Claude Haiku 4.5 vs Claude Sonnet 4.6 for Translation

What Translation demands: accurate cross-language rendering (multilingual quality), fidelity to source meaning (faithfulness), cultural/idiomatic adaptation, tone/persona preservation, safe handling of sensitive content, and the ability to process long artifacts or produce structured localization outputs. In our testing the Translation task uses two checks: multilingual and faithfulness; both models scored 5/5 on those checks and share rank 1 of 52 for Translation. Use supporting benchmarks from our internal suite to explain differences: Sonnet 4.6 shows stronger safety_calibration (5 vs 2) and creative_problem_solving (5 vs 4), which matters for deciding when to refuse or reframe harmful content and for producing idiomatic, culturally adaptive translations. Both models tie on multilingual (5) and faithfulness (5), tool_calling (5), long_context (5), persona_consistency (5), and structured_output (both 4), so baseline translation quality is equivalent in straightforward cases. Operational differences that affect task selection: Haiku 4.5 is far less expensive per mTok (input_cost_per_mtok 1, output_cost_per_mtok 5) while Sonnet 4.6 costs more (input_cost_per_mtok 3, output_cost_per_mtok 15) but offers a larger context_window (1,000,000 vs 200,000) and larger max_output_tokens (128,000 vs 64,000) for very large documents or multi-file localization bundles.

Where Claude Sonnet 4.6 shines (choose Sonnet when):

• Regulatory/legal translation where incorrect acceptance or unsafe rewrites are costly: Sonnet's safety_calibration 5 vs Haiku 2 lowers risk of permitting or mishandling sensitive content while maintaining faithfulness 5.
• High-nuance marketing localization requiring creative adaptation: Sonnet's creative_problem_solving 5 vs Haiku 4 produces more idiomatic, culturally resonant phrasing beyond literal translation.
• Very long-format localization (books, manuals, corpora): Sonnet's context_window 1,000,000 and max_output_tokens 128,000 handle larger documents or monolithic localization jobs better than Haiku's 200,000 / 64,000 limits. Where Claude Haiku 4.5 is preferable (choose Haiku when):
• High-volume, low-cost batch translations or low-latency pipelines: Haiku costs input 1 / output 5 per mTok versus Sonnet 3 / 15, making Haiku roughly one-third the cost ratio in our price data.
• Straightforward document or UI string translation where both models already score 5/5 on multilingual and faithfulness and safety risk is low—Haiku delivers equivalent baseline quality at much lower cost. Shared strengths: both models scored 5/5 on multilingual and faithfulness in our tests, and both tie at top rank for Translation, so for many standard translation tasks quality will be equivalent.

For Translation, choose Claude Haiku 4.5 if you need cost-efficient, low-latency bulk translations where safety risk is low and baseline multilingual fidelity suffices. Choose Claude Sonnet 4.6 if you need stronger safety handling, more creative localization, or very large-context translation (long documents) and can accept higher input/output cost.