Comparison
GPT-5.6 Sol vs Fable 5 vs Mythos 5
OpenAI's launch chart puts its new flagship, Sol, ahead of Claude's Mythos 5 and the now-suspended Fable 5. It's a useful headline — but the numbers are OpenAI's own, and the gap between the models is narrower than the top line suggests. Here's the honest read.
Quick summary
- On OpenAI's Terminal-Bench chart, Sol Ultra leads clearly; standard Sol and Mythos 5 are essentially tied; Fable 5 sits a notch below.
- All four model numbers are OpenAI-reported — independent leaderboards don't yet list them.
- It's a paper comparison for now: Fable 5 is suspended and GPT-5.6 is gated to about 20 partners. Most people can run neither today.
The chart everyone's sharing
OpenAI's announcement leads with Terminal-Bench 2.1, an agentic-coding benchmark. Here are the scores from that chart:
Higher is better, out of 100. OpenAI-reported figures.
Sol Ultra91.9
Sol88.8
Mythos 588.0
Fable 5 · suspended84.3
Gemini 3.1 Pro70.7
GPT-5.6 (OpenAI)
Claude (Anthropic)
Other
Source: OpenAI's launch chart (self-reported). Independent leaderboards don't yet list these models; only Gemini 3.1 Pro's 70.7 is independently verified, and it isn't part of OpenAI's comparison set.
Read it honestly: Sol Ultra's lead is real on this chart, but ultra is a multi-agent mode that spends far more compute. Standard Sol (88.8) and Mythos 5 (88.0) are within a point. Fable 5 at 84.3 trails by a few points — not a generation.
Why to treat the numbers carefully
Every OpenAI and Anthropic score above comes from OpenAI's own launch chart, not an independent test. The public Terminal-Bench leaderboards don't yet list any of these models, and their current top independently-measured score sits well below Sol's claimed 91.9. Only Gemini 3.1 Pro's 70.7 is independently verified — and it isn't part of OpenAI's comparison set.
There's also no published GPT-5.6 score on cybersecurity's ExploitBench — OpenAI only claims Sol is competitive with Mythos while using about a third of the tokens. Treat all of this as vendor framing until independent results land.
What it means while Fable 5 is down
For now this is a paper race. Fable 5 is suspended; GPT-5.6 is limited to about 20 approved partners. If you need to ship today, the question isn't “Sol or Fable 5” — it's which available model fits your task. Use the alternatives guide for that, and keep this comparison as a brief to re-run once both models are actually reachable.
- GPT-5.6: who can use it and when Access, tiers, pricing, and the controversy
- What to use instead right now Model-by-model fallbacks you can actually run
Need the short answer?
Fable 5 is back worldwide as of July 1 — but capped at 50% of your weekly limit until July 7. See the live status, or use GLM-5.2 or the new Sonnet 5 for cheaper work.
Read the brief Fabel 5 spelling guideFAQ
Is GPT-5.6 Sol better than Fable 5?
On OpenAI's own Terminal-Bench chart, yes — Sol 88.8 and Sol Ultra 91.9 versus Fable 5's 84.3. But those are OpenAI-reported numbers, not independent, and standard Sol is within about a point of Claude's Mythos 5.
Where is Terra in the comparison?
Terra isn't on this benchmark chart. OpenAI positions Terra as a balanced tier roughly matching GPT-5.5 at about half the cost, not as a Sol- or Mythos-class competitor.
Can I run either model right now?
Most people can't. Fable 5 is suspended, and GPT-5.6 is restricted to about 20 government-approved partners via API and Codex.
Track what's worth using now
Fable 5 is back — get one email when the next big move lands (Fable pricing, Sonnet 5, GPT-5.6), plus the occasional practical update. No spam, leave anytime.
Sources
This page is independent. Official provider pages are the source of record for access, pricing, and policy.