# For coding agents
Canonical HTML: [For coding agents](https://getred.dev/docs/for-agents). Website source: `b212874eefaf200143affa21c770fbb8855a4f5c`. Documented Red release: v0.9.1. Installer source: `b86a2ca4b92e9547d3b174910c82db8a259f5171`.
Choose version-appropriate instructions, configure language tools, build plugins, and validate changes in Red.
## Start with the installed version
Use this page when helping a user install, configure, or extend Red. Red's built-in coding assistant has its own [Agent guide](https://getred.dev/docs/agent.md). Find documentation through [the documentation index](https://getred.dev/llms.txt); each guide is also available at its URL with `.md` appended.
```shell
red --version
red --help
```
This website's release metadata identifies **v0.9.1**. Compare that with the installed version and read each guide's minimum-version note before applying instructions. Multiple language servers per document and standalone JSON-RPC plugins require Red v0.9.0 or later. Follow [installation](https://getred.dev/docs/getting-started/install.md) and [update instructions](https://getred.dev/docs/getting-started/updating.md) for the user's installation method. `red update --check` checks availability without replacing the executable.
## Identify the configuration layer
| Layer | What belongs there |
| ---------------------- | -------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- |
| Red user configuration | `$XDG_CONFIG_HOME/red/config.toml` when that variable is non-empty; otherwise `~/.config/red/config.toml`. Configure servers, formatters, keybindings, and plugin settings here. |
| Project files | Keep `package.json`, `tsconfig.json`, `eslint.config.js`, `prettier.config.js`, and project dependencies in the workspace. |
| External executables | Install language-server binaries and plugin interpreters separately. Embedded syntax support and a default server definition do not install the server executable. |
Merge changes into existing TOML tables, then run `red --check-config`. A custom server table replaces its built-in entry as a unit, so preserve required selectors and arguments. See [configuration](https://getred.dev/docs/configuration.md) and [language support](https://getred.dev/docs/languages.md).
## Choose the interface
Use terminal commands for installation, package management, and configuration checks; use editor commands for interactive operations. For example, `red plugin list` runs in a terminal, while `:languages reload` and `:messages` run inside Red. Consult the [CLI reference](https://getred.dev/docs/reference/cli.md) and [session guide](https://getred.dev/docs/sessions.md).
Use the documented [JSON-RPC](https://getred.dev/docs/plugins/json-rpc.md) or [Husk](https://getred.dev/docs/husk.md) API to develop plugins. Red launches an RPC plugin as a child process and owns its editor resources. The protocol is not a general remote-control endpoint for arbitrary external clients and has no generic host-action escape hatch.
## Configure TypeScript, ESLint, and Prettier
Follow the complete [TypeScript and ESLint guide](https://getred.dev/docs/languages/typescript-eslint.md), including its recorded compatibility baseline. Keep Red's built-in TypeScript server and register ESLint with overlapping document selectors. Install both server executables on `PATH`, and install ESLint, TypeScript, and Prettier in the project. ESLint also needs the guide's empty-section `workspace/configuration` settings.
Retain external Prettier formatting with `formatting.provider = "auto"` and a language formatter definition. Formatter lookup checks the project's `node_modules/.bin` before `PATH`; do not assume language-server startup uses that same lookup. Add formatter definitions for the other language keys if editing JSX or TSX.
Validate the config and restart Red after server-definition changes, then verify hover, completion, diagnostics from both servers, and an ESLint code action. With the guide's sample, changing quotes and pressing `Space f` should produce `formatted with Prettier`. Record the observed result, not just a successful config check.
## Create and validate a plugin
Start from the complete TypeScript or Python package in the [JSON-RPC tutorial](https://getred.dev/docs/plugins/json-rpc.md), a Markdown outline and table of contents plugin. Red v0.9.0 uses host API `0.19.0` and protocol version `1`; these are distinct from Red's application version. Red v0.9.1 exposes host API `0.20.0` and retains support for `0.19.0` packages. Keep example manifests at the earliest API their features require. Use the tutorial's manifest and initialization response together. The TypeScript version needs Node.js 22.18 or later.
```shell
red plugin install --path ./markdown-outline
red plugin list
```
Open a Markdown file in Red, run `:Outline`, and confirm that the outline panel opens. Listing a package proves installation; invoking its command also exercises process startup and the handshake. If the command does not run, inspect `:messages` and `red.log` in Red's configuration directory. On Red v0.9.1 and later, use `:plugin-status` for the current session's diagnostic details.
For more operations, read the [v0.9.0 protocol reference](https://github.com/codersauce/red/blob/eb5e2b6be15325abd12adbfac816f7844afff42c/docs/RPC_PLUGIN_PROTOCOL.md) and [complete JSON Workbench example](https://github.com/codersauce/red/blob/eb5e2b6be15325abd12adbfac816f7844afff42c/examples/rpc-json-workbench/README.md). Match those references to the user's release before adopting newer APIs.
## Diagnose the failing stage
- **Executable:** a bare RPC command resolves on `PATH`; a command containing a path separator resolves inside the package. Arguments are passed without a shell or `~` expansion.
- **Manifest and handshake:** check API compatibility and ensure returned commands/events match the activation declarations exactly. Wait for `initialized` before calling host methods.
- **Protocol:** reserve stdout for newline-delimited JSON-RPC; log to stderr. Keep reading stdin while awaiting host responses.
- **Host method:** check names and parameters against the protocol. Invalid arguments can return an error while the connection stays active; framing corruption can quarantine the plugin.
On Red v0.9.1 and later, run `:plugin-status` to inspect the current editor session. Quarantined or starting plugins appear with diagnostic details; a separate `red plugin list` process cannot report that live state.
Read `:messages` and `red.log` in Red's configuration directory. Use `red --self-check` for bundled-runtime problems and `red --check-config` for configuration failures. Follow the [troubleshooting guide](https://getred.dev/docs/troubleshooting.md) and the relevant tutorial's failure table. Record the version, exact command, observed error, and smallest reproduction before proposing a fix.