diff --git a/test/tts-config-validator.test.ts b/test/tts-config-validator.test.ts
new file mode 100644
index 00000000000..4cdb9128c45
--- /dev/null
+++ b/test/tts-config-validator.test.ts
@@ -0,0 +1,35 @@
+// app/store/config.ts participates in an import cycle, so a static import can
+// hit a temporal-dead-zone error. Load it dynamically in beforeAll instead.
+let TTSConfigValidator: {
+  engine: (x: string) => string;
+  model: (x: string) => string;
+  voice: (x: string) => string;
+  speed: (x: number) => number;
+};
+
+beforeAll(async () => {
+  // Warm up the import cycle in a working order before loading the target.
+  await import("../app/client/api");
+  ({ TTSConfigValidator } = await import("../app/store/config"));
+});
+
+describe("TTSConfigValidator", () => {
+  test("speed clamps to [0.25, 4.0] and defaults to 1.0 on NaN", () => {
+    expect(TTSConfigValidator.speed(0.1)).toBe(0.25);
+    expect(TTSConfigValidator.speed(10)).toBe(4.0);
+    expect(TTSConfigValidator.speed(2)).toBe(2);
+    expect(TTSConfigValidator.speed(NaN)).toBe(1.0);
+  });
+
+  test("engine passes the value through unchanged", () => {
+    expect(TTSConfigValidator.engine("OpenAI-TTS")).toBe("OpenAI-TTS");
+  });
+
+  test("model passes the value through unchanged", () => {
+    expect(TTSConfigValidator.model("tts-1")).toBe("tts-1");
+  });
+
+  test("voice passes the value through unchanged", () => {
+    expect(TTSConfigValidator.voice("alloy")).toBe("alloy");
+  });
+});