refactor: move transport-specific parameters from FastMCP constructor to run() #1898
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… to run() Transport-specific parameters like `host`, `port`, `json_response`, `stateless_http`, `event_store`, `retry_interval`, `sse_path`, `message_path`, `streamable_http_path`, and `transport_security` no longer belong in the FastMCP constructor since they are irrelevant when using stdio transport. These parameters are now passed to `run()`, `sse_app()`, or `streamable_http_app()` depending on the transport being used. The `run()` method uses `@overload` decorators to provide proper type hints for each transport type. DNS rebinding auto-configuration logic has been moved from the constructor to `sse_app()` and `streamable_http_app()` methods where it can use the actual host parameter. BREAKING CHANGE: Transport-specific parameters must now be passed to run() or the transport app methods instead of the FastMCP constructor. Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>
maxisbey
previously approved these changes
Jan 16, 2026
maxisbey
approved these changes
Jan 16, 2026
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Summary
host,port,json_response,stateless_http,event_store,retry_interval,sse_path,message_path,streamable_http_path,transport_security) from theFastMCPconstructor torun(),sse_app(), andstreamable_http_app()@overloaddecorators torun()for proper type hints per transport typeThis improves the API by separating server configuration from transport configuration. Transport parameters are now only relevant where they're used.
BREAKING CHANGE: Transport-specific parameters must now be passed to
run()or the transport app methods instead of theFastMCPconstructor.Test plan
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