Everything about Claude Sonnet 5

Claude Sonnet 5 at a glance

Anthropic released Claude Sonnet 5 on June 30, 2026. It has a reasoning mode: it can "think" before answering, which helps with multi-step problems but uses more tokens, and therefore more money. Its weights are not published, so it only runs remotely, through the Anthropic API or partner hosts (44 listed on models.dev). That makes it 4 months old as of October 22, 2026.

We file it under mid-range models (34 models in this category on the site).

Measured performance

According to results published by Epoch AI (checked on October 22, 2026), Claude Sonnet 5 has a capability index of 79.3 out of 100, computed on 5 benchmarks from our basket.

It is not among the top 30 of the weekly ranking.

• GPQA Diamond (PhD-level science questions): 90.5% — the best tracked model, Gemini 4 Argon, reaches 96.4%
• OTIS Mock AIME (competition mathematics problems): 94.7% — the best tracked model, GPT-5.5 Pro, reaches 100%
• FrontierMath (very hard research-level mathematics): 65.6% — the best tracked model, GPT-6 Astra, reaches 93.7%
• FrontierCode (advanced programming tasks): 42.7% — the best tracked model, Claude Opus 5.5, reaches 54.6%

What it can do

Its context window reaches 1,000,000 tokens, roughly 1,500 pages of text at 500 words per page: enough to load a whole book or a mid-sized codebase. A single answer can run to 50,000 tokens.

It accepts as input: text, image and PDF. Its knowledge stops at January 31, 2026: beyond that, it needs web search or your documents.

It can call tools (functions, APIs), which makes it a possible foundation for an AI agent.

Pricing and budget

Claude Sonnet 5 costs $2 per million input tokens and $10 per million output tokens (median of 44 providers, checked on October 22, 2026).

In practice, an agent task that reads 20,000 tokens and writes 2,000 costs about $0.06, or $60 for 1,000 such tasks.

That is 2.3 times the median output price of mid-range models ($4.38).

To estimate your own budget, use the agent cost calculator.

What is it good for?

Given its category, Claude Sonnet 5 is mainly aimed at a balance between quality and cost, for everyday uses that do not justify a frontier model.

Its FrontierCode result (42.7%, above the median of tracked models) makes it a serious candidate for coding agents.

Its very large context window makes it worth considering for analysing large sets of documents in a single request.

Before adopting it, test it on your own examples: benchmarks measure standard tasks, not your job.

Alternatives

In the same category, the models closest to Claude Sonnet 5 are:

• Gemini 3.1 Pro Preview (Google DeepMind, index 79.3)
• Grok 4.5 (xAI, index 79.1)
• Mistral Large 4 (Mistral AI, index 79.7)
• Grok 4.7 (xAI, index 79.9)