AI One-Shot Rust Rewrite of TerminalTextEffects: 43x Faster Startup

Melvin Vivas · X post · 2026-08-10 · Open on X

Topics: AI Dev Tools & Productivity, Industry Trends & Job Market · Level: intermediate

Summary

An AI model called Fable rewrote the Python library TerminalTextEffects in Rust in one shot, using 11M tokens. Startup time dropped from 87 ms to 2 ms and rendering got 9.6x faster. The result has zero dependencies and ships as a single 3 MB executable. Melvin's takeaway is that AI now makes performance rewrites practical.

Key points

• The whole TerminalTextEffects library was rewritten from Python to Rust in one shot, using 11M tokens.
• Startup time fell from 87 ms to 2 ms.
• Rendering speed improved 9.6x.
• The rewrite has zero dependencies and is a single 3 MB executable.
• Lesson: coding agents make rewriting libraries for speed much cheaper.

Resources mentioned

• Claude Code artifact: Rust rewrite of TerminalTextEffects · other · x.com · free
  Shared Claude Code artifact showing the AI-generated Rust rewrite.
• TerminalTextEffects · repo · github.com · free
  Python library for visual text effects in the terminal; the original that was rewritten.
• Fable · tool · anthropic.com · paid
  Named as what the creator used with Devin for this build; the post gives no details about what it is.
  Also in: Demo: One-Shotting a Flappy Bird iPhone App with Devin and Fable 5.1 (Melvin Vivas on X · notes), Subagents with mixed models: a strong planner and a fast executor (Melvin Vivas on X · notes), Cognition's SWE-2 Coding Model Now in Devin (Melvin Vivas on X · notes), GPT-6 Astra Access Across Plans vs Fable on Claude Max (Melvin Vivas on X · notes) and 10 more

Try this

• Use a coding agent to rewrite a slow Python CLI or library in Rust, and measure startup and runtime speedups.