Twitter/X

Charlie Marsh (founder of Astral, acquired by OpenAI) posed four concrete open…

Brief

Ryan Peterman's interview with Charlie Marsh (Astral founder, acquired by OpenAI) on 2026-06-25 examines AI-driven whole-codebase migrations to Rust, with Marsh warning about losing understanding, trading known for unknown bugs, rollout safety, and required abstraction knowledge. The episode recounts a Zig→Rust migration, LLM-code effects on open source, and performance/optimization lessons.

Why it matters

Charlie Marsh (founder of Astral, acquired by OpenAI) posed four concrete open questions about AI-driven full-codebase rewrites to Rust: 'Maybe you don't understand the code anymore, right?', 'You're trading known issues for new unknown issues', 'how do you roll that out safely?', and 'How well do they need to understand things at different levels of abstraction?'

Key details

  • Ryan Peterman's interview (published 2026-06-25) covers full-codebase language migrations including a Zig→Rust migration (chapter at 20:10), LLM-generated code and open source (28:40), and performance optimizations (35:34); episode is available on YouTube, Spotify, Apple Podcasts and via a transcript link.
Source evidence

Thoughts on rewriting your entire codebase to Rust with AI, @charliermarsh (OpenAI & Astral) interesting open questions:

• "Maybe you don't understand the code anymore, right?"
• "You're trading known issues for new unknown issues"
• "how do you roll that out safely?"
• "How well do they need to understand things at different levels of abstraction?"

Video

Ryan Peterman (@ryanlpeterman)

Charlie Marsh (@charliermarsh) is the founder of Astral, the Python devtool startup that was acquired by OpenAI. I inteviewed him about how software engineering is changing and learnings from starting his own company as an engineer.

In this episode:

• Full codebase language migrations using AI
• LLM generated code impact on open source
• Performance optimizations and Rust
• How to hit the front page of Hacker News
• Learnings from starting a company as an engineer

Where to watch:

• YouTube - piped.video/Iw65FD4MGgs
• Spotify - open.spotify.com/episode/2sf…
• Apple Podcasts - podcasts.apple.com/us/podcas…
• Transcript - developing.dev/p/openai-eng-…

Thank you to the sponsor of this episode for supporting my work:

• WorkOS: makes your app Enterprise Ready with easy to use APIs to add SSO, SCIM, RBAC, and more in just a few lines of code, check them out at workos.com/

Chapters:

00:00 - Intro
00:40 - Origin story
06:04 - The front page of Hacker News
14:35 - Why he chose Rust
20:10 - Full codebase migration from Zig to Rust
28:40 - LLM generated code and open source
35:34 - Performance optimizations
44:54 - Optimization with AI and combating slop
01:02:08 - Learnings as an eng starting a company
01:17:55 - Top technical talk recommendation
01:18:56 - Advice for his younger self
01:22:00 - Outro

Video

— https://nitter.net/ryanlpeterman/status/2069042727627743476#m