# Context ruler

> What fills a model's context window. Sample data: context of four requests on a 128K scale, split into system, history, tools, docs and output.

- Type 081 · Part of a whole
- Component: `<ContextRuler>`, the same name as the Figma component
- Install: `npx shadcn add @chartory/context-ruler` (free in Hearth: the public registry, no token; Signal with Code and Complete)
- Type page: https://usechartory.com/charts/context-ruler

## Installation

1. **Set up the registry once.** This chart is free in Hearth and MIT licensed: no token. Add @chartory to components.json once (the URL alone, no headers), or skip this when another chart is already installed. [Installation guide](https://usechartory.com/docs/installation)

2. **Add the chart.** One command adds the Context ruler component to your project.

```bash
npx shadcn add @chartory/context-ruler
```

3. **Use it.** Pass your rows. The props are the Figma properties.

usage.tsx:

```tsx
import { ContextRuler }
  from "@/components/chartory/context-ruler"

<ContextRuler
  data={requestContext}
  size="m"
  legend
/>
```

## Props

### `<ContextRuler>`

Every prop but data is a Figma property with the same name and values.

| Prop | Type | Default | Note |
| --- | --- | --- | --- |
| data | ContextRulerData | Required | The chart's data. The tables below list every field. |
| size | "xs" \| "s" \| "m" \| "l" | "m" | The size class. Each one is laid out again from the data. |
| legend | boolean | true | Shows the legend row under the plot. |
| color | "cat-1" \| "cat-2" \| "cat-3" \| "cat-4" | "cat-1" | The data colour of the primary marks (data/primary). |

### ContextRulerData

The data prop: one object for the whole chart.

| Prop | Type | Default | Note |
| --- | --- | --- | --- |
| max | number | Required | The top of the value scale. |
| limit | number | Required | The limit. |
| ticks | number[] | Required | The axis tick values. |
| kinds | ContextRulerKind[] | Required | One entry per kind: label and colour. |
| rows | ContextRulerRow[] | Required | One entry per row. |

### ContextRulerKind

One object per entry in kinds.

| Prop | Type | Default | Note |
| --- | --- | --- | --- |
| label | string | Required | The name shown on the chart. |
| tok | string | Required | The colour token, e.g. "data/primary". |

### ContextRulerRow

One object per entry in rows.

| Prop | Type | Default | Note |
| --- | --- | --- | --- |
| label | string | Required | The name shown on the chart. |
| segs | number[] | Required | The segments. |

## Context ruler: a React and Figma chart in four sizes

### What does a context ruler show?

A context ruler draws each request's context as a bar on a token scale, split into system, history, tools, documents and output. You see what takes the room and how close each request is to the limit. Use it for LLM apps and agents.

Chartory ships it as a Figma component and a React component with the same name. The code installs from the shadcn registry with one command and lands in your project as a file you own.

### What is the Context ruler component?

It is one **<ContextRuler>** component. Its props are the Figma properties with the same names and values, and the props table above lists them. The data is tokens per part, per request.

Sizes **XS**, **S**, **M** and **L** re-lay the chart out from the data instead of scaling it, so labels stay readable at every size.

### When should I use it?

- **Is there a token limit?** Yes means the context ruler fits.
- **Are requests compared?** Yes means the context ruler fits.
- **Is it the split, not the trend?** Yes means the context ruler fits.

### When does another type fit better?

- **Parts of one total, no limit.** Use Stacked bars instead.
- **One request in detail.** Use Flame graph instead.
- **Usage over time.** Use Area chart instead.

## Context ruler questions

### Does the Context ruler chart work with shadcn/ui?

Yes. It installs through the shadcn registry with the shadcn CLI, and the file lands in your project.

### How do I install it?

It is free in Hearth and MIT licensed: add the @chartory registry URL once, no token, then run npx shadcn add @chartory/context-ruler. The Installation guide has the steps.

### Can my coding agent install it?

Yes. Connect the Chartory MCP server and ask for the context ruler chart; the agent runs the same command and you review the diff.

### What data does it expect?

Tokens per part, per request. The sample data comes with the component, and the props table lists every field.

### Which sizes does it ship in?

XS, S, M and L, in Figma and in code. Each size is laid out again from the data, so text and lines keep their size.

### Is it in the Figma file too?

Yes. chart/081-context-ruler has the same properties as the component.

### Does it follow light and dark mode?

Yes. Every paint is a token, so the chart follows light and dark mode and the collection you pick.

### Which plan has the code?

None for Hearth: it is free in the public registry, no token. The Signal collection (@chartory/signal) comes with Code and Complete.