GPT-5.6 Luna vs GPT-5.6 Sol
Head-to-head technical comparison of intelligence, capabilities, and API pricing.
Which should you use?
GPT-5.6 Sol leads on the composite index by 3.7 points (92 vs 95.7).
Cost is the sharper difference: GPT-5.6 Sol is 20x the input price of GPT-5.6 Luna ($4 against $0.2 per 1M), so at volume the choice is usually decided by budget rather than benchmarks.
Pick GPT-5.6 Luna when
- Cheaper input tokens — $0.2 against $4 per 1M, so GPT-5.6 Sol costs 20x as much to feed.
- Better value per point of measured capability: $0.002 per index point against $0.042.
Pick GPT-5.6 Sol when
- Higher composite index — 95.7 against 92, a gap of 3.7 points.
- Ahead on Arena Elo by 28 points (1483 vs 1455), which is outside the board's published confidence intervals.
- Stronger on MMLU-Pro: 95.1% against 92%.
Value per point of measured capability, at list input pricing: GPT-5.6 Luna $0.002 · GPT-5.6 Sol $0.042 per index point. Run your own token mix through the token cost calculator — a comparison at list price ignores caching and batch discounts, which move real bills more than this gap does.
Where these numbers come from
Figures as of 2026-09-14. Arena Elo and pricing are read from the public board and each vendor's own pricing page; see the full leaderboard for all 34 models and which columns are measured rather than estimated, or the benchmark matrix for scores benchmark by benchmark.
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