SDK version: 0.2.115 · CLI: 2.1.206 · Platform: macOS (darwin)

Bug

When the claude subprocess dies mid-run (observed repeatedly when a Pro/Max
subscription hits its rate-limit window and the CLI exits with code 1), the
SDK logs Fatal error in message reader: Command failed with exit code 1
but the query() async stream neither terminates nor raises — a consumer
awaiting the next message waits forever.

Repro sketch

import asyncio
from claude_agent_sdk import ClaudeAgentOptions, query

async def main():
    stream = query(
        prompt="Write a long essay.",
        options=ClaudeAgentOptions(model="claude-haiku-4-5", tools=[], max_turns=1),
    )
    async for msg in stream:   # kill the spawned `claude` process mid-generation:
        print(type(msg).__name__)  #   pkill -f "claude.*stream-json"
    print("stream ended")          # <- never reached; no exception either

asyncio.run(main())

Killing the subprocess externally reproduces it deterministically; the
organic trigger we hit was subscription rate-limit exhaustion.

Expected

Process death should end the stream: either raise ProcessError (ideal, with
the exit code) or terminate the iteration, so consumers can react instead of
hanging. receive_messages()'s internal reader appears to catch the fatal
error without closing the memory channel the consumer is blocked on.

Impact / workaround

Any consumer without an explicit timeout hangs indefinitely; timeouts that
cancel the iteration can additionally leak the transport if cleanup tasks are
scheduled on a loop that closes right after. We work around it in
langchain-claude-cli with a per-message inactivity watchdog plus an explicit
stream.aclose() executed inside the still-running loop.