixes waste time and create new bugs. Systematic debugging finds the root cause before any fix is attempted.

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

The Iron Law for RLM Debugging:

NO FIXES WITHOUT ROOT CAUSE INVESTIGATION FIRST

When to Use

Mandatory Phase 1.5 when:

Requirement is a bug fix
Test failures need investigation
Unexpected behavior reported
Performance problems
Integration issues

Use ESPECIALLY when:

Under time pressure (emergencies make guessing tempting)
"Just one quick fix" seems obvious
Previous fix attempts failed
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)

Phase 1.5 Insertion

Phase 1.5 is inserted between Phase 1 (AS-IS) and Phase 2 (TO-BE Plan) when debugging is required:

Phase 0: 00-requirements.md
    ↓
Phase 1: 01-as-is.md (captures current behavior)
    ↓
Phase 1.5: 01.5-root-cause.md ← NEW (this skill)
    ↓
Phase 2: 02-to-be-plan.md (includes fix plan based on root cause)

The Four Phases of Systematic Debugging

dot

digraph debugging_phases {
    rankdir=TB;
    
    phase1 [label="Step 1:\nRoot Cause Investigation", shape=box, style=filled, fillcolor="#ffcccc"];
    phase2 [label="Step 2:\nPattern Analysis", shape=box, style=filled, fillcolor="#ffffcc"];
    phase3 [label="Step 3:\nHypothesis & Testing", shape=box, style=filled, fillcolor="#ccffcc"];
    phase4 [label="Step 4:\nFix Implementation", shape=box, style=filled, fillcolor="#ccccff"];
    
    phase1 -> phase2 -> phase3 -> phase4;
    
    // Feedback loops
    phase3 -> phase1 [label="hypothesis\nfailed", style=dashed];
    phase4 -> phase1 [label="fix\nfailed", style=dashed];
}

Step 1: Root Cause Investigation

BEFORE attempting ANY fix:

1.1 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

Record in Phase 1.5 artifact:

markdown

## Error Analysis

**Error Message:** [verbatim]
**Stack Trace:** [key frames]
**File:Line:** [locations]
**Error Code:** [if applicable]
**Key Insight:** [what the error is telling you]

1.2 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

Record in Phase 1.5 artifact:

markdown

## Reproduction Verification

**Steps:**
1. [exact step]
2. [exact step]
3. [exact step]

**Reproducible:** Yes / No / Intermittent
**Frequency:** [X out of Y attempts]
**Deterministic:** Yes / No

1.3 Check Recent Changes

What changed that could cause this?
Git diff, recent commits
New dependencies, config changes
Environmental differences

Record in Phase 1.5 artifact:

markdown

## Recent Changes Analysis

**Git History:** [relevant commits]
**Dependency Changes:** [package.json, requirements.txt, etc.]
**Config Changes:** [relevant files]
**Environment:** [OS, runtime versions]
**Likely Culprit:** [most suspicious change]

1.4 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.

Record in Phase 1.5 artifact:

markdown

## Multi-Layer Evidence

**Layer 1: [Component Name]**
- Input: [data]
- Output: [data]
- Status: ✅ Working / ❌ Broken

**Layer 2: [Component Name]**
- Input: [data from Layer 1]
- Output: [data]
- Status: ✅ Working / ❌ Broken

**Failure Boundary:** Layer X → Layer Y
**Root Cause Location:** [specific component]

1.5 Trace Data Flow

WHEN error is deep in call stack:

Trace backward:

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

Record in Phase 1.5 artifact:

markdown

## Data Flow Trace

**Error Location:** [file:line - function]
**Bad Value:** [what was wrong]

**Call Stack Trace:**
1. [deepest] `functionA()` at fileA:line - received [value]
2. `functionB()` at fileB:line - passed [value]
3. `functionC()` at fileC:line - passed [value]
4. [source] `functionD()` at fileD:line - ORIGIN of bad value

**Root Cause:** [source location] - [explanation]

Step 2: Pattern Analysis

Find the pattern before fixing:

2.1 Find Working Examples

Locate similar working code in same codebase
What works that's similar to what's broken?

2.2 Compare Against References

If implementing pattern, read reference implementation COMPLETELY
Don't skim - read every line
Understand the pattern fully before applying

2.3 Identify Differences

What's different between working and broken?
List every difference, however small
Don't assume "that can't matter"

2.4 Understand Dependencies

What other components does this need?
What settings, config, environment?
What assumptions does it make?

Record in Phase 1.5 artifact:

markdown

## Pattern Analysis

**Working Example:** [file:location]
**Broken Code:** [file:location]

**Key Differences:**
| Aspect | Working | Broken |
|--------|---------|--------|
| [X] | [value] | [value] |
| [Y] | [value] | [value] |

**Likely Cause:** [difference that explains the bug]
**Dependencies:** [what the code needs to work]

Step 3: Hypothesis and Testing

Scientific method:

3.1 Form Single Hypothesis

State clearly: "I think X is the root cause because Y"
Write it down
Be specific, not vague

3.2 Test Minimally

Make the SMALLEST possible change to test hypothesis
One variable at a time
Don't fix multiple things at once

3.3 Verify Before Continuing

Did it work? Yes → Phase 4
Didn't work? Form NEW hypothesis
DON'T add more fixes on top

3.4 When You Don't Know

Say "I don't understand X"
Don't pretend to know
Ask for help
Research more

Record in Phase 1.5 artifact:

markdown

## Hypothesis Testing

### Hypothesis 1
**Statement:** [clear hypothesis]
**Rationale:** [why you think this]
**Test:** [minimal change to verify]
**Result:** [confirmed/rejected]
**Evidence:** [output/observation]

### Hypothesis 2 (if needed)
[...]

**Confirmed Root Cause:** [final hypothesis]

Step 4: Fix Summary (Handoff to Phase 2 Planning)

Fix the root cause, not the symptom:

4.1 Create Failing Test Case

Simplest possible reproduction
Automated test if possible
One-off test script if no framework
MUST have before fixing
This becomes part of Phase 3's test plan

4.2 Root Cause Summary for Phase 2

Summarize root cause found
Document the fix approach
Reference evidence from Phase 1.5

Record in Phase 1.5 artifact:

markdown

## Root Cause Summary

**Root Cause:** [one sentence]
**Location:** [file:line]
**Explanation:** [paragraph explaining why]
**Fix Approach:** [high-level]
**Test Strategy:** [how to verify fix]

## Phase 1.5 Gate

Coverage: [Did we find root cause?]
Approval: [Ready to proceed to Phase 3 with fix plan?]

Red Flags - STOP and Follow Process

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"
Proposing solutions before tracing data flow
"One more fix attempt" (when already tried 2+)

ALL of these mean: STOP. Return to Phase 2.

Common Rationalizations (STOP)

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"	Untested fixes don't stick. Test first proves it.
"Multiple fixes at once saves time"	Can't isolate what worked. Causes new bugs.
"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.

If 3+ Fix Attempts Failed

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?

Document in Phase 1.5:

markdown

## Architectural Concern

**Fix Attempts:** [number]
**Pattern:** [what happens with each fix]
**Recommendation:** [architectural change vs. symptom fix]
**Next Steps:** [escalate, refactor, or accept risk]

Phase 1.5 Artifact Template

File:

/.codex/rlm/<run-id>/01.5-root-cause.md

markdown

Run: `/.codex/rlm/<run-id>/`
Phase: `01.5 Root Cause Analysis`
Status: `DRAFT` | `LOCKED`
Inputs:
- `/.codex/rlm/<run-id>/01-as-is.md`
- [relevant addenda]
Outputs:
- `/.codex/rlm/<run-id>/01.5-root-cause.md`
Scope note: This document records systematic debugging process and identified root cause.

## Error Analysis

[Section 2.1 - verbatim errors, stack traces]

## Reproduction Verification

[Section 2.2 - exact steps, reproducibility]

## Recent Changes Analysis

[Section 2.3 - git history, dependencies]

## Evidence Gathering

[Section 2.4 - multi-layer diagnostics if applicable]

## Data Flow Trace

[Section 2.5 - backward trace to source]

## Pattern Analysis

[Section 3 - working vs broken comparison]

## Hypothesis Testing

[Section 4 - scientific method log]

## Root Cause Summary

**Root Cause:** [one sentence]
**Location:** [file:line]
**Detailed Explanation:** [paragraph]
**Fix Strategy:** [approach for Phase 3]
**Test Plan:** [how to verify]

## Traceability

- R1 (Bug fix requirement) -> Root cause identified at [location] | Evidence: [section]

## Coverage Gate

- [ ] Error messages analyzed
- [ ] Reproduction verified
- [ ] Recent changes reviewed
- [ ] Data flow traced to source
- [ ] Pattern analysis completed
- [ ] Hypothesis tested and confirmed
- [ ] Root cause documented
- [ ] Fix strategy defined

Coverage: PASS / FAIL

## Approval Gate

- [ ] Root cause identified (not just symptom)
- [ ] Fix approach clear
- [ ] Test strategy defined
- [ ] No "quick fixes" attempted
- [ ] Ready to proceed to Phase 3

Approval: PASS / FAIL

LockedAt: [when locked]
LockHash: [sha256]

Integration with RLM

Phase 1 → 1.5 Transition

When Phase 1 (AS-IS) identifies a bug/issue that needs fixing:

Lock Phase 1 (
```
01-as-is.md
```
)
Create Phase 1.5 (
```
01.5-root-cause.md
```
) with Status: DRAFT
Execute systematic debugging
Lock Phase 1.5 when root cause found
Proceed to Phase 3 with root cause knowledge

Phase 1.5 → 3 Transition

Phase 3 (

02-to-be-plan.md

) builds ON Phase 1.5:

markdown

## Root Cause Reference

Root cause identified in `01.5-root-cause.md`:
- Location: [file:line]
- Cause: [summary]
- Full analysis: [reference]

## Fix Plan

Based on root cause analysis:
1. [specific fix steps]
2. [test strategy from Phase 1.5]

References

REQUIRED: Use this skill for all bug-fix requirements
TRIGGERS: When requirement involves debugging/fixing
OUTPUT:
```
01.5-root-cause.md
```
artifact
NEXT: Phase 3 (TO-BE Plan) incorporates findings

rlm-debugging

NPX Install

Tags

SKILL.md Content

RLM Systematic Debugging (Phase 1.5)

Overview

When to Use

Phase 1.5 Insertion

The Four Phases of Systematic Debugging

Step 1: Root Cause Investigation

1.1 Read Error Messages Carefully

1.2 Reproduce Consistently

1.3 Check Recent Changes

1.4 Gather Evidence in Multi-Component Systems

1.5 Trace Data Flow

Step 2: Pattern Analysis

2.1 Find Working Examples

2.2 Compare Against References

2.3 Identify Differences

2.4 Understand Dependencies

Step 3: Hypothesis and Testing

3.1 Form Single Hypothesis

3.2 Test Minimally

3.3 Verify Before Continuing

3.4 When You Don't Know

Step 4: Fix Summary (Handoff to Phase 2 Planning)

4.1 Create Failing Test Case

4.2 Root Cause Summary for Phase 2

Red Flags - STOP and Follow Process

Common Rationalizations (STOP)

If 3+ Fix Attempts Failed

Phase 1.5 Artifact Template

Integration with RLM

Phase 1 → 1.5 Transition

Phase 1.5 → 3 Transition

References