I had a great time at CwC Japan showing off some cool features of the Claude Platform: Prompt Caching, Tool Search, Programmatic Tool use, compaction, and Advisor. All get better with Fable 5:-) thanks @rodhowarth for being a great demo partner

I’d heard from some that they felt model progress since December was incremental, things were slowing down. But Anthropic was only publicly offering their second best model. This model card kind of reminds me of that scene in The Princess Bride where Inigo Montoya says “I’m not left handed”.

Claude Fable 5 is our first generally available Mythos-class model. It ships with new safety classifiers that may flag certain prompts in dual-use domains like cyber and bio. We've added fallbacks: a refused request retries on Claude Opus 4.8 instead of dead-ending.

You can get a taste of Fable for a fraction of the cost with Advisor... platform.claude.com/docs/en/…

As a powerful model, Fable does hit classifiers a bit more frequently, so we developed an easy solution with server side fallbacks: platform.claude.com/docs/en/…

Fable has been a huge change for how I work. I am able to delegate high level long running, complex tasks and with minimal oversight. I can't wait to see what you build! anthropic.com/claude/fable

We just published internal data on how much of Claude's development is already being done by Claude: - Over 80% of all code merged into our codebase is now written by Claude - It's been months since many researchers at Anthropic hand-wrote code - The typical Anthropic engineer ships 8x as much code as they did in 2024 - On the most open-ended engineering tasks, Claude's success rate jumped from ~26% to 76% in 6 months - When research sessions went off-track, Claude proposed a better next step than the human took 64% of the time We're not at recursive self-improvement yet, but it could come sooner than most expect. I highly recommend reading the full blog post.

And... claude knows how to use ant CLI very well, give it a try!

Small new in the Claude API: set max_tokens on the advisor tool to cap its output. Predictable cost and latency for agents that consult an advisor every step, and stop_reason: "max_tokens" tells you when the cap was hit so your agent can adapt. platform.claude.com/docs/en/…

there's a ton of demand right now for excellent infra talent, definitely outpacing supply im hiring engineers who have tackled megascale, multicloud product infra to work on the Claude Platform. help me find them 🙂

The easy way to migrate to 4.8... takes all our best practices and applies them to your code in one step...

Opus 4.8 is out: better judgment, catches its own mistakes. My favorite API addition: mid-conversation system messages. Append {"role":"system","content":"new rules"} mid-task. Instructions update without breaking the prompt cache, and reminders keep long runs on track.

Lots of good tips here

Claude Console now gives diagnostics on prompt cache misses. it will attribute cache misses to messages, system prompt, tool, or model changes.

Welcome to the @StainlessAPI team. So happy to be working even more closely together ❤️

The Claude Platform on AWS is now generally available. AWS customers get the full set of Claude API features, with AWS authentication, billing, and commitment retirement.

My @ClaudeDevs Code with Claude talk is up: Getting more out of the Claude Platform. I built an agent for superheroes — turns out the real villain was the token bill. Caching, context management, and the Advisor took it down. 🦸 youtube.com/watch?v=7oO37GRh…

Had a blast on stage at Code with Claude with @mariorod1 — how @github ships Claude to millions of devs across Copilot and pushes quality up cost down: caching, harnesses, and the new Advisor pattern. Thanks Mario 🙏 @ClaudeDevs youtube.com/watch?v=y5TmF_6o…

We are significantly raising the API rate limits for Opus for tier 1-4. Build away! anthropic.com/news/higher-li…

come say hi at Code With Claude tomorrow! ill be giving a talk w @jess__yan on some new things we’re excited to share. join the livestream here: claude.com/code-with-claude