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Claude Code adopts Rust port of Bun for runtime (v2.1.181) | My AI Guide
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Claude Code adopts Rust port of Bun for runtime (v2.1.181)

By Harsh Desai
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TL;DR

Claude Code v2.1.181 and later versions use the Rust port of Bun. Startup times improved 10 percent on Linux.

What changed

Claude Code v2.1.181 switched its runtime to the Rust port of Bun. Developers and Vibe Builders on Linux see a 10 percent faster startup while Basic Users notice nothing different in daily sessions.

Specs

Why it matters

Developers gain measurable speed on Linux compared to the prior JavaScript Bun version inside Claude Code. Vibe Builders keep the same workflow for quick iterations without any adjustment. Basic Users continue using the tool exactly as before.

What to watch for

Compare startup times against alternatives such as standard Bun-based editors. Developers should run the strings grep command on their own Claude Code binary to confirm the Rust port version.

Who this matters for

  • Vibe Builders: Run Claude Code v2.1.181 or later to get faster startup times during rapid prototyping sessions.

Harsh’s take

Shipping a Rust port of Bun inside Claude Code without breaking workflows is a masterclass in silent infrastructure upgrades. Most users will not notice the change, which is exactly the point of a successful runtime migration. For builders, this transition proves that performance optimization does not require breaking changes. Keep your local Claude Code installation updated to benefit from these incremental speed gains without altering your existing prompts or scripts.

by Harsh Desai

Source:simonwillison.net

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