Fix Streamable HTTP Accept header quality-factor handling
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Assessment
- Difficulty
- 3/5
- Estimated time
- 1-2 days
- Newbie friendliness
- 68/100
Research direction
Start by tracing Streamable HTTP request handling and the check_accept_headers example in the issue, focusing on how Accept parameters are parsed. Verify behavior with the provided application/json;q=0 and text/event-stream;q=1.0 request, and consider additional quality-factor cases; done means explicitly unacceptable media types are not treated as accepted under RFC 7231 semantics.
Written by the indexing model from the issue text.
Description
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Description
Streamable HTTP currently ignores q=0 values in the Accept header, so requests that explicitly mark a media type as unacceptable can still be accepted. This violates RFC 7231 semantics for content negotiation and can cause clients and servers to disagree about which response format is actually allowed.
Example Code
from starlette.requests import Request
def check_accept_headers(request: Request) -> tuple[bool, bool]:
accept_header = request.headers.get("accept", "")
accept_types = [media_type.strip().split(";")[0].strip().lower() for media_type in accept_header.split(",")]
has_wildcard = "*/*" in accept_types
has_json = has_wildcard or any(t in ("application/json", "application/*") for t in accept_types)
has_sse = has_wildcard or any(t in ("text/event-stream", "text/*") for t in accept_types)
return has_json, has_sse
# Example: client explicitly rejects JSON
request = Request({"type": "http", "method": "GET", "headers": [(b"accept", b"application/json;q=0, text/event-stream;q=1.0")]})
print(check_accept_headers(request))
# -> (True, True)
Python & MCP Python SDK
Python 3.12.10
MCP Python SDK: 1.28.1
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- Python
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- Merged PRs (30d)
- 30
Contributor guide
First steps
- Read the whole issue, then the project's contributing guide.
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- Open a pull request that references the issue number.
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