diff --git a/.changeset/preserve-oauth-scope-surface.md b/.changeset/preserve-oauth-scope-surface.md
new file mode 100644
index 000000000..2056ba413
--- /dev/null
+++ b/.changeset/preserve-oauth-scope-surface.md
@@ -0,0 +1,5 @@
+---
+"@executor-js/sdk": patch
+---
+
+Preserve an integration's declared OAuth scopes when same-origin authorization-server metadata describes a different authorization or token endpoint.
diff --git a/packages/core/sdk/src/oauth-scope-union.test.ts b/packages/core/sdk/src/oauth-scope-union.test.ts
index 2895878fd..744e6f941 100644
--- a/packages/core/sdk/src/oauth-scope-union.test.ts
+++ b/packages/core/sdk/src/oauth-scope-union.test.ts
@@ -107,6 +107,8 @@ const serveMetadataServer = (config: {
     | "error"
     | null;
   readonly authServerScopes?: readonly string[];
+  readonly authServerAuthorizationPath?: string;
+  readonly authServerTokenPath?: string;
 }) =>
   Effect.gen(function* () {
     const baseUrlRef = { value: "" };
@@ -133,8 +135,8 @@ const serveMetadataServer = (config: {
       ) {
         return HttpServerResponse.jsonUnsafe({
           issuer: base,
-          authorization_endpoint: `${base}/authorize`,
-          token_endpoint: `${base}/token`,
+          authorization_endpoint: `${base}${config.authServerAuthorizationPath ?? "/authorize"}`,
+          token_endpoint: `${base}${config.authServerTokenPath ?? "/token"}`,
           response_types_supported: ["code"],
           code_challenge_methods_supported: ["S256"],
           scopes_supported: config.authServerScopes,
@@ -325,6 +327,49 @@ describe("oauth.start integration-driven scopes", () => {
       ),
   );
 
+  it.effect("keeps declared scopes when same-origin metadata describes another OAuth surface", () =>
+    Effect.scoped(
+      Effect.gen(function* () {
+        const server = yield* serveMetadataServer({
+          authServerScopes: ["mcp:connect"],
+          authServerAuthorizationPath: "/oauth/mcp",
+        });
+        const plugins = [
+          memoryCredentialsPlugin(),
+          makeScopePlugin({ scopes: ["file_content:read", "file_comments:write"] }),
+        ] as const;
+        const { executor } = yield* makeTestWorkspaceHarness({ plugins });
+        yield* executor.acme.seed();
+
+        yield* executor.oauth.createClient({
+          owner: "org",
+          slug: CLIENT,
+          authorizationUrl: server.authorizationEndpoint,
+          tokenUrl: server.tokenEndpoint,
+          grant: "authorization_code",
+          clientId: "test-client",
+          clientSecret: "test-secret",
+        });
+
+        const started = yield* executor.oauth.start({
+          owner: "org",
+          client: CLIENT,
+          clientOwner: "org",
+          name: ConnectionName.make("main"),
+          integration: INTEG,
+          template: TEMPLATE,
+        });
+        expect(started.status).toBe("redirect");
+        if (started.status !== "redirect") return;
+
+        expect(scopesFromAuthorizeUrl(started.authorizationUrl)).toEqual([
+          "file_content:read",
+          "file_comments:write",
+        ]);
+      }),
+    ),
+  );
+
   it.effect(
     "(d) for MCP, the resource's own scopes_supported wins over a divergent authorization server",
     () =>
diff --git a/packages/core/sdk/src/oauth-service.ts b/packages/core/sdk/src/oauth-service.ts
index ea1fd3fa3..5130dcb77 100644
--- a/packages/core/sdk/src/oauth-service.ts
+++ b/packages/core/sdk/src/oauth-service.ts
@@ -54,6 +54,7 @@ import {
   discoverProtectedResourceMetadata,
   OAuthDiscoveryError,
   registerDynamicClient as registerDynamicClientDcr,
+  type OAuthAuthorizationServerMetadata,
 } from "./oauth-discovery";
 import {
   assertSupportedOAuthEndpointUrl,
@@ -414,6 +415,14 @@ const canonicalUrlString = (value: string): string => {
   return url.toString();
 };
 
+const oauthMetadataMatchesClient = (
+  client: Pick<LoadedOAuthClient, "authorizationUrl" | "tokenUrl">,
+  metadata: OAuthAuthorizationServerMetadata,
+): boolean =>
+  canonicalUrlString(metadata.authorization_endpoint) ===
+    canonicalUrlString(client.authorizationUrl) &&
+  canonicalUrlString(metadata.token_endpoint) === canonicalUrlString(client.tokenUrl);
+
 const isWellKnownOAuthMetadataUrl = (value: string): boolean => {
   const path = new URL(value.trim()).pathname.toLowerCase();
   return (
@@ -494,7 +503,8 @@ export const makeOAuthService = (deps: OAuthServiceDeps): OAuthService => {
         Effect.catch(() => Effect.succeed(null)),
         Effect.provide(httpClientLayer),
       );
-      return intersectScopes(requestedScopes, as?.metadata.scopes_supported);
+      if (!as || !oauthMetadataMatchesClient(client, as.metadata)) return requestedScopes;
+      return intersectScopes(requestedScopes, as.metadata.scopes_supported);
     }).pipe(Effect.catch(() => Effect.succeed(requestedScopes)));
 
   // Caps on server-controlled discovery input — a hostile or buggy server must