Official updates for developers building with @ClaudeAI
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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
claude.dev/blog/building-wit…
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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.
claude.dev/blog/automating-e…
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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.
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.
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We’re extending preserved thinking with Sonnet 5.5 to curb distillation attacks via account-switching. Thinking stays in the original org that generated it, so if you switch accounts mid-session, Claude will reread the session and generate new thinking. platform.claude.com/docs/en/…
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Sonnet 5.5 is available now in the Claude Platform and Claude Code.
We granted all Pro, Max, and Team users a reset last Tuesday. If you haven’t used it yet, you can still apply it whenever you want, before Oct 22. clau.de/reset
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What is effort really? When do you change it it and why not just use max effort for everything?
I dove deep into this problem, looking into evals and doing my own tests and I was quite surprised by the results.
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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!
claude.com/blog/build-plugin…
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Plugins are the main way for third-party developers to create extensions for Claude. Over the coming weeks, one discovery experience will roll out across Claude and Claude Code.
Read the blog to learn more: claude.com/blog/build-plugin…
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Go build plugins for Claude!
claude.com/docs/build/overvi…
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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.
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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:
claude.dev/blog/what-a-task-…
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Claude FM 🎵 music for thinking and building nitter.net/i/broadcasts/1YGNrbqpR…
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ClaudeDevs retweeted
Claude Tag in Slack can now use your personal connectors!
You can now securely access that Drive doc, Salesforce account, or Warehouse table that you have personal access to right where the work happens.
Avail. on Teams today and Enterprise next week
claude.com/blog/claude-tag-n…
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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. We've seen some coordinated attacks on our systems in recent weeks, and this is one layer of defense.
In recent testing, 99.7% of accounts using Claude Code, Claude.ai, or Cowork did not hit any of these newly "billable blocks." The classifiers behind the blocks we’re resuming charging for today are tuned to have a <0.1% false positive rate. We know that's not 0%, and we're going to keep improving them so they interrupt your work less often. If you think a request has been blocked incorrectly, please report it with /feedback in Claude Code. platform.claude.com/docs/en/…
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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!
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.
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