Language Server Protocol

Fresh has native support for the Language Server Protocol (LSP), providing powerful code intelligence features across multiple programming languages.

Core Features

Fresh’s LSP integration provides:

Real-time Diagnostics

See errors and warnings in your code as you type

Code Completion

Get intelligent code completion suggestions

Go-to-Definition

Quickly jump to the definition of a symbol

Diagnostics Panel

The diagnostics panel provides a centralized view of all errors and warnings in your code.

Open the Panel

Open the diagnostics panel with Show Diagnostics Panel or Toggle Diagnostics Panel from the command palette.

Navigate Issues

Up/Down: Scroll the editor to preview each diagnostic’s location
Enter: Jump to the diagnostic and focus the editor
F8: Jump to next diagnostic without the panel
Shift+F8: Jump to previous diagnostic

Code Folding

When the LSP server provides foldingRange, fold indicators appear in the gutter. See Editing — Code Folding for more details.

Built-in LSP Support

Fresh includes built-in LSP configurations for many languages. Simply install the server and Fresh will use it automatically:

Language	LSP Server	Install Command
Rust	rust-analyzer	`rustup component add rust-analyzer`
Go	gopls	`go install golang.org/x/tools/gopls@latest`
TypeScript/JavaScript	typescript-language-server	`npm install -g typescript-language-server typescript`
Python	pylsp	`pip install python-lsp-server`
Java	jdtls	`brew install jdtls`
Zig	zls	`brew install zls`
LaTeX	texlab	`brew install texlab`
Markdown	marksman	`brew install marksman`
C/C++	clangd	`brew install llvm`

Python LSP Configuration

The default Python server is pylsp. Fresh also supports several alternative Python language servers:

pyright
basedpyright
pylsp with plugins

Recommended for type checking with strong TypeScript-like type analysis.

{
  "lsp": {
    "python": {
      "command": "pyright-langserver",
      "args": ["--stdio"],
      "enabled": true
    }
  }
}

Install: npm install -g pyright or pip install pyright

Enhanced pyright fork with additional features.

{
  "lsp": {
    "python": {
      "command": "basedpyright-langserver",
      "args": ["--stdio"],
      "enabled": true
    }
  }
}

Install: pip install basedpyright or uv pip install basedpyright

pylsp supports various plugins for enhanced functionality:

{
  "lsp": {
    "python": {
      "command": "pylsp",
      "args": [],
      "enabled": true,
      "initialization_options": {
        "pylsp": {
          "plugins": {
            "pycodestyle": { "enabled": true },
            "pylint": { "enabled": true }
          }
        }
      }
    }
  }
}

Configuring LSP for a New Language

To add LSP support for a language, configure two sections in your ~/.config/fresh/config.json:

Define the language

Add the language to the languages section with file extensions:

{
  "languages": {
    "csharp": {
      "extensions": ["cs"],
      "grammar": "c_sharp",
      "comment_prefix": "//",
      "auto_indent": true
    }
  }
}

Configure the LSP server

Add the language server configuration to the lsp section:

{
  "lsp": {
    "csharp": {
      "command": "/path/to/csharp-language-server",
      "args": [],
      "enabled": true
    }
  }
}

The language name (e.g., "csharp") must match in both sections. Fresh includes built-in language definitions for Rust, JavaScript, TypeScript, and Python.

Configuring Language Detection via Settings UI

You can also configure language detection using the Settings UI instead of editing config.json directly:

Open Settings

Use Edit → Settings… or the command palette (Ctrl+P) and search for “Settings”

Navigate to Languages

Go to the Languages section

Add or Edit a Language

Click on an existing language to edit it, or add a new one

Configure Detection

Set the following fields:

Extensions: File extensions that should use this language (e.g., cs for C#, rs for Rust)
Filenames: Specific filenames without extensions (e.g., Makefile, .bashrc, .zshrc)
Grammar: The syntax highlighting grammar to use (must match a grammar name from syntect)

Example: Adding Shell Script Detection for Dotfiles

To make Fresh recognize .bashrc, .zshrc, and similar files as shell scripts:

Open Settings

Open Settings (Edit → Settings…)

Configure bash language

Go to Languages → bash (or create a new bash entry)

Add filenames

Add filenames: .bashrc, .zshrc, .bash_profile, .profile

Set grammar

The grammar should be set to Bourne Again Shell (bash) or similar

The filenames field supports glob patterns like *.conf, *rc, or /etc/**/rc.* for matching files without standard extensions. Fresh checks filenames first, then extensions, allowing dotfiles without traditional extensions to get proper syntax highlighting.

Getting Started

Core Features

Configuration

Advanced Features

Plugins

Reference

Language Server Protocol

Core Features

Real-time Diagnostics

Code Completion

Go-to-Definition

Diagnostics Panel

Code Folding

Built-in LSP Support

Python LSP Configuration

Configuring LSP for a New Language

Configuring Language Detection via Settings UI

Example: Adding Shell Script Detection for Dotfiles

Build docs developers (and LLMs) love

Getting Started

Core Features

Configuration

Advanced Features

Plugins

Reference

​Core Features

Real-time Diagnostics

Code Completion

Go-to-Definition

​Diagnostics Panel

​Code Folding

​Built-in LSP Support

​Python LSP Configuration

​Configuring LSP for a New Language

​Configuring Language Detection via Settings UI

​Example: Adding Shell Script Detection for Dotfiles

Build docs developers (and LLMs) love

Core Features

Diagnostics Panel

Code Folding

Built-in LSP Support

Python LSP Configuration

Configuring LSP for a New Language

Configuring Language Detection via Settings UI

Example: Adding Shell Script Detection for Dotfiles