diff --git a/apps/api/src/integration-platform/controllers/oauth.controller.spec.ts b/apps/api/src/integration-platform/controllers/oauth.controller.spec.ts
index 619cb13dc..cf3fdefc3 100644
--- a/apps/api/src/integration-platform/controllers/oauth.controller.spec.ts
+++ b/apps/api/src/integration-platform/controllers/oauth.controller.spec.ts
@@ -692,94 +692,6 @@ describe('OAuthController', () => {
       fetchSpy.mockRestore();
     });
 
-    it('persists installation_id on the connection for the GitHub App install flow', async () => {
-      const futureDate = new Date(Date.now() + 600000);
-      mockOAuthStateRepository.findByState.mockResolvedValue({
-        state: 'valid_gh_state',
-        providerSlug: 'github-app',
-        organizationId: 'org_1',
-        userId: 'user_1',
-        codeVerifier: null,
-        redirectUrl: null,
-        expiresAt: futureDate,
-      });
-      mockedGetManifest.mockReturnValue({
-        id: 'github-app',
-        name: 'GitHub App',
-        category: 'Development',
-        auth: {
-          type: 'oauth2',
-          config: {
-            authorizeUrl:
-              'https://github.com/apps/{APP_SLUG}/installations/new',
-            tokenUrl: 'https://github.com/login/oauth/access_token',
-            appInstallFlow: true,
-          },
-        },
-        capabilities: [],
-        isActive: true,
-      } as never);
-      mockOAuthCredentialsService.getCredentials.mockResolvedValue({
-        clientId: 'client_123',
-        clientSecret: 'secret_456',
-        scopes: [],
-        source: 'platform',
-      });
-      mockProviderRepository.findBySlug.mockResolvedValue({
-        id: 'provider_gh',
-      });
-      mockConnectionRepository.findByProviderAndOrg.mockResolvedValue({
-        id: 'conn_gh',
-        metadata: {},
-        variables: {},
-        lastSyncAt: null,
-      });
-      mockConnectionRepository.update.mockResolvedValue({
-        id: 'conn_gh',
-        metadata: {},
-        variables: {},
-        lastSyncAt: null,
-      });
-      mockConnectionService.activateConnection.mockResolvedValue({
-        id: 'conn_gh',
-      });
-
-      const fetchSpy = jest.spyOn(global, 'fetch').mockResolvedValue({
-        ok: true,
-        status: 200,
-        json: () => Promise.resolve({ access_token: 'gh_user_token' }),
-        text: () => Promise.resolve(''),
-      } as unknown as Response);
-
-      await controller.oauthCallback(
-        {
-          code: 'auth_code',
-          state: 'valid_gh_state',
-          installation_id: '987654',
-          setup_action: 'install',
-        },
-        mockRequest,
-        mockResponse,
-      );
-
-      await new Promise<void>((resolve) => setImmediate(resolve));
-
-      expect(mockConnectionRepository.update).toHaveBeenCalledWith(
-        'conn_gh',
-        expect.objectContaining({
-          metadata: expect.objectContaining({
-            githubInstallationId: '987654',
-            githubSetupAction: 'install',
-          }),
-        }),
-      );
-      const redirectUrl = (mockResponse.redirect as jest.Mock).mock.calls[0][0];
-      expect(redirectUrl).toContain('success=true');
-      expect(redirectUrl).toContain('provider=github-app');
-
-      fetchSpy.mockRestore();
-    });
-
     describe('session defense-in-depth', () => {
       const futureDate = new Date(Date.now() + 600000);
       const validState = {
diff --git a/apps/api/src/integration-platform/controllers/oauth.controller.ts b/apps/api/src/integration-platform/controllers/oauth.controller.ts
index 4f3436dac..8007d2249 100644
--- a/apps/api/src/integration-platform/controllers/oauth.controller.ts
+++ b/apps/api/src/integration-platform/controllers/oauth.controller.ts
@@ -39,9 +39,6 @@ interface OAuthCallbackQuery {
   state: string;
   error?: string;
   error_description?: string;
-  // GitHub App installation flow returns these alongside `code`.
-  installation_id?: string;
-  setup_action?: string;
 }
 
 @Controller({ path: 'integrations/oauth', version: '1' })
@@ -425,27 +422,13 @@ export class OAuthController {
         });
       }
 
-      // GitHub App installation flow: persist the installation id (and setup
-      // action) on the connection. The token stored above is a user-to-server
-      // token, but recording the installation id means a future server-to-server
-      // (installation access token) upgrade needs no re-connect.
-      if (query.installation_id) {
-        const metadata =
-          connection.metadata &&
-          typeof connection.metadata === 'object' &&
-          !Array.isArray(connection.metadata)
-            ? (connection.metadata as Record<string, unknown>)
-            : {};
-        connection = await this.connectionRepository.update(connection.id, {
-          metadata: {
-            ...metadata,
-            githubInstallationId: query.installation_id,
-            ...(query.setup_action
-              ? { githubSetupAction: query.setup_action }
-              : {}),
-          },
-        });
-      }
+      // NOTE: GitHub's App install flow returns an `installation_id` on this
+      // callback, but that value is attacker-spoofable — GitHub's own docs say
+      // not to rely on it — so we intentionally do NOT persist it here, and
+      // nothing reads it today. If/when GitHub App installation-token auth is
+      // added, resolve the installation via `GET /user/installations` with the
+      // user token (which also proves the user owns it) rather than trusting the
+      // value from this callback.
 
       await this.connectionService.activateConnection(connection.id);