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so what was it

oh, it was a different version of GPT-5

@Bayesian What's the deal for this market? It's doubtful we're going to be seeing any new info.

We have https://openrouter.ai/announcements/gpt-5-is-now-live which says "Earlier iterations of this model were available as Horizon Alpha and Horizon Beta" and https://x.com/OpenRouterAI/status/1953522983084999001 which says "GPT-5 replaces the Horizon Alpha and Beta stealth models on OpenRouter. They were early checkpoints in the GPT-5 family of models."

But looking at the various benchmarks it seems clear that the Horizon models were not GPT-5-nano:

GPT-5-nano benchmarks according to rankedagi.com:

• SWE-Bench Verified: 54.7%

• Aider Polyglot: 48.4%

• GPQA Diamond: 71.2%

• AIME 2025 I&II: 85.2%

• Svelte Bench: 16.7%.

It's hard to find benchmarks for the Horizon models but it seems they do much better. Note that they did well on Svelte Bench specifically: https://x.com/khromov/status/1952995621830369504

GPT-5-mini gets 21.1% on Svelte Bench while GPT-5 gets 78.9%. Note that although GPT-5 benchmarks are mixed up with GPT-5-Thinking vs non-thinking and Horizon models were non-CoT, which likely explains the ways in which Horizon models outperformed GPT-5, Horizon models also underperformed GPT-4o in many areas, so I'm sure the answer is more complex.

But it seems like there is ~0 chance that the horizon models were GPT-5-nano.

Thoughts?

@satchlj I pretty much agree, ty for the comment. @traders does anyone think it's at all likely that horizon alpha is gpt-5 nano?

@Bayesian they have very different outputs at similar parameters and have very different scores, so no

See related market: https://manifold.markets/satchlj/what-model-is-horizon-alpha-on-open