Update UI with application data - Rixx UI

Pass application data separately from model-generated source. This avoids serializing sensitive or large tool results into the language channel and lets the host update values without regenerating UI.

const source = `root = Metric(label="Open incidents", value=$data.openCount)`;

<RUIRenderer data={{ openCount: incidents.length }}>{source}</RUIRenderer>;

Binding roots

Root	Host input
`$data`	Read-only committed application or tool data
`$context`	Read-only rendering context
`$draft`	Read-only host-provided draft values
`$item`	Current item inside an `Each` template

Bindings are values, not expressions. The allowlisted pure functions can compare, compose booleans, select fallbacks, count or sum values, format values, and choose responsive values; they cannot perform I/O or mutate state.

“Trusted data” means the host controls the channel, not that every value is safe for every operation. Validate server/tool data before use, minimize sensitive fields, and never turn bound strings into HTML, code, URLs, or authorization decisions without the relevant policy check.

Host inputs may change while source remains stable. Rixx UI reevaluates bindings against the new input without asking a model to regenerate the component graph.