Surge benchmarks Fable 5.1, Muse Spark 1.3 and Gemini 3.8 Flash, with Astra results due next week
Surge has finished benchmarking Claude Fable 5.1, Muse Spark 1.3 and Gemini 3.8 Flash, while its GPT-6 Astra evaluation is still running and results are planned for next week.
Four major frontier models shipped last week: Claude Fable 5.1, Muse Spark 1.3, Gemini 3.8 Flash, and GPT-6 Astra. We’ve completed Surge benchmark evaluations for the first three; Astra is still running. Fable 5.1 leads on overall capability. It scores 68.7 on the Tuesday Work Index, our composite measure of frontier AI at work, and takes the top spot on Chartography, HANDBOOK.md, and EnterpriseBench: CoreCraft. Muse Spark 1.3 tops ComplexConstraints, our benchmark for professional instruction following. Its xHigh operating point reaches 51.9% for $54.25, on the cost-performance Pareto frontier. Gemini 3.8 Flash makes its biggest move on frontier mathematics. On Riemann-bench, Gemini 3.8 Flash (High) rises from 39.2% to 51.2%, a 12-point generational improvement. At $69.59, it also lands directly on the benchmark’s cost-performance Pareto frontier. In short: ‣ Fable 5.1 pushes absolute capability higher. ‣ Muse Spark 1.3 combines top-tier complex instruction following with strong efficiency. ‣ Gemini 3.8 Flash delivers a large step forward in mathematical reasoning at competitive cost. Our Astra evaluation is still running, and we plan to publish results next week. Read the full analysis: https://surgehq.ai/blog/fable-5-1-tuesday-work-index