fix: terminal scroll preservation on tab switch and alt buffer exit

emain/emain-window.ts

@@ -433,7 +433,7 @@ export class WaveBrowserWindow extends BaseWindow {
             await Promise.all([p1, p2]);
         } else {
             console.log("reusing an existing tab, calling wave-init", tabView.waveTabId);
-            const p1 = this.repositionTabsSlowly(35);
+            const p1 = this.repositionTabsSlowly(35, true);
             const p2 = tabView.webContents.send("wave-init", tabView.savedInitOpts); // reinit
             await Promise.all([p1, p2]);
         }
@@ -452,13 +452,16 @@ export class WaveBrowserWindow extends BaseWindow {
         }, 30);
     }
 
-    private async repositionTabsSlowly(delayMs: number) {
+    private async repositionTabsSlowly(delayMs: number, skipIntermediate: boolean = false) {
         const activeTabView = this.activeTabView;
         const winBounds = this.getContentBounds();
         if (activeTabView == null) {
             return;
         }
-        if (activeTabView.isOnScreen()) {
+        if (skipIntermediate || activeTabView.isOnScreen()) {
+            // For already-initialized tabs (skipIntermediate=true) or tabs already on screen,
+            // go directly to final bounds to avoid an intermediate resize that causes
+            // xterm.js buffer reflow and scroll position loss.
             activeTabView.setBounds({
                 x: 0,
                 y: 0,

frontend/app/view/term/osc-handlers.ts

@@ -318,6 +318,12 @@ export function handleOsc16162Command(data: string, blockId: string, loaded: boo
         case "R":
             globalStore.set(termWrap.shellIntegrationStatusAtom, null);
             if (terminal.buffer.active.type === "alternate") {
+                // Save scroll position before alternate buffer exit (only if user scrolled up)
+                const normalBuffer = terminal.buffer.normal;
+                const isAtBottom = normalBuffer.baseY >= normalBuffer.length - terminal.rows;
+                if (!isAtBottom) {
+                    termWrap.savedBaseY = normalBuffer.baseY;
+                }
                 terminal.write("\x1b[?1049l");
             }
             break;

frontend/app/view/term/termwrap.ts

@@ -104,6 +104,9 @@ export class TermWrap {
     lastPasteData: string = "";
     lastPasteTime: number = 0;
 
+    // Scroll position preservation across buffer swaps (alt screen exit)
+    savedBaseY: number | null = null;
+
     constructor(
         tabId: string,
         blockId: string,
@@ -197,6 +200,19 @@ export class TermWrap {
         this.heldData = [];
         this.handleResize_debounced = debounce(50, this.handleResize.bind(this));
         this.terminal.open(this.connectElem);
+
+        // Restore scroll position after alternate buffer exit (buffer swap)
+        this.toDispose.push(
+            this.terminal.buffer.onBufferChange(() => {
+                if (this.savedBaseY !== null) {
+                    const restoreY = this.savedBaseY;
+                    this.savedBaseY = null;
+                    requestAnimationFrame(() => {
+                        this.terminal.scrollToLine(restoreY);
+                    });
+                }
+            })
+        );
         this.handleResize();
         const pasteHandler = this.pasteHandler.bind(this);
         this.connectElem.addEventListener("paste", pasteHandler, true);
@@ -465,8 +481,19 @@ export class TermWrap {
     handleResize() {
         const oldRows = this.terminal.rows;
         const oldCols = this.terminal.cols;
+        // Save scroll position before fit (only if user scrolled up from bottom)
+        const buffer = this.terminal.buffer.active;
+        const wasAtBottom = buffer.baseY >= buffer.length - this.terminal.rows;
+        const fitSavedY = wasAtBottom ? null : buffer.baseY;
         this.fitAddon.fit();
-        if (oldRows !== this.terminal.rows || oldCols !== this.terminal.cols) {
+        // Only restore scroll if rows/cols actually changed (reflow happened)
+        const dimsChanged = oldRows !== this.terminal.rows || oldCols !== this.terminal.cols;
+        if (fitSavedY !== null && dimsChanged) {
+            requestAnimationFrame(() => {
+                this.terminal.scrollToLine(fitSavedY);
+            });
+        }
+        if (dimsChanged) {
             const termSize: TermSize = { rows: this.terminal.rows, cols: this.terminal.cols };
             RpcApi.ControllerInputCommand(TabRpcClient, { blockid: this.blockId, termsize: termSize });
         }