[BUG] Spanish output missing all accents and ñ for the last three weeks

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?

For about the last three weeks, Claude Code has stopped generating correct Spanish text. Instead of normal Spanish, it now outputs text with:

• No accented vowels at all (á, é, í, ó, ú are missing)
• No "ñ" characters (they are replaced or omitted)
• All sentences look like "ninguna tilde ni las enes", as if the model had "forgotten" proper Spanish orthography

This happens:

• Consistently in regular chat and code tasks
• Across different projects and prompts where Spanish used to work correctly before

Environment:

• Claude Code extension in VS Code
• OS: Windows
• Region/keyboard: Spanish (Spain)

What Should Happen?

_Claude should generate correct Spanish text, including all standard diacritics (tildes: á, é, í, ó, ú) and the "ñ" character.

All Spanish output should follow proper orthography and spelling rules as it did before this issue started.

Important: If I explicitly ask Claude to correct the text after generation, it DOES fix the accents and ñ properly. However, I have to manually request this correction every single time it writes Spanish text in any web form or application, which is very inefficient.

Error Messages/Logs

No error messages appear in the console. The issue is purely in the text output - Claude generates Spanish text without any accented characters (á, é, í, ó, ú) or ñ characters.

The extension works normally otherwise, but the linguistic quality of Spanish output has degraded significantly.

Steps to Reproduce

1. Open Claude Code in VS Code
2. Ask Claude to write a paragraph in standard Spanish (for example: "Escribe un texto breve en español estándar sobre entrenamiento de fuerza")
3. Observe that the response contains no accented characters and no "ñ" at all

Example of incorrect output received:
"El entrenamiento de fuerza es fundamental para mejorar la composicion corporal y la salud osea."

Expected output should include proper accents:
"El entrenamiento de fuerza es fundamental para mejorar la composición corporal y la salud ósea."

Claude Model

Opus

Is this a regression?

Yes, this worked in a previous version

Last Working Version

_No response_

Claude Code Version

v2.0.70

Platform

Anthropic API

Operating System

Windows

Terminal/Shell

PowerShell

Additional Information

Scope of the Issue:

This issue affects Claude Code in multiple contexts:

• VS Code extension (Claude Code IDE extension)
• Terminal/CLI usage

Both environments produce Spanish text without accents or ñ characters. The issue is consistent regardless of the interface being used.