Log Inspection

Query and inspect observability hook logs from JSONL files.

Arguments

Subcommand is the first argument:

• sessions -- List all sessions with event counts and duration
• timeline [session-id] -- Chronological event list with seq numbers
• trace <tool-use-id> -- Show pre/post pairing for a tool invocation
• agents -- Subagent lifecycle (start/stop/duration)
• team -- TeammateIdle and TaskCompleted activity
• stats -- Aggregate statistics (event breakdown, tool usage, corruption count)
• coverage -- Which of 14 event types have been observed
• daily -- Show daily summaries from sessions-index.jsonl (v1.6.0)

Log File Location

Look for log files at:

{project}/.claude/logs/hooks/events-{YYYY-MM-DD}.jsonl
{project}/.claude/logs/hooks/events-{YYYY-MM-DD}.jsonl.gz  (compressed cold logs)

Use Glob to find all available log files:

Glob(".claude/logs/hooks/events-*.jsonl")
Glob(".claude/logs/hooks/events-*.jsonl.gz")

Note: Files older than 7 days are automatically compressed to .jsonl.gz (configurable via CLAUDE_HOOK_LOG_COMPRESS_AFTER_DAYS). DuckDB reads .jsonl.gz natively; use zcat | jq on Unix for manual inspection.

Workflow

Step 1: Locate Log Files

Find all hook log files in the project:

Glob(".claude/logs/hooks/events-*.jsonl")
Glob(".claude/logs/hooks/events-*.jsonl.gz")
Glob(".claude/logs/hooks/sessions-index.jsonl")

If no log files exist, inform the user that logging must be enabled via CLAUDE_HOOK_LOG_EVENTS_ENABLED=1.

Step 2: Execute Subcommand

sessions

Parse sessions-index.jsonl if it exists. Use the type field to discriminate entries (session_start, session_end, agent_start, agent_stop). For backward compatibility, entries without type are inferred from the presence of started_at (session_start) or ended_at (session_end). Otherwise, scan event log files for sessionstart and sessionend events. Display:

Session ID	Started	Ended	Model	Events	Duration

The enriched index also includes cwd, transcript_path, model, and agent_type on session_start entries.

timeline [session-id]

Read the log file and display events in seq order. If session-id is provided, filter to that session. Display:

seq  timestamp            event              tool_name    pid
1    2026-02-15T18:13:23  sessionstart       -            12345
2    2026-02-15T18:13:24  userpromptsubmit   -            12345
3    2026-02-15T18:13:25  pretooluse         Read         12346
4    2026-02-15T18:13:25  posttooluse        Read         12346

trace <tool-use-id>

Find pretooluse and posttooluse/posttoolusefailure entries with the given tool_use_id. Display the pair showing timing and success/failure.

agents

First check sessions-index.jsonl for agent_start and agent_stop entries (direct lookup, no event scanning needed). Fall back to scanning event log files for subagentstart and subagentstop events if index is missing. Display:

Agent ID	Type	Started (seq)	Stopped (seq)	Duration

team

First check sessions-index.jsonl for task_completed and teammate_idle entries (direct lookup, added in v1.8.0). Fall back to scanning event log files for teammateidle and taskcompleted events if index entries are missing. Display:

Time	Type	Teammate	Team	Task Subject

stats

Parse all entries and compute:

• Event breakdown: Count of each event type
• Tool usage: Most frequently used tools (from pretooluse events)
• Error rate: posttoolusefailure count / total tool uses
• Avg duration_ms: Average hook processing time
• Corruption count: Lines that fail JSON parsing
• Unique sessions: Count of distinct session_id values
• Seq range: Min and max seq values

Use Bash with Python one-liners for aggregation. For .jsonl.gz files, use gzip.open to read:

python3 -c "
import json, gzip, glob
from collections import Counter
events = Counter()
tools = Counter()
errors = 0
corrupt = 0
durations = []
sessions = set()

def read_lines(path):
    if path.endswith('.gz'):
        with gzip.open(path, 'rt', encoding='utf-8') as f:
            return f.readlines()
    with open(path, 'r', encoding='utf-8') as f:
        return f.readlines()

for path in sorted(glob.glob('.claude/logs/hooks/events-*.jsonl') + glob.glob('.claude/logs/hooks/events-*.jsonl.gz')):
    for line in read_lines(path):
        line = line.strip()
        if not line:
            continue
        try:
            e = json.loads(line)
            events[e.get('event','')] += 1
            if 'tool_name' in e:
                tools[e['tool_name']] += 1
            if e.get('event') == 'posttoolusefailure':
                errors += 1
            durations.append(e.get('duration_ms', 0))
            sessions.add(e.get('session_id',''))
        except json.JSONDecodeError:
            corrupt += 1
print(f'Events: {dict(events)}')
print(f'Top tools: {tools.most_common(10)}')
print(f'Error rate: {errors}/{events.get(\"pretooluse\",0)} tool uses')
print(f'Avg duration: {sum(durations)/len(durations):.2f}ms' if durations else 'No entries')
print(f'Corrupted lines: {corrupt}')
print(f'Unique sessions: {len(sessions)}')
"

Note: hook_event_name was removed from entries in v1.4.0 and fully suppressed from extra_fields in v1.7.0.

coverage

Check which of the 14 event types have been captured. Display:

Event Coverage Report
=====================
[x] pretooluse (142 events)
[x] posttooluse (140 events)
[x] userpromptsubmit (8 events)
[ ] precompact (0 events)
...
Coverage: 12/14 event types observed

The 14 required types are: pretooluse, posttooluse, posttoolusefailure, permissionrequest, notification, userpromptsubmit, stop, subagentstart, subagentstop, precompact, sessionstart, sessionend, teammateidle, taskcompleted.

daily

Parse sessions-index.jsonl for daily_summary entries (v1.6.0). Display:

Date	Events	Sessions	Errors	Avg Duration

Daily summaries are generated automatically on the first sessionstart of each day for the previous day's logs.

Step 3: Format Output

Present results in a clear, readable format. Use markdown tables where appropriate. Include the log file path and date range in the header.

DuckDB Queries (Advanced)

For large log files, suggest DuckDB for analytical queries:

-- Load JSONL directly
SELECT event, count(*) as cnt
FROM read_json_auto('.claude/logs/hooks/events-2026-02-15.jsonl')
GROUP BY event ORDER BY cnt DESC;

-- Tool usage with timing
SELECT tool_name, count(*) as uses, avg(duration_ms) as avg_ms
FROM read_json_auto('.claude/logs/hooks/events-2026-02-15.jsonl')
WHERE event = 'pretooluse'
GROUP BY tool_name ORDER BY uses DESC;

-- Find corrupted entries (seq gaps)
SELECT seq, lag(seq) OVER (ORDER BY seq) as prev_seq
FROM read_json_auto('.claude/logs/hooks/events-2026-02-15.jsonl')
WHERE seq - lag(seq) OVER (ORDER BY seq) > 1;

Usage Examples

# List sessions
/claude-code-observability:log-inspection sessions

# Timeline for current session
/claude-code-observability:log-inspection timeline

# Trace a specific tool call
/claude-code-observability:log-inspection trace toolu_01abc123

# Event type coverage
/claude-code-observability:log-inspection coverage

# Full statistics
/claude-code-observability:log-inspection stats