diff --git a/apps/sim/app/api/auth/instagram/authorize/route.test.ts b/apps/sim/app/api/auth/instagram/authorize/route.test.ts
index 12e6415d52f..5340ef5adb7 100644
--- a/apps/sim/app/api/auth/instagram/authorize/route.test.ts
+++ b/apps/sim/app/api/auth/instagram/authorize/route.test.ts
@@ -1,4 +1,5 @@
 import { createMockRequest } from '@sim/testing'
+import { createRouteContext } from '@sim/testing/helpers/http'
 import { authMockFns } from '@sim/testing/mocks/auth.mock'
 import { oauthUtilsMock, oauthUtilsMockFns } from '@sim/testing/mocks/oauth-utils.mock'
 import { urlsMockFns } from '@sim/testing/mocks/urls.mock'
@@ -45,7 +46,7 @@ describe('Instagram authorize route', () => {
       'https://sim.test/api/auth/instagram/authorize?workspaceId=workspace-1&draftId=draft-exact'
     )
 
-    const response = await GET(request)
+    const response = await GET(request, createRouteContext({}))
 
     expect(response.status).toBe(307)
     expect(response.headers.get('set-cookie')).toContain(
@@ -54,6 +55,20 @@ describe('Instagram authorize route', () => {
     expect(mocks.createCredentialConnection).not.toHaveBeenCalled()
   })
 
+  it('refuses a cross-site workspace launch before creating a connection draft', async () => {
+    const request = createMockRequest(
+      'GET',
+      undefined,
+      { 'sec-fetch-site': 'cross-site' },
+      'https://sim.test/api/auth/instagram/authorize?workspaceId=workspace-1'
+    )
+
+    const response = await GET(request, createRouteContext({}))
+
+    expect(response.status).toBe(403)
+    expect(mocks.createCredentialConnection).not.toHaveBeenCalled()
+  })
+
   it('returns a conflict when a different connection intent is already active', async () => {
     mocks.createCredentialConnection.mockRejectedValue(
       new OrchestrationError(
@@ -68,7 +83,7 @@ describe('Instagram authorize route', () => {
       'https://sim.test/api/auth/instagram/authorize?workspaceId=workspace-1'
     )
 
-    const response = await GET(request)
+    const response = await GET(request, createRouteContext({}))
 
     expect(response.status).toBe(409)
     await expect(response.json()).resolves.toEqual({
diff --git a/apps/sim/app/api/auth/instagram/authorize/route.ts b/apps/sim/app/api/auth/instagram/authorize/route.ts
index 17f21e99e66..58c78a2d3f5 100644
--- a/apps/sim/app/api/auth/instagram/authorize/route.ts
+++ b/apps/sim/app/api/auth/instagram/authorize/route.ts
@@ -6,6 +6,7 @@ import { parseRequest } from '@/lib/api/server'
 import { getSession } from '@/lib/auth'
 import { requireConfiguredOAuthClient } from '@/lib/core/config/env-capabilities.server'
 import { asOrchestrationError } from '@/lib/core/orchestration/types'
+import { isCrossSiteSessionRequest } from '@/lib/core/security/same-origin'
 import { getBaseUrl } from '@/lib/core/utils/urls'
 import { isSameOrigin } from '@/lib/core/utils/validation'
 import { withRouteHandler } from '@/lib/core/utils/with-route-handler'
@@ -41,6 +42,12 @@ export const GET = withRouteHandler(async (request: NextRequest) => {
     let credentialDraftId = draftId
 
     if (workspaceId && !draftId) {
+      // The query alone picks the workspace, so a cross-site page must not be
+      // able to start this launch with the viewer's session cookie.
+      if (isCrossSiteSessionRequest(request)) {
+        logger.warn('Rejected cross-site Instagram workspace launch', { userId: session.user.id })
+        return NextResponse.json({ error: 'Cross-site launch refused' }, { status: 403 })
+      }
       try {
         const connection = await createCredentialConnection.execute({
           principal: { kind: 'session', userId: session.user.id, sessionId },
diff --git a/scripts/check-test-types.baseline.json b/scripts/check-test-types.baseline.json
index e24d2c69d44..9188621c97b 100644
--- a/scripts/check-test-types.baseline.json
+++ b/scripts/check-test-types.baseline.json
@@ -14,9 +14,6 @@
   "apps/sim/app/api/auth/forget-password/route.test.ts": {
     "TS2554": 8
   },
-  "apps/sim/app/api/auth/instagram/authorize/route.test.ts": {
-    "TS2554": 2
-  },
   "apps/sim/app/api/auth/oauth/credentials/route.test.ts": {
     "TS2322": 1,
     "TS2345": 2,