Anthropic releases Claude Sonnet 5.5 — 30% faster, Opus-5.5-level scores on several benchmarks at $2/$10
Six days after Opus 5.5, Anthropic released Claude Sonnet 5.5 (`claude-sonnet-5-5`) on September 28, 2026. It keeps Sonnet 5's price ($2/$10 per million tokens) but runs 30%+ faster and costs up to 30% less per task because it uses fewer tokens and tool calls. It nearly matches Opus 5.5 on GDPval-AA and OSWorld and beats it on Terminal-Bench 4.0.
Key facts
- Released September 28, 2026; model id claude-sonnet-5-5; on Claude Platform, AWS/Bedrock, Google Cloud and Microsoft Foundry
- Pricing per 1M tokens: $2 input / $10 output; cache reads $0.20; cache writes $2.50 (same as Sonnet 5)
- Terminal-Bench 4.0: 70.6% (Sonnet 5: 10.3%; Opus 5.5: 66.4%)
- GDPval-AA v2.1: 1844 (Opus 5.5: 1846; Sonnet 5: 1449); AA-Briefcase v1.1: 1811
- OSWorld 2.1: 80.1% (Opus 5.5: 81.8%); CursorBench 4.0: 55.5%; FrontierCode 1.1 (High): 46.2%
- Context 1M tokens, max output 128K, adaptive thinking, default effort 'high', knowledge cutoff June 2026 (docs comparison table)
- First Sonnet model to beat Pokémon Red working only from screenshots (per press coverage)
- Cyber safeguards similar to Opus 5.5; biology safeguards match Sonnet 5; Haiku 5.5 promised 'in the coming weeks'
What happened
Anthropic shipped Claude Sonnet 5.5 on September 28, 2026 as the "faster, lower-cost complement" to Opus 5.5 (released Sept 22). Anthropic says it is strongest at well-scoped everyday tasks, fixing bugs, and making polished documents, slides and spreadsheets. It also has "a strong eye for design".
Benchmarks from the announcement page (Sonnet 5.5 / Sonnet 5 / Opus 5.5):
| Benchmark | Sonnet 5.5 | Sonnet 5 | Opus 5.5 |
|---|---|---|---|
| Terminal-Bench 4.0 | 70.6% | 10.3% | 66.4% |
| FrontierCode 1.1 (High) | 46.2% | 42.4% | 54.4% |
| CursorBench 4.0 | 55.5% | 34.1% | 57.8% |
| GDPval-AA v2.1 | 1844 | 1449 | 1846 |
| AA-Briefcase v1.1 | 1811 | 1359 | 1822 |
| OSWorld 2.1 | 80.1% | 57.0% | 81.8% |
Price is unchanged from Sonnet 5 ($2/$10). Anthropic says the per-task savings come from using fewer tokens and tool calls. New anti-distillation classifiers and "preserved thinking" also apply. YouTube reviewers quickly ran Sonnet 5.5 vs Opus 5.5 comparisons, and several argued Sonnet 5.5 is the better value.
Why it matters
Sonnet 5.5 roughly matches the new flagship on knowledge-work and computer-use benchmarks at half the price. That squeezes the value of the Opus tier within a week of its launch and continues the 2026 price war with OpenAI's GPT-6 Sol and Luna.
Changelog
- 2026-09-29: created
Videos (18)
Introducing Claude Sonnet 5.5
Claude · 2026-09-28 · officialThis short promotional teaser serves as a brand bumper and announcement title card for Anthropic's Claude Sonnet 5.5. It features a rapid montage of sensory, natural, and mechanical imagery synced to rising sound effects and an orchestral tone, concluding with the model's name and the Claude logo framed against an…
I Tested Sonnet 5.5 vs Opus 5.5. What You Need to Know.
Nate Herk | AI Automation · 2026-09-28 · reviewNate Herk from AI Automation Society (AIS) benchmarks Anthropic’s Claude Sonnet 5.5 against Claude Opus 5.5 across seven real-world workflow tasks. He compares both models on execution time, input/output token usage, API cost, and aesthetic/functional output quality. Ultimately, Sonnet 5.5 wins 4 to 3 based largely…
I Tested Sonnet 5.5 vs Opus 5.5 (WILD RESULTS)
Brock Mesarich | AI for Non Techies · 2026-09-28 · reviewAn independent presenter evaluates and benchmarks Anthropic’s Claude Sonnet 5, Sonnet 5.5, Opus 5.5, and Fable 5.1 by having each model generate a full 3D interactive browser game from an identical detailed prompt. He tests the playable outputs in real-time, assessing gameplay, visual quality, and stability while…
Sonnet 5.5 Is Faster, Cheaper, and Better Than Opus 5.5. What Is Going On?
Universe of AI · 2026-09-28 · reviewA commentator from the YouTube channel Universe of AI reviews the surprise release of Anthropic’s Claude Sonnet 5.5 on September 28, 2026, just ahead of OpenAI DevDay 2026. The video walks through official benchmarks, side-by-side generation demos, third-party tests, and Artificial Analysis charts evaluating Sonnet…
Sonnet 5.5 created its own show reel
AI WITH Rithesh · 2026-09-29 · ai-madeUploaded by the channel AI WITH Rithesh, this video is an AI-generated animated musical showreel celebrating the launch of Anthropic's Claude Sonnet 5.5. Set to a gentle synthesized vocal ballad, the piece visualizes the model's capabilities—such as coding, debugging, agentic execution, and honesty about…
I Tested Sonnet 5.5 (Here Is What You Need to Know)
Никита Ефимов | ИИ и автоматизация · 2026-09-29 · reviewNikita Efimov reviews Anthropic's newly released Claude Sonnet 5.5, analyzing its benchmark performance, pricing structure, and cost efficiency relative to Claude Opus 5.5 and Claude Fable 5.1. He demonstrates why Sonnet 5.5's 50% cheaper token price does not necessarily translate to lower task costs on complex…
More videos (12)
- Claude Sonnet 5.5 Just Dropped Akinyemi Bajulaiye · 2026-09-29
- Claude Sonnet 5.5 Is INSANE – Seriously, This Model Is Ridiculous! Bijan Bowen · 2026-09-29
- Vibe Coding With Claude Sonnet 5.5 BridgeMind · 2026-09-29
- Anthropic Just Dropped Claude Sonnet 5.5 (MAJOR UPGRADE) Brock Mesarich | AI for Non Techies · 2026-09-29
- Claude Sonnet 5.5 is LIVE & Somehow Beating Opus 5.5 Chase AI · 2026-09-29
- I Tested Sonnet 5.5 vs Opus 5.5 vs GPT 6 Astra (No Hype Assessment) Chase AI · 2026-09-29
- NEW Sonnet 5.5 Is Opus 5 Level Mehul Mohan · 2026-09-29
- Claude Sonnet 5.5 a TERMINÉ OpenAI : Claude est devenu cheaté Melvynx · 2026-09-29
- Sonnet 5.5 is Here! It's Insane at Making Videos (7 Incredible Examples) Peter Yang · 2026-09-29
- Claude Sonnet 5.5 - Benchmarks and Pricing | Beats Opus 5.5 and GPT-6 Sol? United Top Tech · 2026-09-29
- Sonnet 5.5 Just Changed Design Forever (free prompts) Viktor Oddy · 2026-09-29
- HUGE Fable 5.5 LEAK, Sonnet 5.5 IS INSANE, GPT 6.1, Qwen 4.0, Kimi K3.1 & More! AI NEWS WorldofAI · 2026-09-29
All videos with Gemini's descriptions: videos · llms-full.txt
Related posts (1)
- Introducing Claude Sonnet 5.5 Claude @claudeai · x · 2026-09-28
Launch post for the second model of the Claude 5.5 family.
Related events
- Anthropic releases Claude Opus 5.5 — Fable-5.1-level performance at $4/$20, first model of the Claude 5.5 family ★★★★★
- Anthropic releases Claude Sonnet 5, "the most agentic Sonnet yet" ★★★
Sources (8)
- officialIntroducing Claude Sonnet 5.5 (Anthropic)
- paperClaude Sonnet 5.5 System Card
- docsSonnet 5.5 migration guide
- pressTechCrunch: Anthropic releases Sonnet 5.5
- pressVentureBeat: Sonnet 5.5 with 30% cost reduction per task
- pressSiliconANGLE: Sonnet 5.5 runs 30% faster
- pressThurrott: Anthropic Releases Claude Sonnet 5.5
- videoIntroducing Claude Sonnet 5.5 (official video)
id: 2026-09-28-claude-sonnet-5-5 · updated 2026-09-29 · open in the interactive timeline