# Pi

> The agent engine, with its login, its configuration, its tools and its models.

[Pi](https://github.com/earendil-works/pi) is built into Solipsist. There's nothing to install: the agents run inside
the Solipsist process, using Pi as a library.

## What it needs

A model it can call. Any one of these:

- an [OpenRouter key](https://solipsist.sh/docs/start/openrouter/) in `SOLIPSIST_OPENROUTER_KEY` (or `pi.openrouter_key`),
- a login saved in Pi: run `pi`, then `/login`,
- a provider in Pi's own `models.json`, such as a [model on your computer](https://solipsist.sh/docs/start/local-models/).

Until one of those exists, the status bar says **Connect a model**, and asking for something opens a dialog that says
how, instead of starting a run that would fail.

## It is your Pi

Solipsist reads Pi's configuration the way the `pi` command does in the folder you run it from: `~/.pi/agent`, and a
project `.pi` in the folder. Your saved logins, skills and settings work here too. Pi's session files for a run are
kept where `pi` keeps them for that folder, so you can open one in `pi` afterwards.

## Tools

An agent may use the tools in `pi.tools` (`SOLIPSIST_PI_TOOLS`, comma-separated). The default is `read`, `grep`,
`find`, `ls`, `bash`, `write` and `edit`. It leaves out MCP, codemode and tool search, so an agent never starts your MCP
servers.

- `write` and `edit` can only write to the page's images folder. The page itself is never written by an agent: it
  answers with a suggestion, and you decide.
- `bash` runs where Solipsist runs and isn't sandboxed. Remove it from `pi.tools` if you don't want an agent to run
  commands.

A permission prompt from a Pi extension can't be answered, because nobody is at the keyboard. It is refused and shows
in the [agent panel](https://solipsist.sh/docs/reference/agent-panel/) as an error.

## Models

The picker shows a shortlist (`pi.models`, with your `agent.preferred_models` pinned to the top) and can search every
model your Pi can run. Solipsist reads Pi's model list from its files and doesn't ask the network, so the list is as
fresh as the last time you ran `pi`. To refresh it, run `pi` once.

A model is `<provider>/<model>`, for example `openrouter/anthropic/claude-haiku-5.5`. On a page it's saved as
`pi:<provider>/<model>`.

## In the file

The settings are in [Configuration](https://solipsist.sh/docs/reference/configuration/): `pi.models`, `pi.tools` and `pi.openrouter_key`.

Source: https://solipsist.sh/docs/engines/pi/