OpenCode Custom YAML LSP

Published on May 01, 2026

I’ve been using OpenCode as my go-to coding agent for personal development. I’ll be describing my workflow in an upcoming post.

Rails makes heavy use of YAML for configuration files as well as for handling localization translations. Even a small app may have hundreds of YAML entries for localization. I’ve noticed that OpenCode sometimes struggles with editing YAML files and ensuring correct indentation and key consistency.

YAML is on the list of supported LSP, but I’ve had issues with OpenCode initializing these LSPs, especially within a Rails project. Thus, I’ve added the following workaround to my opencode.json config file to address this issue using a globally installed yaml-language-server.

First, we need to install the LSP server with:

bun add -g yaml-language-server

Next, I’ve added the following configuration to ~/.config/opencode/opencode.json:

{
  "$schema": "https://opencode.ai/config.json",
  "lsp": {
    "yaml-ls": {
      "disabled": true
    },
    "custom-yml": {
      "command": ["bun", "x", "yaml-language-server", "--stdio"],
      "extensions": [".yaml", ".yml"]
    }
  }
}

The key is to disable the default yaml-ls LSP; without this change, the custom-yml does not kick in.

I believe this PR should make this configuration unnecessary in the future. For now, this is a suitable workaround and OpenCode is able to edit YAML files in my Rails projects without issues. It should even recognize duplicate keys and formatting issues automatically. How nice!