description: > Debug a specific session by inspecting its full event chain (PreToolUse, PostToolUse, Stop, SubagentStop, Compaction, APIError, TurnDuration, Notification events), agent hierarchy (recursive parent/child tree with subagent_type and depth), token usage with compaction baselines, workflow intelligence data (orchestration DAG, error propagation by depth), and session metadata (thinking_blocks, turn_count, total_turn_duration_ms).

Session Debug

Debug and inspect a Claude Code session from Agent Monitor data.

Input

The user provides: $ARGUMENTS

This may be:

• A session ID to debug
• "latest" or "last" for the most recent session
• "errors" to find and debug the most recent errored session

Procedure

1. Identify the target session:

   • If session ID given: GET /api/sessions/{id} from http://localhost:4820
   • If "latest": GET /api/sessions?limit=1 (default sort: most recently updated first)
   • If "errors": GET /api/sessions?limit=10&status=error

2. Collect full session data:

   • Session metadata: status, model, cwd, timestamps, duration
   • Events: GET /api/events?session_id={session_id} — full event timeline
   • Agents: GET /api/agents?session_id={session_id} — all agents in session
   • Cost: GET /api/pricing/cost/{session_id}

3. Analyze the session:

   Session Lifecycle

   • Start time → first event → last event → end time
   • Status transitions (active → working → completed/error)
   • Total duration and active-vs-idle time

   Event Chain Analysis

   • Chronological event list with timestamps and durations
   • Identify the critical path (longest chain of dependent events)
   • Flag events that took unusually long
   • Highlight error events with full error context

   Agent Inspection

   • List all agents: type, task, status, duration
   • Subagent tree visualization (parent → children)
   • Agents that failed and their last known state
   • Agent switching patterns (when and why new agents spawned)

   Tool Execution Trace

   • Every tool invocation in order with: tool name, duration, success/failure
   • Failed tool calls with error messages
   • Tool retry patterns (same tool called multiple times)

   Anomaly Detection

   • Events out of expected order
   • Gaps in event timeline (>30s with no events)
   • Duplicate events or agent states
   • Token usage spikes (compaction indicators)

4. Diagnosis:

   • Root cause hypothesis (if errors present)
   • Contributing factors
   • Remediation suggestions

Output Format

Present as a debug report with:

• Session summary header (ID, status, model, duration, cost)
• Color-coded timeline (✅ success, ❌ error, ⚠️ warning, ℹ️ info)
• Agent tree diagram
• Diagnosis section with numbered findings