Artificial Analysis' Intelligence Index: Sonnet 5.5 (max) ranks above GPT-6 Astra (max) and behind only Opus 5.5 (max) but has the highest token use of them all

With max effort, Sonnet 5.5 gains 18 points over Sonnet 5 and moves to #2 on the Intelligence Index, behind only Opus 5.5 (max).

Artificial Analysis 2026-09-29

Context & Ripple Effects

Artificial Analysis’ earlier coding-agent measure put GPT-6 Astra alongside several leading models but below Fable 5.1, showing that its competitive position depends on the workload being tested in the coding-agent benchmark. Sonnet 5.5’s result changes the comparison on the Intelligence Index while making output-token consumption an equally visible part of the result.

The index had already tracked a tightening frontier, including max-reasoning GLM-5.3’s 60-point result in August. Sonnet 5.5’s 18-point gain over Sonnet 5 places a mid-tier Claude model near the top of this particular ranking, but with the largest output-token use among the compared models.

First-order effects

Sonnet 5.5 (max) becomes the second-ranked model on the Intelligence Index, ahead of GPT-6 Astra (max), giving buyers a stronger quality result to weigh in model selection.
Its highest-in-comparison token use makes output consumption a direct constraint for teams considering the higher-effort setting.

Second-order effects

OpenAI and other model providers face a comparison in which benchmark standing and token efficiency diverge, pushing evaluation toward performance per output token rather than rank alone.
Enterprise buyers comparing Sonnet 5.5 with GPT-6 Astra will need to test task-level token use alongside benchmark scores, making cost per useful task a more relevant procurement measure.

Third-order effects

If high-reasoning configurations keep raising benchmark scores through greater token use, model competition will increasingly separate raw capability leadership from economical deployment.
Independent indices are becoming a venue for exposing that trade-off across models, rather than treating a single intelligence score as a complete purchasing signal.

The trend: Frontier-model competition is shifting from benchmark rank alone toward the balance between reasoning performance and tokens consumed per useful task.

Discussion

@kimmonismus @kimmonismus on x
Anthropic is dominating the AA Benchmark. Even with their mid-tier model. The top three models are all from Anthropic. Tomorrow, OpenAI's DevDay will either be a huge success - if they unveil something better - or end up overshadowed by Anthropic.
@artificialanlys @artificialanlys on x
Anthropic has launched Claude Sonnet 5.5: it scores 56 on the Artificial Analysis Intelligence Index, just 2 points behind Opus 5.5 (max), but at the highest Output Tokens per Task we've seen With max effort, Sonnet 5.5 gains 18 points over Sonnet 5 and to #2 on the Intelligence …
@miaai_lab Mia on x
what is happening?????
@rynorhn Ryan Orhan on x
SONNET IS ABOVE ASTRA 😭😭😭 what the actual fuck did anthropic do openai you better fucking deliver tomorrow.
@synthwavedd Leo on x
Claude Sonnet 5.5 scores 56 on Artificial Analysis' Intelligence Index. That puts it behind only Claude Opus 5.5, above GPT-6 Astra and miles above GPT-6 Sol. Pretty nuts.
@cameron.stream Cameron on bluesky
I wouldn't say that it's roughly Opus. It seems to have pretty different behavior as it relates to token consumption. — Sonnet 5.5 seems to be kind of a token hog, so it's a different style of use. Opus is smart out of the gate, Sonnet works. — artificialanalysis.ai/article…
@claudeai Claude on x
A thread of early experiments with Claude Sonnet 5.5. A fall foliage simulator by @_re_pete, made with Sonnet 5 vs Sonnet 5.5.
@claudeai Claude on x
Introducing Claude Sonnet 5.5, the second model in the Claude 5.5 family. It's a clear upgrade over Sonnet 5, runs more than 30% faster, and costs up to 30% less for most work.
@levie Aaron Levie on x
At Box, we've been testing Sonnet 5.5 in early access on our complex work eval with the Box Agent, and Sonnet 5.5 is another strong jump from Sonnet 5 on knowledge work with enterprise content. Across the board we saw a 4 pt overall improvement on our hardest tests, but it was ro…
@addyosmani Addy Osmani on x
Today we launched Claude Sonnet 5.5! 30% faster and costs up to 30% less than Sonnet 5 for most work. Strong for well-scoped everyday tasks (fixing bugs, creating docs, slides). @RLanceMartin had models paint the same photo in code. You can see the jump:
@simonw Simon Willison on x
The most important thing about Sonnet 5.5 is that it's now the model that powers the free tier on https://claude.ai/ - so all of this stuff can be done by free users ChatGPT's free tier is still GPT-5.6 Luna, which is a lot less capable
@claudedevs @claudedevs on x
Claude Sonnet 5.5 is out! We wrote a guide for building with it: • choosing between Sonnet 5.5 and Opus 5.5 • migrating from Sonnet 5 and tuning effort • using it in Claude Code https://claude.dev/...
@anthropicai @anthropicai on x
Claude Sonnet 5.5 is now available:
@kunchenguid Kun Chen on x
how did sol go from a fable competitor to a sonnet equivalent in just a few weeks?
@icesolst @icesolst on x
Lmao Anthropic used my photo without credit/permission, never beating the stealing allegations. They're in the middle of MULTIPLE LAWSUITS for exactly this, yet do not care.
@ericmaskfr Eric on x
Sonnet 5.5, the Fortnite test I was not ready for it to one-shot something this close to the real game
@dani_avila7 Daniel San on x
Absolutely recommend keeping Opus 5.5 as the Coordinator model and Sonnet 5.5 as the Thread model. Read the full tutorial to learn how to configure these models inside Claude Projects 👇
@cursor_ai @cursor_ai on x
Sonnet 5.5 is now available in Cursor! It's a strong model, performing on par with Opus in many tasks.
@trq212 @trq212 on x
A lot of times when I talk about higher level abstractions like projects, claude tag and dynamic workflows, I hear concerns about token cost. With Sonnet + Opus 5.5 I think this sort intelligence is should be very available. Try Sonnet 5.5 in particular when making workflows.
@deryatr_ Derya Unutmaz on x
Claude Sonnet 5.5 looks massively improved over Sonnet 5, above GPT-6 Sol, and is claimed to be cheaper at completing tasks then even Sonnet 5! Benchmarks also appear very similar to Opus 5.5, so the advantage of using Opus is unclear, slightly better but more expensive?
@astropol0 Astro Polo on x
Sonnet 5.5 is literally free for everyone... anyone can try it on Claude Code... an Opus 5.5 level model is accessible to everyone you gotta love Anthropic here..
@mikeyk Mike Krieger on x
Sonnet 5.5, the second release in the 5.5 family, is out! It's 30%+ faster than Sonnet 5 and up to 30% cheaper for most work.
@tokengremlin @tokengremlin on x
This is how you challenge OpenAI. Anthropic launched Sonnet 5.5 just one day before DevDay. And the model is fantastic, exactly like many of us already knew. It only falls behind Opus 5.5 in a few areas that honestly aren't that important. Overall, this is an incredible launch. A…
@hesamation @hesamation on x
Dario dropping models faster than ever since calling for “pacing” the frontier
@mweinbach Max Weinbach on x
It seems like Anthropic has fixed their smaller models, Opus 5.5 is genuinely fantastic and Sonnet 5.5 seem to be extremely good too (trying it out now) Prices of models are going down, intelligence is going up, speed is going up. It's such a great trend.
@bcherny Boris Cherny on x
Sonnet 5.5 fixing a bug with Claude Code. 30% faster and 30% less usage.
@__alpoge__ Levent on x
“Claude Haiku 5.5 ... will join the Claude 5.5 family in the coming weeks.” https://www.anthropic.com/...
@shub0414 Shub on x
please don't nerf Opus 5.5 please don't nerf Opus 5.5 please don't nerf Opus 5.5 please don't nerf Opus 5.5
@robertjbye Robert Bye on x
30% faster and 30% less. Also my favourite model for day to day queries, quick bits of work, and sub agents.
@hesamation @hesamation on x
WTH, Anthropic is doing some voodoo magic to make their models smarter and more efficient at the same time: > 30%+ faster according to Anthropic > 76% fewer tokens than Sonnet 5 (497k → 121k) according to Balyasny > ~14% fewer output tokens according to Slack [image] [embedded po…
@kimmonismus @kimmonismus on x
Let that sink in: “it costs up to 30% less per task than its predecessor. It also generates output more than 30% faster, making it our fastest Sonnet model to date.
@alexfinn Alex Finn on x
This is bigger news than it appears I've had early access to Sonnet 5.5 for a bit now and honestly at first I couldn't tell the difference between this and Opus 5.5 It's a fraction of the price of Opus, which already felt like you got an absurd amounts of usage out of for cheap I…
@claudedevs @claudedevs on x
Sonnet 5.5 is smarter, more efficient, and 30% faster than Sonnet 5. We've seen as much as 20% lower costs on the Claude Platform and 30% more usage in Claude Code. Use it for well-scoped everyday tasks like fixing bugs and quickly iterating on features.
@haider1 Haider on x
damn sonnet 5.5 is better than opus 5.5 on Terminal-Bench, basically tied with it on knowledge work and computer use, while being 2x cheaper anthropic really compressed most of the opus experience into sonnet this time
@matthewberman Matthew Berman on x
Sonnet 5.5 basically Opus 5.5 but 50% cheaper and much faster. I've been early testing it and it's incredible. If this is pacing the frontier, sign me up. Demos down below 👇 3D simulation is solved:
@kunchenguid Kun Chen on x
sonnet 5.5 is here! very good addition that finally gives a cheaper workhorse in the anthropic line-up haiku coming soon
@alexalbert__ Alex Albert on x
Sonnet 5.5 has the same feel I liked about Opus 5.5. It writes clearly, it's very fast, and it's a major capabilities jump over Sonnet 5. Really great model to iterate with.
@ash_twtz Mr Ash on x
The fourth tier model of a 5 year old company is beating the flagship model of a trillion dollar company like Google. This is absolutely insane.
@claudeai Claude on x
On our automated behavioral audit, Sonnet 5.5 improves on or matches Sonnet 5 on most measures of alignment and honesty. It's also the first Sonnet model with cyber safeguards and fallbacks like those on our most capable models. Routine software development is unaffected.
@kimmonismus @kimmonismus on x
HOLY these Benchmarks are insane! It even surpasses Opus 5.5 in Terminal Bench 4.0! What is Anthropic doing?! this is nuts!
@claudeai Claude on x
Sonnet 5.5 also has a knack for design. It adds polish to user interfaces and follows templates to create slides that need minimal editing.
@claudeai Claude on x
On several benchmarks, Sonnet 5.5 at Low or Medium effort beats Sonnet 5's best score for about a tenth of the cost.
@claudeai Claude on x
Sonnet 5.5 is priced the same as Sonnet 5, but it typically needs far fewer tokens to do the same work. In our testing, it costs up to 30% less per task than its predecessor. It also generates output more than 30% faster, making it our fastest Sonnet model to date.
@claudeai Claude on x
Sonnet 5.5 improves on Sonnet 5 across benchmarks, in some cases dramatically. It's a faster, lower-cost complement to Claude Opus 5.5, strongest at well-scoped everyday tasks, fixing bugs, and creating polished documents, slides, and spreadsheets.
@synthwavedd Leo on x
Anthropic are on a cooking spree. Sonnet 5.5 is here and it's only slightly worse than Opus 5.5, and in some areas even outperforms it, at a price point of $2 per Mtok in and $10 per Mtok out. A leap over Sonnet 5 🫡
r/ClaudeAI r on reddit
Introducing Claude Sonnet 5.5, the second model in the Claude 5.5 family
Mike Krieger Mike Krieger on linkedin
We just shipped Claude Sonnet 5.5! — Sonnet 5.5 is the model to help you get more work done, faster. …
@peark.es George Pearkes on bluesky
Anthropic continues to take the premium approach with Sonnet 5.5, same cost as Sonnet 5 (though they claim it is much more token efficient, I obviously have no idea if that's true or not).
r/singularity r on reddit
Claude Sonnet 5.5 Released
r/accelerate r on reddit
Introducing Claude Sonnet 5.5

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