Editors

VS Code

Install from the Marketplace →

Or from inside the editor: open Extensions (Ctrl+Shift+X / Cmd+Shift+X), search for HCL Schema, and pick the one published by avestura. From a terminal:

code --install-extension avestura.hcl-schema

The binary for your platform ships with the extension, so there is nothing else to install — no Go toolchain, no PATH setup. Packages are published per platform (Windows, macOS, Linux and Alpine, on x64 and arm64, plus 32-bit ARM), so the download is around 4 MB rather than carrying every platform's binary.

Point a file at a schema and it starts working:

__schema = "./service.schema.hcl"

name = "checkout"

Settings

Setting	Default	Meaning
hclSchema.cliPath	""	Path to the binary. Empty uses the bundled one.
hclSchema.strict	false	Apply draft 2026-09 rules to older schemas
hclSchema.offline	false	Never fetch remote schemas
hclSchema.cacheDir	""	Where cached remote schemas live

Commands

Run these from the command palette (Ctrl+Shift+P / Cmd+Shift+P):

• HCL Schema: Validate active file
• HCL Schema: Restart language server
• HCL Schema: Show output — the server's log, for when something looks wrong

Troubleshooting

If nothing happens on an HCL file, check in this order:

1. The file has a __schema attribute, and the path it names resolves.
2. Show output reports the server starting rather than an error.
3. If you set hclSchema.cliPath, the binary there is version 0.1.0 or later — an older one has no lsp subcommand. Clear the setting to fall back to the bundled binary.

The language server

Any LSP client can use it:

hclschema lsp

Capability	What it gives you
publishDiagnostics	Validation of the unsaved buffer
completion	Declared attributes and blocks; enum values on an attribute
hover	The description, type, bounds and default from the schema
definition	Jump from a use in the instance to its declaration in the schema
documentSymbol	An outline of the document

Why a server rather than a linter invocation

The previous integration ran the CLI against the file on disk on every keystroke, so unsaved edits were checked against stale content. The server holds the buffer and checks that.

Neovim

vim.api.nvim_create_autocmd('FileType', {
  pattern = 'hcl',
  callback = function(args)
    vim.lsp.start({
      name = 'hclschema',
      cmd = { 'hclschema-cli', 'lsp' },
      root_dir = vim.fs.root(args.buf, { '.git' }),
    })
  end,
})

Helix

# languages.toml
[language-server.hclschema]
command = "hclschema-cli"
args = ["lsp"]

[[language]]
name = "hcl"
language-servers = ["hclschema"]

Anything else

The server speaks LSP over stdio with Content-Length framing. Point your client at hclschema-cli lsp and give it the hcl language id. It advertises full-document sync, so there is no incremental-sync support to negotiate.