fix: move pane zoom into attach cmd chain for reliable initial zoom

- Pass initialPane to attach() so zoom runs inside the shell command
  chain where tmux is guaranteed to exist (no external race)
- Send initialPane in the first resize WS message (atomic, single msg)
- Remove pendingPane from WsData (dead code from iterative patching)
- Fix unzoom: use shell conditional instead of broken tmux if-shell

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

dev-dashboard/backend/src/server.ts

@@ -73,7 +73,6 @@ function errorResponse(message: string, status = 500): Response {
 interface WsData {
   worktree: string;
   attached: boolean;
-  pendingPane: number | null;
 }
 
 function makeCallbacks(ws: { send: (data: string) => void; readyState: number }) {
@@ -101,7 +100,7 @@ Bun.serve<WsData>({
     const wsMatch = url.pathname.match(/^\/ws\/(.+)$/);
     if (wsMatch) {
       const worktree = decodeURIComponent(wsMatch[1]);
-      const upgraded = server.upgrade(req, { data: { worktree, attached: false, pendingPane: null } });
+      const upgraded = server.upgrade(req, { data: { worktree, attached: false } });
       if (upgraded) return undefined as unknown as Response;
       return new Response("WebSocket upgrade failed", { status: 400 });
     }
@@ -128,16 +127,9 @@ Bun.serve<WsData>({
             write(worktree, msg.data);
             break;
           case "selectPane":
-            if (typeof msg.pane === "number") {
-              if (ws.data.attached) {
-                // Attach already completed — apply directly
-                console.log(`[ws:${ts()}] selectPane direct pane=${msg.pane} worktree=${worktree}`);
-                selectPane(worktree, msg.pane);
-              } else {
-                // Attach still in progress — queue for post-attach
-                ws.data.pendingPane = msg.pane;
-                console.log(`[ws:${ts()}] selectPane queued pane=${msg.pane} worktree=${worktree}`);
-              }
+            if (ws.data.attached && typeof msg.pane === "number") {
+              console.log(`[ws:${ts()}] selectPane pane=${msg.pane} worktree=${worktree}`);
+              selectPane(worktree, msg.pane);
             }
             break;
           case "resize":
@@ -146,7 +138,11 @@ Bun.serve<WsData>({
               ws.data.attached = true;
               console.log(`[ws:${ts()}] first resize (attaching) worktree=${worktree} cols=${msg.cols} rows=${msg.rows}`);
               try {
-                await attach(worktree, msg.cols, msg.rows);
+                const initialPane = typeof msg.initialPane === "number" ? msg.initialPane : undefined;
+                if (initialPane !== undefined) {
+                  console.log(`[ws:${ts()}] initialPane=${initialPane} worktree=${worktree}`);
+                }
+                await attach(worktree, msg.cols, msg.rows, initialPane);
                 const { onData, onExit } = makeCallbacks(ws);
                 setCallbacks(worktree, onData, onExit);
                 const scrollback = getScrollback(worktree);
@@ -154,12 +150,6 @@ Bun.serve<WsData>({
                 if (scrollback) {
                   ws.send(JSON.stringify({ type: "scrollback", data: scrollback }));
                 }
-                // Apply any pane zoom queued while attach was in progress
-                if (ws.data.pendingPane !== null) {
-                  console.log(`[ws:${ts()}] applying pendingPane=${ws.data.pendingPane} worktree=${worktree}`);
-                  selectPane(worktree, ws.data.pendingPane);
-                  ws.data.pendingPane = null;
-                }
               } catch (err: unknown) {
                 const errMsg = err instanceof Error ? err.message : String(err);
                 console.log(`[ws:${ts()}] attach failed worktree=${worktree}: ${errMsg}`);

dev-dashboard/backend/src/terminal.ts

@@ -51,7 +51,8 @@ function killTmuxSession(name: string): void {
 export async function attach(
   worktreeName: string,
   cols: number,
-  rows: number
+  rows: number,
+  initialPane?: number
 ): Promise<string> {
   console.log(`[term:${ts()}] attach(${worktreeName}) cols=${cols} rows=${rows} existing=${sessions.has(worktreeName)}`);
   if (sessions.has(worktreeName)) {
@@ -68,14 +69,17 @@ export async function attach(
   // Kill stale session with same name if it exists (leftover from previous server run)
   killTmuxSession(gName);
 
+  const paneTarget = `${gName}:${windowTarget}.${initialPane ?? 0}`;
   const cmd = [
     `tmux new-session -d -s "${gName}" -t "${tmuxSession}"`,
     `tmux set-option -t "${gName}" mouse on`,
     `tmux set-option -t "${gName}" set-clipboard on`,
     `tmux select-window -t "${gName}:${windowTarget}"`,
-    // Unzoom if a previous session left a pane zoomed (zoom state is shared)
-    `tmux if-shell -t "${gName}:${windowTarget}" "#{window_zoomed_flag}" "resize-pane -Z -t ${gName}:${windowTarget}"`,
-    `tmux select-pane -t "${gName}:${windowTarget}.0"`,
+    // Unzoom if a previous session left a pane zoomed (zoom state is shared across grouped sessions)
+    `if [ "$(tmux display-message -t '${gName}:${windowTarget}' -p '#{window_zoomed_flag}')" = "1" ]; then tmux resize-pane -Z -t '${gName}:${windowTarget}'; fi`,
+    `tmux select-pane -t "${paneTarget}"`,
+    // On mobile, zoom the selected pane to fill the window
+    ...(initialPane !== undefined ? [`tmux resize-pane -Z -t "${paneTarget}"`] : []),
     `stty rows ${rows} cols ${cols}`,
     `exec tmux attach-session -t "${gName}"`,
   ].join(" && ");

dev-dashboard/frontend/src/lib/Terminal.svelte

@@ -107,10 +107,11 @@
 
     ws.onopen = () => {
       fitAddon.fit();
-      ws.send(JSON.stringify({ type: "resize", cols: term.cols, rows: term.rows }));
+      const msg: Record<string, unknown> = { type: "resize", cols: term.cols, rows: term.rows };
       if (isMobile && initialPane !== undefined) {
-        sendSelectPane(initialPane);
+        msg.initialPane = initialPane;
       }
+      ws.send(JSON.stringify(msg));
     };
 
     ws.onclose = () => {