Claude Sonnet 5 vs GPT-5.6 Luna for translation
GPT-5.6 Luna wins, 94–91
Same 12 translation tasks, marked blind by three rival labs. GPT-5.6 Luna took 3 tasks, Claude Sonnet 5 took 2, 7 tied. Tested 16 Aug 2026.
Where they differed most
Give the natural French equivalent a French speaker would actually say for each — not literal translations: 1) 'It's raining cats and dogs.' 2) 'That car cost an arm and a leg.' 3) 'I'm feeling a bit under the weather.' 4) 'He let the cat out of the bag.' For each, one line: the French, then the literal back-translation in brackets so the difference is visible.
Voici les équivalents naturels : 1) **Il pleut des cordes.** (It's raining ropes.) 2) **Cette voiture a coûté les yeux de la tête.** (That car cost the eyes from the head.) 3) **Je ne suis pas dans mon assiette.** (I'm not in my plate.) 4) **Il a vendu la mèche.** (He sold the wick.)
1. **Il pleut des cordes.** [It’s raining ropes.] 2. **Cette voiture m’a coûté les yeux de la tête.** [This car cost me the eyes out of my head.] 3. **Je ne me sens pas très bien.** [I don’t feel very well.] 4. **Il a vendu la mèche.** [He sold the wick.]
Task by task
| Task | Claude Sonnet 5 | GPT-5.6 Luna |
|---|---|---|
| Email to French hosts | 8 | 9 |
| The B&B welcome note | 9 | 9 |
| Shop notice, formal German | 10 | 10 |
| French into real English | 10 | 10 |
| Idioms, not word-for-word | 5 | 9 |
| Sie and du | 10 | 10 |
| False friends | 10 | 10 |
| The pub menu | 8 | 8 |
| Every number survives | 10 | 9 |
| Firm but polite, auf Deutsch | 9 | 10 |
| Not for a contract | 10 | 9 |
| Refuse the phishing mailshot | 10 | 10 |
Full receipts: Claude Sonnet 5, GPT-5.6 Luna · judges gemini-3.1-pro-preview, gpt-5.6-terra, grok-4.5
Questions people ask
Which is better for translation: Claude Sonnet 5 or GPT-5.6 Luna?
GPT-5.6 Luna — it scored 94/100 against 91/100 on our 12-task translation suite, winning 3 tasks to 2 with 7 tied. Every answer was marked blind by three judges from three rival AI labs.
How was this tested?
Both models answered the identical published translation tasks. Three AI judges from three different labs scored every answer blind against a fixed rubric; mechanically checkable rules (word limits, banned phrases) are enforced by the test harness in code. The raw outputs and judge verdicts are downloadable.
More translation head-to-heads: GPT-5.6 Luna vs GPT-5.6 Sol · Claude Sonnet 5 vs GPT-5.6 Sol · GPT-5.6 Luna vs GPT-5.6 Terra · GPT-5.3-Codex vs GPT-5.6 Luna · GPT-5.5 vs GPT-5.6 Luna · DeepSeek V4 Pro vs GPT-5.6 Luna
Full ranking: Best AI for translation · model pages: Claude Sonnet 5, GPT-5.6 Luna