Trace Skill

Quick Ref: Trace design decisions through CASS sessions, handoffs, git, and artifacts. Output: .agents/research/YYYY-MM-DD-trace-*.md

YOU MUST EXECUTE THIS WORKFLOW. Do not just describe it.

When to Use

• Trace HOW architectural decisions evolved
• Find WHEN a concept was introduced
• Understand WHY something was designed a certain way
• Build provenance chain for design decisions

For knowledge artifact lineage (learnings, patterns, tiers), use /provenance instead.

CLI dependencies: cass (session search). If cass is unavailable, skip transcript search and rely on git log, handoff docs, and .agents/ artifacts for decision tracing.

Execution Steps

Given /trace <concept>:

Step 1: Classify Target Type

Determine what kind of provenance to trace:

IF target is a file path (contains "/" or "."):
  → Use /provenance (artifact lineage)

IF target is a git ref (sha, branch, tag):
  → Use git-based tracing (Step 2b)

ELSE (keyword/concept):
  → Use design decision tracing (Step 2a)

Step 2a: Design Decision Tracing (Concepts)

Launch parallel search agents using Task tool:

Tool: Task
Parameters:
  subagent_type: "Explore"
  model: "haiku"
  description: "CASS search: <concept>"
  prompt: |
    Search session transcripts for: <concept>

    Run this command:
    cass search "<concept>" --json --limit 10

    Parse the JSON output and extract:
    - Session dates (created_at field, convert from Unix ms)
    - Session paths (source_path field)
    - Agents used (agent field)
    - Relevance scores (score field)
    - Key snippets (snippet/content fields)

    Return a structured list sorted by date (oldest first).

Tool: Task
Parameters:
  subagent_type: "Explore"
  model: "haiku"
  description: "Handoff search: <concept>"
  prompt: |
    Search handoff documents for: <concept>

    1. List handoff files:
       ls -la .agents/handoff/*.md 2>/dev/null

    2. Search for concept mentions:
       grep -l "<concept>" .agents/handoff/*.md 2>/dev/null

    3. For each matching file, extract:
       - File date (from filename YYYY-MM-DD)
       - Context around the mention (grep -B5 -A5)
       - Related decisions or questions

    Return a structured list sorted by date.

Tool: Task
Parameters:
  subagent_type: "Explore"
  model: "haiku"
  description: "Git search: <concept>"
  prompt: |
    Search git history for: <concept>

    1. Search commit messages:
       git log --oneline --grep="<concept>" | head -20

    2. For interesting commits, get details:
       git show --stat <commit-sha>

    3. Extract:
       - Commit dates
       - Commit messages
       - Files changed
       - Authors

    Return a structured list sorted by date.

Tool: Task
Parameters:
  subagent_type: "Explore"
  model: "haiku"
  description: "Research search: <concept>"
  prompt: |
    Search research and learning artifacts for: <concept>

    1. Search research docs:
       grep -l "<concept>" .agents/research/*.md 2>/dev/null

    2. Search learnings:
       grep -l "<concept>" .agents/learnings/*.md 2>/dev/null

    3. Search patterns:
       grep -l "<concept>" .agents/patterns/*.md 2>/dev/null

    4. For each match, extract:
       - File date (from filename or modification time)
       - Context around the mention
       - Related concepts

    Return a structured list sorted by date.

Wait for all 4 agents to complete.

Step 2b: Git-Based Tracing (Commits/Refs)

For git refs, trace the commit history:

# Get commit details
git show --stat <ref>

# Get commit ancestry
git log --oneline --ancestry-path <ref>..HEAD | head -20

# Find related commits
git log --oneline --all --grep="$(git log -1 --format=%s <ref> | head -c 50)" | head -10

Step 3: Build Timeline

Merge results from all sources into a single timeline:

| Date | Source | Event | Evidence |
|------|--------|-------|----------|
| YYYY-MM-DD | CASS | First mention in session | session-id, snippet |
| YYYY-MM-DD | Handoff | Decision recorded | handoff-file, context |
| YYYY-MM-DD | Git | Implementation committed | commit-sha, message |
| YYYY-MM-DD | Research | Documented in research | research-file |

Deduplication rules:

• Same content within 24 hours = single event (note multiple sources)
• Same session ID = single event
• Preserve ALL sources as evidence

Sorting:

• Chronological order (oldest first)
• Show evolution of the concept over time

Step 4: Extract Key Decisions

For each event in timeline, identify:

• What changed: The decision or evolution
• Why: Reasoning if available
• Who: Session/author/commit author
• Evidence: Link to source (session path, file, commit)

Step 5: Write Trace Report

Write to: .agents/research/YYYY-MM-DD-trace-<concept-slug>.md

# Trace: <Concept>

**Date:** YYYY-MM-DD
**Query:** <original concept>
**Sources searched:** CASS, Handoffs, Git, Research

## Summary

<2-3 sentence overview of how the concept evolved>

## Timeline

| Date | Source | Event | Evidence |
|------|--------|-------|----------|
| ... | ... | ... | ... |

## Key Decisions

### Decision 1: <title>
- **Date:** YYYY-MM-DD
- **Source:** <CASS session / Handoff / Git commit>
- **What:** <what was decided>
- **Why:** <reasoning if known>
- **Evidence:** <link/path>

### Decision 2: <title>
...

## Evolution Summary

<How the concept changed over time, key inflection points>

## Current State

<Where the concept stands now based on most recent evidence>

## Related Concepts

- <related concept 1> - see `/trace <concept1>`
- <related concept 2> - see `/trace <concept2>`

## Sources

### CASS Sessions
| Date | Session Path | Score |
|------|--------------|-------|
| ... | ... | ... |

### Handoff Documents
| Date | File | Context |
|------|------|---------|
| ... | ... | ... |

### Git Commits
| Date | SHA | Message |
|------|-----|---------|
| ... | ... | ... |

### Research/Learnings
| Date | File |
|------|------|
| ... | ... |

Step 6: Report to User

Tell the user:

1. Concept traced successfully
2. Timeline of evolution (key dates)
3. Most significant decisions
4. Location of trace report
5. Related concepts to explore

Handling Edge Cases

No CASS Results

IF cass search returns 0 results:
  - Log: "No session transcripts mention '<concept>'"
  - Continue with other sources
  - Note in report: "Concept not found in session history"

No Handoff Documents

IF .agents/handoff/ doesn't exist OR no matches:
  - Log: "No handoff documents mention '<concept>'"
  - Continue with other sources
  - Note in report: "Concept not documented in handoffs"

Ambiguous Concept (Too Many Results)

IF CASS returns >20 results:
  - Show top 10 by score
  - Ask user: "Many sessions mention this. Want to narrow by date range or workspace?"
  - Suggest related but more specific concepts

All Sources Empty

IF all 4 searches return nothing:
  - Report: "No provenance found for '<concept>'"
  - Suggest: "Try related terms: <suggestions>"
  - Ask: "Is this concept documented somewhere else?"

Key Rules

• Search ALL sources – CASS, handoffs, git, research
• Build timeline – chronological evolution is the goal
• Cite evidence – every claim needs a source
• Handle gaps gracefully – not all concepts are in all sources
• Write report – trace must produce .agents/research/ artifact

Relationship to /provenance

Use /provenance for: “Where did this learning come from?” Use /trace for: “How did we decide on this architecture?”

Examples

# Trace a design decision
/trace "three-level architecture"

# Trace a role/concept
/trace "Chiron"

# Trace a pattern
/trace "brownian ratchet"

# Trace a feature
/trace "parallel wave execution"