> ## Documentation Index
> Fetch the complete documentation index at: https://platform.stepfun.ai/docs/llms.txt
> Use this file to discover all available pages before exploring further.
# Pi
Pi is an open-source terminal coding agent maintained by earendil-works, with tools for reading files, editing code, and running commands. A custom provider connects it to Step Plan through the Anthropic Messages API.
## Requirements
* macOS, Linux, or Windows with Node.js 22.19 or later and npm.
* An active [Step Plan subscription](https://platform.stepfun.ai/step-plan), available quota, and access to the model.
* An API key from the [StepFun platform API keys page](https://platform.stepfun.ai/interface-key).
Run the following commands in your terminal to check your environment:
```bash theme={"theme":{"light":"light-plus","dark":"dark-plus"}}
node --version
npm --version
```
If your Node.js version is `v22.19.0` or later and npm successfully returns a version number, you can proceed with installing Pi.
## Install Pi
Install Pi 0.87.1:
```bash theme={"theme":{"light":"light-plus","dark":"dark-plus"}}
npm install -g --ignore-scripts @earendil-works/pi-coding-agent@0.87.1
```
Check the installed version:
```bash theme={"theme":{"light":"light-plus","dark":"dark-plus"}}
pi --version
```
## Configure Step Plan
### Set the API key
Set the environment variable in the terminal that will launch Pi. Replace `YOUR_STEP_API_KEY` with your key.
```bash theme={"theme":{"light":"light-plus","dark":"dark-plus"}}
export STEP_API_KEY="YOUR_STEP_API_KEY"
```
```powershell theme={"theme":{"light":"light-plus","dark":"dark-plus"}}
$env:STEP_API_KEY = "YOUR_STEP_API_KEY"
```
### Add models
1. Open `~/.pi/agent/models.json`. If `PI_CODING_AGENT_DIR` is set, use `models.json` in that directory instead.
2. Merge the following `providers.stepfun` entry into the file, preserving other providers. If the file does not exist, create the directory and save this JSON.
```json theme={"theme":{"light":"light-plus","dark":"dark-plus"}}
{
"providers": {
"stepfun": {
"baseUrl": "https://api.stepfun.ai/step_plan",
"api": "anthropic-messages",
"apiKey": "$STEP_API_KEY",
"models": [
{ "id": "step-5-preview", "input": ["text", "image"], "contextWindow": 1000000 },
{ "id": "step-3.7-flash", "input": ["text", "image"], "contextWindow": 256000 }
]
}
}
}
```
| Field | Description |
| - | - |
| `providers.stepfun` | Provider identifier, selected with `--provider stepfun`. |
| `baseUrl` | Step Plan configuration URL. Pi appends `/v1/messages`, producing `/step_plan/v1/messages`. |
| `api` | `anthropic-messages` selects the Anthropic Messages protocol. |
| `apiKey` | `$STEP_API_KEY` references the variable in the process environment. |
| `models[].input` | Input types the client may send. |
| `models[].contextWindow` | Context window used by the client, expressed as an integer token count. |
[Step 5 Preview](/docs/en/guides/models/step-5-preview) has a 1M-token context window; [Step 3.7 Flash](/docs/en/guides/models/step-3.7-flash) has a 256K-token window. The configuration uses `1000000` and `256000`, respectively.
### Set the default model
Merge these fields into `settings.json` in the same configuration directory:
```json theme={"theme":{"light":"light-plus","dark":"dark-plus"}}
{
"defaultProvider": "stepfun",
"defaultModel": "step-5-preview"
}
```
## Start Pi
Run Pi from your project directory:
```bash theme={"theme":{"light":"light-plus","dark":"dark-plus"}}
pi
```
To select the provider and model at launch, use:
```bash theme={"theme":{"light":"light-plus","dark":"dark-plus"}}
pi --provider stepfun --model step-5-preview
```
## Verify the integration
### Check model configuration
```bash theme={"theme":{"light":"light-plus","dark":"dark-plus"}}
pi auth check --provider stepfun --json
pi --list-models stepfun
```
An authentication status of `ready` means the client can resolve its credentials. The model list should include the configured IDs, with a 1M window for Step 5 Preview and a 256K window for Step 3.7 Flash.
### Test a conversation
```bash theme={"theme":{"light":"light-plus","dark":"dark-plus"}}
pi --provider stepfun --model step-5-preview --print "Reply only with OK."
```
Expected output: `OK`.
### Test tool calls
Create a separate test directory on a machine with Python installed. Add a `README.md` containing `Pi Step Plan test`, start Pi from that directory, and enter:
```text theme={"theme":{"light":"light-plus","dark":"dark-plus"}}
Read README.md and create hello.py that prints exactly "Hello, StepFun!".
Run hello.py with an available Python interpreter and report the command and output.
Do not modify other files.
```
Check the file-reading, creation, and command records. Confirm that `hello.py` exists and outputs `Hello, StepFun!`.
### Check usage
In the [StepFun platform](https://platform.stepfun.ai) usage details, match the request time, model ID, and billing source to confirm that the call used Step Plan.
## Common questions
Check that the active configuration directory contains valid JSON in `models.json` and the correct IDs under `providers.stepfun.models`. Open `/model` to reload the file, or restart Pi and run `pi --list-models stepfun`.
Set `STEP_API_KEY` in the terminal that launches Pi. Check that the key is complete, valid, and belongs to the account for the configured endpoint. A saved `stepfun` credential in `auth.json` takes precedence, so check that entry as well.
Set `api` to `anthropic-messages` and `baseUrl` to `https://api.stepfun.ai/step_plan`. Pi appends `/v1/messages`; the configuration URL ends at `/step_plan`.
Check the model's `contextWindow`: use `1000000` for `step-5-preview` and `256000` for `step-3.7-flash`. Reload the model list after saving and select the model again.
This documentation is built and hosted on [Mintlify](https://mintlify.com), a developer documentation platform.