By the toolist.ai editors. Researched from public sources, not hands-on tested by toolist.ai. Updated November 3, 2026; prices checked November 3, 2026.

Claude Opus 5.5 vs Claude Sonnet 5.5

Verdict

Claude Sonnet 5.5 is the better buy for terminal and agent work, and Claude Opus 5.5 for reasoning-heavy work. Sonnet costs half as much per token ($2 and $10 per million against $4 and $20) and leads on Terminal-Bench 4.0 (64% against 60%). Opus 5.5 scores higher on the other four Artificial Analysis scores both have, including the Intelligence Index at max effort (59 against 55) and Terminal-Bench-Science (59% against 53%).

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

Choose Claude Opus 5.5 if

  • Your work is reasoning-heavy research: 68% against 53% on HLE-Diamond
  • You run at the default effort and want the higher score there: 48 at medium against 42 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 terminal work: 64% against 60% on Terminal-Bench 4.0
  • Cost matters: Sonnet's input and output prices are half of Opus 5.5's
  • You want faster answers: 103 output tokens a second at high effort against 77.9 for Opus at medium
  • 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		 59.0 source55.0 source
Intelligence Index at everyday effort 48.0 (medium effort, the API default) source42.0 (high effort, the API default) source
Terminal-Bench 4.0
max effort		 60.0% source64.0% source
HLE-Diamond
max effort		 68.0% source53.0% source
Terminal-Bench-Science 0.1
max effort		 59.0% source53.0% source
Output speed 77.9 tokens/s (medium effort, Artificial Analysis) source103 tokens/s (high effort, Artificial Analysis) source

Benchmark and speed data from Artificial Analysis where linked.

Read more

Sources