# Agent harness quickstart

> Run your own agent loop with Harny in a few lines of Python, on your own model key.

## Install

Install the SDK. It needs Python 3.10 or newer.

```bash
pip install harny
```

## Run a first agent

Save this as a script. Use your app key, which starts with `fsa_`. In real code, read it from your environment, for example from `HARNY_APP_KEY`, instead of writing it in the file.

```python
import asyncio
from harny import HarnyClient
from harny.agent import Agent, AgentConfig, FileSessionStore

async def main():
    async with HarnyClient(api_key="fsa_...") as harny:   # your app key, read from the environment in real code
        agent = await Agent.create(
            harny=harny,
            preset="cost_first",                           # resolved against Harny's model roster
            config=AgentConfig(instructions="You help one person with their calendar."),
            store=FileSessionStore("./data/sessions"),
        )
        result = await agent.run(user="demo-user", message="Put the dentist on Thursday at 3pm")
        print(result.answer, [p.public() for p in result.pending_confirmations])

asyncio.run(main())
```

The loop runs in your code. The presets are `cost_first`, `quality_first`, and `regulated`.

## Model key

Harny never sees your model key. Put it in the provider's conventional variable, for example `ANTHROPIC_API_KEY`. The SDK reads it from there. You can also pass it as `api_key=` with `provider=` in code.

## What the result holds

`agent.run` returns a result with these fields:

- `run_id`: the id of this run.
- `answer`: the reply text for the person.
- `stopped_reason`: one of `completed`, `cut_off`, `max_steps`, `spend_cap`, `timeout`, `model_error`, or `blocked`.
- `steps` and `actions`: what the agent did during the run.
- `pending_confirmations`: actions that wait for a yes.
- `usage`, `cost_usd`, `model`, and `trace_id`.

## Default limits

A run uses these defaults:

- `actions`: `("calendar.create_event",)`
- `allow_undo`: `True`
- `max_steps`: 6
- `run_timeout_s`: 90
- spend cap: 100,000 tokens

## Confirm a pending action

An action that needs a yes comes back in `pending_confirmations`. Each item is a pending confirmation. Your code approves or refuses it. The model cannot do this.

```python
await agent.confirm(pending, approve=True)   # or approve=False to refuse
```

Which actions wait for a yes depends on the permission settings of your app. See [Permissions](/docs/agent-harness/permissions).

## Where runs show up

Set `record_runs=True` to send a short summary of each run after it ends. The summary holds the step kind, tool name, outcome, duration, and token counts. It never holds the person's message or the answer text. A failed send does not change the run.

Every action is also recorded. Harny records each one with `POST /v1/actions`, and you can list and export the records.

## Next

- [Agent harness overview](/docs/agent-harness/overview)
- [Permissions](/docs/agent-harness/permissions)
- [Long jobs](/docs/agent-harness/long-jobs)