# Choose the AI model

> Pick Auto, Haiku 4.5, Sonnet 4.6 or Opus 4.7 for Plexii and PlexiDesk's AI, from the box you type in or from the Advanced tab in Settings.

Source: https://plexiidesk.com/help/plexii-models
Section: Plexii assistant > Meet Plexii
Plans: All plans
Updated: 2026-10-15

PlexiDesk lets you choose which AI model does the thinking. Leave it on **Auto** and PlexiDesk picks a suitable model for each kind of job, or choose one model to use for everything. The choice is one setting, which you can change from the box you type in to Plexii or from Settings.

Choose a model when you want quicker, lighter answers for everyday questions, or more depth for long plans and hard problems.

## Before you start

- **Every plan** includes the model picker.
- **Plexii needs AI to run.** When you are signed in it runs on PlexiDesk credits, or you can use your own Anthropic key. See [AI credits and where your AI runs](https://plexiidesk.com/help/ai-credits).
- **The choice belongs to this computer.** It is saved on this computer, so if you use PlexiDesk on more than one computer, choose on each one.

## The four choices

| Choice | Cost mark | What it is for |
| --- | --- | --- |
| **Auto** | mixed | PlexiDesk chooses for each kind of job, for example Haiku for summaries and Sonnet for reasoning. This is where every new install starts. |
| **Haiku 4.5** | $ | The fastest and lowest-cost model. Good for chat and summaries, lighter on deep reasoning. |
| **Sonnet 4.6** | $$ | Strong reasoning at a good speed. |
| **Opus 4.7** | $$$ | The most capable model, for deeper reasoning and longer plans. It is the slowest and costs the most. |

The dollar signs show how the models compare on cost: one sign costs least, three cost most. **Auto** is marked **mixed** because the model, and so the cost, depends on the job.

## Choose a model while you talk to Plexii

1. Open Plexii. See [Meet Plexii, your assistant](https://plexiidesk.com/help/ai-assistant).
2. In the row of controls under the box you type in, click the model button. It shows the name of the model in use, such as **Auto**, and its tooltip begins **Model —**.
3. A menu opens above the button. Each choice shows its cost mark, its name and a line about what it is good for. A tick marks the one in use.
4. Click the model you want. The menu closes and the button shows the new name.

Your next message uses the new model. The same button sits in the **AI Chat** tab when a widget is open in focus mode, and it changes the same setting. See [Open widgets full screen and side by side](https://plexiidesk.com/help/canvas-focus-mode).

## Choose a model in Settings

1. Click the gear at the right-hand end of the header. Its tooltip says **Appearance settings**, and it opens **Settings**.
2. Click the **Advanced** tab.
3. Scroll to the bottom, to **AI model**.
4. Click **Auto**, **Haiku 4.5**, **Sonnet 4.6** or **Opus 4.7**. The one in use is highlighted and has a tick.

This is the same setting as the button under the Plexii box. Change it in either place and the other follows straight away.

## See what Auto does

While **Auto** is chosen, **Settings** > **Advanced** > **AI model** shows an **Auto routing** list under the choices. It names each kind of AI work in PlexiDesk and the model Auto uses for it, with its cost mark. For example:

- **Chat**, which is your conversations with Plexii, uses Sonnet.
- Quick summaries and sorting jobs, such as tidying a capture or tagging a file, use Haiku.
- Building a custom widget from a description uses Opus.

When you choose a single model instead, the list is hidden, because that model is used for everything.

## What the setting covers

The model you choose applies to Plexii's answers and to most of the AI work across PlexiDesk, not only the conversation in front of you. It is not saved per conversation: switching conversations keeps the same model.

## Tips

- **Start on Auto.** It gives your conversations with Plexii a strong reasoning model and keeps quick background jobs on the lower-cost one.
- **Try Haiku 4.5 for quick back-and-forth.** Short questions and summaries come back faster.
- **Switch to Opus 4.7 for a hard problem, then switch back.** Because the setting covers most of PlexiDesk's AI, leaving Opus on means most AI jobs use the highest-cost model.

## Common questions

**Does the model change what Plexii can see?** No. Every model searches the same workspace and shows the same sources. The model decides how Plexii reasons and writes, not what it reads. See [What Plexii can read and search](https://plexiidesk.com/help/plexii-what-plexii-reads).

**Does each conversation remember its own model?** No. There is one model setting for this computer, and every conversation uses it.

**I changed the model but the answer looks the same.** The new model applies from your next message. Answers already in the conversation are not rewritten. To get a fresh answer, point at the reply and click **Ask again**. See [Ask Plexii a question](https://plexiidesk.com/help/plexii-ask).

**Why does it cost more on some days?** If you are on **Auto**, the cost follows the jobs you run. If you chose **Opus 4.7**, most AI jobs use it. See [AI credits and where your AI runs](https://plexiidesk.com/help/ai-credits).

## Related tasks

- [Meet Plexii, your assistant](https://plexiidesk.com/help/ai-assistant)
- [Ask Plexii a question](https://plexiidesk.com/help/plexii-ask)
- [AI settings](https://plexiidesk.com/help/settings-ai)
- [AI credits and where your AI runs](https://plexiidesk.com/help/ai-credits)
- [Find, reopen and manage conversations](https://plexiidesk.com/help/plexii-conversations)