The Every team runs as much work as possible through agents. To help the whole team share skills when a new model comes out, they built a company agent on Claude Managed Agents that everyone uses in Slack. Once it caught on internally, they released it to their subscribers.

We’re expanding our Cyber Verification Program to give security professionals broader access to our most capable models. Through this program, verified security professionals can access Claude Mythos 5.1, Opus 5.5, and Sonnet 5.5 with safeguards designed for defensive work.

Expanding the Cyber Verification Program

We’re launching a new, expanded version of our Cyber Verification Program (CVP), which makes advanced cyber capabilities and reduced blocking classifiers available to qualifying security professionals.

anthropic.com

Cloud sessions run Claude Code on a fresh VM for each task, so you can start several at once and they keep going when you close your laptop. We wrote a field guide with seven workflows that suit them, plus how to connect GitHub on the first try. https://claude.dev/blog/claude-code-in-the-cloud

Claude Code in the cloud: a field guide to cloud sessions / claude.dev Blog

Cloud sessions run Claude Code on a fresh VM for each task. Four real sessions, seven workflows that suit them, and how to connect GitHub without getting stuck.

claude.dev

Claude now works inside Google Docs, Sheets, and Slides, and those files also open inside Claude. In Google Workspace, Claude sits in a sidebar next to your file, reads what you have open, and edits it in place. You can approve each edit before it lands.

The Claude Startups program is expanding to more founders. Members can get a year of Claude Team, API credits, special offers on the tools a startup runs on, and office hours with Anthropic’s Applied AI team.

We're adding a new plugin to Claude Code: You should Know. It scans Claude's output for important information you might miss to help keep you in the loop. Enable it with: /plugin enable cc-plugin-you-should-know@builtin

Lots of inventive things made with Claude these past few weeks. A few of our favorites: A working watermill, built with Opus 5.5.

In physics, an “impedance mismatch” occurs when two systems each work well but are poorly matched.

Claude-shaped science

Matthew Schwartz describes what happened when he stopped fighting Claude and allowed Claude to find “Claude-shaped” problems. This led him to build BootLoops, a toolkit for exact calculations in quantitative science, which he has been applying across scientific fields alongside experts.

anthropic.com

You can now mod Claude Code: - Change how it behaves - Customize the UI - Swap in your own features Write one with a few lines of TypeScript, or have Claude build it for you. Mods ship inside plugins, so you install them with /plugin in the CLI or desktop app. A few examples:

For two weeks, start a design, deck, or doc in the Claude app, and the work that follows in that conversation uses 50% less of your usage limits. Give it a try with Claude Sonnet 5.5. It has a strong eye for design and builds slides that need minimal editing.

Anthropic {bot}@anthropicai.xmirror.bot · 3w ago

You can also now make decks, docs, and designs in your conversation. Draft the one-pager in Claude Docs, turn it into a deck with Claude Slides, and mock up a matching visual in Claude Design, all from one place.

https://Claude.dev is our new home for developers building with Claude. You'll find engineering deep dives, Claude Code and API guides, tips from the teams building Claude, and some fun easter eggs.

Claude Founder House is coming to SF Tech Week (Oct 6–8) and Stockholm (Oct 14). Come for talks, workshops, and office hours with our team, plus time to meet others building with Claude. Whether you're a founder, a CEO, or a builder, there's a session for you.

What do you want from AI? We’re launching a new study with Anthropic Interviewer to learn more about your experiences using AI, what role you want it to play in your life and the world, and what you want from the companies building it.

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/blog/building-with-claude-sonnet-5-5/

Claude can now help you build evaluations and hillclimb on them. In this article, we share guidance on eval design & skills that Claude Code can use to improve your applications. https://claude.dev/blog/automating-eval-design-and-hillclimbing/

Automating eval design and hillclimbing with Claude / claude.dev Blog

Principles for designing evals and hillclimbing against them without fooling yourself, and how the claude-api skill's build-eval and hillclimb commands put them to work.

claude.dev

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.

Sonnet 5.5 is smarter, more efficient, and 30% faster than Sonnet 5. It costs up to 30% less for most work, so your Claude Code usage goes further too. Use it for well-scoped everyday tasks like fixing bugs and quickly iterating on features.

Anthropic {bot}@anthropicai.xmirror.bot · last wk.

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.

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.

Claude Sonnet 5.5 is now available:

Claude (@claudeai) 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.

x.com

It’s now easier to build plugins for Claude. We built a new portal to submit your plugin, track review, and see usage. Plugins package MCP and skills, and are becoming the way to build for Claude. MCP usage across Claude products is up 110x this year!

Build plugins for Claude with the directory submission portal | Claude by Anthropic

Submit plugins to the Claude directory through a new directory submission portal. Package MCP connectors and Agent Skills, track your plugin through review, and see how it's used and found once it's live

claude.com

Claude Code will now try to find a graceful stopping point when you hit your 5-hour limit mid-task, instead of cutting off mid-edit. It gets a small, fixed allowance pulled from your weekly limit to wrap up what it can.

Opus 5.5 is 20% cheaper per input and output token than Opus 5, and 60% cheaper on cache reads. So what does that actually do to the cost of a task in Claude Code? We ran the numbers, and built a calculator so you can run yours from /usage: https://claude.dev/blog/what-a-task-costs-on-opus-5-5/

What a task costs on Opus 5.5 / claude.dev Blog

The same token price can cost very different amounts per task. Learn what Claude Code tasks cost on Opus 5.5 and which settings change the bill.

claude.dev

New on the Science Blog: Yes, Claude can do Nine Loops.

Claude gives us N=4 super Yang-Mills to nine loops

Claude gives us N=4 super Yang-Mills to nine loops

anthropic.com

Claude FM 🎵 music for thinking and building https://x.com/i/broadcasts/1YGNrbqpRvNGw Link: https://t.co/ORVEHOr1Dh Link: https://x.com/i/broadcasts/1YGNrbqpRvNGw

Claude Opus 5.5 has been out for a few days. Some of our favorite things people have explored and discovered with it so far: https://x.com/RyanSael/status/2102591147927654847?s=20

Today, we'll resume charging for requests our safeguards block before Claude responds. This only applies in categories with low false positive rates: biology, distillation attacks, and frontier LLM development.

Refusals and fallback

How Claude Fable and Claude Opus models return classifier refusals and how to retry refused requests on a fallback model.

platform.claude.com

Sorry for any confusion! Cloud sessions run on your Pro or Max plan, like the rest of Claude Code. This promo is an optional one-time credit that your cloud sessions spend first, before falling back onto your normal plan usage. We hope you enjoy the credits!

Anthropic {bot}@anthropicai.xmirror.bot · 2w ago

Cloud sessions are officially available and out of research preview! They let you keep Claude Code working, even when your laptop is closed. Existing subscribers get a one-time credit to try them: $100 on Pro, $250 on Max.

In the Democratic Republic of the Congo, global health organizations including @CEPIvaccines, @WHOAFRO, and @inrb_kinshasa are using Claude to accelerate their response to an outbreak of an unusual Ebola variant. Read the full piece here: https://www.anthropic.com/features/ebola-response

The Situation Report

A rare Ebola strain is spreading in the DRC, with no confirmed vaccine. Global health organizations are using Claude to respond as fast as possible.

anthropic.com

We've just added local support to Projects in Claude Code, so threads can now run on your own machine.

Anthropic {bot}@anthropicai.xmirror.bot · 3w ago

Today we're rolling out Projects in Claude Code on desktop and web. A project is one conversation with Claude. It splits the work into threads itself, runs them as parallel cloud sessions, passes context between them, and keeps going when you leave. In beta for select users.

Cloud sessions are officially available and out of research preview! They let you keep Claude Code working, even when your laptop is closed. Existing subscribers get a one-time credit to try them: $100 on Pro, $250 on Max.