diff --git a/apps/api/src/routes/localAuth.ts b/apps/api/src/routes/localAuth.ts
index 624e71e..68bd47e 100644
--- a/apps/api/src/routes/localAuth.ts
+++ b/apps/api/src/routes/localAuth.ts
@@ -97,6 +97,29 @@ export function resetLoginAttempts(username: string): void {
   loginAttempts.delete(username.trim());
 }
 
+/**
+ * IN-03: evict stale rate-limit entries to bound the in-memory map size.
+ *
+ * An entry is stale (and safe to drop) when it is neither inside an active rate-limit
+ * window nor inside an active lockout TTL:
+ *   - locked-out entries expire LOCKOUT_TTL_MS after lockedAt
+ *   - non-locked entries expire once their lockedUntil window has passed
+ *
+ * Called opportunistically at the top of each login request. Dropping an entry is
+ * behaviourally identical to the entry having naturally expired, so eviction never
+ * weakens the brute-force defense — it only reclaims memory for identities no longer
+ * under active rate-limiting.
+ */
+function evictStaleLoginAttempts(now: number): void {
+  for (const [k, v] of loginAttempts) {
+    const lockoutExpired = v.lockedOut ? now - v.lockedAt >= LOCKOUT_TTL_MS : true;
+    const windowExpired = now >= v.lockedUntil;
+    if (lockoutExpired && windowExpired) {
+      loginAttempts.delete(k);
+    }
+  }
+}
+
 // Pre-computed dummy hash used to run verifyPassword on unknown-username paths
 // (timing defense — prevents timing-oracle username enumeration, RESEARCH Pitfall 2).
 // WR-03: hashPassword is now async. Kick off the computation once at module load and keep
@@ -115,6 +138,9 @@ localAuthRouter.post('/local/login', zValidator('json', loginSchema, noEchoHook)
   const key = username; // loginSchema .trim()s the username; the map key matches resetLoginAttempts
 
   const now = Date.now();
+  // IN-03: opportunistically reclaim memory from entries that are no longer actively
+  // rate-limited or locked out. Cheap at household scale; bounds the map under input churn.
+  evictStaleLoginAttempts(now);
   const attempt = loginAttempts.get(key);
 
   // 423: account locked (>= LOCKOUT_FAILURES failures). CR-04: the lockout auto-expires