diff --git a/src/services/memory/cache.js b/src/services/memory/cache.js
index 7d84d8c..58aabdd 100644
--- a/src/services/memory/cache.js
+++ b/src/services/memory/cache.js
@@ -152,6 +152,14 @@ export function createMemoryCache(options = {}) {
       runtimeNamespaces.clear();
       totalRuntimeEvents = 0;
     },
+    prune(predicate) {
+      if (typeof predicate !== 'function') return;
+      for (const key of store.keys()) {
+        if (predicate(key)) {
+          store.delete(key);
+        }
+      }
+    },
     setRuntimeEvent(scope, event, ttlMs = MINUTE_MS) {
       const now = Date.now();
       removeExpired(now);
diff --git a/src/services/memory/index.js b/src/services/memory/index.js
index 1c9ec82..d109b85 100644
--- a/src/services/memory/index.js
+++ b/src/services/memory/index.js
@@ -227,6 +227,24 @@ function recordThroughput(samples, now) {
   }
 }
 
+function invalidateAgentCache(agentId) {
+  if (!agentId) return;
+  // If the cache supports prune (it should), use it to remove entries for this agent.
+  if (typeof cache.prune === 'function') {
+    cache.prune((key) => {
+      try {
+        const parsed = JSON.parse(key);
+        return parsed.agent_id === agentId;
+      } catch {
+        return false;
+      }
+    });
+  } else {
+    // Fallback if cache implementation doesn't support prune
+    cache.clear();
+  }
+}
+
 /**
  * Ingests agent events and stores them as memory records.
  *
@@ -255,7 +273,22 @@ export async function ingestEvents(events, options = {}) {
       }
     },
   });
-  cache.clear();
+
+  const uniqueAgents = new Set();
+  if (options.agent_id) uniqueAgents.add(options.agent_id);
+  for (const event of events) {
+    if (event.agent_id) uniqueAgents.add(event.agent_id);
+  }
+  for (const record of records) {
+    if (record.agent_id) uniqueAgents.add(record.agent_id);
+  }
+
+  if (uniqueAgents.size > 0) {
+    for (const agentId of uniqueAgents) invalidateAgentCache(agentId);
+  } else {
+    cache.clear();
+  }
+
   return records;
 }
 
@@ -372,7 +405,16 @@ export async function runPruneCycle(options = {}) {
   });
   emitMetric(options, 'memory_pruned_total', { count: prunable.length, retention_ms: retentionMs });
 
-  cache.clear();
+  const uniqueAgents = new Set();
+  for (const memory of prunable) {
+    if (memory.agent_id) uniqueAgents.add(memory.agent_id);
+  }
+
+  if (uniqueAgents.size > 0) {
+    for (const agentId of uniqueAgents) invalidateAgentCache(agentId);
+  } else if (prunable.length > 0) {
+    cache.clear();
+  }
 
   const result = { pruned: prunable };
   if (Number.isFinite(options.scheduleEveryMs) && options.scheduleEveryMs > 0) {
@@ -397,7 +439,11 @@ export async function runPruneCycle(options = {}) {
 export async function pinMemory(id, options = {}) {
   const repository = options.repository ?? memoryRepository;
   const updated = await repository.setPinned(id, true);
-  cache.clear();
+  if (updated && updated.agent_id) {
+    invalidateAgentCache(updated.agent_id);
+  } else {
+    cache.clear();
+  }
   return updated;
 }
 
@@ -414,7 +460,11 @@ export async function pinMemory(id, options = {}) {
 export async function unpinMemory(id, options = {}) {
   const repository = options.repository ?? memoryRepository;
   const updated = await repository.setPinned(id, false);
-  cache.clear();
+  if (updated && updated.agent_id) {
+    invalidateAgentCache(updated.agent_id);
+  } else {
+    cache.clear();
+  }
   return updated;
 }
 
@@ -431,8 +481,14 @@ export async function unpinMemory(id, options = {}) {
  */
 export async function markMemoryMerged(id, mergedInto, options = {}) {
   const repository = options.repository ?? memoryRepository;
+  const memory = await inspectMemory(id, { repository });
   const merged = await repository.markMerged(id, mergedInto);
-  cache.clear();
+
+  if (memory && memory.agent_id) {
+    invalidateAgentCache(memory.agent_id);
+  } else {
+    cache.clear();
+  }
   return merged;
 }
 
diff --git a/test/memory-cache.test.mjs b/test/memory-cache.test.mjs
index 702fbc6..3fa252b 100644
--- a/test/memory-cache.test.mjs
+++ b/test/memory-cache.test.mjs
@@ -77,3 +77,16 @@ test('blocks decrypted/session-sensitive data from durable promotion without san
   assert.equal(events[1].durable_eligible, true);
   assert.equal(cache.getMetrics().runtime_sensitive_events_blocked, 1);
 });
+
+test('prunes cache entries based on predicate', () => {
+  const cache = createMemoryCache();
+  cache.set('key1', 'value1');
+  cache.set('key2', 'value2');
+  cache.set('other', 'value3');
+
+  cache.prune((key) => key.startsWith('key'));
+
+  assert.equal(cache.get('key1'), undefined);
+  assert.equal(cache.get('key2'), undefined);
+  assert.equal(cache.get('other'), 'value3');
+});