Building canvases

A canvas is a client-side browser application that runs in a sandboxed iframe inside PostHog. Its source lives in PostHog — not in a repository — and you read and write it through the canvas-* tools. Never write a canvas to a local file; publishing through the tool is what saves it.

Canvas work can start from any ordinary task. A dedicated canvas mode or pre-created canvas is not required. When the user asks for a board, document, form, visualization, or small app that should live in PostHog, treat that as a canvas request and follow this skill.

This skill owns freeform canvases (standalone apps). Two other canvas kinds exist: grid canvases (widget grids, including the user's home canvas) and component canvases (reusable widgets grids place). When the target is a grid or home canvas, a placement, or a reusable widget/component, load composing-grid-canvases instead — it owns the store search → configure → fork → build ladder and the layout patch loop. Authoring a component's source still uses the implementation companions below.

Resolve the target canvas