# Models

Set the model for one run with a flag, inside a session with the model command, or permanently with the model key. The Catalog holds what Eva knows.

A model reference is `provider/model`. Out of the box, Eva starts on
`anthropic/claude-opus-5`.

## Set the model for one run

```bash
eva --model anthropic/claude-sonnet-5
```

The flag works on every command, including `--print`.

## Set it inside a session

```
/model anthropic/claude-sonnet-5
```

With no argument, `/model` shows the current model and offers the ones Eva
knows about.

## Set it permanently

The top-level `model` key in config:

```yaml title="~/.eva/config.yaml"
model: anthropic/claude-sonnet-5
```

[Configuration](/configure/configuration) explains where that file goes and
which layer wins when several set it.

## What the catalog ships

| Reference                    | Context window |
| ---------------------------- | -------------- |
| `anthropic/claude-opus-5`    | 1,000,000      |
| `anthropic/claude-sonnet-5`  | 1,000,000      |
| `anthropic/claude-opus-4-8`  | 1,000,000      |
| `anthropic/claude-haiku-4-5` | 200,000        |
| `openai/gpt-5.6`             | 1,050,000      |
| `openai/gpt-5.4`             | 1,050,000      |
| `openai/gpt-5.4-mini`        | 400,000        |
| `openai/gpt-5.4-nano`        | 400,000        |
| `openai/gpt-4o-mini`         | 128,000        |

A model behind a [compatible endpoint](/configure/providers#compatible-endpoints)
joins this list when its entry names it, and runs either way when you type
its reference.

## The Catalog

The **Catalog** is the Domain holding providers, their models, and the
default. Provider plugins write to it and nothing owns it, so adding a
provider is adding a plugin rather than editing a list.

The Catalog also holds **Price** — what a vendor publishes per million
tokens, vendored into the binary so boot needs no network. Price feeds an
Estimate and never a Cost; [cost and usage](/use/cost) explains why those
stay apart.

## Credentials and retries

A model runs behind a provider, and the provider owns both. One API key in
the environment connects each of the first-party providers, and retries are
tunable per run. [Providers](/configure/providers) has the whole of it.

## More harnesses

The harnesses you already pay for — driven behind the same contract — arrive
with the multi-harness stage. [The roadmap](/about/roadmap) says when.


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