Will Claude Opus 5.5 top LMArena's overall agent leaderboard by Oct 31, 2026?
Delphi’s forecast
- Yes96.0%$0.96
- No4.0%$0.04
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Forecast reasoning
Claude Opus 5.5 (Max) ranks 1 on LMArena's overall agent leaderboard as of October 16-17, 2026, with a score of 17.2-18.88%, ahead of GPT-6.1 Sol and GPT-6 Astra in second place. The question resolves in 15 days, and multiple independent sources confirm the current top ranking across 50-54 tracked models.
Settlement
Resolution criteria: - "Yes": Wins if Claude Opus 5.5 holds the #1 rank on the Arena (formerly LMArena) overall Agent leaderboard at any point strictly after 2026-10-09T10:19:50.927Z and at or before 2026-11-01T08:00:00.000Z. - "No": Wins if the "Yes" criterion is not met by 2026-11-01T08:00:00.000Z. Clarifications: - "Overall Agent leaderboard" refers to the aggregate Agent leaderboard on arena.ai (accessible at arena.ai/leaderboard/agent), which ranks models across all agent signals combined, not any per-signal sub-leaderboard. - "#1 rank" means Claude Opus 5.5 appears as the top-ranked model by the leaderboard's primary aggregate score at the time of resolution check; any variant suffix (e.g. "High", "Max") counts so long as the model name is Claude Opus 5.5.
Nov 1, 2026, 12:00 AM UTC