Arena raises $200M Series B at $3.1B valuation, launches Alignment Index
jfiance · x · 2026-10-09
Arena (LMArena) announced a $200M Series B at a $3.1B valuation.
The platform reports tens of millions of monthly users doing complex coding and agentic work, with most tokens now going to deep, dozens-of-turns single-threaded workflows where it evaluates agents while humans work in flow state — building leaderboards by observing whether tasks actually get done.
It also launched the Arena Alignment Index, which scores models by observing human-AI collaboration, arguing benchmarks should represent actual human value.
Related event: LMArena Raises $200M Series B at $3.1B Valuation, Launches Alignment Index(9 posts)→
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