By the toolist.ai editors. Researched from public sources, not hands-on tested by toolist.ai. Updated October 13, 2026; prices checked October 13, 2026.

Claude Opus 5.5 vs Claude Sonnet 5.5

Verdict

Claude Sonnet 5.5 is the better buy for coding agents, and Claude Opus 5.5 for reasoning-heavy knowledge work. Sonnet costs half as much per token ($2 and $10 per million against $4 and $20) and scores higher on two of the eight Artificial Analysis benchmarks both have: the Coding Agent Index (68.4 against 66.0) and Terminal-Bench 4.0 (63.6% against 59.6%). Opus wins the other six, including the Intelligence Index (57.6 against 56.0) and Humanity's Last Exam (61.4% against 55.0%).

Verdict based on published prices, limits and benchmarks, not on our own tests.

Choose Claude Opus 5.5 if

  • Your work is knowledge work or research (1866 against 1838 Elo on GDPval-AA; 61.4% against 55.0% on Humanity's Last Exam)
  • You run at the default effort and want the higher score there (51.2 at medium against 46.8 at high on the Intelligence Index)
  • You want Anthropic's recommended starting model, which is Opus 5.5
  • You need fast mode, which Anthropic offers for Opus 5.5 and not for Sonnet 5.5

Choose Claude Sonnet 5.5 if

  • You run coding agents (68.4 against 66.0 on the Coding Agent Index; 63.6% against 59.6% on Terminal-Bench 4.0)
  • Cost matters: every token costs half, so the support chatbot workload is $1,000 a month against $2,000
  • You want faster answers (96.8 output tokens a second at high effort against 78.8 for Opus at medium, and 14.6 seconds to the first token against 26.6)
  • You use the Claude apps on the Free plan, which includes Sonnet and not Opus

Price

Input costs 2 times as much on Claude Opus 5.5 as on Claude Sonnet 5.5. Output costs 2 times as much on Claude Opus 5.5 as on Claude Sonnet 5.5.

Per million tokensClaude Opus 5.5Claude Sonnet 5.5
Input$4 source$2 source
Cached input$0.20 source$0.10 source
Output$20 source$10 source

Claude Opus 5.5: Cache writes cost $5 per million tokens (5-minute cache) or $8 (1-hour cache). The Batch API costs half. There is no long-context surcharge. Fast mode costs $8 in and $40 out.

Claude Sonnet 5.5: Cache writes cost $2.50 per million tokens (5-minute cache) or $4 (1-hour cache). The Batch API costs half. There is no long-context surcharge and no fast mode.

Worked example: what a month costs

We priced three monthly workloads at the standard rates. The provider does not publish these figures.

WorkloadClaude Opus 5.5Claude Sonnet 5.5
Support chatbot
100,000 replies, each 3,000 input and 400 output tokens, no caching (300M in, 40M out)		 $2,000$1,000
Document Q&A
5,000 questions over the same 60,000-token document set (90% cache hits), 800 output tokens each (300M in, 4M out)		 $254$127
Coding agent
200 tasks, each 1.5 million input tokens (90% cache hits) and 50,000 output tokens (300M in, 10M out)		 $374$187

Price your own workload

ModelCost a month
Claude Opus 5.5 $300
Claude Sonnet 5.5 $150

Standard API prices, no batch or priority discounts. Cached input is billed at the cache-read price; cache-write charges are not included. Reasoning models bill their thinking as output tokens.

Limits and release dates

Claude Opus 5.5Claude Sonnet 5.5
ReleasedSeptember 22, 2026 sourceSeptember 28, 2026 source
Context window1,000,000 tokens source1,000,000 tokens source
Maximum output128,000 tokens source128,000 tokens source
Knowledge cutoffJune 2026 sourceJune 2026 source
Input and outputText and images in; text out sourceText and images in; text out source
API model nameclaude-opus-5-5claude-sonnet-5-5

Benchmarks

Scores as published by the provider or measured by Artificial Analysis; higher is better. A dash means no score was published.

BenchmarkClaude Opus 5.5Claude Sonnet 5.5
Artificial Analysis Intelligence Index
max effort		 57.6 source56.0 source
Intelligence Index at everyday effort 51.2 (medium effort, the API default) source46.8 (high effort, the API default) source
Coding Agent Index
Claude Code harness, max effort		 66.0 source68.4 source
Terminal-Bench 4.0
max effort		 59.6% source63.6% source
Humanity's Last Exam
max effort		 61.4% source55.0% source
GDPval-AA v2.1 (Elo)
max effort		 1866 source1838 source
SciCode
max effort		 66.9% source61.0% source
Terminal-Bench-Science 0.1
max effort		 59.0% source53.3% source
Output speed 78.8 tokens/s (medium effort, Anthropic API) source96.8 tokens/s (high effort, Anthropic API) source

Benchmark and speed data from Artificial Analysis where linked.

Read more

Sources