Project settings (project.yaml)

A project picks its renderer once, in a small descriptor next to its other specs/ui files:

type: Project
renderer: redwood   # vaadin | redwood

Key	Values	Default
`type`	`Project` (required — it is how the file is recognised)	—
`renderer`	`vaadin` (served by `io.mateu:mateu-vaadin`) or `redwood` (served by `io.mateu:mateu-redwood`)	`vaadin`

There is one per project. It conventionally lives at specs/ui/project.yaml, and any file under specs/ui/ with type: Project is found too. A project without one uses the defaults, so it renders with Vaadin. The file is covered by the generated authoring schema (specs-schema.json, the type: Project branch), so editors complete and validate it.

Who reads it

Before this file existed, three unrelated places each decided the renderer. A served app’s Maven dependency decided it on the server. The visual editor had a switch for each session, and Play and the static bundle always used Vaadin. They now read the project’s choice:

Where	What it does with `renderer`
Visual editor	The canvas, the board, Play and Export always use the project’s renderer — there is no per-page or per-session switch. Opening `project.yaml` itself shows a small settings form. See the visual editor.
Play	Plays the mount in the project’s renderer. With Redwood, the whole mount runs in the real Redwood app, including the menu, routes and Play’s back/forward.
Static bundle	`mateu-bundle:bundle` ships the project’s renderer, and the editor’s Export writes a manifest that renderer can read. See static UI.
IDEs	IntelliJ (Settings → Tools → Mateu) and VS Code (the `mateu.renderer` setting, or Mateu: Project Settings…) have a project-level renderer selector. The selector reads and writes this file, and the file is the source of truth. See IDE tooling.

A served app: the dependency decides, the server warns

The renderer a served app shows is still decided by the renderer jar on its classpath. With io.mateu:mateu-vaadin it serves Vaadin, and with io.mateu:mateu-redwood it serves Redwood. project.yaml does not switch it. If the two disagree, the app your users get is not the one you designed in the editor. The server therefore logs one warning at startup:

WARN  ProjectRendererCheck -- The project descriptor (specs/ui/project.yaml) says renderer: redwood,
but this server serves vaadin (io.mateu:mateu-vaadin is on the classpath). … Depend on
io.mateu:mateu-redwood instead of io.mateu:mateu-vaadin, or set renderer: vaadin in the descriptor.

The warning is never a failure. A team may serve Vaadin while it tries Redwood out in the editor. Nothing is logged when there is no descriptor, or when the server is headless (no renderer jar on the classpath, for an API behind a separately deployed frontend). The C# and Python servers do not serve a renderer bundle, so the check does not apply to them.

To switch a served app, change the dependency and the descriptor together:

<dependency>
  <groupId>io.mateu</groupId>
  <artifactId>mateu-redwood</artifactId>   <!-- was: mateu-vaadin -->
  <version>${mateu.version}</version>
</dependency>

Project settings (project.yaml)

Who reads it

A served app: the dependency decides, the server warns

See also