Claude Fable 5 vs GPT-5.6 Sol: Choosing Between Two Flagships
Both models became their vendor's flagship within the last two months, but their pricing structures couldn't be more different -- Fable 5 costs more on output, Sol is cheaper across the board. Here's the spec comparison, a cost estimate, and how to choose.
Claude Fable 5 officially launched on 2026-06-09. GPT-5.6 Sol launched with the GPT-5.6 family on 2026-07-09. As of this update (2026-08-08), both remain their respective vendor's flagship-tier model, with no newer version having replaced either. Re-checked 2026-09-21: both vendors have since shipped a higher tier (Anthropic's docs now list Claude Fable 5.1; the OpenAI pricing archive leads with gpt-6-astra). This page still compares Fable 5 and Sol.
Last verified: 2026-08-08.
Spec and Price Comparison
Pricing and context window figures come from official pricing pages and the LiteLLM authoritative pricing table (re-checked 2026-09-21). See the methodology note below for the SWE-Bench Pro score caveat -- Sol's equivalent score hasn't been separately published.
| Model | Input price (per million tokens) | Output price (per million tokens) | Context window | SWE-Bench Pro |
|---|---|---|---|---|
| Claude Fable 5 | $10.00 | $50.00 | ~1,000,000 tokens | 80.3% (official methodology, see note below) |
| GPT-5.6 Sol | $4.00 | $20.00 | ~1,050,000 tokens | Not separately published by OpenAI |
Three Things Worth Knowing
The scoring methodology: 80.3% isn't a neutral reproduction
Fable 5's 80.3% on SWE-Bench Pro was produced using Anthropic's own evaluation scaffolding, and independent evaluators' reproductions differ from the official number. That's not an accusation of a fabricated score -- the evaluation method itself affects results. The full breakdown lives in our dedicated piece, "SWE-Bench Pro: How Fable 5's Score Was Actually Calculated" -- we won't re-argue it here. Sol's side is simpler: OpenAI hasn't separately published a SWE-Bench Pro score for it, we couldn't find reliable public data, so this field is left blank rather than guessed.
Completely different pricing structures
Sol's current official price is $4.00 input / $20.00 output per million tokens; the official page marks it as promotional pricing available at least through November 21, 2026 (checked 2026-09-21) -- $5/$30 was the pre-promo standard. At current prices Fable 5's output costs 2.5x Sol's ($50 vs $20) and its input 2.5x ($10 vs $4). Sol was untouched in the 2026-07-30 GPT-5.6 family-wide cut (Terra -20%, Luna -80%).
Context windows are close -- not a deciding factor
Fable 5 sits around 1,000,000 tokens, Sol around 1,050,000 -- essentially tied on the long-context dimension. That's not where the real choice lies; pricing structure and how much you trust the 80.3% figure matter more.
How to Choose
Guidance by budget sensitivity and task complexity -- not a single "which is stronger" verdict.
Budget-sensitive, high volume: lean Sol
Sol's output price is 40% of Fable 5's, and its input price is also 40% (our conversion from the current $20/$4 vs $50/$10). If your workflow is high-frequency, high-volume calls -- test generation in CI, bulk code review -- that price gap gets amplified by volume, and Sol's bill advantage becomes significant.
Chasing the benchmark number, budget isn't the constraint: Fable 5
If the absolute SWE-Bench Pro number matters more to you and budget isn't the primary constraint, Fable 5's 80.3% is currently tied for the top of that leaderboard -- provided you accept the caveat about the official evaluation methodology noted above.
Not sure? Run a small side-by-side first
Both models are callable on QCode with the same key, so instead of debating which is "stronger" in the abstract, run a small batch of your own real tasks against both and decide from there -- actual performance on your codebase and task types tells you more than a benchmark number.
Timeline
Key dates for both models over the last two months.
Claude Fable 5 officially launches
Anthropic releases Fable 5 at an official $10.00 input / $50.00 output (per million tokens) price, with a context window of about 1,000,000 tokens.
GPT-5.6 family launches, with Sol as the flagship tier
OpenAI releases the three-tier GPT-5.6 family (Sol/Terra/Luna). Sol is the top tier, priced at $5.00 input / $30.00 output (per million tokens), with a context window of about 1,050,000 tokens.
GPT-5.6 family-wide price cut, Sol unchanged
Terra dropped 20%, Luna dropped 80% -- Sol's price stayed exactly where it was, the only tier untouched in this round of cuts.
Primary Sources
Anthropic's official Fable 5 launch page; vellum.ai's breakdown of SWE-Bench Pro scoring methodology; LiteLLM model_prices_and_context_window.json (the authoritative source for pricing data, verified 2026-08-08).
FAQ
What's Sol's SWE-Bench Pro score?
OpenAI hasn't separately published a SWE-Bench Pro score for GPT-5.6 Sol, and we couldn't find reliable public data for it. This page leaves that field blank rather than substituting or estimating a number from another leaderboard.
Can Fable 5's 80.3% be directly compared against other models?
Treat it with caution. That score comes from Anthropic's own evaluation scaffolding, not a neutral third-party reproduction, and independent evaluators report different results. The full methodology breakdown is in our dedicated piece, "SWE-Bench Pro: How Fable 5's Score Was Actually Calculated."
Roughly how much would a mid-complexity PR cost on each model?
This is an estimate only, not measured usage data: assuming a mid-complexity PR consumes about 150K input tokens and 20K output tokens, Fable 5 would run about $1.5 (input) + $1.0 (output) = roughly $2.5; Sol at the current promotional $4/$20 would run about $0.6 (input) + $0.4 (output) = roughly $1.0 (our conversion). Actual consumption varies a lot with codebase size, context length, and task complexity -- recalculate with your own real workload.
Can I use both models on QCode?
Yes, both Claude Fable 5 and GPT-5.6 Sol are currently in QCode's callable model list, switchable with the same key -- no separate activation needed.
Create a QCode account
Plans from ¥60 / $8.57. One key across Claude, GPT, and Gemini models.
Related Guides
Claude Fable 5 Complete Pricing Guide
Input/output pricing, cache pricing, and billing details
SWE-Bench Pro: How Fable 5's Score Was Actually Calculated
Breaking down the 80.3% methodology against independent reproductions
GPT-5.6 Sol vs Terra vs Luna: How to Choose
Positioning and selection guidance across the GPT-5.6 tiers
This site is not affiliated with Anthropic or OpenAI. Pricing and benchmark data follow official and authoritative third-party sources; information on this page is current as of 2026-08-08 and may change. Cost estimates are for reference only and do not represent measured usage data.