OAuth-protected MCP servers (e.g. Hospitable) return 200 text/html on an
unauthenticated HEAD probe — a login/landing page the server cannot substitute
for a real MCP response without a Bearer token. The preflight cannot
distinguish this from a misconfigured URL, so it raises NonMcpEndpointError
before the OAuth browser flow has a chance to run.
Add `and self._auth_type != "oauth"` to the preflight condition in
MCPServerTask.run(). The probe is inapplicable to OAuth servers: their URL
legitimacy is established by .well-known/oauth-protected-resource during the
OAuth handshake, not by a GET content-type check.
Concrete repro: Hospitable (https://mcp.hospitable.com/mcp) returns
`200 text/html` to an unauthenticated httpx HEAD. Without the guard:
✗ NonMcpEndpointError at `hermes mcp test`
With the guard:
✓ Connected (1487ms) — 63 tools discovered
Relation to open PRs:
- #37598 adds a POST probe fallback for POST-only non-OAuth servers (e.g.
DocuSeal), but only passes when POST returns 2xx + MCP content-type.
Hospitable returns 401 on the POST probe (Bearer challenge), so #37598
does not cover this case.
- #49463 extends the POST probe to also pass on non-2xx auth challenges
(making it OAuth-aware), but is labeled duplicate of #37598 and may not
land independently.
This fix is complementary: it handles OAuth servers with zero extra
round-trips rather than adding a POST probe step.
Tests:
- test_oauth_server_html_response_raises_without_skip: documents that
_preflight_content_type raises NonMcpEndpointError for 200 text/html
(the underlying issue), with an OAuth-server docstring.
- test_run_skips_preflight_for_oauth: verifies that run() does NOT invoke
_preflight_content_type when auth_type=="oauth", using class-level
monkeypatching so the gate is exercised without a live MCP transport.
23 passed tests/tools/test_mcp_preflight_content_type.py
homelab-ha-agent
d05cc8f4d6