diff --git a/packages/core/src/mcp/oauth.ts b/packages/core/src/mcp/oauth.ts
index fc8616bd6e5..8f5dd348b99 100644
--- a/packages/core/src/mcp/oauth.ts
+++ b/packages/core/src/mcp/oauth.ts
@@ -168,7 +168,12 @@ export const provider = (options: Options): OAuthClientProvider => {
       if (!resource) return identity
       if (!checkResourceAllowed({ requestedResource: identity, configuredResource: resource }))
         throw new Error(`Protected resource ${resource} does not cover ${identity}`)
-      return new URL(resource)
+      const canonical = new URL(resource)
+      // The transport dials the configured URL with extra query parameters and some servers echo
+      // that back as the resource. Query is transport detail, not identity: the token stays bound
+      // to the configured URL so a later refresh names the same resource the login did.
+      if (canonical.origin === identity.origin && canonical.pathname === identity.pathname) return identity
+      return canonical
     },
     ...(options.clientMetadataUrl ? { clientMetadataUrl: options.clientMetadataUrl } : {}),
     ...(redirect ? { state: () => redirect.state } : {}),
diff --git a/packages/core/test/mcp-oauth.test.ts b/packages/core/test/mcp-oauth.test.ts
index bc169813d8a..76a9ce55b87 100644
--- a/packages/core/test/mcp-oauth.test.ts
+++ b/packages/core/test/mcp-oauth.test.ts
@@ -324,6 +324,44 @@ describe("MCP OAuth", () => {
     expect(probes.some((probe) => probe.includes("codemode"))).toBe(false)
   })
 
+  test("keeps the configured URL as the resource when metadata echoes the dialed query", async () => {
+    const tokenRequests: URLSearchParams[] = []
+    const server = Bun.serve({
+      port: 0,
+      async fetch(request) {
+        const url = new URL(request.url)
+        if (url.pathname === "/.well-known/oauth-authorization-server")
+          return Response.json({
+            issuer: url.origin,
+            authorization_endpoint: `${url.origin}/authorize`,
+            token_endpoint: `${url.origin}/token`,
+            response_types_supported: ["code"],
+          })
+        if (url.pathname === "/.well-known/oauth-protected-resource/mcp")
+          return Response.json({ resource: `${url.origin}/mcp${url.search}`, authorization_servers: [url.origin] })
+        if (request.method === "POST" && url.pathname === "/token") {
+          tokenRequests.push(new URLSearchParams(await request.text()))
+          return Response.json({ access_token: "next", token_type: "Bearer" })
+        }
+        return new Response(null, { status: 404 })
+      },
+    })
+    const url = `${server.url.origin}/mcp`
+    const oauthProvider = await connectProvider(
+      remote(url),
+      memoryCredentials([credential({ access: "expired", refresh: "refresh", url })]),
+    )
+
+    // The transport dials with ?codemode=false and follows the 401 challenge to metadata that echoes it.
+    await auth(oauthProvider, {
+      serverUrl: `${url}?codemode=false`,
+      resourceMetadataUrl: new URL(`${server.url.origin}/.well-known/oauth-protected-resource/mcp?codemode=false`),
+    }).finally(() => server.stop(true))
+
+    expect(tokenRequests[0]?.get("grant_type")).toBe("refresh_token")
+    expect(tokenRequests[0]?.get("resource")).toBe(url)
+  })
+
   test("finds resource metadata through the 401 header when the well-known path is not served", async () => {
     const server = Bun.serve({
       port: 0,