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

# Language servers

> Humboldt reads the code the way the compiler does when a language server is there: where a symbol is defined, who references it, what a name is, what the parser complains about.

## What the model gets

| Tool          | Answers                                                   |
| ------------- | --------------------------------------------------------- |
| `definition`  | Where the symbol at a position is defined                 |
| `references`  | Every reference to it, declaration included               |
| `hover`       | Its type and documentation                                |
| `symbols`     | The symbols in one file, or one name across the workspace |
| `diagnostics` | The errors and warnings for a file                        |

After every `write_file` and `edit_file`, the file's diagnostics end the result, so the model reads the error before it runs anything.

## Install one

A language server comes from a [plugin](/docs/plugins). The official marketplace carries one per language; install the server binary yourself, then the plugin.

```bash theme={"dark"}
npm i -g pyright
hum plugin marketplace add metaphi-labs/plugins
hum plugin install pyright-lsp@metaphi
```

| Plugin              | Files                     | Binary                                                                                |
| ------------------- | ------------------------- | ------------------------------------------------------------------------------------- |
| `che4z-cobol-lsp`   | `.cbl` `.cob` `.cpy`      | Broadcom's COBOL Language Support engine, fetched by the plugin's `bin/che4z-install` |
| `cobol-lsp`         | `.cbl` `.cob` `.cpy`      | none: a single Python file, for a machine that cannot run the engine                  |
| `pyright-lsp`       | `.py`                     | `pyright-langserver`                                                                  |
| `typescript-lsp`    | `.ts` `.tsx` `.js` `.jsx` | `typescript-language-server`                                                          |
| `gopls-lsp`         | `.go`                     | `gopls`                                                                               |
| `rust-analyzer-lsp` | `.rs`                     | `rust-analyzer`                                                                       |
| `clangd-lsp`        | `.c` `.cc` `.cpp` `.h`    | `clangd`                                                                              |
| `jdtls-lsp`         | `.java`                   | `jdtls`                                                                               |
| `csharp-lsp`        | `.cs`                     | `csharp-ls`                                                                           |
| `kotlin-lsp`        | `.kt`                     | `kotlin-language-server`                                                              |
| `swift-lsp`         | `.swift`                  | `sourcekit-lsp`                                                                       |
| `php-lsp`           | `.php`                    | `intelephense`                                                                        |
| `lua-lsp`           | `.lua`                    | `lua-language-server`                                                                 |

When one of those binaries is on PATH and the working directory holds its language, Humboldt says so once at the start of a session, with the install command. Nothing starts until you install the plugin.

## Your own

```toml theme={"dark"}
# ~/.hum/config.toml or <repo>/.hum/config.toml
[[lsp]]
name = "cobol"
command = "cobol-language-support"
args = ["--stdio"]
extensions = [".cbl", ".cpy"]
```

Or in a plugin's `.lsp.json`, with the server's own options:

```json theme={"dark"}
{"cobol": {"command": "cobol-language-support", "args": ["--stdio"],
           "extensionToLanguage": {".cbl": "cobol", ".cpy": "cobol"},
           "initializationOptions": {"copybookPaths": ["Copybooks"]}, "settings": {}, "diagnostics": true}}
```

`settings` answers the server's `workspace/configuration` requests section by section and is sent once as `workspace/didChangeConfiguration`; `initializationOptions` rides on `initialize`. `diagnostics = false` keeps navigation and stops the lines after every write.

## Behaviour

* A server starts on the first question about one of its files, in the working directory, and stops with the session.
* It runs with the reach of its own process. The sandbox does not extend to it.
* Every call is on the session transcript. `meta.lsp` lists the servers, the plugin each came from, and the files they served.
* A server that is missing, dies or does not answer says so on the tool result. The session goes on.
* Sub-agents and unattended Harbor runs do not get these tools.

```
/tools            # the servers beside the tool servers
```