From a9f418a9ea9a28f4dfcfe5d406ad198c646ab08b Mon Sep 17 00:00:00 2001
From: Brian Love <brian@liveloveapp.com>
Date: Mon, 6 Apr 2026 13:53:10 -0700
Subject: [PATCH] fix(stream-resource): persist thread ID across messages +
 smooth scroll

Two critical fixes:

1. Thread persistence: The bridge's onThreadId callback was not
   connected to currentThreadId tracking. Each submit() created a
   brand new thread, losing all conversation history. Fix: wrap
   the transport's onThreadId to update currentThreadId before
   calling the consumer's callback.

2. Smooth scroll: Replace setTimeout + scrollTop assignment with
   requestAnimationFrame + scrollTo({behavior:'smooth'}). Only
   auto-scrolls when user is near bottom (<150px), so reading
   earlier messages isn't interrupted by new content.
---
 .../compositions/chat-debug/chat-debug.component.ts   |  7 ++++++-
 libs/chat/src/lib/compositions/chat/chat.component.ts | 11 +++++++++--
 .../src/lib/internals/stream-manager.bridge.ts        | 10 +++++++++-
 3 files changed, 24 insertions(+), 4 deletions(-)

diff --git a/libs/chat/src/lib/compositions/chat-debug/chat-debug.component.ts b/libs/chat/src/lib/compositions/chat-debug/chat-debug.component.ts
index bef110142..e47acfd48 100644
--- a/libs/chat/src/lib/compositions/chat-debug/chat-debug.component.ts
+++ b/libs/chat/src/lib/compositions/chat-debug/chat-debug.component.ts
@@ -226,7 +226,12 @@ export class ChatDebugComponent {
       this.ref().isLoading(); // track
       const el = this.scrollContainer()?.nativeElement;
       if (el) {
-        setTimeout(() => el.scrollTop = el.scrollHeight, 0);
+        const isNearBottom = el.scrollHeight - el.scrollTop - el.clientHeight < 150;
+        if (isNearBottom) {
+          requestAnimationFrame(() => {
+            el.scrollTo({ top: el.scrollHeight, behavior: 'smooth' });
+          });
+        }
       }
     });
   }
diff --git a/libs/chat/src/lib/compositions/chat/chat.component.ts b/libs/chat/src/lib/compositions/chat/chat.component.ts
index b869dd0f7..4c2ba586b 100644
--- a/libs/chat/src/lib/compositions/chat/chat.component.ts
+++ b/libs/chat/src/lib/compositions/chat/chat.component.ts
@@ -189,13 +189,20 @@ export class ChatComponent {
   private readonly messageCount = computed(() => this.ref().messages().length);
 
   constructor() {
-    // Auto-scroll to bottom when new messages arrive or loading state changes
+    // Auto-scroll to bottom when new messages arrive.
+    // Only scrolls if user is already near the bottom (within 150px),
+    // so reading earlier messages isn't interrupted.
     effect(() => {
       this.messageCount(); // track
       this.ref().isLoading(); // track
       const el = this.scrollContainer()?.nativeElement;
       if (el) {
-        setTimeout(() => el.scrollTop = el.scrollHeight, 0);
+        const isNearBottom = el.scrollHeight - el.scrollTop - el.clientHeight < 150;
+        if (isNearBottom) {
+          requestAnimationFrame(() => {
+            el.scrollTo({ top: el.scrollHeight, behavior: 'smooth' });
+          });
+        }
       }
     });
   }
diff --git a/libs/stream-resource/src/lib/internals/stream-manager.bridge.ts b/libs/stream-resource/src/lib/internals/stream-manager.bridge.ts
index 0620a6a69..a59a8f52b 100644
--- a/libs/stream-resource/src/lib/internals/stream-manager.bridge.ts
+++ b/libs/stream-resource/src/lib/internals/stream-manager.bridge.ts
@@ -30,8 +30,16 @@ export interface StreamManagerBridge {
 export function createStreamManagerBridge<T, ResolvedBag extends BagTemplate = BagTemplate>(
   { options, subjects, threadId$, destroy$ }: StreamManagerBridgeOptions<T, ResolvedBag>
 ): StreamManagerBridge {
+  // Intercept onThreadId to update currentThreadId when the transport
+  // auto-creates a thread. Without this, each submit() creates a new thread
+  // because currentThreadId stays null.
+  const userOnThreadId = options.onThreadId;
+  const wrappedOnThreadId = (id: string) => {
+    currentThreadId = id;
+    userOnThreadId?.(id);
+  };
   const transport: StreamResourceTransport =
-    options.transport ?? new FetchStreamTransport(options.apiUrl, options.onThreadId);
+    options.transport ?? new FetchStreamTransport(options.apiUrl, wrappedOnThreadId);
 
   let currentThreadId: string | null = null;
   let lastPayload: unknown = null;