Reactor DevTools

@openprose/reactor-devtools is the visualizer for the @openprose/reactor harness. It reads the SDK's append-only, content-addressed receipt ledger and animates the DAG the way React DevTools' "highlight updates" animates a component tree: nodes flash on render, dim-pulse on memo-skip, go red on fail, per-facet edges light on propagation, and a fresh-vs-reused token meter tracks the thesis -- cost scales with surprise, not the clock.

The standalone command is reactor-devtools. It ships deliberately decoupled from the CLI (no @openprose/reactor-cli dependency); folding it in behind a reactor dev verb is the intended end-state, with the standalone bin as the interim surface.

Replay-first

DevTools is replay-first: you point it at a saved state directory and it re-derives the whole run from the durable trail. Replay needs zero running reactor and zero model key -- the receipts and world-models on disk are the complete record.

reactor-devtools <state-dir>
# reactor-devtools: replaying 92 receipt(s) across 14 node(s)
#   open http://127.0.0.1:4555/

A state directory is what reactor run and reactor serve already persist: the receipt ledger, the world-models, and the compiled topology. Open it and the run plays back, beat for beat.

React DevTools for the Reactor

The Reactor borrows its shape from React, and so does its DevTools. If you have used React DevTools' "highlight updates," you understand this in one screen:

The shot React DevTools can't take is the one that matters most here: a node that correctly did nothing. A quiet Reactor is a screen full of dim grey pulses and a flat cost line, and that is the point.

Two ways to read a run

DevTools meets two different readers -- a human at a browser and an agent at a terminal:

• The viewer -- reactor-devtools <state-dir> boots a local server and a no-build SPA: the layered DAG, a live cost meter, the ordered receipt timeline, and a scrubber that steps the cascade. See The viewer.
• --describe -- a headless, browser-free text dump of the same run: per-node dispositions, the cost rollup, chain-verification, and a one-line-per-frame trace. The surface an agent (or a CI gate) reads to check a run without rendering pixels. See --describe.

Where it sits in the stack

DevTools is a pure, near-zero-dependency reader. Its only runtime dependency is @openprose/reactor itself; every read goes through the SDK's createReplaySession shaping helper -- imported from the package's curated . front door -- so the viewer never re-implements the reconciler's moved-facet diff or its propagation. The SDK stays headless and zero-dep; every opinionated UI choice is quarantined in this package.

@openprose/reactor        the harness -- compiles + runs, writes receipts
  └─ "@openprose/reactor" : createReplaySession    shapes the ledger into a replay (ordering, moved facets, cost)
@openprose/reactor-cli    the CLI -- `reactor run` / `serve` persist the state-dir
@openprose/reactor-devtools   this package -- reads the state-dir, animates it

createReplaySession is re-exported from the curated . front door, so the import is just import { createReplaySession } from "@openprose/reactor" -- no deep subpath. See the SDK front door for the full reference.

Install

npm install -g @openprose/reactor-devtools

The package ships the reactor-devtools bin and an importable library. Its one runtime dependency is @openprose/reactor; the server is built on Node's node:http and the front-end is a hand-rolled, no-build SVG SPA. No web framework, no graph library, no bundler.

Where to go next