> ## Documentation Index
> Fetch the complete documentation index at: https://docs.fallow.tools/llms.txt
> Use this file to discover all available pages before exploring further.

# Neovim

> Real-time fallow diagnostics in Neovim via the built-in LSP client: unused code, duplication, circular dependencies, and complexity, with hover, quick-fix code actions, and code lens.

Neovim talks to the same `fallow-lsp` language server that powers the VS Code extension, through Neovim's built-in LSP client. The setup is intentionally thin: it launches the existing binary instead of re-implementing any analysis in the editor, so results match the CLI and CI exactly.

<Info>
  Requires Neovim 0.11+ for the `vim.lsp.config` / `vim.lsp.enable` API shown below. Older versions can still attach `fallow-lsp` through `nvim-lspconfig` or a manual `vim.lsp.start`.
</Info>

## What works

* **Real-time diagnostics** for unused files, exports, types, dependencies, enum and class members, unresolved imports, unlisted dependencies, duplicate exports, circular dependencies, and code duplication
* **Opt-in security candidate diagnostics** when you raise the `security-sink` or `security-client-server-leak` rule to `warn` or `error` in your fallow config. Candidates surface as advisory `information` squiggles (unverified, verify before acting); the hover leads with the confidence signals and points to `fallow security --file` for the full trace, and a quick-fix dismisses the candidate. Default off, so squiggles appear only after you raise the rule.
* **Hover information** with export usage counts, unused status, and duplicate block locations
* **Quick-fix code actions** to remove unused exports or delete unused files
* **Code lens** with export reference counts, where Neovim surfaces them

## Installation

<Steps>
  <Step title="Install Fallow so fallow-lsp is on your PATH">
    ```sh theme={null}
    npm install -g fallow
    ```

    Or add it as a project devDependency (`npm install -D fallow`) and point `cmd` at `node_modules/.bin/fallow-lsp`.
  </Step>

  <Step title="Confirm Neovim can see the binary">
    ```sh theme={null}
    fallow-lsp --version
    ```
  </Step>

  <Step title="Register and enable the server">
    Add the configuration below to your Neovim config, then open a TypeScript or JavaScript project.
  </Step>
</Steps>

## Configuration

```lua theme={null}
vim.lsp.config("fallow", {
	cmd = { "fallow-lsp" },
	filetypes = { "javascript", "typescript", "javascriptreact", "typescriptreact" },
	root_markers = { ".fallowrc.json", "package.json", ".git" },
	init_options = {
		-- Every issue type is enabled by default. List only the ones you
		-- want to turn off; any key you omit stays enabled.
		issueTypes = {
			["circular-dependencies"] = false,
		},
	},
})

vim.lsp.enable("fallow")
```

`init_options` is optional; `cmd`, `filetypes`, and `root_markers` alone are enough to attach.

### Issue-type toggles

Fallow reads per-issue toggles from LSP initialization options. Set an issue type to `false` to hide it in editor diagnostics without touching your project config. The keys are Fallow's issue types in kebab-case (`unused-exports`, `unresolved-imports`, `circular-dependencies`, and so on); a client can fetch the live catalog through the custom `fallow/issueTypes` request to stay in sync.

### Scope to changed files

Pass a git ref as `changedSince` to scope diagnostics to files changed since that ref, mirroring `fallow dead-code --changed-since`. This is the Neovim equivalent of the VS Code `fallow.changedSince` setting, useful for adopting fallow on a legacy codebase without surfacing every pre-existing finding:

```lua theme={null}
init_options = {
	changedSince = "fallow-baseline",
},
```

<Note>
  **When diagnostics appear.** Fallow delivers diagnostics through the LSP 3.17 pull model and refreshes them on save. The first analysis runs when the server attaches, so a freshly opened buffer shows findings once the initial pass completes (or after the next save), not necessarily the instant the file opens. Cross-file findings anchored to files you have not opened (for example `package.json` for unlisted dependencies) are pushed so they still surface.
</Note>

## Binary resolution

Neovim runs `cmd` exactly as configured. If `fallow-lsp` is not on Neovim's `PATH`, point `cmd` at an absolute path:

```lua theme={null}
vim.lsp.config("fallow", {
	cmd = { "/absolute/path/to/fallow-lsp" },
	filetypes = { "javascript", "typescript", "javascriptreact", "typescriptreact" },
	root_markers = { ".fallowrc.json", "package.json", ".git" },
})
```

## Verifying the setup

1. Open a TypeScript or JavaScript project.
2. Run `:checkhealth vim.lsp`.
3. Confirm `fallow` is attached:

   ```vim theme={null}
   :lua vim.print(vim.lsp.get_clients({ name = "fallow" }))
   ```

## See also

<CardGroup cols={3}>
  <Card title="VS Code extension" icon="window" href="/integrations/vscode">
    The richer editor surface: sidebar views, status bar, and fix preview.
  </Card>

  <Card title="Agent integration" icon="robot" href="/integrations/mcp">
    How AI agents use fallow via CLI and MCP.
  </Card>

  <Card title="Analysis areas" icon="magnifying-glass" href="/analysis/dead-code">
    All issue types the language server reports.
  </Card>
</CardGroup>