diff --git a/src/agents/auth-profiles.getsoonestcooldownexpiry.test.ts b/src/agents/auth-profiles.getsoonestcooldownexpiry.test.ts
new file mode 100644
index 00000000000..acc6777c064
--- /dev/null
+++ b/src/agents/auth-profiles.getsoonestcooldownexpiry.test.ts
@@ -0,0 +1,77 @@
+import { describe, expect, it } from "vitest";
+import type { AuthProfileStore } from "./auth-profiles.js";
+import { getSoonestCooldownExpiry } from "./auth-profiles.js";
+
+function makeStore(usageStats?: AuthProfileStore["usageStats"]): AuthProfileStore {
+  return {
+    version: 1,
+    profiles: {},
+    usageStats,
+  };
+}
+
+describe("getSoonestCooldownExpiry", () => {
+  it("returns null when no cooldown timestamps exist", () => {
+    const store = makeStore();
+    expect(getSoonestCooldownExpiry(store, ["openai:p1"])).toBeNull();
+  });
+
+  it("returns earliest unusable time across profiles", () => {
+    const store = makeStore({
+      "openai:p1": {
+        cooldownUntil: 1_700_000_002_000,
+        disabledUntil: 1_700_000_004_000,
+      },
+      "openai:p2": {
+        cooldownUntil: 1_700_000_003_000,
+      },
+      "openai:p3": {
+        disabledUntil: 1_700_000_001_000,
+      },
+    });
+
+    expect(getSoonestCooldownExpiry(store, ["openai:p1", "openai:p2", "openai:p3"])).toBe(
+      1_700_000_001_000,
+    );
+  });
+
+  it("ignores unknown profiles and invalid cooldown values", () => {
+    const store = makeStore({
+      "openai:p1": {
+        cooldownUntil: -1,
+      },
+      "openai:p2": {
+        cooldownUntil: Infinity,
+      },
+      "openai:p3": {
+        disabledUntil: NaN,
+      },
+      "openai:p4": {
+        cooldownUntil: 1_700_000_005_000,
+      },
+    });
+
+    expect(
+      getSoonestCooldownExpiry(store, [
+        "missing",
+        "openai:p1",
+        "openai:p2",
+        "openai:p3",
+        "openai:p4",
+      ]),
+    ).toBe(1_700_000_005_000);
+  });
+
+  it("returns past timestamps when cooldown already expired", () => {
+    const store = makeStore({
+      "openai:p1": {
+        cooldownUntil: 1_700_000_000_000,
+      },
+      "openai:p2": {
+        disabledUntil: 1_700_000_010_000,
+      },
+    });
+
+    expect(getSoonestCooldownExpiry(store, ["openai:p1", "openai:p2"])).toBe(1_700_000_000_000);
+  });
+});