feat: persist scroll position per conversation tab

- Added scrollPosition to Conversation interface
- Save scroll position when switching away from a tab
- Restore exact scroll position when switching back
- Uses -1 to indicate auto-scroll mode (scroll to bottom)
- Prevents interference between scroll restore and auto-scroll

src/lib/components/Terminal.svelte

@@ -1,6 +1,6 @@
 <script lang="ts">
   import { claudeStore, type TerminalLine } from "$lib/stores/claude";
-  import { afterUpdate } from "svelte";
+  import { afterUpdate, tick } from "svelte";
   import ConversationTabs from "./ConversationTabs.svelte";
   import Markdown from "./Markdown.svelte";
   import HighlightedText from "./HighlightedText.svelte";
@@ -10,6 +10,8 @@
   let shouldAutoScroll = true;
   let lines: TerminalLine[] = [];
   let currentSearchQuery = "";
+  let currentConversationId: string | null = null;
+  let isRestoringScroll = false;
 
   searchQuery.subscribe((value) => {
     currentSearchQuery = value;
@@ -19,14 +21,46 @@
     lines = value;
   });
 
+  claudeStore.activeConversationId.subscribe(async (newId) => {
+    if (!newId) return;
+
+    // Save current conversation's scroll position before switching
+    if (currentConversationId && currentConversationId !== newId && terminalElement) {
+      const position = shouldAutoScroll ? -1 : terminalElement.scrollTop;
+      claudeStore.saveScrollPosition(currentConversationId, position);
+    }
+
+    currentConversationId = newId;
+
+    // Restore scroll position for the new conversation after DOM updates
+    await tick();
+    if (terminalElement) {
+      const savedPosition = claudeStore.getScrollPosition(newId);
+      isRestoringScroll = true;
+      if (savedPosition === -1) {
+        // Auto-scroll to bottom
+        shouldAutoScroll = true;
+        terminalElement.scrollTop = terminalElement.scrollHeight;
+      } else {
+        // Restore to saved position
+        shouldAutoScroll = false;
+        terminalElement.scrollTop = savedPosition;
+      }
+      // Small delay to prevent the scroll handler from overriding our restore
+      setTimeout(() => {
+        isRestoringScroll = false;
+      }, 50);
+    }
+  });
+
   function handleScroll() {
-    if (!terminalElement) return;
+    if (!terminalElement || isRestoringScroll) return;
     const { scrollTop, scrollHeight, clientHeight } = terminalElement;
     shouldAutoScroll = scrollHeight - scrollTop - clientHeight < 100;
   }
 
   afterUpdate(() => {
-    if (shouldAutoScroll && terminalElement) {
+    if (shouldAutoScroll && terminalElement && !isRestoringScroll) {
       terminalElement.scrollTop = terminalElement.scrollHeight;
     }
   });

src/lib/stores/claude.ts

@@ -64,6 +64,8 @@ export const claudeStore = {
   deleteConversation: conversationsStore.deleteConversation,
   switchConversation: conversationsStore.switchConversation,
   renameConversation: conversationsStore.renameConversation,
+  saveScrollPosition: conversationsStore.saveScrollPosition,
+  getScrollPosition: conversationsStore.getScrollPosition,
 
   getGrantedTools: (): string[] => {
     let tools: string[] = [];

src/lib/stores/conversations.ts

@@ -21,6 +21,7 @@ export interface Conversation {
   grantedTools: Set<string>;
   pendingPermission: PermissionRequest | null;
   pendingQuestion: UserQuestionEvent | null;
+  scrollPosition: number;
   createdAt: Date;
   lastActivityAt: Date;
 }
@@ -55,6 +56,7 @@ function createConversationsStore() {
       grantedTools: new Set(),
       pendingPermission: null,
       pendingQuestion: null,
+      scrollPosition: -1, // -1 means "scroll to bottom" (auto-scroll)
       createdAt: new Date(),
       lastActivityAt: new Date(),
     };
@@ -106,6 +108,7 @@ function createConversationsStore() {
     ($conv) => $conv?.pendingPermission || null
   );
   const pendingQuestion = derived(activeConversation, ($conv) => $conv?.pendingQuestion || null);
+  const scrollPosition = derived(activeConversation, ($conv) => $conv?.scrollPosition ?? -1);
 
   return {
     // Expose derived stores for compatibility
@@ -118,6 +121,7 @@ function createConversationsStore() {
     isProcessing: { subscribe: isProcessing.subscribe },
     grantedTools: { subscribe: grantedTools.subscribe },
     pendingRetryMessage: { subscribe: pendingRetryMessage.subscribe },
+    scrollPosition: { subscribe: scrollPosition.subscribe },
 
     // New conversation-specific stores
     conversations: { subscribe: conversations.subscribe },
@@ -325,6 +329,22 @@ function createConversationsStore() {
       });
     },
 
+    saveScrollPosition: (id: string, position: number) => {
+      conversations.update((convs) => {
+        const conv = convs.get(id);
+        if (conv) {
+          conv.scrollPosition = position;
+        }
+        return convs;
+      });
+    },
+
+    getScrollPosition: (id: string): number => {
+      const convs = get(conversations);
+      const conv = convs.get(id);
+      return conv?.scrollPosition ?? -1;
+    },
+
     // Methods that operate on the active conversation
     setSessionId: (id: string | null) => {
       ensureInitialized();