Environment:
- anthropic 0.93.0
- Python 3.11
Description:
client.beta.sessions.events.stream() returns a Stream[BetaManagedAgentsStreamSessionEvents] , but its iterator yields nothing because
Stream.__stream__ (in anthropic/_streaming.py) is hardcoded to match
only Messages API event names:
if sse.event == "completion": ...
if sse.event in ("message_start", "message_delta", "message_stop",
"content_block_start", "content_block_delta",
"content_block_stop", "message"): ...
if sse.event == "ping": continue
if sse.event == "error": raise ...
# No else — unknown event types silently dropped None of the managed agents event types: session.status_, agent.message,
agent.tool_use, agent.tool_result, agent.thinking, span.model_request_,
session.error, etc. in this if chain. They are all dropped.
Minimal repro (no server required):
from unittest.mock import MagicMock
from anthropic._streaming import Stream, SSEDecoder, ServerSentEvent
# Build a fake SSE response with managed agents events
sse_bytes = b"""data: {"id":"evt_1","type":"session.status_running"}
data: {"id":"evt_2","type":"agent.message","content":[{"type":"text","text":"hi"}]}
data: {"id":"evt_3","type":"session.status_idle","stop_reason":{"type":"end_turn"}}
"""
class FakeResponse:
def iter_bytes(self):
yield sse_bytes
def close(self): pass
# Mimic how events.stream() constructs the Stream
stream = Stream.__new__(Stream)
stream.response = FakeResponse()
stream._cast_to = object
stream._client = MagicMock()
stream._client._process_response_data = lambda data, cast_to, response: data
stream._decoder = SSEDecoder()
stream._iterator = stream.__stream__()
received = list(stream)
print(f"Stream yielded {len(received)} events out of 3 sent")
# Prints: Stream yielded 0 events out of 3 sent Expected: Stream yields 3 events matching the discriminated union.
Actual: Stream yields 0 events.
Impact: Every consumer of client.beta.sessions.events.stream()
is affected — managed agents streaming is entirely broken in 0.93.0.
events.list() still works for polling; only the streaming method is broken.
Suggested fix: Either add the managed agents event names to the
existing if chain, or fall through unknown sse.event values to
process_data(data=sse.json(), cast_to=cast_to, response=response)
so the discriminated union parsing kicks in.
Environment:
Description:
client.beta.sessions.events.stream()returns aStream[BetaManagedAgentsStreamSessionEvents], but its iterator yields nothing becauseStream.__stream__(inanthropic/_streaming.py) is hardcoded to matchonly Messages API event names:
None of the managed agents event types: session.status_, agent.message,
agent.tool_use, agent.tool_result, agent.thinking, span.model_request_,
session.error, etc. in this if chain. They are all dropped.
Minimal repro (no server required):
Expected: Stream yields 3 events matching the discriminated union.
Actual: Stream yields 0 events.
Impact: Every consumer of
client.beta.sessions.events.stream()is affected — managed agents streaming is entirely broken in 0.93.0.
events.list()still works for polling; only the streaming method is broken.Suggested fix: Either add the managed agents event names to the
existing if chain, or fall through unknown
sse.eventvalues toprocess_data(data=sse.json(), cast_to=cast_to, response=response)so the discriminated union parsing kicks in.