Claude Extended Thinking in Other Languages

Claude developer guides note that Extended Thinking performs best in English, even though final outputs can be generated in any language Claude supports. Instruct the model to conduct its internal deliberation in English before writing the final response in the target language.

<instructions> Analyze the sovereign debt restructuring proposal in <document>{{DOC}}</document>. Conduct all internal step-by-step reasoning in English, then write your final executive report in formal Japanese inside <final_report_ja> tags. </instructions>