diff --git a/mobile/src/session/mobile-native-chat-terminal-write-lock.test.ts b/mobile/src/session/mobile-native-chat-terminal-write-lock.test.ts
new file mode 100644
index 00000000000..c15ce3c826e
--- /dev/null
+++ b/mobile/src/session/mobile-native-chat-terminal-write-lock.test.ts
@@ -0,0 +1,20 @@
+import { afterEach, describe, expect, it } from 'vitest'
+import {
+  acquireMobileNativeChatTerminalWrite,
+  releaseMobileNativeChatTerminalWrite,
+  resetMobileNativeChatTerminalWritesForTests
+} from './mobile-native-chat-terminal-write-lock'
+
+describe('mobile-native-chat-terminal-write-lock', () => {
+  afterEach(resetMobileNativeChatTerminalWritesForTests)
+
+  it('allows composed writes on different terminals to proceed concurrently', () => {
+    expect(acquireMobileNativeChatTerminalWrite('terminal-a')).toBe(true)
+
+    expect(acquireMobileNativeChatTerminalWrite('terminal-b')).toBe(true)
+    expect(acquireMobileNativeChatTerminalWrite('terminal-a')).toBe(false)
+
+    releaseMobileNativeChatTerminalWrite('terminal-a')
+    releaseMobileNativeChatTerminalWrite('terminal-b')
+  })
+})