diff --git a/keep-ui/shared/lib/__tests__/oauth2proxy-auth.test.ts b/keep-ui/shared/lib/__tests__/oauth2proxy-auth.test.ts
index 4342993be6..82f1b22fcd 100644
--- a/keep-ui/shared/lib/__tests__/oauth2proxy-auth.test.ts
+++ b/keep-ui/shared/lib/__tests__/oauth2proxy-auth.test.ts
@@ -222,4 +222,28 @@ describe("authorizeOAuth2Proxy", () => {
 
     expect(user!.id).toBe("email@example.com");
   });
+
+  it("returns tenantId matching backend SINGLE_TENANT_UUID", () => {
+    const headers = makeHeaders({
+      "x-forwarded-user": "Test User",
+      "x-forwarded-email": "test@example.com",
+    });
+
+    const user = authorizeOAuth2Proxy(headers, defaultConfig);
+
+    expect(user).not.toBeNull();
+    expect(user!.tenantId).toBe("keep");
+  });
+
+  it("never returns undefined tenantId for a valid user", () => {
+    const headers = makeHeaders({
+      "x-forwarded-email": "user@example.com",
+    });
+
+    const user = authorizeOAuth2Proxy(headers, defaultConfig);
+
+    expect(user).not.toBeNull();
+    expect(user!.tenantId).toBeDefined();
+    expect(user!.tenantId).not.toBe("undefined");
+  });
 });
diff --git a/keep-ui/shared/lib/oauth2proxy-auth.ts b/keep-ui/shared/lib/oauth2proxy-auth.ts
index 8fe146edfb..e03f264c51 100644
--- a/keep-ui/shared/lib/oauth2proxy-auth.ts
+++ b/keep-ui/shared/lib/oauth2proxy-auth.ts
@@ -51,5 +51,6 @@ export function authorizeOAuth2Proxy(
     email: emailValue || userValue || "oauth2proxy-user",
     accessToken: accessToken || `oauth2proxy:${identity}`,
     role: groups || undefined,
+    tenantId: "keep",
   };
 }