Vietnamese typing broken in Claude Code (Unikey, EVKey): cause and fixes

Short answer: this is a bug in Claude Code's input box with Vietnamese input methods; it has nothing to do with your API key or RocketKey. The quickest fix: press Ctrl+G to write the prompt in a text editor, save and close it, and the text lands in Claude Code.

Symptoms

Typing Vietnamese with Unikey, OpenKey or EVKey (Telex or VNI) directly in Claude Code's terminal can give you:

• Lost letters: các comes out as c or cá.
• Doubled letters: xin chào becomes xin chaào.
• Accents in the wrong place or stray characters.

Claude still understands and answers Vietnamese normally; only your typing is affected.

Why it happens

Vietnamese input methods work by deleting the letter you just typed and sending the accented one instead (delete a, send á). According to bug reports on Claude Code's GitHub, Claude Code's input box does not handle this delete-then-replace sequence correctly, so letters get lost or doubled. It was first reported in September 2025 with Unikey Telex on Windows, then on macOS and Linux with OpenKey, EVKey and VNI. As of 25 October 2026 those issues were closed for inactivity, with no fix from Anthropic noted on them.

Fix 1: write in an editor with Ctrl+G (recommended)

Per Claude Code's documentation, Ctrl+G (or Ctrl+X Ctrl+E) opens the input in your default text editor:

1. In Claude Code, press Ctrl+G.
2. Type your Vietnamese text in the editor that opens. The input method works normally there.
3. Save the file and close the editor. The text goes into Claude Code's input.
4. Press Enter to send.

On macOS and Linux the default editor usually comes from the VISUAL or EDITOR environment variable. To use VS Code, set EDITOR="code --wait": --wait makes Claude Code wait until you close the file before reading it.

Fix 2: type elsewhere and paste

Write the sentence in Notepad, a notes app or any chat box, then paste it into Claude Code. Pasting does not go through the input method, so nothing breaks. Good when you only type Vietnamese now and then.

Fix 3: use Claude Code in VS Code

The Claude Code extension for VS Code has its own input box in the VS Code window instead of a terminal, which usually avoids the input method bug. Setting up the extension with a RocketKey key is in the Claude Code guide, section "Claude Code extension for VS Code".

Fix 4: type Vietnamese without accents

Switch the input method off (often Ctrl+Shift or Alt+Z, depending on your settings) and type without accents, for example sua loi dang nhap trong auth.ts. Claude understands unaccented Vietnamese fairly well. If you want accented replies, add "trả lời bằng tiếng Việt có dấu".

About community patches

GitHub has a few community scripts that edit Claude Code's installed files to fix this. RocketKey does not recommend them: they run third-party code on your machine, were tested only with some versions and input methods, and are overwritten whenever Claude Code updates itself. The four fixes above are safer.

FAQ

Does the bug use extra allowance? No. Mistyped characters stay in the input box; only what you send is counted.

Will another key or model fix it? No. The bug is in Claude Code's input handling, not the key or the model.

Are Codex, Cline or Cursor affected? Cline and Cursor have their chat box inside the editor window, which usually takes input methods like any text field. If another command-line tool shows the same bug, fixes 1, 2 and 4 still apply.

Other Claude Code problems? See Common errors or the FAQ.