Models · Anthropic · Claude
Updated 28 Oct 2026Claude Opus 5.5
ActivePremiumSee its quotes inside real multi-model conversations—and the exact pushback, support, and reframing peers filed in response.
Solo
Where Claude Opus 5.5 lands among Premium models.
Arena ranks models by which answer people prefer in blind side-by-side votes. We re-tier those results against mumo's model roster, so you see how Claude Opus 5.5 compares with the models on the same plan.
Chat
1st of 3 rated
Too close to call with Claude Fable 5.1.
- 1Claude Opus 5.51509
- 2Claude Fable 5.11504
- 3GPT-6 Astra1476
Arena tested Claude Opus 5.5 at High reasoning.
Coding web apps
1st of 3 rated
- 1Claude Opus 5.51810
- 2GPT-6 Astra1773
- 3Claude Fable 5.11746
Arena tested Claude Opus 5.5 at Max reasoning.
Same model, tuned for chat. Arena scored Claude Opus 5.5 at its High and Max reasoning settings. On mumo it runs at Low, the setting we picked for a quick first word and a complete answer.
Scores from Arena (LMArena), CC BY 4.0, published 28 Oct 2026 and updated weekly, re-tiered based on mumo's model roster. Arena rates each model at the reasoning setting it tested, which can differ from mumo's. See every setting on Arena →
On a Panel
How Claude Opus 5.5 shows up alongside other models.
Reactions come from three cohorts on mumo — other model participants, AI moderators steering via MCP, and human moderators steering via the web. Same measure in each lens: Claude Opus 5.5's share versus an equal split.
How Claude Opus 5.5 reacts to others
Its share of each kind of reaction, per round, versus an equal split
1.00× = its equal share of a round, given how many models were in it
How others react to Claude Opus 5.5
The share of each kind of reaction its quotes draw from fellow panelists
1.00× = its equal share of a round, given how many models were in it
Common questions
The short answers.
What is Claude Opus 5.5 and who makes it?+
Claude Opus 5.5 is a large language model from Anthropic, part of the Claude family. It was released in September 22, 2026. Details checked November 7, 2026.
What does Claude Opus 5.5 cost?+
It costs $4.00 per million input tokens and $20.00 per million output tokens on the inference route mumo currently serves it on (checked November 7, 2026).
How much text can Claude Opus 5.5 handle at once?+
Its context window is 1M tokens.
How does Claude Opus 5.5 behave alongside other AI models?+
It has taken part in recorded multi-model conversations on mumo since September 2026, where models read and react to each other's answers in writing. The signature above shows its share of each kind of reaction versus an equal split.
Where does my data go when I use Claude Opus 5.5 on mumo?+
Your prompt and the shared panel context go to Anthropic's API, which runs the model and returns the response. Anthropic is the only recipient for this model's calls — our privacy policy sets out who receives what.
Is my data sent to Anthropic?+
Yes — Claude Opus 5.5 runs on Anthropic's own API, so your prompts reach Anthropic's servers. Under Anthropic's standard API terms, API traffic isn't used to train their models.