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 4 parallel search agents (CASS, Handoff, Git, Research) and wait for all to complete.

Backend: Agents use Task(subagent_type="Explore") which maps to task(subagent_type="explore") in OpenCode. See skills/shared/SKILL.md ("Runtime-Native Spawn Backend Selection") for the shared contract.

Read references/discovery-patterns.md for agent definitions and prompts.

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

Read references/discovery-patterns.md for git-based tracing commands.

Step 3: Build Timeline

Merge results from all sources into a single chronological timeline (oldest first). Deduplicate same-day/same-session events. Every claim needs a source citation.

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

Read references/report-template.md for the full report format and deduplication rules.

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

Read references/edge-cases.md for handling: no CASS results, no handoffs, ambiguous concepts (>20 results), and all-sources-empty scenarios. General principle: continue with remaining sources and note gaps in the report.

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

Skill	Purpose	Input	Output
/provenance	Artifact lineage	File path	Tier/promotion history
/trace	Design decisions	Concept/keyword	Timeline of evolution

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"

Tracing an Architectural Decision

User says: /trace "agent team protocol"

What happens:

1. Agent classifies target as concept (not file path or git ref)
2. Agent launches 4 parallel agents: CASS search, handoff search, git log search, research artifact search
3. CASS finds 8 sessions mentioning "agent team", handoff finds 2 docs, git finds 3 commits, research finds 1 analysis
4. Agent builds chronological timeline from 2026-01-15 (first mention) to 2026-02-08 (latest update)
5. Agent extracts 5 key decisions: initial SendMessage design, TeamCreate addition, deliberation protocol, in-process mode, delegate mode
6. Agent writes trace report to .agents/research/2026-02-13-trace-agent-team-protocol.md with full timeline and citations

Result: Complete evolution timeline showing how agent team protocol developed across 7 sessions with source citations.

Tracing from Git Commit

User says: /trace abc1234

What happens:

1. Agent detects git ref format (short sha)
2. Agent runs git-based tracing commands to get commit details, changed files, related commits
3. Agent uses git log --grep to find related work
4. Agent searches .agents/ for contemporary research/plans
5. Agent builds timeline focused on that specific change
6. Agent writes report showing commit context, what changed, why (from commit message and related docs)

Result: Trace report links commit to broader design context from surrounding artifacts.

Troubleshooting

Problem	Cause	Solution
CASS returns no results	Session search not installed or query too specific	Check which cass. If missing, skip CASS and rely on handoffs/git/research. Try broader query terms.
Timeline has gaps	Not all decisions documented in searchable artifacts	Note gaps in report. Suggest interviewing team members or checking Slack/email archives for missing context.
Too many results (>50 matches)	Very broad concept or high-frequency term	Read references/edge-cases.md for ambiguous concept handling. Narrow query or filter by date range. Ask user for more specific aspect to trace.
Empty trace report (all sources failed)	Concept genuinely undocumented or typo	Verify spelling. Try synonyms. Report to user: "No documented history found. This may be a new concept or may need different search terms."