Fix Claude Code connection errors on Windows (ECONNREFUSED, Bun crash)

Two common errors when installing and using Claude Code on Windows are being unable to reach the API (Unable to connect to API: ECONNREFUSED when you run a prompt) and a native compiler crash (Bun has crashed: Internal assertion failure). The full fix: remove the deprecated NPM install, clear the old caches/config, then reinstall using the Native Stable build.

Quick reference

Open PowerShell and run these commands in order.

1. Remove the old NPM install (if any):

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   npm uninstall -g @anthropic-ai/claude-code

2. Delete the broken config and cache files:

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   Remove-Item -Path "$env:USERPROFILE\.claude" -Recurse -Force
   Remove-Item -Path "$env:USERPROFILE\.claude.json" -Force
   Remove-Item -Path ".claude" -Recurse -Force
   Remove-Item -Path ".mcp.json" -Force

3. Reinstall with the Native Stable build:

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   & ([scriptblock]::Create((irm https://claude.ai/install.ps1))) stable

Step by step

Step 1: Remove the NPM build (deprecated)

Originally many people installed Claude Code through Node.js (npm install -g @anthropic-ai/claude-code). Anthropic's docs now mark this as deprecated. Running via Node.js on Windows often causes local port-resolution problems - most typically the ECONNREFUSED error mid-prompt when the connection to the local server drops.

Remove the old build from NPM:

npm uninstall -g @anthropic-ai/claude-code

Step 2: Clear the cache and config files

When you move from NPM to the native build (compiled with the Bun core), the old JSON/YAML config format may be incompatible. When Bun tries to read that file it can crash with: panic: Internal assertion failure - Bun has crashed... yaml_parse(500).

To avoid leftovers from the old install, delete all the config cache (note: your old terminal chat history will be lost and the tool returns to its default state).

For your user account's home folder:

Remove-Item -Path "$env:USERPROFILE\.claude" -Recurse -Force
Remove-Item -Path "$env:USERPROFILE\.claude.json" -Force

If there's a config file in the project folder where you opened PowerShell:

Remove-Item -Path ".claude" -Recurse -Force
Remove-Item -Path ".mcp.json" -Force

Step 3: Install the Native Stable build

The native build (a standalone .exe) runs lighter and skips the OS dependency. To avoid a too-new Latest build hitting a Bun compiler bug on Windows (for example v2.1.100), it's best to pin to the Stable channel:

& ([scriptblock]::Create((irm https://claude.ai/install.ps1))) stable

Troubleshooting / notes

• Rule out a proxy: sometimes the ECONNREFUSED error comes from an HTTP agent forced onto the Windows terminal. Check for hidden proxy environment variables with $env:HTTP_PROXY or $env:HTTPS_PROXY, and clear them like $env:HTTP_PROXY="" if you find a stray proxy.
• Extra system requirement: running claude with the native build doesn't need Administrator, but the machine must have Git for Windows installed, because Claude quietly uses its bundled Bash emulation library.