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fix(server): let MCP work behind a proxy on the same host - #295
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Behind cloudflared, Caddy or a sidecar every request reaches aeman on a loopback address with the public Host, which the MCP SDK's DNS-rebinding guard answers with 403. Clients got a token and then a refusal on every call. /mcp is behind the bearer gate in OAuth mode, so turn the guard off there. Signed-off-by: Andrei Kvapil <kvapss@gmail.com>
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November 6, 2026 18:41
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Behind a proxy on the same host (cloudflared, Caddy, a sidecar) every request reaches aeman on a loopback address with the public Host. The MCP SDK's DNS-rebinding guard answers that with 403
invalid Host header, so a client finishes the OAuth flow and then gets refused on every call. We hit this running prod on a laptop with cloudflared pointing at 127.0.0.1.In OAuth mode
/mcpalready sits behind the bearer gate, and a rebinding page has no token to send, so the guard is turned off there. Requests without a token still get the 401 with the resource metadata.Pinned as G84, with a test that sends an initialize through a loopback address with the public Host.