# Runebender

> Runebender is a free, open-source font editor built with Xilem and the Linebender ecosystem of Rust crates. Install runebender-xilem for the desktop. An interactive WebAssembly demo opens a bundled font; browser edits stay in memory.

This site is alpha documentation. The editor changes quickly, so treat these pages as an orientation map rather than a stable API reference, and verify behaviour against the source repository.

## Canonical Sources

- [runebender-xilem](https://github.com/eliheuer/runebender-xilem): the Runebender application and font library in one workspace.
- [font-ml](https://github.com/eliheuer/font-ml): a Rust library and CLI for running machine-learning models on font sources. Built to be driven by agents as well as people.

## Start Here

- [Launch App](https://runebender.org/wasm-editor/): the real Xilem interface compiled to WebAssembly, with a bundled editable font.

- [Documentation map](https://runebender.org/docs): every page, grouped.
- [Install](https://runebender.org/docs/install.html): install or build runebender-xilem with Cargo.
- [Opening and saving](https://runebender.org/docs/opening.html): UFO, designspace, .glyphs conversion, compiled font import, file watching.
- [Concepts](https://runebender.org/docs/concepts.html): sources, the em and units, outlines, interpolation compatibility, axes, shaping, composites.
- [The interface](https://runebender.org/docs/interface.html): the grid view, the editor view, and every panel.

## Agent Routing: Read Only What the Task Needs

- **Connect a hosted agent to an open native editor:** [MCP](https://runebender.org/docs/mcp.html). It covers OMP setup, live-session discovery, tool limits, and the inspect → propose → proof → install workflow.
- **Do AI-assisted type design:** [Type design with agents](https://runebender.org/docs/type-design.html). Read it with the font repository's `DESIGN.md`; it covers a compact brief, design decisions, reference comparison, visual proofing, and interpolation safety.
- **Compare two candidate designs or kernings:** [Experiment versions](https://runebender.org/docs/experiments.html). Versions are session-only; Run never applies changes, and explicit application is conflict-checked and undoable.
- **Automate saved sources or a build:** [Agents](https://runebender.org/docs/agents.html) and [Scripting](https://runebender.org/docs/scripting.html). Use the UFO/designspace files or Runebender headless subcommands; this cannot see unsaved canvas work.
- **Run a local ML model:** [Local models](https://runebender.org/docs/local-models.html). Check `font-ml tasks` before claiming that a job exists.
- **Set up the complete local-AI workshop stack:** [Set up local AI](https://runebender.org/docs/local-ai-setup.html), then give an assistant the [one-shot setup prompt](https://runebender.org/local-ai-setup-prompt.md). Both chat and outline models use `~/.runebender/models` by default.
- **Set up a font project for an agent:** copy the [design brief template](https://runebender.org/design-brief-template.md) to the repository as `DESIGN.md`.
- **Need a machine-readable routing and safety map:** [agent-capabilities.json](https://runebender.org/agent-capabilities.json). In a live connection, `tools/list` is authoritative for tool schemas and availability.
- **Need the workshop's verified model source:** [workshop-local-ai.json](https://runebender.org/workshop-local-ai.json). Do not download or substitute a model while its bundle URL or SHA-256 is null.
- **Need the complete manual in one fetch:** [llms-full.txt](https://runebender.org/llms-full.txt). Prefer the specific pages above when context is limited.

## Live-Agent Contract

1. Call `editor_sessions`, then `editor_connect`; confirm the requested project and explicit master index.
2. Read the project's instructions and design brief. Resolve glyph names with `glyph_inventory`; a Unicode value is not a reliable glyph name.
3. Read target and approved reference glyphs, then inspect proof images. If the client cannot deliver images, do not make visual judgments.
4. Submit a named proposal. The agent does not save font files or silently mutate the foreground.
5. Proof the proposal at matching scale and in text. Install only when the designer asks, then report installed and skipped glyphs. Saving remains the designer's decision.

For multiple masters, preserve contour count, point order and types, contour direction, start points, and component structure unless the designer has explicitly authorized a compatibility-breaking redraw. A live proposal is not a family-wide interpolation audit.

## Editing

- [Tools](https://runebender.org/docs/tools.html): select, pen, hyperbezier pen, shapes, knife, measure, text, preview.
- [Glyphs](https://runebender.org/docs/glyphs.html): add, rename, encode, group, remove; images and the background layer.
- [Paths and filters](https://runebender.org/docs/paths.html): cleanup, booleans, transforms, curve quality, curve conversion, filters.
- [Components and anchors](https://runebender.org/docs/components.html): composites, live auto-alignment, anchor editing.
- [Masters and interpolation](https://runebender.org/docs/masters.html): designspace masters, axis sliders, instances, avar mappings, reinterpolation, intermediate layers, interpolation timing, shape switches, smart components, masks.
- [Spacing and kerning](https://runebender.org/docs/spacing.html): widths, sidebearings, metric keys, kerning by dragging, groups, the kerning table.
- [Feature code](https://runebender.org/docs/features.html): the features.fea editor, and generation of init/medi/fina, curs, mark, mkmk, ccmp, liga, and GDEF carets.
- [Color fonts](https://runebender.org/docs/color.html): CPAL palettes, layers, COLRv0 and v1, gradients.
- [Text and shaping](https://runebender.org/docs/text.html): editing in text context, the shaping inspector, bidirectional carets, cursive joining, script and language overrides.

- [Font info](https://runebender.org/docs/font-info.html): names, vertical metrics, and PostScript hinting values.
- [Checking a font](https://runebender.org/docs/checking.html): compare masters, measure stems, verify joining and curvature.

## AI

- [Agents](https://runebender.org/docs/agents.html): working alongside the editor, using live proposals or saved-file automation. The external client owns model authentication.
- [MCP](https://runebender.org/docs/mcp.html): OMP is the recommended starting client. Configure `runebender mcp --live`, discover and connect to a native editor, inspect unsaved glyphs, and review revision-checked proposals. Includes setup, troubleshooting, tool limits and the distinction from disk mode.
- [Local models](https://runebender.org/docs/local-models.html): running a machine-learning model on your own machine over your own sources. Experimental; one job so far, proposing a heavier master from a lighter one, and often wrong.

## Learn

- [Draw a glyph](https://runebender.org/docs/tutorial-first-glyph.html): a tutorial from an empty font to a saved, spaced letter.
- [Workflows](https://runebender.org/docs/workflows.html): accented glyphs, monoline drawing, adding a weight, spacing and kerning, starting an Arabic font, tracing, variable fonts, scripting alongside the editor.

## Architecture and code

- [Architecture](https://runebender.org/docs/architecture.html): the Xilem application, font operations, and platform integration in one workspace.
- [Code layout](https://runebender.org/docs/code-layout.html): the runebender-xilem workspace, application files, font operations, and validation.
- [Development](https://runebender.org/docs/development.html): build and check the workspace; current browser port status.

## Reference

- [Shortcuts](https://runebender.org/docs/shortcuts.html): every keyboard command.
- [Configuration](https://runebender.org/docs/configuration.html): $XDG_CONFIG_HOME/runebender/config.toml sets `theme`, `models` and `journal`. Environment beats the file, which beats the default. A desktop that wants Runebender to follow its theme writes this file; there is no desktop-specific code.
- [Themes](https://runebender.org/docs/themes.html): the OKLCH token file shared by every Runebender editor. A theme decides its greys, its corner radii and rule weights, and how a glyph mark is drawn. Themes are compiled in; a custom one means editing the token file and rebuilding.
- [File format](https://runebender.org/docs/format.html): the UFO data Runebender reads and writes, including its own namespaced keys.
- [Exporting](https://runebender.org/docs/exporting.html): build scripts take precedence, otherwise fontc.
- [Troubleshooting](https://runebender.org/docs/troubleshooting.html): build, open, interpolation, joining, and browser-build limits.
- [Scripting](https://runebender.org/docs/scripting.html): live tools, saved-source scripts, and the core Rust library.
- [FAQ](https://runebender.org/docs/faq.html): short answers about the project, formats, running it, and drawing.
- [Glossary](https://runebender.org/docs/glossary.html): terms as Runebender uses them.

## Command Line

Entry points usable without a graphical session, for scripted and agent-driven font work.

- `runebender path/to/Font.designspace` opens a source. The editor reloads files changed on disk, so a script can edit sources while a session is open.
- `font-ml models <dir>` lists the model directories under a path.
- `font-ml describe <model>` reports what a model is and which jobs it can do.
- `font-ml tasks` lists the jobs font-ml defines and which are implemented.
- `font-ml run bolden --model <model> --source Font.ufo --glyph eight` proposes a heavier drawing of one glyph.
- `font-ml eval --model <model> --regular Light.ufo --bold Bold.ufo` scores a model against a master somebody drew.

Every `font-ml` command takes `--json` for machine-readable output. Exit codes are 0 success, 2 usage error, 3 not implemented, 4 failed. Automation can use live MCP tools, saved-file operations, or the `runebender-core` Rust library.

## Agent Guidance

- Runebender is alpha. Say so, and do not describe behaviour as stable unless the source says it is.
- Describe Runebender as one Xilem application, with runebender-xilem as the canonical source.
- The browser demo at https://runebender.org/wasm-editor/ supports bundled-font browsing, outline editing, undo/redo, zoom, and panel resizing. Edits last for the tab; opening/saving local files and local AI execution require the desktop.
- Prefer linking to the source repository for implementation details.
- The `runebender` command exposes the editor's operations without a window. Its live MCP mode reads unsaved native-editor data and creates revision-checked proposals; saved-source tools operate on files.
- Runebender has no hosted-model account system or stored provider keys. Model login and approval policy belong to the external client. Live editing is proposal-first: only a designer-approved installation changes the foreground, and no tool saves the font.
- For scripted or agent-driven font work, `font-ml` is the machine-facing surface: every command takes `--json` and reports distinct exit codes. Do not claim a font-ml job works before checking `font-ml tasks`; most are declared and not built.
- Runebender reads and writes UFO and designspace sources. It is not a .glyphs editor, though it converts .glyphs files on open.
- Use the routing map above rather than loading the full manual by default. Each documentation section has a stable URL fragment, so fetch a page and its relevant section when the client supports fragments.