Anthropic shipped a virtual pet system called Buddy inside Claude Code today, timed to April Fools' Day. Type /buddy in your terminal and an ASCII creature hatches next to your input line, complete with its own name, personality, and opinions about your code.
The feature was spoiled early. On March 31, security researcher Chaofan Shou discovered that Claude Code version 2.1.88 had shipped with a 59.8 MB source map file containing the tool's entire TypeScript source. Developers found the src/buddy/ directory within hours and started cataloging species. Anthropic confirmed the source code leak was caused by human error, not a security breach.
There are 18 species (duck, dragon, axolotl, capybara, ghost, mushroom, among others) across five rarity tiers from Common to Legendary, plus a 1% chance of a Shiny variant. Each pet is deterministically generated from your user ID using FNV-1a hashing, so one account always produces the same creature. You can't reroll. Stats include DEBUGGING, PATIENCE, CHAOS, WISDOM, and SNARK, with one peak stat and one dump stat per buddy.
The architecture has two layers. A "bones" layer computes species, rarity, and stats from your ID hash every session. A "soul" layer uses Claude to generate a unique name and personality on first hatch, then stores it. The bones layer always overwrites stored values, which functions as anti-cheat. When unmuted, your buddy watches your session and comments via speech bubbles. Call it by name and Claude steps aside to let the pet respond independently.
Requires Claude Code v2.1.89 or later and a Pro subscription. The community has already built species galleries and stat checkers. Someone filed a GitHub Issue requesting an RPG evolution system tied to token consumption.
Bottom Line
Your Buddy species is permanently locked to your account via deterministic hashing, so there's no rerolling for a Legendary Capybara.
Quick Facts
- 18 species across 5 rarity tiers (Common to Legendary)
- 1% Shiny variant chance, independent of rarity
- 5 stats per buddy: DEBUGGING, PATIENCE, CHAOS, WISDOM, SNARK
- Requires Claude Code v2.1.89+ and Pro subscription
- Source code leaked March 31 via npm source map file in v2.1.88
