/session-scan

name: session-scan
description: Compute metrics for Claude Code sessions. Discovers via ccrider, filters trivial, computes friction/opportunity/fingerprint scores. Use for broad session triage.
argument-hint: "[--since DATE] [--project NAME] [--limit N] [--list] [--rescan]"
disable-model-invocation: true

Session Scan (Tier 1)

Compute deterministic metrics for sessions discovered via ccrider MCP.

STOP — Read Before Executing

**NEVER call `mcp__ccrider__get_session_messages` in main context.** Each response is 5-50KB of JSON. Fetching N sessions directly = context crash.

**You MUST delegate all scoring to subagents.** The main context only does: discovery, deduplication, subagent spawning, and result collection.

Requirements

Requires **ccrider MCP**. If not available:

> ccrider MCP is required. See: <https://github.com/neilberkman/ccrider>

Usage

/session-scan                         # Last 7 days, up to 50 sessions
/session-scan --since 2026-02-01      # Since specific date
/session-scan --project enaia         # Filter by project name
/session-scan --limit 20              # Cap session count
/session-scan --list                  # Discovery only, no scoring
/session-scan --rescan                # Recompute already-scanned sessions

What Main Context Does

1. Parse Arguments

Extract from `$ARGUMENTS`:

• **`--since DATE`**: ISO date filter (default: 7 days ago)
• **`--project NAME`**: Filter by project path substring
• **`--limit N`**: Max sessions to process (default: 50)
• **`--list`**: Discovery only — show table, skip scoring
• **`--rescan`**: Recompute metrics for already-scanned sessions

2. Discover Sessions (safe — response is ~1KB)

mcp__ccrider__list_recent_sessions(limit: N, project: PROJECT, after_date: SINCE)

Filter out sessions with < 10 messages. If `--list`: show table and stop.

3. Deduplicate

Read `.claude/session-metrics/metrics.jsonl` (if exists). Skip sessions already scanned unless `--rescan` flag is set. Report: "N new sessions to scan (M already in ledger)"

4. Resolve Scorer Path

Glob: **/session-scan/references/compute-metrics.py

Store as `SCORER_PATH` (absolute). `PROJECT_ROOT` = current working directory.

5. Spawn ONE Subagent Per Session

**DO NOT fetch messages yourself. DO NOT run Python yourself.** **You MUST use the Task tool to spawn subagents.**

For EACH unscanned session, spawn a haiku subagent using this template:

Task(subagent_type="general-purpose", model="haiku", mode="bypassPermissions", prompt="""
Score one Claude Code session. Steps:

1. Fetch messages:
   mcp__ccrider__get_session_messages(session_id: "{SESSION_ID}", last_n: 200)

2. Write the full tool result (messages JSON) to:
   {PROJECT_ROOT}/.claude/session-metrics/_tmp_{SHORT_ID}.json

3. Run scorer and capture result in ONE Bash command:
   python3 {SCORER_PATH} {PROJECT_ROOT}/.claude/session-metrics/_tmp_{SHORT_ID}.json --session-id {SESSION_ID} --project {PROJECT_NAME} > {PROJECT_ROOT}/.claude/session-metrics/_result_{SHORT_ID}.json && rm {PROJECT_ROOT}/.claude/session-metrics/_tmp_{SHORT_ID}.json

4. Report back: "Scored {SHORT_ID}: friction=X.XX fingerprint=Y"

If ccrider fails, report the error and exit.
""")

**Spawn ALL subagents in parallel.** Wait for all to complete.

6. Collect Results

for f in .claude/session-metrics/_result_*.json; do
  cat "$f" >> .claude/session-metrics/metrics.jsonl
  rm "$f"
done

7. Display Results

Show summary table sorted by friction (descending):

| ID       | Project | Date       | Type        | Friction | Opportunity | Tier2? |
|----------|---------|------------|-------------|----------|-------------|--------|
| ffa155ee | enaia   | 2026-02-18 | bug-fix     | 0.42     | 0.65        | Yes    |
| 90a74843 | wedding | 2026-02-17 | feature     | 0.15     | 0.20        | No     |

If Tier 2 eligible: suggest `/session-deep-dive --from-scan`.

8. Update Scan Metadata

Write `.claude/session-metrics/latest-scan.json`:

{
  "scanned_at": "2026-02-20T14:30:00Z",
  "sessions_discovered": 25,
  "sessions_scanned": 18,
  "sessions_skipped": 7,
  "tier2_eligible": 5
}

Scoring Reference

See `references/scoring-guide.md` for full algorithm documentation.

• **Friction Score** (0-1): Weighted signals, sigmoid-normalized
• **Fingerprint**: Rule-based classifier (6 types)
• **Plugin Opportunity** (0-1): Missed `/phx:` commands
• **Tier 2 Eligible**: friction > 0.35 OR opportunity > 0.5 OR plugin used OR msgs > 50

Iron Laws

1. **NEVER call `get_session_messages` in main context** — WILL crash context 2. **ONE subagent per session** — each fetches exactly ONE session 3. **`mode="bypassPermissions"` on every Task** — subagents need Write+Bash 4. **Absolute paths in subagent prompts** — subagents don't inherit context 5. **Result files, not direct append** — avoid jsonl race conditions 6. **NEVER modify existing metrics.jsonl entries** — append-only ledger 7. **ALWAYS delete temp and result files** after processing