Uploaded August 2026 | Updated September 2026, 2 weeks ago
with Addy Osmani, Author and Director of Engineering.
See the full episode on The Pragmatic Engineer Podcast
with Addy Osmani, Author and Director of Engineering.
See the full episode on The Pragmatic Engineer Podcast



![Building Claude Code with Boris Cherny
Boris Cherny is the creator and Head of Claude Code at Anthropic. He previously spent five years at Meta as a Principal Engineer and is the author of the book Programming TypeScript.
In this episode of Pragmatic Engineer, we went through how Claude Code was built and what it means when engineers no longer write most of the code themselves.
We discuss how Claude Code evolved from a side project into a core internal tool at Anthropic and how Boris uses it day-to-day. We go deep into workflow details, including parallel agents, PR structure, deterministic review patterns, and how the system retrieves context from large codebases. We also get into how Claude Cowork was built.
As coding becomes more accessible, the role of engineers shifts rather than shrinks. We examine what that shift means in practice, which skills become more important, and why the lines between product, engineering, and design are blurring.
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*Brought to you by our season partners:*
• Statsig — The unified platform for flags, analytics, experiments, and more. http://statsig.com/pragmatic
• Sonar – The makers of SonarQube, the industry standard for automated code review. https://www.sonarsource.com/pragmatic/?utm_medium=paid&utm_source=pragmaticengineer&ut[…]egory=Paid&s_source=Paid%20Other&s_origin=pragmaticengineer
• WorkOS – Everything you need to make your app enterprise ready. https://workos.com/
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*The Pragmatic Engineer deepdives relevant for this episode:*
• How Claude Code is built https://newsletter.pragmaticengineer.com/p/how-claude-code-is-built
• How Anthropic built Artifacts https://newsletter.pragmaticengineer.com/p/how-anthropic-built-artifacts
• How Codex is built https://newsletter.pragmaticengineer.com/p/how-codex-is-built
• Real-world engineering challenges: building Cursor https://newsletter.pragmaticengineer.com/p/cursor
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*Where to find Boris Cherny:*
• X: https://x.com/bcherny
• LinkedIn: https://www.linkedin.com/in/bcherny
• Website: https://borischerny.com
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*In this episode, we cover:*
(00:00) Intro
(11:15) Lessons from Meta
(19:46) Joining Anthropic
(23:08) The origins of Claude Code
(32:55) Boriss Claude Code workflow
(36:27) Parallel agents
(40:25) Code reviews
(47:18) Claude Codes architecture
(52:38) Permissions and sandboxing
(55:05) Engineering culture at Anthropic
(1:05:15) Claude Cowork
(1:12:48) Observability and privacy
(1:14:45) Agent swarms
(1:21:16) LLMs and the printing press analogy
(1:30:16) Standout engineer archetypes
(1:32:12) What skills still matter for engineers
(1:35:24) Book recommendations
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See the transcript and other references from the episode at https://newsletter.pragmaticengineer.com/podcast
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Production and marketing by https://penname.co/. Building Claude Code with Boris Cherny](https://i.ytimg.com/vi/julbw1JuAz0/mqdefault.jpg)





![Building Pi, and what makes self-modifying software so fascinating
Mario Zechner is the creator of Pi, a minimalist, self-modifying AI coding agent, that is the foundation upon which OpenClaw (created by Peter Steinberger) is built. Meanwhile, Armin Ronacher is the creator of Flask, and a longtime user of Pi. The pair are also friends.
I sat down with Mario and Armin for the latest episode of the Pragmatic Engineer Podcast for an interesting conversation about AI and their reservations about it – even though both are heavily invested in building AI-powered tools.
Mario explains why he built Pi, and gives his take on why it has become so popular. Armin walks us through how he uses AI tools, including building a game with Pi, and why he always puts human judgment firmly at the heart of his approach.
We cover the risks of over-automation, the limits of agentic workflows, and why strong engineers with informed judgment still matter. We also get into the challenges of working with code written by non-engineers, and whether open source can withstand a tidal wave of agent-generated code.
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*Brought to you by our season partners:*
• Statsig — The unified platform for flags, analytics, experiments, and more. http://statsig.com/pragmatic
• Sonar – The makers of SonarQube, the industry standard for automated code review. https://www.sonarsource.com/pragmatic/?utm_medium=paid&utm_source=pragmaticengineer&ut[…]egory=Paid&s_source=Paid%20Other&s_origin=pragmaticengineer
• WorkOS – Everything you need to make your app enterprise ready. https://workos.com/
—
*The Pragmatic Engineer deepdives relevant for this episode:*
• The impact of AI on software engineers in 2026: key trends https://newsletter.pragmaticengineer.com/p/the-impact-of-ai-on-software-engineers-2026
• Cycles of disruption in the tech industry https://newsletter.pragmaticengineer.com/p/cycles-of-disruption-in-the-tech
• The AI engineering stack https://newsletter.pragmaticengineer.com/p/the-ai-engineering-stack
• The creator of OpenClaw: I ship code that I dont read https://newsletter.pragmaticengineer.com/p/the-creator-of-clawd-i-ship-code
• What is inference engineering? Deepdive https://newsletter.pragmaticengineer.com/p/what-is-inference-engineering
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*Where to find Mario Zechner:*
• X: https://x.com/badlogicgames
• LinkedIn: https://www.linkedin.com/in/mariozechner
• Website: https://mariozechner.at
*Where to find Armin Ronacher:*
• X: https://x.com/mitsuhiko
• LinkedIn: https://www.linkedin.com/in/arminronacher
• Website: https://mitsuhiko.at
• Blog: https://lucumr.pocoo.org
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*In this episode, we cover:*
(00:00) Intro
(07:30) How Mario, Armin, and Peter Steinberger met
(15:15) How 30 dev teams use AI agents: learnings
(21:50) The importance of judgment
(24:26) Challenges when non-engineers write code
(28:30) Downsides of over-automation
(32:18) Pi
(48:09) OpenClaw + Pi
(50:54) “Clankers”
(57:32) Open source and AI
(1:00:22) Complexity as the enemy
(1:02:50) Building an AI-native startup
(1:11:52) “Slow the F down”
(1:16:40) MCPs vs. CLI
(1:25:03) Predictions and staying up to date
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See the transcript and other references from the episode at https://newsletter.pragmaticengineer.com/podcast
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Production and marketing by https://penname.co/. Building Pi, and what makes self-modifying software so fascinating](https://i.ytimg.com/vi/n5f51gtuGHE/mqdefault.jpg)
