diff --git a/apps/desktop/electron/terminal-ipc.ts b/apps/desktop/electron/terminal-ipc.ts
index 8a4eb61118..92f2560c32 100644
--- a/apps/desktop/electron/terminal-ipc.ts
+++ b/apps/desktop/electron/terminal-ipc.ts
@@ -31,6 +31,21 @@ export interface TerminalIpcApi {
   disposeAllTerminalSessions: () => void
 }
 
+// macOS accepts the bare charset name "UTF-8" as a locale; glibc does not, so
+// every Linux pane would print `bash: warning: setlocale: LC_CTYPE: cannot
+// change locale (UTF-8)`. Reuse the user's LANG there, else the glibc-guaranteed
+// C.UTF-8. Pure: the platform arrives as data so tests need not fake the host.
+export function terminalLcCtype(
+  env: { LANG?: string; LC_CTYPE?: string },
+  platform: NodeJS.Platform = process.platform
+): string {
+  if (env.LC_CTYPE) {
+    return env.LC_CTYPE
+  }
+
+  return platform === 'darwin' ? 'UTF-8' : env.LANG || 'C.UTF-8'
+}
+
 export function registerTerminalIpc({
   isWindows,
   findOnPath,
@@ -156,10 +171,7 @@ export function registerTerminalIpc({
     delete env.COLORFGBG
 
     env.COLORTERM = 'truecolor'
-    // macOS accepts the bare charset name "UTF-8"; glibc does not, and bash
-    // warns: setlocale: LC_CTYPE: cannot change locale (UTF-8). Prefer LANG or C.UTF-8 on Linux.
-    env.LC_CTYPE =
-      env.LC_CTYPE || (process.platform === 'darwin' ? 'UTF-8' : env.LANG || 'C.UTF-8')
+    env.LC_CTYPE = terminalLcCtype(env)
     env.TERM = 'xterm-256color'
     env.TERM_PROGRAM = 'Hermes'
     env.TERM_PROGRAM_VERSION = app.getVersion()
diff --git a/apps/desktop/electron/terminal-lc-ctype.test.ts b/apps/desktop/electron/terminal-lc-ctype.test.ts
new file mode 100644
index 0000000000..f05d1227f4
--- /dev/null
+++ b/apps/desktop/electron/terminal-lc-ctype.test.ts
@@ -0,0 +1,17 @@
+import assert from 'node:assert/strict'
+
+import { test, vi } from 'vitest'
+
+// terminal-ipc.ts imports the Electron and native PTY modules at module scope;
+// neither loads under plain node, and this test only needs the pure locale helper.
+vi.mock('electron', () => ({ app: {}, ipcMain: {} }))
+vi.mock('node-pty', () => ({ default: {} }))
+
+import { terminalLcCtype } from './terminal-ipc'
+
+test('terminalLcCtype never hands glibc the bare "UTF-8" locale on Linux', () => {
+  assert.equal(terminalLcCtype({ LANG: 'en_US.UTF-8' }, 'linux'), 'en_US.UTF-8')
+  assert.equal(terminalLcCtype({}, 'linux'), 'C.UTF-8')
+  assert.equal(terminalLcCtype({ LANG: 'en_US.UTF-8', LC_CTYPE: 'de_DE.UTF-8' }, 'linux'), 'de_DE.UTF-8')
+  assert.equal(terminalLcCtype({ LANG: 'en_US.UTF-8' }, 'darwin'), 'UTF-8')
+})