fix: preserve configured Authorization in external MCP passthrough#3177
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walker-tx merged 3 commits intoJun 3, 2026
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External MCP tools with requires_oauth=true forwarded the gating OAuth token (presented to the local Gram MCP server) upstream as "Authorization: Bearer <token>", overwriting any Authorization header the user configured via env/user config in BuildHeaders. This broke setups where the local server is OAuth-guarded but the upstream MCP expects a static credential (e.g. "Basic ..."): the upstream rejected the forwarded gating token with 401. Forward the gating OAuth token only when no explicit Authorization was already set from config. Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
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subomi
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Address review nit: rename the case to "system config Authorization wins over oauth token" so it is explicit and parallel to the user config case. Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
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Summary
External MCP tools with
requires_oauth=trueforwarded the gating OAuth token (the token presented to the local Gram MCP server) upstream asAuthorization: Bearer <token>, overwriting anyAuthorizationheader the user configured via env/user config inBuildHeaders(server/internal/externalmcp/config.go).This broke setups where the local server is OAuth-guarded but the upstream MCP expects a static credential (e.g.
Basic ...): the upstream rejected the forwarded gating token with401.Fix
Forward the gating OAuth token only when no explicit
Authorizationwas already set from config. Config-providedAuthorizationnow wins; the gating token remains the fallback when none is configured.Tests
Added two
TestBuildHeadersWithOAuthTokencases: config-provided and user-config-providedAuthorizationeach take precedence over the OAuth token.Resolves AIS-83.
🤖 Generated with Claude Code
Summary by cubic
Preserves the configured Authorization header in external MCP passthrough; only forwards the gating OAuth token if no Authorization is set. Prevents upstream 401s for MCPs that require static credentials (addresses AIS-83).
BuildHeadersinserver/internal/externalmcp/config.goto applyBearer <oauthToken>only when Authorization isn’t set by system or user config.server.Written for commit 87df9ec. Summary will update on new commits.