Why AI Companies Are Moving to Rust

In September, GitHub said one engineer and a team of AI agents moved the Copilot agent runtime to Rust. Bun, the runtime under Claude Code, was rewritten in Rust with Claude agents. OpenAI's Codex CLI went Rust in 2025. But almost everyone in AI writes Python, so what's going on? In this video we follow one prompt down the stack and look at where the Rust actually is: the agent CLI, the tokenizer, the model weights, the server front door and your Python tools. Then we look at why Python servers and C++ both run into trouble, why AI agents suddenly made big rewrites cheap, and where Rust doesn't help (Cloudflare's outage, compile times, Microsoft's 2030 walk-back). Short version: Python stays where people think and try things, Rust takes the parts that run all day, and CUDA C++ still does the GPU maths. All numbers are the companies' own, as stated in their posts: - GitHub, Migrating the GitHub Copilot runtime to Rust: https://github.blog/ai-and-ml/generative-ai/migrating-the-github-copilot-runtime-to-rust-using-copilot/ - Bun, Rewriting Bun in Rust: https://bun.com/blog/bun-in-rust - OpenAI Codex CLI is going native: https://github.com/openai/codex/discussions/1174 - tiktoken: https://github.com/openai/tiktoken - Safetensors joins the PyTorch Foundation: https://huggingface.co/blog/safetensors-joins-pytorch-foundation - vLLM Rust front-end RFC: https://github.com/vllm-project/vllm/issues/40846 - uv: https://github.com/astral-sh/uv - What's new in Python 3.14: https://docs.python.org/3/whatsnew/3.14.html - Chromium memory safety: https://www.chromium.org/Home/chromium-security/memory-safety/ - Google, Rust in Android: https://blog.google/security/rust-in-android-move-fast-fix-things/ - LWN, The state of the kernel Rust experiment: https://lwn.net/Articles/1050174/ - Cloudflare outage, Nov 18 2025: https://blog.cloudflare.com/18-november-2025-outage/ - The Register on Microsoft's 2030 post: https://www.theregister.com/2025/12/24/microsoft_rust_codebase_migration/ - Astral to join OpenAI: https://astral.sh/blog/openai ## Chapters 0:00 Three coding agents, one language 0:34 Follow one prompt down the stack 1:21 Python is fine, Python servers aren't 2:15 Why not just C++ 3:06 Agents made rewrites cheap 3:58 Where Rust doesn't help 4:45 How it fits together