feat(FN-1724): merge fusion/fn-1724

packages/core/src/store.test.ts

@@ -1214,18 +1214,15 @@ describe("TaskStore", () => {
       expect(settings.experimentalFeatures).toEqual({ "feature-b": true });
     });
 
-    it("can remove an experimental feature by setting it to undefined (field stays)", async () => {
-      // Note: We cannot selectively remove a single key from experimentalFeatures
-      // since it's a simple Record<string, boolean> not a nested object with special handling.
-      // Users should replace the entire object if they need to remove specific keys.
-
+    it("can remove an experimental feature by setting it to null (selective removal)", async () => {
+      // Features can be selectively removed by setting them to null
       await store.updateSettings({
         experimentalFeatures: { "feature-a": true, "feature-b": true },
       });
 
-      // Replace with only feature-b
+      // Remove feature-a by setting it to null (cast needed for TypeScript type safety)
       await store.updateSettings({
-        experimentalFeatures: { "feature-b": true },
+        experimentalFeatures: { "feature-a": null } as unknown as Record<string, boolean>,
       });
 
       const settings = await store.getSettings();

packages/core/src/store.ts

@@ -793,6 +793,32 @@ export class TaskStore extends EventEmitter<TaskStoreEvents> {
         }
       }
 
+      // Handle experimentalFeatures merging (similar to promptOverrides)
+      const incomingExperimentalFeatures = (projectPatch as Record<string, unknown>)["experimentalFeatures"];
+      if (
+        incomingExperimentalFeatures !== undefined &&
+        typeof incomingExperimentalFeatures === "object" &&
+        incomingExperimentalFeatures !== null &&
+        !Array.isArray(incomingExperimentalFeatures)
+      ) {
+        // experimentalFeatures: { key: value } → merge with existing
+        const incomingMap = incomingExperimentalFeatures as Record<string, unknown>;
+        const existingMap = ((config.settings as unknown as Record<string, unknown>)["experimentalFeatures"] as Record<string, boolean>) ?? {};
+        const mergedMap: Record<string, boolean> = { ...existingMap };
+
+        for (const [key, value] of Object.entries(incomingMap)) {
+          // null values remove the feature
+          if (value === null) {
+            delete mergedMap[key];
+          } else if (typeof value === "boolean") {
+            mergedMap[key] = value;
+          }
+        }
+
+        (config.settings as unknown as Record<string, unknown>)["experimentalFeatures"] = mergedMap;
+        (projectPatch as Record<string, unknown>)["experimentalFeatures"] = mergedMap;
+      }
+
       const globalSettings = await this.globalSettingsStore.getSettings();
       const previousMerged: Settings = { ...DEFAULT_SETTINGS, ...globalSettings, ...config.settings } as Settings;
       const updatedProjectSettings = { ...config.settings, ...projectPatch };