--- title: "Claude Sonnet 5.5 for Your Company | By The People Tech" description: "Claude Sonnet 5.5, released 28 September 2026, is 30% faster than Sonnet 5, and Sonnet 4.5 retires from the API on 30 November 2026. How to migrate." url: https://bythepeople.tech/claude/whats-new/claude-sonnet-5-5 --- [Claude for Business](/claude) [What’s New](/claude/whats-new) Sonnet 5.5 and the Sonnet 4.5 retirement Model + Deadline Released 28 September 2026 · 2 min read # The everyday model got faster, and _cheaper_ per task. Claude Sonnet 5.5 runs more than 30% faster than Sonnet 5 and costs up to 30% less per task, at the same list price. Two days later Anthropic set a retirement date for Sonnet 4.5. Sonnet 4.5 retires in **28** days 30 Nov 2026 · claude-sonnet-4-5-20250929 Move to Claude Sonnet 5.5 Price per M tokens $2 in · $10 out Speed vs Sonnet 5 30%+ faster Cost per task Up to 30% less Timeline 1. 28 Sep Sonnet 5.5 released 2. 30 Sep Sonnet 4.5 retirement announced 3. 7 Oct Cache reads halved to $0.10 4. 30 Nov Sonnet 4.5 stops working on the API On this page * [What changed](#changed) * [Sonnet or Opus?](#rule) * [What it means](#means) * [Migration checklist](#steps) * [Questions](#questions) Reviewed by [Fatjon (Tony) Kalemaj](/about-us/fatjon-tony-kalemaj) COO & Head of Applied AI 01 · What changed ## What Anthropic shipped. Anthropic positions Sonnet 5.5 for well-scoped everyday work: polished documents, slides, spreadsheets and bug fixes. Opus 5.5 stays the model for complex, open-ended work that needs sustained judgment. Anything in your firm still calling Sonnet 4.5 through the API has until 30 November 2026 to move. Speed and cost 30%+ faster And up to 30% less per task, because it needs fewer tokens to do the same work. Price $2 / $10 Per million input / output tokens, same as Sonnet 5. Cache reads now $0.10. Retirement 30 Nov 2026 Sonnet 4.5 leaves the Claude API. Anthropic recommends moving to Sonnet 5.5. The one-line rule for your team ### Sonnet 5.5 For the work you can describe in a sentence: board packs, client updates, reformatting a model output into a slide. ### Opus 5.5 For the work you would hand to your most senior analyst: reading a long agreement, forming a view. 02 · What it means ## What it means for _your_ seat. ### Leadership The cost of everyday AI work keeps falling while the list price stays flat. That makes it cheaper to put Claude in front of more people, which is where the return actually comes from. ### Your teams Board packs, client updates, reformatting a model output into a slide: Sonnet 5.5 is built for that work and is fast enough to iterate on. Keep Opus 5.5 for reading a long agreement or forming a view. ### IT and engineering Code written for Sonnet 5 can break in five ways, including forced tool use returning a 400 error and a new way to turn off up-front thinking. Anything still on Sonnet 4.5 through the API has until 30 November to move. 03 · Before 30 November ## Migration checklist. 0 of 3 done 1. 01 · Find anything on Sonnet 4.5 : Ask whoever owns your integrations for every API call that names claude-sonnet-4-5. Each one needs a tested replacement before 30 November 2026. 2. 02 · Write the one-line model rule : Sonnet for drafting and formatting, Opus for judgment. A rule nobody has to look up is a rule people follow. 3. 03 · Re-run one real task : Take a document task your team did last week and run it on Sonnet 5.5. Compare time and quality. That comparison is worth more than any benchmark. Sources Facts and dates are Anthropic’s own. What it means and what to do are our view, from the firms we work with. Drafted with Claude from these sources, reviewed by Fatjon (Tony) Kalemaj and published 13 October 2026. * [Anthropic: Introducing Claude Sonnet 5.5](https://www.anthropic.com/claude-sonnet-5-5) * [Claude Platform release notes, 28 and 30 Sep 2026](https://platform.claude.com/docs/en/release-notes/overview) * [Claude model deprecations](https://platform.claude.com/docs/en/resources/model-deprecations) ## The short answers. ### When does Claude Sonnet 4.5 retire? On 30 November 2026, from the Claude API. Anthropic announced it on 30 September and recommends moving to Sonnet 5.5. ### Does Sonnet 5.5 cost more than Sonnet 5? No. It is $2 per million input tokens and $10 per million output tokens, the same as Sonnet 5, and Anthropic says it costs up to 30% less per task because it needs fewer tokens. Cache reads cost $0.10 per million since 7 October 2026. ### Should my company use Sonnet or Opus? Sonnet 5.5 for well-scoped everyday work such as drafting, formatting, slides and spreadsheets. Opus 5.5 for complex, open-ended work that needs sustained judgment. Anthropic places Sonnet 5.5 two points below Opus 5.5 on GDPval-AA. Read next [30 October 2026 : Claude Opus 4.8 fast mode deprecation](/claude/whats-new/claude-opus-4-8-fast-mode-deprecation) [28 October 2026 : Smart reports, surveys and pooled group budgets](/claude/whats-new/claude-enterprise-smart-reports-pooled-budgets) [23 October 2026 : Claude chat and Cowork unify for Enterprise](/claude/whats-new/claude-cowork-chat-unified-enterprise) Newsletter ## Never miss a _deadline_ again. One email when something ships or retires that matters to a company: what changed, what it means, the date and what to do. Unsubscribe any time. Work email How did you hear about us? How did you hear about us? ChatGPT Claude Perplexity Another AI assistant Google or Bing search LinkedIn YouTube Someone referred me An event or webinar Our newsletter Somewhere else ## Need help moving before 30 November? Our forward deployed engineers work inside client teams to find, test and move what still runs on Sonnet 4.5. [Book 30 minutes with Tim](https://calendly.com/timminer-1/chat-with-tim) [hello@bythepeople.tech](mailto:hello@bythepeople.tech?subject=Claude%3A%20Sonnet%205.5%20and%20the%20Sonnet%204.5%20retirement)