Higher Reasoning Effort Yields Diminishing Returns
Hesamation · x · 2026-07-13
This post provides a cheat sheet on "reasoning effort vs. performance vs. cost," comparing the trade-offs of increasing reasoning effort across models like GPT-5.6, Opus 4.8, and Fable 5.
The core conclusion: Beyond HIGH, price increases typically outpace intelligence gains. Cited results from the Coding Agent Index show that some cheaper tiers lag only slightly in task performance but cost significantly less. For example:
- Terra Max is only slightly above Fable 5 Max, but costs about 76% less per task
- Sol XHigh is only 1 point lower than Max, with API costs around 26% lower
- Luna Max is stronger than Opus 4.8 Max, but costs roughly 80% less per task
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