feat(tui): auto copy-on-select for transcript text

Drag in the transcript already highlighted but you had to press Cmd+C to
land it on the clipboard, and the highlight cleared on copy — most users
never realised selection existed. Now drag-release fires copySelectionNoClear
so the text is on the clipboard immediately while the highlight stays put,
matching iTerm2's "Copy to pasteboard on selection" default. Esc clears.

Behaviour:
- Single click in the input still positions the cursor (TextInput onClick).
- Single click in the transcript still does nothing destructive.
- Double / triple click select word / line, then drag extends.
- /copyselect [on|off|toggle] (alias /cos) flips the setting at runtime,
  HERMES_TUI_DISABLE_COPY_ON_SELECT=1 disables at startup, persists via
  display.tui_copy_on_select in config.yaml.

Help overlay now lists drag-select, multi-click, and click-to-position
so the gestures are discoverable.

Made-with: Cursor

tui_gateway/server.py

@@ -3134,6 +3134,27 @@ def _(rid, params: dict) -> dict:
         _write_config_key("display.tui_mouse", nv)
         return _ok(rid, {"key": key, "value": "on" if nv else "off"})
 
+    if key == "copy_on_select":
+        raw = str(value or "").strip().lower()
+        display = (
+            _load_cfg().get("display")
+            if isinstance(_load_cfg().get("display"), dict)
+            else {}
+        )
+        current = bool(display.get("tui_copy_on_select", True))
+
+        if raw in ("", "toggle"):
+            nv = not current
+        elif raw == "on":
+            nv = True
+        elif raw == "off":
+            nv = False
+        else:
+            return _err(rid, 4002, f"unknown copy_on_select value: {value}")
+
+        _write_config_key("display.tui_copy_on_select", nv)
+        return _ok(rid, {"key": key, "value": "on" if nv else "off"})
+
     if key in ("prompt", "personality", "skin"):
         try:
             cfg = _load_cfg()
@@ -3281,6 +3302,14 @@ def _(rid, params: dict) -> dict:
         display = _load_cfg().get("display")
         on = display.get("tui_mouse", True) if isinstance(display, dict) else True
         return _ok(rid, {"value": "on" if on else "off"})
+    if key == "copy_on_select":
+        display = _load_cfg().get("display")
+        on = (
+            display.get("tui_copy_on_select", True)
+            if isinstance(display, dict)
+            else True
+        )
+        return _ok(rid, {"value": "on" if on else "off"})
     if key == "mtime":
         cfg_path = _hermes_home / "config.yaml"
         try:

ui-tui/src/app/interfaces.ts

@@ -86,6 +86,7 @@ export interface UiState {
   bgTasks: Set<string>
   busy: boolean
   compact: boolean
+  copyOnSelect: boolean
   detailsMode: DetailsMode
   detailsModeCommandOverride: boolean
   info: null | SessionInfo

ui-tui/src/app/slash/commands/core.ts

@@ -107,6 +107,27 @@ export const coreCommands: SlashCommand[] = [
     }
   },
 
+  {
+    aliases: ['cos'],
+    help: 'toggle auto copy-on-drag-release [on|off|toggle]',
+    name: 'copyselect',
+    run: (arg, ctx) => {
+      const current = ctx.ui.copyOnSelect
+      const next = flagFromArg(arg, current)
+
+      if (next === null) {
+        return ctx.transcript.sys('usage: /copyselect [on|off|toggle]')
+      }
+
+      patchUiState({ copyOnSelect: next })
+      ctx.gateway
+        .rpc<ConfigSetResponse>('config.set', { key: 'copy_on_select', value: next ? 'on' : 'off' })
+        .catch(() => {})
+
+      queueMicrotask(() => ctx.transcript.sys(`copy-on-select ${next ? 'on' : 'off'}`))
+    }
+  },
+
   {
     aliases: ['new'],
     help: 'start a new session',

ui-tui/src/app/uiStore.ts

@@ -1,6 +1,6 @@
 import { atom } from 'nanostores'
 
-import { MOUSE_TRACKING } from '../config/env.js'
+import { COPY_ON_SELECT, MOUSE_TRACKING } from '../config/env.js'
 import { ZERO } from '../domain/usage.js'
 import { DEFAULT_THEME } from '../theme.js'
 
@@ -10,6 +10,7 @@ const buildUiState = (): UiState => ({
   bgTasks: new Set(),
   busy: false,
   compact: false,
+  copyOnSelect: COPY_ON_SELECT,
   detailsMode: 'collapsed',
   detailsModeCommandOverride: false,
   info: null,

ui-tui/src/app/useConfigSync.ts

@@ -44,6 +44,7 @@ export const applyDisplay = (cfg: ConfigFullResponse | null, setBell: (v: boolea
   setBell(!!d.bell_on_complete)
   patchUiState({
     compact: !!d.tui_compact,
+    copyOnSelect: d.tui_copy_on_select !== false,
     detailsMode: resolveDetailsMode(d),
     detailsModeCommandOverride: false,
     inlineDiffs: d.inline_diffs !== false,

ui-tui/src/app/useMainApp.ts

@@ -142,11 +142,73 @@ export function useMainApp(gw: GatewayClient) {
 
   const hasSelection = useHasSelection()
   const selection = useSelection()
+  const copyOnSelect = ui.copyOnSelect
 
   useEffect(() => {
     selection.setSelectionBgColor(ui.theme.color.selectionBg)
   }, [selection, ui.theme.color.selectionBg])
 
+  // Auto copy-on-select: when a drag completes with a real selection
+  // (anchor + focus, not a bare click), push the text to the clipboard
+  // without clearing the highlight. Matches iTerm2's "Copy to pasteboard
+  // on selection" — drag → release → already on clipboard, paste anywhere.
+  // Subscribes once and tracks the previous isDragging on a ref so the
+  // effect doesn't re-attach on every selection tick.
+  const wasDraggingRef = useRef(false)
+  const lastCopiedRef = useRef<{ anchor: string; focus: string } | null>(null)
+
+  useEffect(() => {
+    if (!copyOnSelect) {
+      wasDraggingRef.current = false
+
+      return
+    }
+
+    const fingerprint = (s: { anchor: { col: number; row: number } | null; focus: { col: number; row: number } | null }) => ({
+      anchor: s.anchor ? `${s.anchor.row}:${s.anchor.col}` : '',
+      focus: s.focus ? `${s.focus.row}:${s.focus.col}` : ''
+    })
+
+    return selection.subscribe(() => {
+      const state = selection.getState()
+
+      if (!state) {
+        return
+      }
+
+      const dragging = state.isDragging
+      const prev = wasDraggingRef.current
+      wasDraggingRef.current = dragging
+
+      if (!state.anchor) {
+        lastCopiedRef.current = null
+
+        return
+      }
+
+      if (!prev || dragging || !state.focus) {
+        return
+      }
+
+      const fp = fingerprint(state)
+      const last = lastCopiedRef.current
+
+      if (last && last.anchor === fp.anchor && last.focus === fp.focus) {
+        return
+      }
+
+      lastCopiedRef.current = fp
+
+      void selection.copySelectionNoClear().then(text => {
+        if (text) {
+          const len = text.length
+
+          turnController.pushActivity(`copied ${len} char${len === 1 ? '' : 's'} · Esc to clear`, 'info')
+        }
+      })
+    })
+  }, [copyOnSelect, selection])
+
   const composer = useComposerState({
     gw,
     onClipboardPaste: quiet => clipboardPasteRef.current(quiet),

ui-tui/src/config/env.ts

@@ -2,6 +2,9 @@ const truthy = (v?: string) => /^(?:1|true|yes|on)$/i.test((v ?? '').trim())
 
 export const STARTUP_RESUME_ID = (process.env.HERMES_TUI_RESUME ?? '').trim()
 export const MOUSE_TRACKING = !truthy(process.env.HERMES_TUI_DISABLE_MOUSE)
+// Drag-release auto-copies the selected text. Off by default for terminals
+// that do clipboard their own way; opt out with the env var or /copyselect.
+export const COPY_ON_SELECT = !truthy(process.env.HERMES_TUI_DISABLE_COPY_ON_SELECT)
 export const NO_CONFIRM_DESTRUCTIVE = truthy(process.env.HERMES_TUI_NO_CONFIRM)
 
 // Skip AlternateScreen — TUI renders into the primary buffer so the host

ui-tui/src/content/hotkeys.ts

@@ -16,7 +16,11 @@ const copyHotkeys: [string, string][] = isMac
     : [['Ctrl+C', 'copy selection / interrupt / clear draft / exit']]
 
 export const HOTKEYS: [string, string][] = [
+  ['drag', 'select text in transcript (auto-copies on release)'],
+  ['double / triple click', 'select word / line'],
+  ['click input', 'position cursor inside the prompt'],
   ...copyHotkeys,
+  ['Esc', 'clear selection'],
   [action + '+D', 'exit'],
   [action + '+G / Alt+G', 'open $EDITOR (Alt+G fallback for VSCode/Cursor)'],
   [action + '+L', 'redraw / repaint'],

ui-tui/src/gatewayTypes.ts

@@ -61,6 +61,7 @@ export interface ConfigDisplayConfig {
   streaming?: boolean
   thinking_mode?: string
   tui_compact?: boolean
+  tui_copy_on_select?: boolean
   tui_mouse?: boolean
   tui_statusbar?: 'bottom' | 'off' | 'on' | 'top' | boolean
 }

ui-tui/src/types/hermes-ink.d.ts

@@ -139,12 +139,17 @@ declare module '@hermes/ink' {
   export function useExternalProcess(): (run: RunExternalProcess) => Promise<void>
   export function withInkSuspended(run: RunExternalProcess): Promise<void>
   export function useInput(handler: InputHandler, options?: { readonly isActive?: boolean }): void
+  export type InkSelectionState = {
+    readonly anchor: { readonly col: number; readonly row: number } | null
+    readonly focus: { readonly col: number; readonly row: number } | null
+    readonly isDragging: boolean
+  }
   export function useSelection(): {
     readonly copySelection: () => Promise<string>
     readonly copySelectionNoClear: () => Promise<string>
     readonly clearSelection: () => void
     readonly hasSelection: () => boolean
-    readonly getState: () => unknown
+    readonly getState: () => InkSelectionState | null
     readonly subscribe: (cb: () => void) => () => void
     readonly shiftAnchor: (dRow: number, minRow: number, maxRow: number) => void
     readonly shiftSelection: (dRow: number, minRow: number, maxRow: number) => void