fix(agent-memory): preserve live weight components on a partial config write

applyConfig rebuilt the weights vector from the constructor defaults each
pass, so a config that set only one weight component silently reset the other
two — a footgun for the proposal engine, which nudges a single knob. A partial
write now starts from the live weights and overlays only what's present; a
fully-absent weights config still falls back to the constructor values.

Author: jamby77

packages/agent-memory/src/MemoryStore.ts

@@ -147,7 +147,15 @@ export class MemoryStore {
 
   private applyConfig(raw: Record<string, string>): void {
     let threshold = this.initialThreshold;
-    const weights: RecallWeights = { ...this.initialWeights };
+    // Weights are a partial update: if any component is in the config, start
+    // from the LIVE weights and overlay only what's present, so tuning one knob
+    // (the proposal engine's common case) doesn't reset the others. With no
+    // weight field at all, fall back to the constructor values like the rest.
+    const weightFieldPresent =
+      raw['recall.weights.similarity'] !== undefined ||
+      raw['recall.weights.recency'] !== undefined ||
+      raw['recall.weights.importance'] !== undefined;
+    const weights: RecallWeights = { ...(weightFieldPresent ? this.weights : this.initialWeights) };
     let halfLifeSeconds = this.initialHalfLifeSeconds;
     let maxItemsPerScope = this.initialMaxItemsPerScope;
 

packages/agent-memory/src/__tests__/MemoryStore.config.test.ts

@@ -159,6 +159,25 @@ describe('MemoryStore config refresh', () => {
     expect(store.currentConfig().weights).toEqual(DEFAULT_WEIGHTS);
   });
 
+  it('preserves the live weight components when only a subset is written', async () => {
+    let hash: Record<string, string> = {
+      'recall.weights.similarity': '0.2',
+      'recall.weights.recency': '0.7',
+      'recall.weights.importance': '0.1',
+    };
+    const client = mockClient((command) => (command === 'HGETALL' ? configReply(hash) : 'OK'));
+    const store = new MemoryStore({ client, name: 'mem', embedFn: fakeEmbed(8) });
+
+    await store.refreshConfig();
+    expect(store.currentConfig().weights).toEqual({ similarity: 0.2, recency: 0.7, importance: 0.1 });
+
+    // A partial write that nudges only similarity must keep the live recency
+    // and importance, not reset them to the constructor defaults.
+    hash = { 'recall.weights.similarity': '0.5' };
+    await store.refreshConfig();
+    expect(store.currentConfig().weights).toEqual({ similarity: 0.5, recency: 0.7, importance: 0.1 });
+  });
+
   it('live-applies a looser threshold to recall', async () => {
     const client = mockClient((command) => {
       if (command === 'HGETALL') {