diff --git a/src/agents/model-suppression.test.ts b/src/agents/model-suppression.test.ts
new file mode 100644
index 00000000000..bc93e41bde2
--- /dev/null
+++ b/src/agents/model-suppression.test.ts
@@ -0,0 +1,57 @@
+import { beforeEach, describe, expect, it, vi } from "vitest";
+
+const mocks = vi.hoisted(() => ({
+  resolveManifestBuiltInModelSuppression: vi.fn(),
+  resolveProviderBuiltInModelSuppression: vi.fn(),
+}));
+
+vi.mock("../plugins/manifest-model-suppression.js", () => ({
+  resolveManifestBuiltInModelSuppression: mocks.resolveManifestBuiltInModelSuppression,
+}));
+
+vi.mock("../plugins/provider-runtime.js", () => ({
+  resolveProviderBuiltInModelSuppression: mocks.resolveProviderBuiltInModelSuppression,
+}));
+
+import { shouldSuppressBuiltInModel } from "./model-suppression.js";
+
+describe("model suppression", () => {
+  beforeEach(() => {
+    mocks.resolveManifestBuiltInModelSuppression.mockReset();
+    mocks.resolveProviderBuiltInModelSuppression.mockReset();
+  });
+
+  it("uses manifest suppression before runtime hooks", () => {
+    mocks.resolveManifestBuiltInModelSuppression.mockReturnValueOnce({
+      suppress: true,
+      errorMessage: "manifest suppression",
+    });
+
+    expect(
+      shouldSuppressBuiltInModel({
+        provider: "openai",
+        id: "gpt-5.3-codex-spark",
+        config: {},
+      }),
+    ).toBe(true);
+
+    expect(mocks.resolveProviderBuiltInModelSuppression).not.toHaveBeenCalled();
+  });
+
+  it("falls back to runtime hooks when no manifest suppression matches", () => {
+    mocks.resolveProviderBuiltInModelSuppression.mockReturnValueOnce({
+      suppress: true,
+      errorMessage: "runtime suppression",
+    });
+
+    expect(
+      shouldSuppressBuiltInModel({
+        provider: "openai",
+        id: "gpt-5.3-codex-spark",
+        config: {},
+      }),
+    ).toBe(true);
+
+    expect(mocks.resolveProviderBuiltInModelSuppression).toHaveBeenCalledOnce();
+  });
+});