---
title: Effort and models — Claude basics, lesson 3
description: The model is which Claude does the work; effort is how long it thinks first. The four models, the five effort levels, instibrain's xhigh, and ultrathink.
url: https://instibrain.ai/guides/claude-basics/effort-and-models
updated: 2026-10-28
site: https://instibrain.ai/llms.txt
---

lesson 3 of 7 · claude basics

# Effort and models.

The model is which Claude does the work. Effort is how long it thinks before it acts.

## new words

**Model**
One version of Claude. Bigger models reason better; smaller ones answer faster.

**Effort**
A level from `low` to `max`. Higher effort thinks longer and checks more.

## the lesson

| Model | Use it for |
| `opus` | Complex work. instibrain starts you on it. |
| `sonnet` | Most everyday tasks, a little faster. |
| `haiku` | Small, simple tasks. The fastest. |
| `fable` | The hardest, longest tasks. Before a Fable request uses paid usage credits, Claude asks you first. |

Effort has five levels: `low`, `medium`, `high`, `xhigh` and `max`. A lower level answers sooner and uses less of your plan. A higher level thinks longer and checks more of its own work.

instibrain's setup sets `xhigh`. Check that yours is set: Opus 5.5 starts at `medium` until a level is chosen. `max` lasts for one session only; the other levels stay until you change them.

For one hard question, write `ultrathink` anywhere in your message. Claude thinks deeper for that one answer, and your level stays the same.

One scale, five levels. max lasts for one session only.

## try it

Type this and press Enter:

```
/effort status
```

If the answer is not `xhigh`, type:

```
/effort xhigh
```

## you should see

- Your effort level.
- After `/effort xhigh`, the level is saved, so your next sessions start at `xhigh` too.
- To see the models, type `/model`. Press Esc to close the list without a change.

---

instibrain is made by WebWork AI, Inc. Everyone uses the same models · the difference is what yours knows.