Typography

Source: design/tokens/typography.tokens.json. Values in px; the apps scale them with the system setting (iOS Dynamic Type, Android font size, Windows text size) through MediaQuery.textScaler. Images: Components.

Font choice

Role	Font	License	Axes
Interface, messages	Atkinson Hyperlegible Next	SIL Open Font License 1.1	variable, weight 200 to 800, with italic
Code, tool names, IDs, metrics	Atkinson Hyperlegible Mono	SIL Open Font License 1.1	variable, weight 200 to 800, with italic

Evidence: package data of @fontsource-variable/atkinson-hyperlegible-next@5.3.0 and @fontsource-variable/atkinson-hyperlegible-mono@5.3.0 (license OFL-1.1, axis wght 200 to 800; https://fontsource.org/fonts/atkinson-hyperlegible-next, retrieved 2026-10-10 [verified]). Source repositories: https://github.com/googlefonts/atkinson-hyperlegible-next and https://github.com/googlefonts/atkinson-hyperlegible-next-mono (retrieved 2026-10-10 [verified]). The font family comes from the Braille Institute and is designed for people with low vision; the "Next" version appeared in 2025 with seven weights and a mono variant [verified through the Fontsource page and press reports, primary page of the Braille Institute not read].

Reasons:

1. Readability as a property of the font. Confusable characters (I, l, 1; 0, O) are clearly distinct. In a chat with IDs, paths, commands and code, this is a working advantage, not decoration.
2. A face of its own. The font is recognizably different from the usual grotesques (Inter, system fonts) of the generic look and different from Discord's house font.
3. One family for text and code. Next and Mono share shapes and letter spacing; metrics in the live box (mono) sit calmly next to running text.
4. Variable. One font file per style covers all weights; this keeps app bundles small.
5. Free license. OFL allows embedding in apps and redistribution; the license text is included (tools/design-tokens/vendor/fonts/*.OFL.txt, likewise in the app package).

Study B recommended system fonts (SF, Segoe UI). The requirement "unmistakable" and readability weigh more; the system fonts remain as fallback in font.family.*.

Rejected: Inter (generic look), system font alone (no face of its own, different per platform), Bricolage Grotesque (strong, but too idiosyncratic for dense lists), fonts close to Material or Discord.

Roles

Components use only these roles, never font.size.* directly.

Role	Character	Use
type.display	very large, extra bold, set tighter	empty states, setup, metric tiles
type.title	large, bold	title of a view, dialog
type.heading	medium, semibold	channel and thread header, sections
type.body	base size, regular	message text on desktop
type.body-strong	base size, semibold	author name
type.body-sm	one step smaller	list rows, channel names, live box
type.label	small, semibold	buttons, chips, badges
type.section	small, bold, set wider	space titles in the sidebar
type.caption	small, regular	timestamps, help texts
type.code	mono, one step below base size	code blocks, inline code
type.code-sm	mono, small, medium	tool chips, costs, token counts

Sizes, weights, line heights and letter spacing are in the generated Token reference; this page gives only names and intent.

Message text on touch devices: density.message-font-size (context touch) instead of the size from type.body, so that the iPhone does not read smaller than the system default.

Rules

• No uppercase by transformation. Long German words ("Benachrichtigungen") become unreadable in capitals. Space titles differ through weight and letter spacing.
• Numbers in mono where they change. Run time, cost, tokens, context in the live box use type.code-sm, so that the line does not jump while counting up.
• Dynamic type size up to 200 percent without loss of content (WCAG 2.2 SC 1.4.4, https://www.w3.org/TR/WCAG22/, retrieved 2026-10-10 [verified]). Rows grow in height; columns collapse into the navigation stack on narrow windows (see 01-product.md).
• Markdown. Headings in messages use at most type.heading; an agent cannot fill the history with display sizes.
• Fallback. If a character is missing in Atkinson (for example CJK), the fallback list from font.family.* applies; the apps bundle no further fonts.

Integration

• Flutter: packages/design_system bundles the variable TTF files of both families (upright and italic, axis wght) from the source repositories at a recorded commit, with the OFL text of each family next to them, under packages/design_system/fonts/; fonts/MANIFEST.json records source URL, commit, SHA-256 and license of every file, and test/fonts_test.dart fails on a changed, missing or extra file or a file without license text (docs/DECISIONS.md D-M4-04-4). The files carry the Google Fonts download names (<Family>-VariableFont_wght.ttf), not the bracket names of the repositories. pubspec.yaml declares the families Atkinson Hyperlegible Next and Atkinson Hyperlegible Mono. DsType (generated, copied into lib/src/generated/ by tokens.py build) supplies the TextStyle constants; dsTextStyle adds the package font name packages/design_system/<family> in front of the fallback list (apps that depend on the package register the fonts under that name) and drives the wght axis from the weight. The theme (buildDsTheme) takes its text theme from the roles through dsTextStyle; the fallback list of font.family.* stays behind it.
• Web console and docs site: WOFF2 from the same version; tokens.css provides the variables --ds-type-*.
• Preview: the WOFF2 files are under tools/design-tokens/vendor/fonts/ and are embedded.