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Building the Claude API for the Frontier

Every Claude launch puts the spotlight on the model, but just as much work goes into making sure the API evolves with it.

Lucca SiaudzionisguestJake Dejnohost

Nov 12, 202618mWatch on YouTube

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EPISODE INFO

Released: November 12, 2026
Duration: 18m
Channel: Claude
Watch on YouTube: ▶ Open ↗

EPISODE DESCRIPTION

Every Claude launch puts the spotlight on the model, but just as much work goes into making sure the API evolves with it. That means adding new controls, retiring outdated ones, and helping developers rethink how they build with each new release. Jake Dejno (Member of Technical Staff, Claude Platform) and Lucca Siaudzionis (Member of Technical Staff, Platform Intelligence) discuss how research and customer requests shape what ships, best practices for changing effort mid-conversation without breaking prompt caching, and how Mythos and Fable use the same model weights with different safeguards.** 0:00 - Intro 0:15 - How the Messages API works 1:40 - Deciding what features to release 4:15 - Handling model versioning and migrations 8:15 - Best practices for managing cost 11:22 - Balancing access and safety with Mythos and Fable 14:41 - What’s next for the API Learn more about the Claude Platform: https://claude.com/platform/api Follow ClaudeDevs on X for product updates and best practices from the Claude Platform team: https://x.com/ClaudeDevs *Claude Managed Agents and changing effort mid-conversation are in beta. **Claude Mythos access is through the Cyber Verification Program.

SPEAKERS

Lucca Siaudzionis
guest
Anthropic/Claude Platform team member focused on building and shipping Claude API capabilities (e.g., Messages API, tooling, rollouts, and safety mechanisms).
Jake Dejno
host
Anthropic/Claude Platform interviewer/host who leads product and engineering discussions about the Claude API and developer experience.

EPISODE SUMMARY

In this episode of Claude, featuring Lucca Siaudzionis and Jake Dejno, Building the Claude API for the Frontier explores Inside Claude’s Messages API: knobs, caching, versioning, and safety tradeoffs Lucca explains the Messages API as the cornerstone of the Claude Platform, combining a familiar chat-and-tools structure with built-in controls that enable deeper behavior tuning than prompting alone.

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