diff --git a/mcp/src/server/store.ts b/mcp/src/server/store.ts
index a53990b4..f41bec61 100644
--- a/mcp/src/server/store.ts
+++ b/mcp/src/server/store.ts
@@ -64,10 +64,78 @@ function initializeStore(): AFSStore {
 // In-Memory Store (fallback)
 // -----------------------------------------------------------------------------
 
-function createMemoryStore(): AFSStore {
+/** Configuration for memory store event retention */
+interface MemoryStoreConfig {
+  /** Maximum number of events to retain (default: 10000) */
+  maxEvents: number;
+  /** Maximum age of events in milliseconds (default: 1 hour) */
+  maxEventAgeMs: number;
+  /** How often to run cleanup in milliseconds (default: 5 minutes) */
+  cleanupIntervalMs: number;
+}
+
+/** Default memory store configuration */
+const DEFAULT_MEMORY_CONFIG: MemoryStoreConfig = {
+  maxEvents: parseInt(process.env.AGENTATION_MAX_EVENTS || "10000", 10),
+  maxEventAgeMs: parseInt(process.env.AGENTATION_EVENT_TTL_MS || String(60 * 60 * 1000), 10), // 1 hour
+  cleanupIntervalMs: parseInt(process.env.AGENTATION_CLEANUP_INTERVAL_MS || String(5 * 60 * 1000), 10), // 5 minutes
+};
+
+function createMemoryStore(config: MemoryStoreConfig = DEFAULT_MEMORY_CONFIG): AFSStore {
   const sessions = new Map<string, Session>();
   const annotations = new Map<string, Annotation>();
   const events: AFSEvent[] = [];
+  let cleanupTimer: ReturnType<typeof setInterval> | null = null;
+
+  /**
+   * Clean up old events based on count and age limits.
+   * This prevents unbounded memory growth in long-running processes.
+   */
+  function cleanupEvents(): void {
+    const now = Date.now();
+    const cutoffTime = now - config.maxEventAgeMs;
+    let removedByAge = 0;
+    let removedByCount = 0;
+
+    // Remove events older than maxEventAgeMs
+    while (events.length > 0) {
+      const oldestEvent = events[0];
+      const eventTime = new Date(oldestEvent.timestamp).getTime();
+      if (eventTime < cutoffTime) {
+        events.shift();
+        removedByAge++;
+      } else {
+        break;
+      }
+    }
+
+    // If still over limit, remove oldest events
+    while (events.length > config.maxEvents) {
+      events.shift();
+      removedByCount++;
+    }
+
+    if (removedByAge > 0 || removedByCount > 0) {
+      process.stderr.write(
+        `[Store] Event cleanup: removed ${removedByAge} expired, ${removedByCount} over limit, ${events.length} remaining\n`
+      );
+    }
+  }
+
+  /**
+   * Add an event and trigger cleanup if needed.
+   */
+  function addEvent(event: AFSEvent): void {
+    addEvent(event);
+
+    // Quick check: if significantly over limit, trigger immediate cleanup
+    if (events.length > config.maxEvents * 1.2) {
+      cleanupEvents();
+    }
+  }
+
+  // Start periodic cleanup
+  cleanupTimer = setInterval(cleanupEvents, config.cleanupIntervalMs);
 
   function generateId(): string {
     return `${Date.now().toString(36)}-${Math.random().toString(36).slice(2, 8)}`;
@@ -85,7 +153,7 @@ function createMemoryStore(): AFSStore {
       sessions.set(session.id, session);
 
       const event = eventBus.emit("session.created", session.id, session);
-      events.push(event);
+      addEvent(event);
 
       return session;
     },
@@ -117,7 +185,7 @@ function createMemoryStore(): AFSStore {
 
       const eventType = status === "closed" ? "session.closed" : "session.updated";
       const event = eventBus.emit(eventType, id, session);
-      events.push(event);
+      addEvent(event);
 
       return session;
     },
@@ -144,7 +212,7 @@ function createMemoryStore(): AFSStore {
       annotations.set(annotation.id, annotation);
 
       const event = eventBus.emit("annotation.created", sessionId, annotation);
-      events.push(event);
+      addEvent(event);
 
       return annotation;
     },
@@ -164,7 +232,7 @@ function createMemoryStore(): AFSStore {
 
       if (annotation.sessionId) {
         const event = eventBus.emit("annotation.updated", annotation.sessionId, annotation);
-        events.push(event);
+        addEvent(event);
       }
 
       return annotation;
@@ -188,7 +256,7 @@ function createMemoryStore(): AFSStore {
 
       if (annotation.sessionId) {
         const event = eventBus.emit("annotation.updated", annotation.sessionId, annotation);
-        events.push(event);
+        addEvent(event);
       }
 
       return annotation;
@@ -217,7 +285,7 @@ function createMemoryStore(): AFSStore {
 
       if (annotation.sessionId) {
         const event = eventBus.emit("thread.message", annotation.sessionId, message);
-        events.push(event);
+        addEvent(event);
       }
 
       return annotation;
@@ -243,7 +311,7 @@ function createMemoryStore(): AFSStore {
 
       if (annotation.sessionId) {
         const event = eventBus.emit("annotation.deleted", annotation.sessionId, annotation);
-        events.push(event);
+        addEvent(event);
       }
 
       return annotation;
@@ -256,6 +324,11 @@ function createMemoryStore(): AFSStore {
     },
 
     close(): void {
+      // Stop periodic cleanup
+      if (cleanupTimer) {
+        clearInterval(cleanupTimer);
+        cleanupTimer = null;
+      }
       sessions.clear();
       annotations.clear();
       events.length = 0;