diff --git a/src/infra/fixed-window-rate-limit.test.ts b/src/infra/fixed-window-rate-limit.test.ts
index 1afc50974d0..8290c1d4176 100644
--- a/src/infra/fixed-window-rate-limit.test.ts
+++ b/src/infra/fixed-window-rate-limit.test.ts
@@ -18,6 +18,35 @@ describe("fixed-window rate limiter", () => {
     expect(limiter.consume()).toMatchObject({ allowed: true, remaining: 1 });
   });
 
+  it("clamps maxRequests and windowMs to at least one", () => {
+    let nowMs = 100;
+    const limiter = createFixedWindowRateLimiter({
+      maxRequests: 0.2,
+      windowMs: 0.4,
+      now: () => nowMs,
+    });
+
+    expect(limiter.consume()).toMatchObject({ allowed: true, remaining: 0, retryAfterMs: 0 });
+    expect(limiter.consume()).toMatchObject({ allowed: false, remaining: 0, retryAfterMs: 1 });
+
+    nowMs += 1;
+    expect(limiter.consume()).toMatchObject({ allowed: true, remaining: 0 });
+  });
+
+  it("reports the remaining retry window after later blocked attempts", () => {
+    let nowMs = 1_000;
+    const limiter = createFixedWindowRateLimiter({
+      maxRequests: 1,
+      windowMs: 1_000,
+      now: () => nowMs,
+    });
+
+    expect(limiter.consume()).toMatchObject({ allowed: true, remaining: 0 });
+
+    nowMs += 250;
+    expect(limiter.consume()).toMatchObject({ allowed: false, retryAfterMs: 750 });
+  });
+
   it("supports explicit reset", () => {
     const limiter = createFixedWindowRateLimiter({
       maxRequests: 1,