fix: preserve Ink composer cursor across agent monitors

ui-tui/src/__tests__/agentsCompact.test.tsx

@@ -8,9 +8,11 @@ import { expect, it, vi } from 'vitest'
 import { renderToScreen } from '../../packages/hermes-ink/src/ink/render-to-screen.js'
 import { cellAtIndex } from '../../packages/hermes-ink/src/ink/screen.js'
 import { applyAgentSnapshot } from '../app/agentRoster.js'
+import { getInputSelection } from '../app/inputSelectionStore.js'
 import { patchUiState, resetUiState } from '../app/uiStore.js'
 import { AgentsOverlay } from '../components/agentsOverlay.js'
 import { AgentsPanelView } from '../components/agentsPanel.js'
+import { TextInput } from '../components/textInput.js'
 import type { GatewayClient } from '../gatewayClient.js'
 import { buildAgentRows } from '../lib/agentRows.js'
 import { DEFAULT_THEME } from '../theme.js'
@@ -61,6 +63,17 @@ it('opens the selected live transcript on Enter while details remain independent
     output = ''
     stdin.write('t')
     await vi.waitFor(() => expect(output).toContain('CHILD_TOOL_OUTPUT'))
+    const cursorSnapshotRef = { current: null }
+    const onChange = vi.fn()
+    view.rerender(<TextInput cursorSnapshotRef={cursorSnapshotRef} onChange={onChange} value="draft" />)
+    await vi.waitFor(() => expect(getInputSelection()?.value).toBe('draft'))
+    stdin.write('\x1b[D')
+    await vi.waitFor(() => expect(getInputSelection()?.start).toBe(4))
+    view.rerender(<Box />)
+    view.rerender(<TextInput cursorSnapshotRef={cursorSnapshotRef} onChange={onChange} value="draft" />)
+    await vi.waitFor(() => expect(getInputSelection()?.start).toBe(4))
+    stdin.write('!')
+    await vi.waitFor(() => expect(onChange).toHaveBeenCalledWith('draf!t'))
   } finally {
     view.unmount()
     view.cleanup()

ui-tui/src/components/agentsOverlay.tsx

@@ -979,7 +979,7 @@ export function AgentsOverlay({ gw, initialHistoryIndex = 0, onClose, t }: Agent
         </Box>
       )}
 
-      <Box flexDirection="column" marginTop={1}>
+      <Box flexDirection="column" flexShrink={0} marginTop={1}>
         <Text color={t.color.accent} wrap="truncate-end">{replayMode ? 'Enter/d detail' : 'Enter/t tail · d detail'} · e steer · x stop · Esc back</Text>
         {flash ? <Text color={t.color.accent} wrap="truncate-end">{flash}</Text> : null}
 

ui-tui/src/components/appLayout.tsx

@@ -3,7 +3,7 @@ import '../sdk/apps/index.js'
 
 import { AlternateScreen, Box, NoSelect, ScrollBox, Text } from '@hermes/ink'
 import { useStore } from '@nanostores/react'
-import { Fragment, memo, useEffect, useMemo, useRef } from 'react'
+import { Fragment, memo, type MutableRefObject, useEffect, useMemo, useRef } from 'react'
 
 import { useGateway } from '../app/gatewayContext.js'
 import type { AppLayoutProps } from '../app/interfaces.js'
@@ -36,7 +36,7 @@ import { MessageLine } from './messageLine.js'
 import { PetKitty, PetSprite } from './petSprite.js'
 import { QueuedMessages } from './queuedMessages.js'
 import { LiveTodoPanel, StreamingAssistant } from './streamingAssistant.js'
-import { TextInput, type TextInputMouseApi } from './textInput.js'
+import { type InputCursorSnapshot, TextInput, type TextInputMouseApi } from './textInput.js'
 
 // Box geometry, kept here so the transcript's reservation math matches the
 // rendered overlay exactly.
@@ -275,8 +275,9 @@ const TranscriptPane = memo(function TranscriptPane({
 const ComposerPane = memo(function ComposerPane({
   actions,
   composer,
+  cursorSnapshotRef,
   status
-}: Pick<AppLayoutProps, 'actions' | 'composer' | 'status'>) {
+}: Pick<AppLayoutProps, 'actions' | 'composer' | 'status'> & { cursorSnapshotRef: MutableRefObject<InputCursorSnapshot | null> }) {
   const ui = useStore($uiState)
   const isBlocked = useStore($isBlocked)
   const sh = (composer.inputBuf[0] ?? composer.input).startsWith('!')
@@ -423,6 +424,7 @@ const ComposerPane = memo(function ComposerPane({
                   accentColor={ui.theme.color.accent}
                   color={ui.theme.color.text}
                   columns={inputColumns}
+                  cursorSnapshotRef={cursorSnapshotRef}
                   mouseApiRef={inputMouseRef}
                   onChange={composer.updateInput}
                   onPaste={composer.handleTextPaste}
@@ -531,6 +533,9 @@ export const AppLayout = memo(function AppLayout({
   const overlay = useStore($overlayState)
   const ui = useStore($uiState)
 
+  const cursorSnapshotRef = useRef<InputCursorSnapshot | null>(null)
+  useEffect(() => { cursorSnapshotRef.current = null }, [ui.sid])
+
   // Inline mode skips AlternateScreen so the host terminal's native
   // scrollback captures rows scrolled off the top; composer + progress
   // stay anchored via normal flex-column flow.
@@ -572,7 +577,7 @@ export const AppLayout = memo(function AppLayout({
             </PerfPane>
 
             <PerfPane id="composer">
-              <ComposerPane actions={actions} composer={composer} status={status} />
+              <ComposerPane actions={actions} composer={composer} cursorSnapshotRef={cursorSnapshotRef} status={status} />
             </PerfPane>
 
             {SHOW_FPS && (

ui-tui/src/components/textInput.tsx

@@ -782,6 +782,7 @@ export function TextInput({
   onSubmit,
   mask,
   mouseApiRef,
+  cursorSnapshotRef,
   voiceRecordKey = DEFAULT_VOICE_RECORD_KEY,
   placeholder = '',
   placeholderColor,
@@ -789,7 +790,7 @@ export function TextInput({
   color,
   focus = true
 }: TextInputProps) {
-  const [cur, setCur] = useState(value.length)
+  const [cur, setCur] = useState(() => cursorSnapshotRef?.current?.value === value ? cursorSnapshotRef.current.cursor : value.length)
   const [sel, setSel] = useState<null | { end: number; start: number }>(null)
   const fwdDel = useFwdDelete(focus)
   const termFocus = useTerminalFocus()
@@ -922,7 +923,7 @@ export function TextInput({
     const ownEcho = self.current && value === vRef.current
     self.current = false
 
-    if (ownEcho) {
+    if (ownEcho || value === vRef.current) {
       return
     }
 
@@ -936,6 +937,12 @@ export function TextInput({
     redo.current = []
   }, [value])
 
+  // The composer unmounts while full-screen monitors own input. Keep its
+  // insertion point with the shell, not with transient steer/secret inputs.
+  useEffect(() => () => {
+    if (cursorSnapshotRef) {cursorSnapshotRef.current = { cursor: curRef.current, value: vRef.current }}
+  }, [cursorSnapshotRef])
+
   useEffect(() => {
     if (!focus) {
       return
@@ -1777,12 +1784,18 @@ export interface PasteEvent {
   value: string
 }
 
+export interface InputCursorSnapshot {
+  cursor: number
+  value: string
+}
+
 interface TextInputProps {
   /** Hex/ansi256 tone for `/skill`, `@ref`, and `[[ token ]]` spans. */
   accentColor?: string
   /** Hex color for typed text (theme text); terminal default when omitted. */
   color?: string
   columns?: number
+  cursorSnapshotRef?: MutableRefObject<InputCursorSnapshot | null>
   focus?: boolean
   mask?: string
   mouseApiRef?: MutableRefObject<null | TextInputMouseApi>