[Bug] Anthropic API: Incorrect UTF-8 Encoding for German Umlauts - Model cheating!

Bug Description
There is a problem with UTF-8 handling for German language output.
The model avoids using correct German umlauts (ä, ö, ü, ß) and instead replaces or omits them, resulting in grammatically and linguistically incorrect text. Proper UTF-8 support for German characters is required.

Environment Info

• Platform: win32
• Terminal: windows-terminal
• Version: 2.0.69
• Feedback ID: 87bf79ff-2e33-4a72-a187-5db301468652

Errors

[{"error":"Error\n    at NO (B:/~BUN/root/claude.exe:58:1143)\n    at <anonymous> (B:/~BUN/root/claude.exe:59:10080)\n    at emit (node:events:92:22)\n    at endReadableNT (internal:streams/readable:861:50)\n    at processTicksAndRejections (native:7:39)\n    at request (B:/~BUN/root/claude.exe:61:2147)\n    at processTicksAndRejections (native:7:39)","timestamp":"2025-12-18T10:39:32.470Z"},{"error":"Error\n    at NO (B:/~BUN/root/claude.exe:58:1143)\n    at <anonymous> (B:/~BUN/root/claude.exe:59:10080)\n    at emit (node:events:92:22)\n    at endReadableNT (internal:streams/readable:861:50)\n    at processTicksAndRejections (native:7:39)\n    at request (B:/~BUN/root/claude.exe:61:2147)\n    at processTicksAndRejections (native:7:39)","timestamp":"2025-12-18T10:39:32.588Z"},{"error":"Error\n    at NO (B:/~BUN/root/claude.exe:58:1143)\n    at <anonymous> (B:/~BUN/root/claude.exe:59:10080)\n    at emit (node:events:92:22)\n    at endReadableNT (internal:streams/readable:861:50)\n    at processTicksAndRejections (native:7:39)\n    at request (B:/~BUN/root/claude.exe:61:2147)\n    at processTicksAndRejections (native:7:39)","timestamp":"2025-12-18T10:39:33.052Z"}]