Based on the article above, here is a new article structured with clear sections, an FAQ, and a conclusion.
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## OpenAI’s GPT-5.6 Splits Into Three Models: Sol, Terra, and Luna
OpenAI has taken a different approach with GPT-5.6, moving away from a single model with configurable “thinking dials.” Instead, GPT-5.6 comes as three distinct large language models: Sol, Terra, and Luna. Each model has its own training regimen, pricing structure, and capability ceiling.
The most talked-about comparison is between **Sol** and **Claude Fable 5**, which is currently Anthropic’s most capable public model. Pricing is a major differentiator:
* **Sol:** $5 per million input tokens, $30 per million output tokens.
* **Fable 5:** $10 per million input tokens, $50 per million output tokens.
* **Luna:** $1 per million input tokens, $6 per million output tokens, making it the cheapest of the three.
Notably, **Luna already outperforms Anthropic’s Opus 4.8 on coding tasks** at a significantly lower price point.
### A Turbulent Month for Claude Fable 5
Fable 5 has faced significant challenges recently. It was banned by the U.S. government on June 12 after researchers discovered a jailbreak that turned the model into an unintended vulnerability scanner. Anthropic pulled it globally for 19 days, rebuilt a new safety classifier, and reintroduced it on July 1 with compressed access. Since its return, Fable 5 has been running on borrowed time, with access extensions announced on tight deadlines (July 7, then July 12, and now July 19), often with only hours’ notice.
The urgency stems from Fable 5’s planned move behind a usage-credits paywall. If Fable exits subscription access after July 19, Anthropic’s best offering for paying subscribers becomes Opus 4.8, which Luna already beats on coding for a fraction of the cost.
### Head-to-Head Benchmark Results
On purely coding benchmarks, the competition is tight:
* **Artificial Analysis Coding Agent Index:** Sol scored 80 vs. Fable’s 77.2, using roughly half the tokens in less than half the time at about a third of the cost.
* **Agents’ Last Exam (professional workflows):** Sol achieved 53.6% vs. Fable’s 40.5%.
* **Terminal-Bench 2.1 (ultra mode):** Sol hit 91.9% vs. Fable’s 83.1%.
On the broader **Intelligence Index**, which aggregates nine benchmarks, Fable 5 edges out GPT-5.6 by a single point, suggesting the capability gap is minimal.
### Beyond Code: Creative Writing and Logic Tests
The article also tested the models on non-coding tasks. In **creative writing**, both models produced novelette-length stories involving time travel paradoxes. Sol was praised for clearer structure and readability, while Fable was noted for a tighter causal loop and more evocative prose.
In **associative thinking** tests (linking a twig, class exploitation, and a lettuce), Fable 5 excelled at burying the argument inside the metaphor, whereas Sol broke its own flow by over-explaining. Both struggled to fully integrate the final lettuce element.
For **logic puzzles** (the bridge-crossing problem), both models initially gave the same answer (17 minutes) without addressing an uncapped assumption in the prompt. Fable 5 provided a longer, more reasoned explanation, but both missed the core issue that the prompt never limited the number of people on the bridge.
In a **one-shot browser game** test, Sol leaned toward a flat, Windows 8.1-style UI, while Fable 5 delivered a more polished, atmospheric result with music and sound effects. Fable 5’s version was judged superior in a single-prompt, no-iteration scenario.
### FAQ
**What are the three models in GPT-5.6?**
They are Sol, Terra, and Luna—three separate models with different training, pricing, and capability levels.
**How much does Sol cost?**
Sol costs $5 per million input tokens and $30 per million output tokens.
**Why was Claude Fable 5 banned?**
It was banned after researchers found a jailbreak that turned it into an unintended vulnerability scanner.
**How does Luna compare to Opus 4.8?**
Luna, the cheapest model, already outperforms Anthropic’s Opus 4.8 on coding tasks.
**What happens to Claude Fable 5 on July 19?**
If no further extension occurs, Fable 5 will revert to a usage-credit paywall at $10/$50, making it more expensive than Sol and Luna.
### Conclusion
Beyond coding, GPT-5.6’s models do not introduce dramatic surprises. **Fable 5 feels like the most robust all-around model**, but the best choice depends heavily on pricing and use case. For users who rely on chat-based tasks rather than terminal work, Fable 5 offers strong quality. However, with Fable 5 facing deadline extensions and potential paywall changes, the value proposition is shifting quickly. Ultimately, which model is “better” comes down to whether you prioritize raw coding performance, reasoning, cost, or conversational usability.
