fix(ui): avoid mobile prompt focus on switch

Stops auto-focusing the prompt on phone session switches and scopes type-to-focus to the active visible prompt, disabling it on coarse pointers.

packages/ui/src/components/instance/instance-shell2.tsx

@@ -823,6 +823,7 @@ const InstanceShell2: Component<InstanceShellProps> = (props) => {
                           instanceId={props.instance.id}
                           instanceFolder={props.instance.folder}
                           escapeInDebounce={props.escapeInDebounce}
+                          isPhoneLayout={isPhoneLayout()}
                           showSidebarToggle={showEmbeddedSidebarToggle()}
                           onSidebarToggle={() => setLeftOpen(true)}
                           forceCompactStatusLayout={showEmbeddedSidebarToggle()}

packages/ui/src/components/prompt-input.tsx

@@ -176,15 +176,26 @@ export default function PromptInput(props: PromptInputProps) {
     ),
   )
 
-  onMount(() => {
+  const isCoarsePointer = () => {
+    if (typeof window === "undefined") return false
+    return Boolean(window.matchMedia?.("(pointer: coarse)")?.matches)
+  }
+
+  createEffect(() => {
+    // Scope global "type-to-focus" behavior to the active, visible prompt only.
+    if (typeof document === "undefined") return
+    if (isCoarsePointer()) return
+    if (props.isActive === false) return
+    if (props.disabled) return
+
     const handleGlobalKeyDown = (e: KeyboardEvent) => {
-      const activeElement = document.activeElement as HTMLElement
+      const activeElement = document.activeElement as HTMLElement | null
 
       const isInputElement =
         activeElement?.tagName === "INPUT" ||
         activeElement?.tagName === "TEXTAREA" ||
         activeElement?.tagName === "SELECT" ||
-        activeElement?.isContentEditable
+        Boolean(activeElement?.isContentEditable)
 
       if (isInputElement) return
 
@@ -192,16 +203,25 @@ export default function PromptInput(props: PromptInputProps) {
       if (isModifierKey) return
 
       const isSpecialKey =
-        e.key === "Tab" || e.key === "Enter" || e.key.startsWith("Arrow") || e.key === "Backspace" || e.key === "Delete"
+        e.key === "Tab" ||
+        e.key === "Enter" ||
+        e.key.startsWith("Arrow") ||
+        e.key === "Backspace" ||
+        e.key === "Delete"
       if (isSpecialKey) return
 
-      if (e.key.length === 1 && textareaRef && !props.disabled) {
-        textareaRef.focus()
+      const textarea = textareaRef
+      if (!textarea || textarea.disabled) return
+
+      // In session cache mode inactive panes are display:none; avoid stealing focus.
+      if (textarea.offsetParent === null) return
+
+      if (e.key.length === 1) {
+        textarea.focus()
       }
     }
 
     document.addEventListener("keydown", handleGlobalKeyDown)
-
     onCleanup(() => {
       document.removeEventListener("keydown", handleGlobalKeyDown)
     })
@@ -435,7 +455,7 @@ export default function PromptInput(props: PromptInputProps) {
                 onFocus={() => setIsFocused(true)}
                 onBlur={() => setIsFocused(false)}
                 disabled={props.disabled}
-                rows={expandState() === "expanded" ? 15 : 4}
+                rows={expandState() === "expanded" ? 15 : 3}
                 spellcheck={false}
                 autocorrect="off"
                 autoCapitalize="off"

packages/ui/src/components/prompt-input/types.ts

@@ -17,6 +17,9 @@ export interface PromptInputProps {
   instanceId: string
   instanceFolder: string
   sessionId: string
+
+  // Used to scope global "type-to-focus" behavior.
+  isActive?: boolean
   onSend: (prompt: string, attachments: Attachment[]) => Promise<void>
   onRunShell?: (command: string) => Promise<void>
   disabled?: boolean

packages/ui/src/components/session/session-view.tsx

@@ -28,6 +28,7 @@ interface SessionViewProps {
   instanceId: string
   instanceFolder: string
   escapeInDebounce: boolean
+  isPhoneLayout?: boolean
   showSidebarToggle?: boolean
   onSidebarToggle?: () => void
   forceCompactStatusLayout?: boolean
@@ -76,6 +77,9 @@ export const SessionView: Component<SessionViewProps> = (props) => {
       (isActive) => {
         if (!isActive) return
 
+        // On phones, focusing the prompt on session switch is disruptive (it raises the OSK).
+        if (props.isPhoneLayout) return
+
         // Don't steal focus from other inputs (command palette, dialogs, selectors, etc.)
         if (typeof document === "undefined") return
         const activeEl = document.activeElement as HTMLElement | null
@@ -314,17 +318,18 @@ export const SessionView: Component<SessionViewProps> = (props) => {
                 </Show>
 
               <PromptInput
-               instanceId={props.instanceId}
-               instanceFolder={props.instanceFolder}
-               sessionId={activeSession.id}
-               onSend={handleSendMessage}
-               onRunShell={handleRunShell}
-               escapeInDebounce={props.escapeInDebounce}
-               isSessionBusy={sessionBusy()}
-               disabled={sessionNeedsInput()}
-               onAbortSession={handleAbortSession}
-               registerPromptInputApi={registerPromptInputApi}
-               />
+                instanceId={props.instanceId}
+                instanceFolder={props.instanceFolder}
+                sessionId={activeSession.id}
+                isActive={props.isActive}
+                onSend={handleSendMessage}
+                onRunShell={handleRunShell}
+                escapeInDebounce={props.escapeInDebounce}
+                isSessionBusy={sessionBusy()}
+                disabled={sessionNeedsInput()}
+                onAbortSession={handleAbortSession}
+                registerPromptInputApi={registerPromptInputApi}
+                />
             </div>
           )
         }}