Bug: /buddy generates different companion on Windows vs WSL for same account

Preflight Checklist

• [x] I have searched existing issues and this hasn't been reported yet
• [x] This is a single bug report (please file separate reports for different bugs)
• [x] I am using the latest version of Claude Code

What's Wrong?

Bug: /buddy generates different companion on Windows vs WSL for same account

Environment

• Claude Code version: v2.1.92
• OS: Windows 11 (PowerShell) + WSL2 (Ubuntu)
• Account: Same Claude Max subscription account on both platforms
• Machine: Same physical machine (AMD Threadripper, Windows + WSL2)

Description

Running /buddy on the same account produces completely different companions on Windows (CMD/PowerShell) and WSL2 — different species, different rarity tier, different stats. This contradicts the expected behavior where the buddy is deterministically generated from the user ID and should be identical across platforms.

Probable Cause

Bun.hash() (used in rollCompanionBones) appears to return platform-dependent values for the same input string on Windows vs Linux, breaking the cross-platform determinism of buddy generation.

Additional Context

Both instances are running Claude Code v2.1.92, authenticated with the same Claude Max account, on the same physical machine. The only difference is the runtime environment (Windows native vs WSL2 Linux).

What Should Happen?

Same account should always produce the same buddy (species, rarity, stats), regardless of platform. Per the buddy system design, Bun.hash(userId + salt) should yield identical results.

Actual Behavior

Two completely different companions are generated — different species and different rarity tier. The ~/.claude.json companion data is stored in separate filesystem locations (C:\Users\<user>\.claude.json vs /home/<user>/.claude.json), but the core issue is that the deterministic hash produces different results on Windows vs Linux.

Error Messages/Logs

Steps to Reproduce

1. Log in to Claude Code on Windows (PowerShell/CMD) with a Claude Max subscription
2. Run /buddy → Companion A hatches (species X, rarity Y)
3. Log in to Claude Code on WSL2 (same machine) with the same account
4. Run /buddy → Companion B hatches (different species, different rarity)

Claude Model

Not sure / Multiple models

Is this a regression?

No, this never worked

Last Working Version

_No response_

Claude Code Version

v2.1.92

Platform

Anthropic API

Operating System

Windows

Terminal/Shell

WSL (Windows Subsystem for Linux)

Additional Information

<img width="2692" height="422" alt="Image" src="https://github.com/user-attachments/assets/e89bf2e1-4916-491d-ba94-04c5218d3a18" />