# How to use the Pi coding agent

> How to use the Pi coding agent: install it, sign in with /login, pick a model, branch sessions with /tree and /fork, compact context and script it with -p.

Part 6 of [Using coding agents: Claude Code, Cursor, Codex and more](https://polylane.com/series/using-coding-agents/)
By Boris Tane, Founder of Polylane · Published October 17, 2026 · 3 min read
Canonical: https://polylane.com/learn/coding-agents/how-to-use-the-pi-coding-agent/

To use Pi, install it with the installer script or npm, run pi in your project and use /login to connect a subscription or API key. Choose a model with /model, branch a session with /tree, /fork or /clone to try another approach, and use /compact when the history grows. For scripts, pi -p runs once and prints the reply.

To use Pi, **install it, run `pi` in your project, connect a model with `/login`, and learn the session commands: `/tree`, `/fork` and `/clone` to try another approach, `/compact` when the history gets long.** For scripts, `pi -p` runs once and prints the answer.

Pi is a minimal, extensible coding agent harness for the terminal. It ships with strong defaults and deliberately leaves out features such as sub-agents and plan mode: you add what you need, or install it as a package. The steps below follow [Pi's documentation](https://github.com/badlogic/pi-mono/tree/main/packages/coding-agent).

## 1. Install Pi

Pi needs Node.js 22.19 or newer. On macOS and Linux:

```bash
curl -fsSL https://pi.dev/install.sh | sh
```

Or with npm:

```bash
npm install -g --ignore-scripts @earendil-works/pi-coding-agent
```

## 2. Start it and sign in

```bash
cd ~/code/my-app
pi
```

Run `/login` inside Pi to connect a subscription or an API key for a built-in provider. The startup header lists the instructions and resources Pi loaded, which is the quickest way to check it picked up what you expected.

## 3. Pick a model and how hard it thinks

| Command | What it does |
| --- | --- |
| `/model` | Select a model |
| `/thinking` | Select how much reasoning the current model uses |
| `/settings` | Change common preferences |
| `/logout` | Remove a provider's access |

From the command line, `--model` selects a model by exact or fuzzy name, and `--provider` limits the lookup to one provider.

## 4. Work in sessions

Pi saves every session. The commands that make that useful:

- **`/new`** starts a fresh session for a new task.
- **`/name`** gives the current session a name you will recognise later.
- **`/resume`** opens another saved session; `pi --continue` from the same folder resumes the most recent one.
- **`/tree`, `/fork` and `/clone`** let you explore another approach without losing the work you have.
- **`/compact`** reduces the conversation history sent to the model when a long session starts to slow down.
- **`/session`** shows the session's file, ID, message count, token usage and cost.

Branching is Pi's answer to a wrong turn: fork before a risky change, and if it goes badly, go back to the branch that worked.

## 5. Script it

```bash
pi -p "summarise the changes on this branch"
pi --mode json "list the failing tests"
```

`-p` runs the prompt once, prints the final reply and exits. `--mode json` streams JSONL events instead, for a program that wants to follow each step.

## Give Pi production context

Pi works from your repository. It can read the code that failed, but not the logs, traces and deploys that show how it failed. [Polylane gives Pi that context](/for/pi/): it connects to the platforms you already run on, so Pi can see when something breaks there.

Using Pi? See [how to give Pi production context with Polylane](https://polylane.com/for/pi/).

## Common questions

**What is Pi?**

A minimal, extensible coding agent harness for the terminal. It ships with strong defaults and leaves out features such as sub-agents and plan mode, which you can add yourself or install as packages.

**What does Pi need to run?**

Node.js 22.19 or newer. Install it with the installer script, or with npm as @earendil-works/pi-coding-agent.

**How do I resume a Pi session?**

Run pi --continue in the same folder to resume the most recent session, or /resume inside Pi to open another saved one.

**How do I try a different approach without losing my work?**

Use /tree, /fork or /clone. Each lets you explore another direction while the existing session stays intact.

**Can I run Pi from a script?**

Yes. pi -p runs the prompt once, prints the final reply and exits, and --mode json streams JSONL events instead.

## Sources

- [Pi coding agent (README)](https://github.com/badlogic/pi-mono/tree/main/packages/coding-agent)
- [Using Pi (Pi docs)](https://github.com/badlogic/pi-mono/blob/main/packages/coding-agent/docs/usage.md)
- [Pi CLI reference (Pi docs)](https://github.com/badlogic/pi-mono/blob/main/packages/coding-agent/docs/cli.md)

## About the author

Boris Tane is the founder of Polylane. He previously founded Baselime, observability for the future of the cloud, which Cloudflare acquired. At Cloudflare he built and led the Workers observability team.

## More in this series

[Using coding agents: Claude Code, Cursor, Codex and more](https://polylane.com/series/using-coding-agents/)

1. [How to use Claude Code: a practical guide](https://polylane.com/learn/coding-agents/how-to-use-claude-code/)
2. [How to add MCP servers to Cursor](https://polylane.com/learn/coding-agents/how-to-add-mcp-servers-to-cursor/)
3. [How to use Codex CLI: install, AGENTS.md, MCP and exec](https://polylane.com/learn/coding-agents/how-to-use-codex-cli/)
4. [How to use OpenCode: install, plan and build, MCP](https://polylane.com/learn/coding-agents/how-to-use-opencode/)
5. [How to add MCP servers to GitHub Copilot in VS Code](https://polylane.com/learn/coding-agents/how-to-add-mcp-servers-to-github-copilot/)
6. [How to use the Pi coding agent](https://polylane.com/learn/coding-agents/how-to-use-the-pi-coding-agent/)

Previous: [How to add MCP servers to GitHub Copilot in VS Code](https://polylane.com/learn/coding-agents/how-to-add-mcp-servers-to-github-copilot/)

Get started with one command: `curl -fsSL https://polylane.com/setup | bash` installs the CLI, connects your coding agents, and creates the account.