fix(tui): copy mouse selections automatically

Copy stable TUI mouse selections on all platforms so Linux users can keep mouse tracking enabled without using Ctrl+C as the copy chord.

ui-tui/src/__tests__/platform.test.ts

@@ -32,10 +32,10 @@ describe('platform action modifier', () => {
 })
 
 describe('isCopyShortcut', () => {
-  it('keeps Ctrl+C as the local non-macOS copy chord', async () => {
+  it('keeps Ctrl+C as interrupt instead of local non-macOS copy', async () => {
     const { isCopyShortcut } = await importPlatform('linux')
 
-    expect(isCopyShortcut({ ctrl: true, meta: false, super: false }, 'c', {})).toBe(true)
+    expect(isCopyShortcut({ ctrl: true, meta: false, super: false }, 'c', {})).toBe(false)
   })
 
   it('accepts client Cmd+C over SSH even when running on Linux', async () => {

ui-tui/src/app/useInputHandlers.ts

@@ -357,8 +357,9 @@ export function useInputHandlers(ctx: InputHandlerContext): InputHandlerResult {
         return
       }
 
-      // On macOS, Cmd+C with no selection is a no-op (Ctrl+C below handles interrupt).
-      // On non-macOS, isAction uses Ctrl, so fall through to interrupt/clear/exit.
+      // Cmd+C with no selection is a no-op; Ctrl+C below handles interrupt.
+      // Local non-macOS terminals keep Ctrl+C as interrupt because selection
+      // already copies on mouse-up while mouse tracking is enabled.
       if (isMac) {
         return
       }

ui-tui/src/app/useMainApp.ts

@@ -17,7 +17,6 @@ import type {
 import { useGitBranch } from '../hooks/useGitBranch.js'
 import { useVirtualHistory } from '../hooks/useVirtualHistory.js'
 import { appendTranscriptMessage } from '../lib/messages.js'
-import { isMac } from '../lib/platform.js'
 import { asRpcResult, rpcErrorMessage } from '../lib/rpc.js'
 import { terminalParityHints } from '../lib/terminalParity.js'
 import { buildToolTrailLine, sameToolTrailGroup, toolTrailLabel } from '../lib/text.js'
@@ -150,19 +149,15 @@ export function useMainApp(gw: GatewayClient) {
     selection.setSelectionBgColor(ui.theme.color.selectionBg)
   }, [selection, ui.theme.color.selectionBg])
 
-  // macOS Terminal.app does not forward Cmd+C to fullscreen TUIs that enable
-  // mouse tracking, so the only reliable native-feeling path is iTerm-style
-  // copy-on-select: once a drag creates a stable TUI selection, write it to
-  // the system clipboard while keeping the highlight visible.
+  // Terminals generally route native selection/copy around fullscreen TUIs
+  // until mouse tracking is enabled; then the app owns selection. Mirror
+  // terminal copy-on-select behavior by writing stable TUI selections to the
+  // clipboard while keeping the highlight visible.
   //
   // Subscribe directly via the ink selection bus (not useSyncExternalStore)
   // so React doesn't re-render MainApp on every drag-move tick. The version
   // ref de-dupes against re-entrant notifications.
   useEffect(() => {
-    if (!isMac) {
-      return
-    }
-
     return selection.subscribe(() => {
       if (!selection.hasSelection()) {
         return

ui-tui/src/content/hotkeys.ts

@@ -5,15 +5,19 @@ const paste = isMac ? 'Cmd' : 'Alt'
 
 const copyHotkeys: [string, string][] = isMac
   ? [
+      ['Mouse select', 'copy selection'],
       ['Cmd+C', 'copy selection'],
       ['Ctrl+C', 'interrupt / clear draft / exit']
     ]
   : isRemoteShell()
     ? [
-        ['Cmd+C', 'copy selection when forwarded by the terminal'],
-        ['Ctrl+C', 'copy selection / interrupt / clear draft / exit']
+        ['Mouse select / Cmd+C', 'copy selection when forwarded by the terminal'],
+        ['Ctrl+C', 'interrupt / clear draft / exit']
+      ]
+    : [
+        ['Mouse select', 'copy selection'],
+        ['Ctrl+C', 'interrupt / clear draft / exit']
       ]
-    : [['Ctrl+C', 'copy selection / interrupt / clear draft / exit']]
 
 export const HOTKEYS: [string, string][] = [
   ...copyHotkeys,

ui-tui/src/lib/platform.ts

@@ -5,8 +5,8 @@
  * as `key.meta`. Some macOS terminals also translate Cmd+Left/Right/Backspace
  * into readline-style Ctrl+A/Ctrl+E/Ctrl+U before the app sees them.
  * On other platforms the action modifier is Ctrl.
- * Ctrl+C stays the interrupt key on macOS. On non-mac terminals it can also
- * copy an active TUI selection, matching common terminal selection behavior.
+ * Ctrl+C stays the interrupt key on local terminals. Remote sessions can still
+ * accept client-forwarded Cmd+C for copying a TUI selection.
  */
 
 export const isMac = process.platform === 'darwin'
@@ -43,7 +43,7 @@ export const isCopyShortcut = (
   env: NodeJS.ProcessEnv = process.env
 ): boolean =>
   ch.toLowerCase() === 'c' &&
-  (isAction(key, ch, 'c') ||
+  ((isMac && isAction(key, ch, 'c')) ||
     (isRemoteShell(env) && (key.meta || key.super === true)) ||
     // VS Code/Cursor/Windsurf terminal setup forwards Cmd+C as a CSI-u
     // sequence with the super bit plus a benign ctrl bit. Accept that shape