Tags and diagnostics

A tag names the kind of node. It is half the node’s identity and the label that appears in diagnostics.

Tags

Create a tag with Frond.tag(value).

tag: Frond.tag("resources/profile"),

The value must be a non-empty string with no whitespace. Use stable, path-like names — resources/profile, services/auth-session — that read well grouped in a list. The tag is part of the node id, so renaming it changes the identity of every node built from the spec. See Identity and keys.

Labels and ids

A node surfaces in two forms:

Form	Shape	Example
Node id	tag:key	resources/profile:v1:{"userId":"u_42"}
Diagnostics label	kind:tag	resource:resources/profile

The label carries the kind, which is why the kind is worth setting even though it does not change behavior.

Snapshots

A node snapshot is the inspectable state of one node. Each carries:

Field	Description
tag, kind, key, label	Identity and naming.
status	Unwired, Invalid, or Wired with a run state of idle, pending, ready, or error.
resultValidity	Current, Stale, or Expired.
operation	The running operation, if any.
operationFailure	The last operation failure.
liveDemand	Whether the node is live, and its sources.

Snapshots are passive — reading one never starts work or creates liveness demand.

Report sinks

The runtime emits events for readiness, operations, validity changes, eviction, liveness, and failures. Attach a sink to receive them. Frond.Diagnostics.createRuntimeReportSink turns raw events into readable reports.

import * as Frond from "@frondruntime/core";

const runtime = Frond.createRuntime({
  sinks: [
    Frond.Diagnostics.createRuntimeReportSink({
      name: "console",
      handleReport: ({ report }) => {
        console.log(report);
      },
    }),
  ],
});

Frond.Diagnostics also exposes createErrorReport for projecting a single failure and serializeCauseChain for flattening an Effect cause into readable frames. See Error projection.

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Next: React provider — the provider and hooks in depth.