rate_limit_event causes MessageParseError instead of being handled gracefully

[hernanvegas]

Bug

When the Claude Code CLI emits a rate_limit_event message (informational,
CLI handles retry internally), the Python SDK crashes with MessageParseError
instead of ignoring it.

Versions

• claude-agent-sdk (Python): 0.1.39
• @anthropic-ai/claude-agent-sdk (TypeScript): 0.2.50

Steps to reproduce

Run any query using the Python SDK. If the CLI encounters a temporary rate
limit (burst/minute limits), it emits a rate_limit_event to the stream.

Expected behavior

The event should be silently ignored, as the CLI already handles the wait/retry
internally. The TypeScript SDK (v0.2.50) does this correctly.

Actual behavior

MessageParseError: Unknown message type: rate_limit_event is raised,
terminating the query prematurely.

Root cause

In _internal/query.py, _read_messages() does not filter rate_limit_event
before passing messages to the stream. It then reaches message_parser.py which
falls into case _: raise MessageParseError(...).

Fix

Add a continue for rate_limit_event in query.py, similar to how
control_cancel_request is handled:

elif msg_type == "rate_limit_event":
    # CLI handles rate limiting internally — skip informational event
    continue

---

[tlewers01]

Looks like issues was just fixed in version 0.1.40

[brayan07]

Confirming this affects our use case as well. We encountered rate_limit_event causing MessageParseError in message_parser.py when using the SDK from an async runner (invoked via n8n without a TTY). The crash terminated the entire stream even though the CLI had already handled the rate limit internally and would have continued.

We worked around it by migrating to claude -p --output-format stream-json (the CLI directly) which bypasses the SDK parser entirely. That workaround is in production and working, but it would be nice to use the SDK as intended.

Can confirm the fix landed in v0.1.40 — case _: now returns None and client.py skips None messages with a debug log. This matches the approach in PR #593. Thanks for the quick turnaround!

[qing-ant]

Duplicate of #601 (and earlier closed issue #583). All report the same root cause: parse_message() in the SDK has no case for the rate_limit_event message type emitted by the CLI, causing MessageParseError. Closing as duplicate — please track #601 for updates.