Pomerium's MCP gateway now handles more of the OAuth complexity that real-world MCP servers require. This update adds upstream OAuth support with token caching and injection, Dynamic Client Registration as a fallback for clients that don't yet support Client ID Metadata Documents, auto-discovery for MCP connect flows, and the first MCP-facing configuration APIs. The result is less manual upstream OAuth configuration, more reliable session handling, and a cleaner experience in the routes portal.
Highlights:
- Upstream OAuth for MCP routes – Pomerium can now discover upstream OAuth metadata, complete upstream authorization flows, cache client and token state, and inject upstream access tokens into MCP traffic when the target server requires them.
- Dynamic Client Registration fallback – Pomerium now supports DCR for upstream OAuth flows, providing a practical path for tools like MCP Inspector while Client ID Metadata Document support matures across the ecosystem.
- Issuer metadata in authorization flows – Pomerium now includes the recommended iss parameter in MCP authorization flows, aligning with the upcoming 2026-07-28 MCP spec. Pomerium's host is returned as the issuer, keeping authorization flows spec-compliant as the standard evolves.
- Auto-discovery for MCP connect flows – MCP connect, disconnect, and authorize endpoints now support auto-discovery, reducing the static upstream OAuth configuration needed for compatible servers.
- Safer metadata fetching – MCP metadata discovery uses SSRF-safe HTTP fetching and stricter protected-resource metadata handling, including path-prefix validation.
- Better routes portal experience – MCP routes now show server indicators and connect/disconnect controls in the routes portal, making MCP-enabled routes easier to identify and manage.
- More reliable upstream auth recovery – Pomerium refreshes expired upstream tokens before forcing reauthentication, recovers upstream auth after late config delivery, and surfaces clearer errors when upstream tokens can't be resolved.
- Config API as MCP tools – A new pkg/mcp/configapi library exposes Pomerium's ConfigService as MCP tools, with generated schemas, sensitive-field handling, and update-safety checks — early building blocks for MCP-driven configuration workflows.
See the MCP support docs to learn how Pomerium secures MCP routes and manages upstream OAuth on behalf of clients.
