September 2026 AI Model Rankings: Fable 5.1 Tops Intelligence Index as Competition Tightens Across GPT-5.6 Sol, Grok 4.6 and Muse Spark 1.3
The start of September 2026 proved to be a rare moment when the roster of the strongest language models had to be almost completely rewritten. Anthropic introduced Fable 5.1 and the restricted Mythos 5.1, Meta updated Muse Spark to version 1.3, Google launched Gemini 3.8 Flash, and Alibaba refreshed Qwen3.8-Max. Summer releases such as GPT-5.6 Sol, Grok 4.6, Kimi K3, GLM-5.3 and DeepSeek V4 Pro stayed in the race and continue to compete with the newcomers.
Compiling a conventional ranking from smartest to least capable has become difficult. Contemporary models run in several reasoning-depth modes, and the gap between low, high and max settings can exceed ten points on a single test. Speed, token consumption, long-context pricing, image support, tool-use quality and the ability to execute long autonomous action sequences now vary widely.
It is therefore more useful to treat the market as several overlapping races. Fable 5.1 currently claims the highest quality for complex reasoning. GPT-5.6 Sol and Grok 4.6 deliver comparable performance at lower cost. Muse Spark 1.3 unexpectedly entered the top tier on capability-to-cost ratio. Gemini 3.8 Flash bets on speed and multimodality. Kimi, GLM, Qwen and DeepSeek have nearly erased the former boundary between Chinese and American models.
How to Compare Models Without Misleading Yourself
The Artificial Analysis Intelligence Index serves as a convenient common scale. This independent metric combines tests on knowledge, programming, scientific reasoning, tool use and long-horizon agent tasks. The methodology is more reliable than vendor tables because models are evaluated under comparable conditions.
Scores cannot be read as an intelligence quotient. A result of 66 versus 61 does not mean the first model is eight percent smarter. The index reflects average performance on a specific test suite. On Russian-language article writing, accounting-document analysis, website layout or debugging enterprise applications the ordering may differ.
Reasoning modes alter the picture even more. GPT-5.6 Sol scores around 61 in max mode, 59 in xhigh and 57 in high. Fable 5.1 reaches 66 only at maximum depth. Gemini 3.8 Flash scores 59 in high, 57 in medium and 52 in low. Comparing Gemini against Claude without specifying the mode is about as useful as comparing cars without stating engine power.
Market Leaders at the Start of September 2026
The current top tier is unusually dense. After Fable 5.1 the gap between several flagships fits within a few points. Expensive models do not always complete a given task more cheaply; some systems generate far more intermediate text, reason longer or invoke external tools more frequently.
- Claude Fable 5.1, max – 66 points, 1 M context, $10/$50 per million tokens, available
- Claude Opus 5, max – 63 points, 1 M context, $5/$25, available
- Muse Spark 1.3, max – 62 points, 1 M context, price not announced, limited access
- GPT-5.6 Sol, max – 61 points, ~1.05 M context, $4/$20, available
- Grok 4.6, high – 61 points, 500 k context, $2/$6, available
- Muse Spark 1.3, xhigh – 61 points, 1 M context, $1.25/$4.25, available
- Kimi K3, max – 60 points, ~1 M context, $3/$15, open weights
- GLM-5.3, max – 60 points, up to 1 M context, $1.40/$4.40, open weights
- Gemini 3.8 Flash, high – 59 points, ~1.05 M context, $0.75/$3.75, available
- Qwen3.8-Max – 58 points (previous snapshot), 1 M context, ~$2/$6, updated to 0902
- DeepSeek V4 Pro 0813, max – 53 points, 1 M context, $0.66–1.32/$1.98–3.96, open weights
Additional caveats apply. Independent tests of the updated Qwen3.8-Max-0902 have not yet produced a comparable final score, so the 58-point figure refers to the prior version. Muse Spark 1.3 maximum mode remains in limited testing; the public xhigh mode scores 61. For Grok 4.6 the best independent result occurs in high mode, while xhigh unexpectedly scores slightly lower.
Pricing also requires notes. The Gemini 3.8 Flash tariff is temporarily reduced until the end of 2026. GPT-5.6 Sol is sold at a temporarily lowered price. DeepSeek pricing changes between peak and off-peak hours. Grok 4.6 doubles in price for requests longer than 200 k tokens. A simple API-price column therefore hides half of the real economics.
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