fix(mcp): isolate OAuth request headers

packages/opencode/src/cli/cmd/mcp.ts

@@ -769,7 +769,10 @@ export const McpDebugCommand = effectCmd({
           prompts.log.info(`WWW-Authenticate: ${wwwAuth}`)
         }
 
-        if (response.status === 401) {
+        if (
+          response.status === 401 &&
+          !Object.keys(serverConfig.headers ?? {}).some((key) => key.toLowerCase() === "authorization")
+        ) {
           prompts.log.warn("Server returned 401 Unauthorized")
 
           // Try to discover OAuth metadata

packages/opencode/src/mcp/index.ts

@@ -226,7 +226,8 @@ export const layer = Layer.effect(
       key: string,
       mcp: ConfigMCPV1.Info & { type: "remote" },
     ) {
-      const oauthDisabled = mcp.oauth === false
+      const oauthDisabled =
+        mcp.oauth === false || Object.keys(mcp.headers ?? {}).some((key) => key.toLowerCase() === "authorization")
       const oauthConfig = typeof mcp.oauth === "object" ? mcp.oauth : undefined
       const url = remoteURL(mcp.url)
       if (!url) {
@@ -797,6 +798,8 @@ export const layer = Layer.effect(
       const mcpConfig = yield* requireMcpConfig(mcpName)
       if (mcpConfig.type !== "remote") throw new Error(`MCP server ${mcpName} is not a remote server`)
       if (mcpConfig.oauth === false) throw new Error(`MCP server ${mcpName} has OAuth explicitly disabled`)
+      if (Object.keys(mcpConfig.headers ?? {}).some((key) => key.toLowerCase() === "authorization"))
+        throw new Error(`MCP server ${mcpName} uses static Authorization`)
       const url = remoteURL(mcpConfig.url)
       if (!url) throw new Error(`Invalid MCP URL for "${mcpName}"`)
 

packages/opencode/test/mcp/headers.test.ts

@@ -49,7 +49,7 @@ const { MCP } = await import("../../src/mcp/index")
 const it = testEffect(MCP.defaultLayer)
 
 describe("mcp.headers", () => {
-  it.instance("headers are passed to transports when oauth is enabled (default)", () =>
+  it.instance("static authorization is passed to transports without oauth", () =>
     Effect.gen(function* () {
       const mcp = yield* MCP.Service
       yield* mcp
@@ -72,8 +72,8 @@ describe("mcp.headers", () => {
           Authorization: "Bearer test-token",
           "X-Custom-Header": "custom-value",
         })
-        // OAuth should be enabled by default, so authProvider should exist
-        expect(call.options.authProvider).toBeDefined()
+        // Static Authorization and OAuth are mutually exclusive.
+        expect(call.options.authProvider).toBeUndefined()
       }
     }),
   )
@@ -105,6 +105,28 @@ describe("mcp.headers", () => {
     }),
   )
 
+  it.instance("case-insensitive authorization disables oauth", () =>
+    Effect.gen(function* () {
+      const mcp = yield* MCP.Service
+      yield* mcp
+        .add("test-server-lowercase-auth", {
+          type: "remote",
+          url: "https://example.com/mcp",
+          headers: { authorization: "Bearer test-token", "X-Custom-Header": "custom-value" },
+        })
+        .pipe(Effect.catch(() => Effect.void))
+
+      expect(transportCalls.length).toBeGreaterThanOrEqual(1)
+      for (const call of transportCalls) {
+        expect(call.options.requestInit?.headers).toEqual({
+          authorization: "Bearer test-token",
+          "X-Custom-Header": "custom-value",
+        })
+        expect(call.options.authProvider).toBeUndefined()
+      }
+    }),
+  )
+
   it.instance("no requestInit when headers are not provided", () =>
     Effect.gen(function* () {
       const mcp = yield* MCP.Service

packages/opencode/test/mcp/oauth-header-isolation.test.ts

@@ -0,0 +1,221 @@
+import { describe, expect, test } from "bun:test"
+import type { OAuthClientProvider } from "@modelcontextprotocol/sdk/client/auth.js"
+import { UnauthorizedError } from "@modelcontextprotocol/sdk/client/auth.js"
+import { StreamableHTTPClientTransport } from "@modelcontextprotocol/sdk/client/streamableHttp.js"
+import type {
+  OAuthClientInformationMixed,
+  OAuthClientMetadata,
+  OAuthTokens,
+} from "@modelcontextprotocol/sdk/shared/auth.js"
+
+const canary = "resource-secret"
+const staticAuthorization = "Bearer static-resource-token"
+const basicAuthorization = `Basic ${btoa("client:secret")}`
+
+describe("MCP OAuth header isolation", () => {
+  test("keeps resource headers out of discovery, registration, and token exchange", async () => {
+    using token = serve(() => Response.json({ access_token: "access", token_type: "Bearer", refresh_token: "refresh" }))
+    using registration = serve(() =>
+      Response.json({
+        client_id: "client",
+        client_secret: "secret",
+        token_endpoint_auth_method: "client_secret_basic",
+        redirect_uris: ["http://127.0.0.1/callback"],
+        client_name: "OpenCode test",
+        grant_types: ["authorization_code", "refresh_token"],
+        response_types: ["code"],
+      }),
+    )
+    using authorizationServer = serve(() =>
+      Response.json({
+        issuer: authorizationServer.origin,
+        authorization_endpoint: `${authorizationServer.origin}/authorize`,
+        token_endpoint: `${token.origin}/token`,
+        registration_endpoint: `${registration.origin}/register`,
+        response_types_supported: ["code"],
+        code_challenge_methods_supported: ["S256"],
+        token_endpoint_auth_methods_supported: ["client_secret_basic"],
+      }),
+    )
+    using metadata = serve(() =>
+      Response.json({
+        resource: `${resource.origin}/mcp`,
+        authorization_servers: [authorizationServer.origin],
+      }),
+    )
+    using resource = serve(
+      () =>
+        new Response(null, {
+          status: 401,
+          headers: { "WWW-Authenticate": `Bearer resource_metadata="${metadata.origin}/prm"` },
+        }),
+    )
+    const provider = createProvider()
+    const transport = new StreamableHTTPClientTransport(new URL(`${resource.origin}/mcp`), {
+      authProvider: provider,
+      requestInit: { headers: { "X-Resource-Canary": canary, aUtHoRiZaTiOn: staticAuthorization } },
+    })
+
+    await transport.start()
+    await expect(transport.send(request())).rejects.toBeInstanceOf(UnauthorizedError)
+    await transport.finishAuth("authorization-code")
+    await transport.close()
+
+    expectResourceHeaders(resource.requests)
+    expectNoResourceHeaders(metadata.requests)
+    expectNoResourceHeaders(authorizationServer.requests)
+    expectNoResourceHeaders(registration.requests)
+    expectNoResourceHeaders(token.requests)
+    expect(registration.requests).toHaveLength(1)
+    expect(token.requests).toHaveLength(1)
+    expectAuthorization(token.requests[0], basicAuthorization)
+    expect(new URLSearchParams(token.requests[0].body).get("grant_type")).toBe("authorization_code")
+  })
+
+  test("keeps resource headers out of token refresh", async () => {
+    using refresh = serve(() => Response.json({ access_token: "fresh-access", token_type: "Bearer" }))
+    using authorizationServer = serve(() =>
+      Response.json({
+        issuer: authorizationServer.origin,
+        authorization_endpoint: `${authorizationServer.origin}/authorize`,
+        token_endpoint: `${refresh.origin}/refresh`,
+        response_types_supported: ["code"],
+        code_challenge_methods_supported: ["S256"],
+        token_endpoint_auth_methods_supported: ["client_secret_basic"],
+      }),
+    )
+    using metadata = serve(() =>
+      Response.json({
+        resource: `${resource.origin}/mcp`,
+        authorization_servers: [authorizationServer.origin],
+      }),
+    )
+    using resource = serve((request) => {
+      if (resource.requests.length === 1) {
+        return new Response(null, {
+          status: 401,
+          headers: { "WWW-Authenticate": `Bearer resource_metadata="${metadata.origin}/prm"` },
+        })
+      }
+      return Response.json({ jsonrpc: "2.0", id: 1, result: {} })
+    })
+    const transport = new StreamableHTTPClientTransport(new URL(`${resource.origin}/mcp`), {
+      authProvider: createProvider({
+        clientInformation: {
+          client_id: "client",
+          client_secret: "secret",
+          token_endpoint_auth_method: "client_secret_basic",
+        },
+        tokens: { access_token: "expired-access", token_type: "Bearer", refresh_token: "refresh-token" },
+      }),
+      requestInit: { headers: { "X-Resource-Canary": canary, authorization: staticAuthorization } },
+    })
+    transport.onmessage = () => {}
+
+    await transport.start()
+    await transport.send(request())
+    await transport.close()
+
+    expect(resource.requests).toHaveLength(2)
+    expectResourceHeaders(resource.requests, ["Bearer expired-access", "Bearer fresh-access"])
+    expectNoResourceHeaders(metadata.requests)
+    expectNoResourceHeaders(authorizationServer.requests)
+    expectNoResourceHeaders(refresh.requests)
+    expect(refresh.requests).toHaveLength(1)
+    expectAuthorization(refresh.requests[0], basicAuthorization)
+    expect(new URLSearchParams(refresh.requests[0].body).get("grant_type")).toBe("refresh_token")
+  })
+})
+
+function createProvider(initial?: {
+  clientInformation?: OAuthClientInformationMixed
+  tokens?: OAuthTokens
+}): OAuthClientProvider {
+  let clientInformation = initial?.clientInformation
+  let tokens = initial?.tokens
+  let codeVerifier = ""
+  return {
+    redirectUrl: "http://127.0.0.1/callback",
+    clientMetadata: {
+      redirect_uris: ["http://127.0.0.1/callback"],
+      client_name: "OpenCode test",
+      grant_types: ["authorization_code", "refresh_token"],
+      response_types: ["code"],
+    } satisfies OAuthClientMetadata,
+    clientInformation: () => clientInformation,
+    saveClientInformation: (value) => {
+      clientInformation = value
+    },
+    tokens: () => tokens,
+    saveTokens: (value) => {
+      tokens = value
+    },
+    redirectToAuthorization: () => {},
+    saveCodeVerifier: (value) => {
+      codeVerifier = value
+    },
+    codeVerifier: () => codeVerifier,
+    state: () => "state",
+  }
+}
+
+function request() {
+  return {
+    jsonrpc: "2.0" as const,
+    id: 1,
+    method: "initialize",
+    params: {
+      protocolVersion: "2025-06-18",
+      capabilities: {},
+      clientInfo: { name: "opencode-test", version: "1" },
+    },
+  }
+}
+
+function expectResourceHeaders(requests: CapturedRequest[], authorization: string | string[] = staticAuthorization) {
+  expect(requests.length).toBeGreaterThan(0)
+  for (const [index, request] of requests.entries()) {
+    expect(request.headers.get("x-resource-canary")).toBe(canary)
+    expectAuthorization(request, Array.isArray(authorization) ? authorization[index] : authorization)
+  }
+}
+
+function expectNoResourceHeaders(requests: CapturedRequest[]) {
+  expect(requests.length).toBeGreaterThan(0)
+  for (const request of requests) {
+    expect(request.headers.get("x-resource-canary")).toBeNull()
+    expect(request.headers.get("authorization")).not.toBe(staticAuthorization)
+  }
+}
+
+function expectAuthorization(request: CapturedRequest, value: string) {
+  expect([...request.headers].filter(([name]) => name === "authorization")).toEqual([["authorization", value]])
+}
+
+interface CapturedRequest {
+  url: string
+  headers: Headers
+  body: string
+}
+
+function serve(handler: (request: CapturedRequest) => Response | Promise<Response>) {
+  const requests: CapturedRequest[] = []
+  const server = Bun.serve({
+    hostname: "127.0.0.1",
+    port: 0,
+    async fetch(request) {
+      const captured = {
+        url: request.url,
+        headers: new Headers(request.headers),
+        body: await request.text(),
+      }
+      requests.push(captured)
+      return handler(captured)
+    },
+  })
+  return {
+    origin: `http://127.0.0.1:${server.port}`,
+    requests,
+    [Symbol.dispose]: () => server.stop(true),
+  }
+}