Release v9.4.1 · kennethreitz/responder

[v9.4.1] - 2026-11-09

A patch release: a declared response model no longer turns a handler that
writes its own body into a 500, and a response with no body stays empty.

response_model= (and an inferred return annotation) validates and
serializes the structured channel only: a returned value, or resp.media.
A handler that assigns resp.content, resp.text, resp.html, a file, or
a stream sends that body unchanged. The model stays on the OpenAPI
operation and on the MCP tool outputSchema. response_model=False still
removes it from both. Previously those routes 500'd unless they opted out,
and opting out also dropped outputSchema.
A response that never sets a body is empty. It is no longer
content-negotiated into JSON null. Assign resp.media = None to send a
JSON null on purpose.
MCP tool descriptions taken from a docstring use the prose above a line
that is exactly ---. The OpenAPI YAML below that line is left out. A
docstring that is only that YAML uses its operation summary, or is empty
when it has none. An explicit description= is kept as given, and OpenAPI
still reads the YAML block.