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GPT-5.6 Sol vs GPT-6 Astra: which is smarter?

GPT-5.6 Sol has an SI-IQ of 140 and GPT-6 Astra has 150. The table compares them area by area using only independent benchmark results.

Data as of Oct 18, 2026 · method 1.0.0

MetricGPT-5.6 SolGPT-6 Astra
SI-IQ140137–143150146–153
Reasoning140154
Math141148
Knowledge139149
DeveloperOpenAIOpenAI
ReleasedJul 9, 2026Sep 3, 2026
AccessAPI accessAPI access
Price in / out (USD per 1M tokens)$4.00 / $20$10 / $50
Benchmarks used99
GPT-5.6 SolGPT-6 Astra
130140150160SI-IQReasoningMathKnowledge

Benchmarks every compared model was tested on

Raw scores as published by the evaluators.

BenchmarkGPT-5.6 SolGPT-6 Astra
Chess Puzzles59.0%74.0%
FrontierMath Tier 482.9%97.6%
FrontierMath Tiers 1–389.1%93.7%
Furniture Assembly not in index56.7%80.0%
GPQA Diamond93.5%95.8%
GPQA Diamond (OpenRouter run)92.3%94.7%
Mystery Game Puzzles58.0%84.0%
OTIS Mock AIME 2024–2025100.0%100.0%
SimpleQA Verified69.7%75.6%
τ²-bench Airline (OpenRouter run)73.3%67.7%

On SI-IQ, GPT-6 Astra is ahead by 10 points, and the 90% intervals do not overlap.

Data sources: Epoch AI, ‘Capabilities & benchmarking’ (CC BY 4.0); LiteLLM, model_prices_and_context_window.json (MIT); Source: OpenRouter (openrouter.ai), licensed under CC BY 4.0: reuse and republish with attribution to OpenRouter (licences and changes).