diff --git a/apps/web/src/http-security.test.ts b/apps/web/src/http-security.test.ts
index 7f23828..0aa3d80 100644
--- a/apps/web/src/http-security.test.ts
+++ b/apps/web/src/http-security.test.ts
@@ -58,6 +58,23 @@ test("InMemoryRateLimiter blocks after the configured request budget is exhauste
   assert.equal(blocked.retryAfterSeconds, 58);
 });
 
+test("InMemoryRateLimiter drops expired buckets during periodic sweeps", () => {
+  const limiter = new InMemoryRateLimiter();
+  const policy = {
+    id: "auth",
+    windowMs: 1_000,
+    maxRequests: 1,
+  };
+
+  assert.deepEqual(limiter.consume(policy, "stale", 1_000), { allowed: true });
+
+  for (let index = 0; index < 99; index += 1) {
+    limiter.consume(policy, `fresh-${index}`, 3_000);
+  }
+
+  assert.deepEqual(limiter.consume(policy, "stale", 3_000), { allowed: true });
+});
+
 test("assertTrustedOrigin accepts configured origins and requires browser origin metadata", () => {
   const request = createMockRequest({
     headers: {
diff --git a/apps/web/src/http-security.ts b/apps/web/src/http-security.ts
index 7489deb..b944488 100644
--- a/apps/web/src/http-security.ts
+++ b/apps/web/src/http-security.ts
@@ -66,8 +66,15 @@ export async function readJsonBody(
 
 export class InMemoryRateLimiter {
   private readonly entries = new Map<string, RateLimitEntry>();
+  private sweepCounter = 0;
 
   consume(policy: RateLimitPolicy, key: string, now = Date.now()): RateLimitDecision {
+    this.sweepCounter += 1;
+
+    if (this.sweepCounter % 100 === 0) {
+      this.deleteExpiredEntries(now);
+    }
+
     const bucketKey = `${policy.id}:${key}`;
     const existing = this.entries.get(bucketKey);
 
@@ -90,6 +97,14 @@ export class InMemoryRateLimiter {
     this.entries.set(bucketKey, existing);
     return { allowed: true };
   }
+
+  private deleteExpiredEntries(now: number): void {
+    for (const [bucketKey, entry] of this.entries.entries()) {
+      if (entry.resetAt <= now) {
+        this.entries.delete(bucketKey);
+      }
+    }
+  }
 }
 
 export function getRateLimitClientIp(request: IncomingMessage): string {
diff --git a/apps/web/src/main.ts b/apps/web/src/main.ts
index f4ad34a..ab22908 100644
--- a/apps/web/src/main.ts
+++ b/apps/web/src/main.ts
@@ -70,6 +70,7 @@ const server = createServer(async (request, response) => {
     }
 
     if (request.method === "POST" && request.url === "/api/auth/register") {
+      assertTrustedOrigin(request, mutationAllowedOrigins);
       enforceRateLimit(request, authRateLimitPolicy);
       const body = await readJsonBody(request, { maxBytes: maxJsonBodyBytes });
       const payload = readAuthPayload(body);
@@ -89,6 +90,7 @@ const server = createServer(async (request, response) => {
     }
 
     if (request.method === "POST" && request.url === "/api/auth/login") {
+      assertTrustedOrigin(request, mutationAllowedOrigins);
       enforceRateLimit(request, authRateLimitPolicy);
       const body = await readJsonBody(request, { maxBytes: maxJsonBodyBytes });
       const payload = readAuthPayload(body);
@@ -108,6 +110,7 @@ const server = createServer(async (request, response) => {
     }
 
     if (request.method === "POST" && request.url === "/api/auth/password-reset/request") {
+      assertTrustedOrigin(request, mutationAllowedOrigins);
       enforceRateLimit(request, authRateLimitPolicy);
       const body = await readJsonBody(request, { maxBytes: maxJsonBodyBytes });
       const payload = readEmailOnlyPayload(body);
@@ -137,6 +140,7 @@ const server = createServer(async (request, response) => {
     }
 
     if (request.method === "POST" && request.url === "/api/auth/password-reset/confirm") {
+      assertTrustedOrigin(request, mutationAllowedOrigins);
       enforceRateLimit(request, authRateLimitPolicy);
       const body = await readJsonBody(request, { maxBytes: maxJsonBodyBytes });
       const payload = readPasswordResetConfirmPayload(body);