Anthropic

Claude Sonnet 5.5

Under evaluation
Maker
Anthropic
Origin
United States
Released
Sep 28, 2026
Category
Language Models

Strengths & weaknesses

  • Anthropic reports at least 30% faster output than Sonnet 5, with fewer tokens needed for many of the same tasks
  • Available across Anthropic, AWS, Google Cloud, and Azure at $2 input/$10 output per million tokens
  • Released on September 28, so this directory has no qualifying independent capability measurements for it yet
  • Anthropic positions Opus 5.5 above it for complex work requiring careful judgment

Evaluation

In assessment · 20% measured

Scored on Claude Sonnet 5.5 · sources as of Sep 29, 2026

  • Reasoningw45—

    No independent measurement yet

  • Accuracyw20—

    No independent measurement yet

  • Writingw15—

    No independent measurement yet

  • Long contextw209.9

    Rule B1,000,000 tokens · Scale 8,192–1,048,576 tokens, 0 to 10 · OpenRouter, context window · Sep 29, 2026

Price & availability

Measured the same way, deliberately kept out of the score: what a model costs doesn’t change what it can do.

w = weight, each criterion’s share of the overall score. Missing marks don’t count for or against. How scoring works

More in Language Models

View all →
Meta

Muse Spark 1.3

9.4/10
  • Meta's first frontier line since it moved off Llama, natively multimodal across text, image and video at $1.25/$4.25 per million tokens
  • Meta reports roughly 20% fewer tool calls and 25% fewer tokens than Muse Spark 1.2 on the same agentic work
  • Proprietary, ending the open-weight position Llama gave Meta, and served by a single provider on OpenRouter
  • 10th of 409 on LMArena's overall text arena — strong, but behind the Anthropic and Google models above it
Google

Gemini 3.8 Flash

9.5/10
  • Highest-rated model in the directory on LMArena's hard prompts after Anthropic's Opus line, on 14,320 votes
  • Google reports 90.8% on Terminal-Bench 2.1, up from 81.6% for 3.7 Flash, at $0.75/$3.75 per million tokens
  • Built on 3.7 Flash rather than a new base model, and Google tells you to stay on 3.7 for efficiency-first work
  • Spends more thinking tokens by design, so the headline price understates what a task actually costs
Moonshot AI

Kimi K3

9.4/10
  • The largest open-weight release yet at 2.8T parameters with 104B active, served by 17 independent providers
  • Moonshot reports 81.2 on FrontierSWE and 88.3 on Terminal-Bench 2.1, and LMArena ranks it 8th of 133 on WebDev
  • $3/$15 per million tokens, several times the price of the open-weight models it competes with
  • Its licence is only open to a point: model-as-a-service businesses over $20M a year need a separate agreement
Alibaba

Qwen3.8 Max

9.4/10
  • 6th of 133 on LMArena's WebDev arena, the highest-rated non-frontier model for building working web apps
  • 2.4T mixture-of-experts with about 95B active and a 1M-token context, at $2/$6 per million tokens
  • Loses to GLM-5.3 on seven of the eight benchmarks both makers publish, at several times the price
  • Served by a single provider on OpenRouter, so there is no fallback if it is unavailable