Troubleshooting DeepSeek Language Switching#

What Was Established#

Local DeepSeek models may intermittently switch from English to Chinese mid-response. This is typically caused by training bias (heavy Chinese dataset influence), loss of context during long conversations, or mixed-language input prompts.

Key Decisions#

To maintain English-only responses, the following parameters and prompting strategies should be applied:

• Explicit Instruction: Always include a system-level or initial prompt instruction to respond exclusively in English.
• Temperature Control: Use lower temperature settings (e.g., 0.3) to make the model more deterministic and less likely to drift.
• Repetition Penalty: Implement a repetition_penalty (e.g., 1.2) to discourage the model from falling into repetitive patterns that might trigger language switching.

Current Configuration#

System Message Pattern#

When using APIs or local inference engines that support system roles: