AMP --stream-json event cheatsheet

amp -x --stream-json writes one JSON object per line (JSONL) using a Claude Code-compatible protocol with a type field discriminator.

Event types

system (subtype: init)

Session initialisation with thread ID, working directory, and available tools.

{"type":"system","subtype":"init","session_id":"T-2775dc92-90ed-4f85-8b73-8f9766029e83","cwd":"/tmp","tools":["Bash","Read","Write"],"mcp_servers":[]}

assistant

Assistant message containing text and/or tool use blocks. Includes per-message token usage.

Text block:

{"type":"assistant","session_id":"T-2775dc92-90ed-4f85-8b73-8f9766029e83","message":{"role":"assistant","content":[{"type":"text","text":"hello"}],"stop_reason":"end_turn","usage":{"input_tokens":50,"output_tokens":10}}}

Tool use block:

{"type":"assistant","session_id":"T-2775dc92-90ed-4f85-8b73-8f9766029e83","message":{"role":"assistant","content":[{"type":"tool_use","id":"toolu_01","name":"Bash","input":{"command":"echo hello"}}],"stop_reason":"tool_use","usage":{"input_tokens":100,"output_tokens":20}}}

Mixed content (text + tool use):

{"type":"assistant","session_id":"T-...","message":{"role":"assistant","content":[{"type":"text","text":"Let me check..."},{"type":"tool_use","id":"toolu_01","name":"Read","input":{"file_path":"src/main.py"}}],"stop_reason":"tool_use","usage":{"input_tokens":80,"output_tokens":30}}}

Subagent message (with parent_tool_use_id):

{"type":"assistant","session_id":"T-...","message":{...},"parent_tool_use_id":"toolu_parent_01"}

user

User message containing tool results.

{"type":"user","session_id":"T-2775dc92-90ed-4f85-8b73-8f9766029e83","message":{"role":"user","content":[{"type":"tool_result","tool_use_id":"toolu_01","content":[{"type":"text","text":"hello"}]}]}}

Error result:

{"type":"user","session_id":"T-...","message":{"role":"user","content":[{"type":"tool_result","tool_use_id":"toolu_01","is_error":true,"content":[{"type":"text","text":"command failed"}]}]}}

result

Final result event. Always the last event in a run.

Success:

{"type":"result","subtype":"success","is_error":false,"result":"hello","duration_ms":1500,"num_turns":1,"session_id":"T-2775dc92-90ed-4f85-8b73-8f9766029e83"}

Error:

{"type":"result","subtype":"error","is_error":true,"result":"","error":"Authentication failed","session_id":"T-err-session-id","duration_ms":100,"num_turns":0}

Notes

• AMP’s protocol is Claude Code-compatible — system(init), assistant, user, result follow the same shapes.
• Tool use and tool results are embedded in message.content blocks (not top-level events like Gemini).
• usage is per-message in assistant events — accumulate input_tokens and output_tokens across messages for session totals.
• parent_tool_use_id in assistant/user messages indicates subagent nesting.
• stop_reason can be end_turn (final text) or tool_use (pending tool call).