# The command line > rxr, the Reactor command line — write a loop in a file, try the draft, test it, publish it and run it from a terminal, as a person or as an AI agent `rxr` is Reactor from a terminal. You write a loop in a file, save it as a draft, try it, test it, publish it and run it, with no page open. An AI agent that works in a terminal can do the same: every command has an output made for a program. `rxr` works in your account as you, and only as far as your role allows. It reaches plutonium.io through the same server an AI tool connects to ([Connect an AI tool](/docs/guide/connect-an-ai-tool.md)), so the two can do the same things. ## Install ``` curl -fsSL https://plutonium.io/install.sh | sh ``` This puts one file, `rxr`, in `~/.local/bin`. It runs on macOS and Linux, on arm64 and x86-64, and it needs nothing else installed. The installer checks the download against a SHA-256 it carries, and installs nothing when they differ. Set `RXR_INSTALL_DIR` to install somewhere else. ## Sign in ``` rxr login ``` `rxr` opens plutonium.io in your browser. Sign in, and a page asks whether to connect `rxr`, with what it could do. Press **Allow**, and the terminal says it is connected. You paste no key. When the terminal is on another machine than your browser, run `rxr login --no-browser`: open the address it prints, press **Allow**, and paste the address the browser ends on. **Settings** lists the connection under **Connected AI tools**, as "rxr on" and the machine's name. **Disconnect** there ends it at once. `rxr logout` forgets the sign-in on one machine. ## Your first loop ``` rxr new support_desk rxr push support_desk.loop.yml rxr run support_desk "Where is my order?" --draft rxr publish support_desk rxr run support_desk "Where is my order?" ``` 1. `rxr new` writes `support_desk.loop.yml`, a small loop that saves as it is. Open the file and change its name, its description and its `entry`, the instruction the loop follows. [Building a Loop](/docs/guide/building-a-loop.md) explains every key. 2. `rxr push` saves the file as the loop's **draft**. A draft serves nobody. When the document has a problem, the answer names each one and where it is. 3. `rxr run --draft` runs the draft as you, and prints what the run does and then its reply. Change the file, push, and run again until it does what you want. 4. `rxr publish` makes the draft the version that runs use. It asks you first. `rxr chat support_desk --draft` is a conversation: each line you type is your next message. With no command at all, `rxr` lists your loops to choose from. To change a loop you have, `rxr pull support_desk` writes its document to a file, and says which version number the changed copy must carry. ## Test cases A loop document can declare test cases: example conversations that must pass before a version publishes ([Testing a Loop](/docs/guide/testing-a-loop.md)). ``` rxr test support_desk ``` This runs each case against the draft and prints a verdict for each, with the reason when one fails. Each case is a run that costs money, so `rxr` asks before it starts them. A case run acts on nothing live. ## Runs | Command | What it does | | --- | --- | | `rxr run ""` | Starts a run and follows it to its reply. `--draft` runs the draft. | | `rxr say ""` | Sends your next message to the same run. | | `rxr watch ` | Follows a run that is working. | | `rxr show --events` | Reads a run now, with each thing it did. | | `rxr approve ` | Allows a step the run waits for. `--decline` refuses it. | | `rxr stop ` | Asks a run to stop. | | `rxr runs` | Lists recent runs. | When a run waits for your approval, `rxr` shows what it asks and waits for your answer. A run costs what any run costs, wherever it was started. ## For an AI agent An agent that drives `rxr` reads `rxr guide`: the whole of this page for a program, with the order of the commands and what each exit status means. - **`--json`** on any command prints one JSON document on standard output, and nothing else. - **No question is asked** when there is no terminal. A step that publishes, or that spends money on test cases, then needs `--yes`: the agent asks you, and passes it when you agree. - **The exit status says what happened**, so a program need not read sentences: | Status | Meaning | | --- | --- | | 0 | Done. | | 1 | plutonium.io refused the request. The message says why, and names the fix. | | 2 | The command line is wrong, or `--yes` is missing. | | 3 | Not signed in. | | 4 | A run waits for an approval. | | 5 | A run ended without success, or a test case failed. | | 6 | plutonium.io could not be reached. | | 7 | The wait ran out and the run is still working. | An AI tool that speaks MCP needs no `rxr`: it connects to the same server. `rxr mcp` prints the lines that add it to Claude Code, Cursor or another tool.