The official source reports this update: v2.3.0. pip install -U mcp . Docs: https://py.sdk.modelcontextprotocol.io/ Mostly fixes, plus three new options. A few things behave differently, so skim these first: Behaviour changes httpx2>=2.10.0 is now required ( #3600 ) It was >=2.5.0 . The new max_sse_event_size option needs it. Nothing to do unless you pin httpx2 below 2.10. A tool with an invalid x-mcp-header annotation fails at registration ( #3620 ) @mcp.tool() , add_tool and Tool.from_function raise InvalidSignature , naming the tool and the problem. Until now the server started, and 2026-07-28 clients silently dropped the tool from their listing.
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Model Context Protocol SDK v2.3.0 requires httpx2 version 2.10.0 or higher.
The v2.3.0 release of the Model Context Protocol SDK requires httpx2 version 2.10.0 or higher. It also adds a new max_sse_event_size option.
3 Oct 20261 verified claims1 sources1 observations
This official update documents a development concerning v2.3.0. Its practical significance depends on the scope and evidence stated by the source.
Read the official source update and verify its stated scope, evidence and timing before acting on it.
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