Jarred Sumner used a prerelease Claude Fable 5 model to rewrite Bun's codebase from Zig into Rust in May 2026.

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Location PART 3 - THE THIRD AXIS CHAPTER 15: DEPLOY NOW, PRAY LATER Zig & Godot

"Jarred Sumner used a prerelease Claude Fable 5 model to rewrite Bun’s codebase from Zig into Rust in May 2026."

Sumner's July 8 account identifies Claude Fable 5 as the prerelease model used for much of the migration. The rewrite occurred between May 3 and May 14, 2026, with Sumner directing and monitoring the process before publicly describing it in July.

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Source title Rewriting Bun in Rust

Source authors Jarred Sumner

Source year 2026

Confidence high

Importance high