Claude Sonnet 5.5
Near-top coding, agents and research for half Opus 5.5's token price; for writing, pick Opus 5.5 or Gemini 3.8 Flash.
This product is made by Anthropic, whose Claude models help draft our reviews. How we keep that from tilting a score
Should you use it?
Pick it if
Most people who code or run agents and want near-top results on a budget or the Free plan.
Best for: Everyday coding and agents with near-top results on a budget (Chat models Top 20)
Skip it if
Writing quality is your main need; Opus 5.5 ranks 2nd on Creative Writing, and the best non-Anthropic pick, Gemini 3.8 Flash, 7th s7.
You give up: Behind the leaders on creative writing; breaking API changes from Sonnet 5
The short version
- What this is
- Anthropic's mid-size model, released 28 Sep 2026, in the Claude apps, Claude Code and the API.
- Why it matters
- It ranks close to Opus 5.5 on coding, agents and hard questions for half the price, so many people can save money.
- Third on arena.ai WebDev, fourth on Agent, third on Expert s1 s3 s6; scores 96 for research and 89 for coding.
- API $2 / $10 per 1M tokens, half of Opus 5.5 s10.
- Weaker at creative writing: rank 24 of 412 s7.
Good at
Weak at
Our take
Sonnet 5.5 is the value pick in Anthropic's line. It ranks third on arena.ai WebDev s1 and second on the Artificial Analysis index s5, close to Opus 5.5, for half the token price s10. Its research and agents ranks still have wide spreads with few votes s3 s6, so they may settle lower as votes come in.
Writing is the gap. It sits at rank 24 on Creative Writing s7, well behind Opus 5.5. Note that its best scores come from the xhigh and max settings; at high effort it scores 47 on the Artificial Analysis index against 56 at max s5.
On the Free plan, Claude's pricing page says Sonnet is included but does not name the version; PCWorld reports Sonnet 5.5 is the free default s9 s15.
Scores by job
A score from 0 to 100 per job, against everything available today. Overall 88 across 3 jobs, the average of the job scores.
New to this? What the scores and labels mean
- 0 to 100
- Our score for one job, like writing or coding, compared with everything else out today. 100 is the best available today. For AI models we build it from public data, such as Arena's blind votes and Epoch AI's independent tests; apps and tools are scored on our own checklist. The same tool can score differently for different jobs, and where two likely ranges overlap, we call it a tie.
- Our verdict
- Use it: a top choice for most people. Worth trying: good, and worth a go. Depends: good for some people or one kind of job. Wait: too early to tell, or not out for everyone yet. Skip: something else does the job better.
- First look
- Just released. We say what it is and whether to bother, and give it a score once public results exist.
- No score yet
- None of the public sources we use covers it yet, or the only evidence is from a source whose numbers we can't use, so we describe it in words instead.
- Best buy
- Nothing cheaper scores as well for that job.
- Best free
- The best score for that job that costs nothing, through a free plan or by running on your own computer.
- Pay as you go
- No monthly plan: you pay for each use, usually through a developer account.
- Checked
- The day we last confirmed the score and the price against the sources. Prices change often, so check the date.
- AI model
- The engine underneath, like GPT or Claude. You use it through an app or, if you code, directly.
- Open source
- Free to download and run on your own computer, so nothing leaves your machine.
#6 of the 15 we have scored for this job.
From blind votes (Arena) and independent tests (Epoch AI) · Arena data, CC BY 4.0, Epoch AI data, CC BY 4.0
2 sourcesData read 20 Oct
#2 of the 21 we have scored for this job.
From blind votes (Arena) · Arena data, CC BY 4.0
1 source so farData read 20 Oct
#4 of the 12 we have scored for this job.
From blind votes (Arena) · Arena data, CC BY 4.0
1 source so farData read 20 Oct
#5 in Arena's blind votes for agents. Those votes give a rank but no rating, so there is no score yet.
#5 in Arena's blind votes for agents (rank only, no score yet) · Arena data, CC BY 4.0
2 sourcesData read 20 OctOn the $20/month plan
Alternatives
Better or cheaper for agents, from our scores, then the ones we'd also look at. The same kind of product comes first.
- Claude Opus 5.5BetterText model#1$20 a monthRanked #1 on Arena's Agent board in agents, against #5 here; $20 a month. First on WebDev and Agent, and much stronger at writing, for twice the token price. GPT-6 Astra, second on both, is the best non-Anthropic option s1 s3. Side by side
- Gemini 4 ArgonCheaperText model#6$4.99 a monthRanked #6 on Arena's Agent board in agents for $4.99 a month, against $20 a month here. Side by side
- Claude Haiku 5.5Text model44CodingPay as you goA twentieth of the token price for simple, high-volume tasks. Side by side
- Gemini 3.8 FlashText model91Writing$19.99 a monthBest non-Anthropic writing pick we review: 7th on Creative Writing, though its rank is preliminary s7. Side by side
Value for money
Where it sits in agents: higher is a better score, further left is cheaper. Green dots are the Best buys.
Evidence
Everything behind the call and the scores, folded so the page stays short. Spotted a wrong price, score or link? Report a mistake.
How we scored this
The research, coding and writing scores are our own, built from public data: blind votes on Arena and, where they cover the job, Epoch AI's independent tests. How we combine them is our method and we don't publish it. For agents, Arena's blind votes give a rank but no rating, so we show the rank and no score yet.
Public leaderboardIndependent test
This product is made by Anthropic, whose Claude models help draft our reviews.
Reviews are drafted with help from AI models, including Anthropic's Claude. Model scores come only from outside leaderboards and independent evaluations, by a written rule.
No one paid for this review or gave us free access, and we earn nothing if you sign up. How we score
Sources 15
- s1arena.ai Code Arena: WebDev leaderboard
- s2arena.ai Text: Coding leaderboard
- s3arena.ai Agent leaderboard
- s4arena.ai Agent Pareto and cost per task
- s5Artificial Analysis LLM leaderboard
- s6arena.ai Text: Expert leaderboard
- s7arena.ai Text: Creative Writing leaderboard
- s8arena.ai Text: Instruction Following leaderboard
- s9Claude plans and pricing
- s10Claude API pricing
- s11Claude privacy: is my data used for model training (consumer)
- s12Claude privacy: is my data used for model training (commercial)
- s13Anthropic: Introducing Claude Sonnet 5.5
- s14Claude Sonnet 5.5 model overview
- s15PCWorld: Claude Sonnet 5.5 is here (29 Sep 2026)
Something here out of date or wrong? Report a mistake and we will check it against the source.
History 5 changes
Every change to a rating, the price or our call, with the reason. Scores are against what exists on the day, so they drift down as better things ship. Older entries come from before we moved to scores.
- New: Coding ratedNew: Agents ratedNew: Research ratedNew: Writing ratedReviewed: coding, agents, research, writing.
- Worse: Coding downBetter: Writing upAudit: re-derived the ratings with our rule of counting each model once on a leaderboard. Coding moved down a step (Text Coding is 16th of distinct models, below its WebDev rank). Writing moved up a step (Instruction Following is 10th of distinct models). best_category now agents. Agent cost relabelled as the 14-day median; PCWorld cited for the free-plan model.
- Marked the agents rating as $20/month: the free Claude plan has no agent features, and the Agent board measures paid API use. Rating unchanged.
- Audit: where the page points to Opus 5.5 as the better option, it now also names the best non-Anthropic option (Gemini 3.8 Flash for writing, GPT-6 Astra for coding and agents). Ranks re-confirmed on arena.ai. Ratings unchanged.
- Plainer how-to-get-it wording; no rating change.
Use it well 4 guides on this site
Pages on this site that help with the jobs above.