What is the difference between Claude Sonnet 4.5 and Horizon Alpha?

Claude Sonnet 4.5 is developed by Anthropic while Horizon Alpha is developed by OpenRouter. Claude Sonnet 4.5 has a 200K token context window vs Horizon Alpha's 256K. You can compare their actual outputs across 26 challenges on Rival to see how they differ in practice.

Which is better, Claude Sonnet 4.5 or Horizon Alpha?

It depends on your use case. Claude Sonnet 4.5 and Horizon Alpha each have strengths in different areas. Rival lets you compare their real outputs side-by-side across 26 challenges so you can judge which fits your needs best.

How much does Claude Sonnet 4.5 cost compared to Horizon Alpha?

Claude Sonnet 4.5 costs $3/M input tokens and Horizon Alpha costs $0/M input tokens. Horizon Alpha is $3.00/M cheaper per input. Check their side-by-side outputs on Rival to see if the price difference is justified by quality.

How can I compare Claude Sonnet 4.5 and Horizon Alpha on Rival?

This page shows a side-by-side comparison of Claude Sonnet 4.5 and Horizon Alpha across shared challenges. You can vote on which model produced the better output in a blind duel. Browsing and voting are free. No account is needed to look; signing in only saves your votes and likes.

Updated Sep 2025

Claude Sonnet 4.5vsHorizon Alpha

Horizon Alpha is cheaper than Claude Sonnet 4.5 at $0/M vs $3/M input tokens.

Claude Sonnet 4.5 and Horizon Alpha compared across 26 shared prompts
Spec	Claude Sonnet 4.5	Horizon Alpha
Input price	$3/M tokens	Free
Output price	$15/M tokens	Free
Context window	200K tokens	256K tokens
Weights	Closed	—
Free API (OpenRouter)	No	No
Released	Sep 2025	Jul 2025