feat(mcp): CIMD client identification for OAuth MCP (salvage #84050) - #89566
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૮ >ﻌ< ა ci reviewran on 90ee4de — fix: never evict pinned CIMD sockets from the callback reser
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The _MAX_RESERVED_SOCKETS cap applied to pinned CIMD sockets too, so under heavy concurrency an ephemeral-reservation churn could close a parked pinned socket before _wait_for_callback adopted it, silently reopening the port-stealing window the pin exists to prevent (#22161). Eviction now skips the pinned range; it is already bounded by _CIMD_PORTS. Follow-up to the #84050 salvage.
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…75576) Some authorization servers and WAFs reject httpx's default User-Agent on the OAuth token endpoint. mcp_servers.<name>.oauth.user_agent now stamps a custom User-Agent onto the two token-endpoint requests (authorization-code exchange and refresh) on both provider construction paths. Opt-in, per-server, token requests only — never MCP traffic or discovery, and no other headers are configurable. Empty/null/non-string values are ignored. Completes the second half of #75576 (the CIMD half landed via #89566).
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…ousResearch#75576) Some authorization servers and WAFs reject httpx's default User-Agent on the OAuth token endpoint. mcp_servers.<name>.oauth.user_agent now stamps a custom User-Agent onto the two token-endpoint requests (authorization-code exchange and refresh) on both provider construction paths. Opt-in, per-server, token requests only — never MCP traffic or discovery, and no other headers are configurable. Empty/null/non-string values are ignored. Completes the second half of NousResearch#75576 (the CIMD half landed via NousResearch#89566).
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…ousResearch#75576) Some authorization servers and WAFs reject httpx's default User-Agent on the OAuth token endpoint. mcp_servers.<name>.oauth.user_agent now stamps a custom User-Agent onto the two token-endpoint requests (authorization-code exchange and refresh) on both provider construction paths. Opt-in, per-server, token requests only — never MCP traffic or discovery, and no other headers are configurable. Empty/null/non-string values are ignored. Completes the second half of NousResearch#75576 (the CIMD half landed via NousResearch#89566).
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…ousResearch#75576) Some authorization servers and WAFs reject httpx's default User-Agent on the OAuth token endpoint. mcp_servers.<name>.oauth.user_agent now stamps a custom User-Agent onto the two token-endpoint requests (authorization-code exchange and refresh) on both provider construction paths. Opt-in, per-server, token requests only — never MCP traffic or discovery, and no other headers are configurable. Empty/null/non-string values are ignored. Completes the second half of NousResearch#75576 (the CIMD half landed via NousResearch#89566).
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Summary
Hermes now identifies itself to OAuth MCP servers with a published Client ID Metadata Document (CIMD) — the client-identification mechanism the MCP 2026-07-28 spec adopted in place of per-install Dynamic Client Registration — falling back to DCR automatically on servers that don't advertise or that reject it.
Salvage of #84050 by @rob-maron, rebased onto current main (post mcp 2.x SDK migration), with one hardening fix on top.
Changes
website/static/oauth/client-metadata.json: the published CIMD document (client_id = its own github.io URL, 10 loopback redirect URIs)tools/mcp_oauth.py: CIMD eligibility (_maybe_use_cimd), pinned callback ports 27890-27894 (spec requires exact redirect-URI match), pinned-socket parking, durable.cimd-offrejection marker, CIMD-aware timeout messagetools/mcp_oauth_manager.py: forwardsclient_metadata_urlto the provider; oninvalid_clientrejection of the document, drops to DCR and records the markerscripts/ci/classify_changes.py: the static JSON is python-relevant (cross-artifact test asserts on it)website/docs/: CIMD/DCR reference section + feature-page noteValidation
Contributor authorship preserved via cherry-pick. Closes #84050; implements the CIMD half of #75576.
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