fix(chat,langgraph): jank — stable @for tracking + empty-array guard (#174)

- chat-message-list: `track message.id` (was `track $index`) so the @for
  doesn't tear down DOM when the messages array briefly shrinks/refills
  during streaming. Loses streaming-md renderer state on every teardown
  → visible flash + missed tokens.
- stream-manager: skip publishing an empty `messages` array during
  streaming (both messages-event and values-event paths). An empty
  payload mid-stream shouldn't wipe the UI; this was the upstream cause
  of the transient empty-array we saw via MutationObserver instrumentation.
- Bumps: @ngaf/chat 0.0.8 → 0.0.9, @ngaf/langgraph 0.0.2 → 0.0.3.

Co-authored-by: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

Author: blove

libs/chat/package.json

@@ -1,6 +1,6 @@
 {
   "name": "@ngaf/chat",
-  "version": "0.0.8",
+  "version": "0.0.9",
   "exports": {
     ".": {
       "types": "./index.d.ts",

libs/chat/src/lib/primitives/chat-message-list/chat-message-list.component.ts

@@ -39,7 +39,7 @@ export function getMessageType(message: Message): MessageTemplateType {
   changeDetection: ChangeDetectionStrategy.OnPush,
   styles: [CHAT_HOST_TOKENS, CHAT_MESSAGE_LIST_STYLES],
   template: `
-    @for (message of messages(); track $index) {
+    @for (message of messages(); track message.id) {
       @let template = findTemplate(getMessageType(message));
       @if (template) {
         <ng-container

libs/langgraph/package.json

@@ -1,6 +1,6 @@
 {
   "name": "@ngaf/langgraph",
-  "version": "0.0.2",
+  "version": "0.0.3",
   "peerDependencies": {
     "@ngaf/chat": "*",
     "@ngaf/licensing": "*",

libs/langgraph/src/lib/internals/stream-manager.bridge.ts

@@ -322,6 +322,10 @@ export function createStreamManagerBridge<T, ResolvedBag extends BagTemplate = B
       // so optimistic human messages and earlier tool messages are preserved.
       if (event.type === 'messages/partial' || event.messageMetadata) {
         subjects.messages$.next(mergeMessages(subjects.messages$.value, normalized));
+      } else if (normalized.length === 0) {
+        // Defensive: skip empty replacements during streaming. An empty
+        // batch shouldn't tear down the entire UI (causes message DOM
+        // teardown + streaming renderer reset = visible jank).
       } else {
         subjects.messages$.next(normalized);
       }
@@ -346,7 +350,9 @@ export function createStreamManagerBridge<T, ResolvedBag extends BagTemplate = B
           // Also sync messages$ from the values state so the full message
           // history (including human messages) is available to consumers.
           const stateMessages = (vals as Record<string, unknown>)['messages'];
-          if (Array.isArray(stateMessages)) {
+          if (Array.isArray(stateMessages) && stateMessages.length > 0) {
+            // Defensive: only sync when state carries messages. An empty
+            // values payload shouldn't wipe the UI mid-stream.
             if (options.toMessage) {
               subjects.messages$.next(stateMessages.map(options.toMessage));
             } else {