Data Model

HookInput

Passed via stdin to get-session-id and read-session.

{
  "hook_type": "stop",
  "session_id": "abc123",
  "session_ref": "/path/to/transcript.jsonl",
  "timestamp": "2026-01-13T12:00:00Z",
  "user_prompt": "Fix the login bug",
  "tool_name": "Write",
  "tool_use_id": "toolu_abc123",
  "tool_input": {"path": "/src/main.go"},
  "raw_data": {}
}

Field	Type	Required	Description
`hook_type`	string	Yes	`session_start`, `session_end`, `user_prompt_submit`, `stop`, `pre_tool_use`, `post_tool_use`
`session_id`	string	Yes	Agent session identifier
`session_ref`	string	Yes	Agent-specific session reference (typically a file path)
`timestamp`	string	Yes	RFC 3339 timestamp
`user_prompt`	string	No	User’s prompt text
`tool_name`	string	No	Tool name (from tool use hooks)
`tool_use_id`	string	No	Tool invocation ID
`tool_input`	object	No	Raw tool input JSON
`raw_data`	object	No	Agent-specific extension data

AgentSession

Used as input to write-session and output from read-session.

{
  "session_id": "abc123",
  "agent_name": "myagent",
  "repo_path": "/path/to/repo",
  "session_ref": "/path/to/transcript.jsonl",
  "start_time": "2026-01-13T12:00:00Z",
  "native_data": null,
  "modified_files": ["src/main.go"],
  "new_files": [],
  "deleted_files": []
}

Field	Type	Description
`session_id`	string	Agent session identifier
`agent_name`	string	Agent registry name
`repo_path`	string	Absolute path to the repository
`session_ref`	string	Path to session in agent’s storage
`start_time`	string	RFC 3339 timestamp
`native_data`	bytes/null	Opaque session content in agent’s native format
`modified_files`	string[]	Files modified during the session
`new_files`	string[]	Files created during the session
`deleted_files`	string[]	Files deleted during the session

Event

Returned by parse-hook. Represents a normalized lifecycle event.

{
  "type": 3,
  "session_id": "abc123",
  "session_ref": "/path/to/transcript.jsonl",
  "prompt": "Fix the login bug",
  "model": "claude-sonnet-4-20250514",
  "timestamp": "2026-01-13T12:00:00Z"
}

Event types:

Value	Name	Description
1	SessionStart	Agent session has begun
2	TurnStart	User submitted a prompt
3	TurnEnd	Agent finished responding
4	Compaction	Context window compression (triggers save + offset reset)
5	SessionEnd	Session terminated
6	SubagentStart	A subagent was spawned
7	SubagentEnd	A subagent completed

Optional event fields: previous_session_id, session_ref, prompt, model, timestamp, tool_use_id, subagent_id, tool_input, subagent_type, task_description, response_message, metadata. Only type and session_id are required.

Supported Agents

External Agent Plugins

HookInput

AgentSession

Event

​HookInput

​AgentSession

​Event

HookInput

AgentSession

Event