[BUG] Built-in microphone button in chat input misrecognizes Japanese speech as garbled English

Preflight Checklist

• [x] I have searched existing issues and this hasn't been reported yet
• [x] This is a single bug report (please file separate reports for different bugs)
• [x] I am using the latest version of Claude Code

What's Wrong?

The microphone (voice input) button in the Claude Code chat input box does not correctly recognize Japanese speech. When speaking Japanese into it, the transcribed text comes out as garbled, phonetically-guessed English words instead of Japanese.

Example: speaking "日本語入力をしたいのですが英語になってしまうのですが、どうしたらよいですか？" produced: "Mihongo ni Loko style of this rock, ihongi naktishima no desegado starai deshak."

For comparison, using Windows' native Voice Typing (Win+H) in the exact same chat input field correctly transcribes the same speech as proper Japanese. This confirms the issue is isolated to the extension's built-in microphone button, not OS-level speech recognition or Windows language settings (Windows display language, region, and keyboard are all set to Japanese; online speech recognition is enabled in Windows settings).

Note: This may be related to #71953, which reports Windows Voice Typing (Win+H) producing garbled text in the same chat input in some environments. However, in my case Win+H works correctly in this field — the issue is isolated specifically to the extension's own built-in microphone button.

What Should Happen?

The microphone button should transcribe Japanese speech into correct Japanese text, matching the user's Windows-configured input language (Japanese) — the same way Windows' native Voice Typing (Win+H) does in the same input field.

Error Messages/Logs

No error message or crash occurs. The microphone button records and transcribes audio successfully, but the resulting text is incorrect (garbled English-like text instead of Japanese).

Steps to Reproduce

1. On Windows, with Windows display/input language set to Japanese, open the Claude Code chat panel in VS Code
2. Click the microphone icon in the chat input box
3. Speak in Japanese, e.g. "日本語入力をしたいのですが英語になってしまうのですが、どうしたらよいですか？"
4. Observe the transcribed text inserted into the chat input is garbled/English-like, e.g. "Mihongo ni Loko style of this rock, ihongi naktishima no desegado starai deshak."

For comparison:

1. Instead of the microphone button, place the cursor in the same chat input field and press Win+H to open Windows' native Voice Typing, then speak the same phrase.
2. Win+H correctly transcribes it as proper Japanese text, confirming the issue is isolated to the extension's built-in microphone button, not Windows-level speech recognition or language settings.

Claude Model

None

Is this a regression?

No, this never worked

Last Working Version

_No response_

Claude Code Version

2.1.206 (Claude Code)

Platform

Anthropic API

Operating System

Windows

Terminal/Shell

PowerShell

Additional Information

Windows Voice Typing (Win+H) works correctly in the exact same chat input field, which points to the bug being specific to the extension's own microphone/dictation implementation rather than the OS.