Anthropic · proprietary on Arena · first on Arena 25 September 2026

claude-opus-5.5-high

5 days in first place

It held first place on Arena in Text (5 days).

Embed

Who held first place

<iframe src="https://jesseahawkins.com/frontier/embed/" title="Frontier: who held first place on each Arena leaderboard, and for how long" width="100%" height="560" style="border:0;max-width:100%" loading="lazy"></iframe>

Credits LMArena.

The open-weights catch-up

<iframe src="https://jesseahawkins.com/frontier/embed/catch-up/" title="Frontier: the days until open weights matched each closed leader" width="100%" height="900" style="border:0;max-width:100%" loading="lazy"></iframe>

Credits LMArena.

The saturation clock

<iframe src="https://jesseahawkins.com/frontier/embed/clock/" title="Frontier: the days from each benchmark’s release to a model at 90%" width="100%" height="640" style="border:0;max-width:100%" loading="lazy"></iframe>

Credits Epoch AI.

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Cite

This page

Jesse Hawkins, “claude-opus-5.5-high · Frontier”, jesseahawkins.com, data retrieved 30 Oct 2026. https://jesseahawkins.com/frontier/claude-opus-5-5-high/. Data: LMArena, Arena leaderboard dataset, revision 4491b06, CC BY 4.0; Epoch AI, Capabilities & benchmarking, CC BY 4.0.

BibTeX

@misc{hawkins2026frontierclaudeopus55high,
  author = {Hawkins, Jesse},
  title = {{claude-opus-5.5-high · Frontier}},
  year = {2026},
  howpublished = {\url{https://jesseahawkins.com/frontier/claude-opus-5-5-high/}},
  note = {Data: LMArena, Arena leaderboard dataset, revision 4491b06, CC BY 4.0; Epoch AI, Capabilities \& benchmarking, CC BY 4.0, retrieved 2026-10-30}
}

Arena · LMArena

LMArena, "Arena leaderboard dataset", Hugging Face, revision 4491b06. https://huggingface.co/datasets/lmarena-ai/leaderboard-dataset. CC BY 4.0.

Benchmarks · Epoch AI

Epoch AI, 'Capabilities & benchmarking'. Published online at epoch.ai. Retrieved from 'https://epoch.ai/benchmarks' [online resource]. CC BY 4.0.

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Text: 5 days in first place

place 3 of 419 on 28 October 2026

1st10th

On the board: 25 September 2026 to 28 October 2026, the newest snapshot
Score: 1516 (1509–1522) on 28 October 2026 · 11,415 votes
First place: 25 September 2026 to 30 September 2026 · 5 days
Catch-up: No open-weights model has matched it in the 33 days since it first took first place.

Vision: best place 2

place 2 of 167 on 19 October 2026

1st10th

On the board: 9 October 2026 to 19 October 2026, the newest snapshot
Score: 1321 (1309–1333) on 19 October 2026 · 3,035 votes

Epoch AI: Claude Opus 5.5

released 22 September 2026 · API access

Chess Puzzles 67.0%
EBR-bench 71.4%
FrontierMath-Tier-4-v2-Private 95.0%
FrontierMath-Tiers-1-3-v2-Private 91.2%
Furniture Assembly 83.3%
GPQA diamond 90.6%
MirrorCode 78.9%
Mystery Game Puzzles 71.0%
OTIS Mock AIME 2024-2025 100.0%
SimpleQA Verified 72.2%
SpireClimb 3.3%

When each vendor retires it

every model’s dates

Anthropic not before 22 Sep 2027 claude-opus-5-5

Sources

Arena scores come from people voting between two anonymous answers. First place is the highest score; the top two are often within each other’s margin of error. LMArena, Arena leaderboard dataset, revision 4491b06, retrieved 30 October 2026; Epoch AI, Capabilities & benchmarking, retrieved 30 October 2026. Both CC BY 4.0. Retirement dates: each vendor’s own deprecation page, quoted and kept, listed with the record.