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The CLI is a thin shell over a server-side, importable API. A backend can do NL → eDSL → IR → (preview + diff) without shelling out or re-implementing the evaluator. Three subpath exports of the reframe-video npm package:
importwhat
reframe-videothe core eDSL + IR — scene, compileScene, composeScene, evaluate, sceneManifest, lintScene, validateScene
reframe-video/compileload + validate + determinism — loadScene, loadSceneFromCode, loadModule, checkDeterminism, SceneLoadError, ValidationIssue
reframe-video/rendererDisplayList → Canvas 2D — renderFrame, drawDisplayList, ImageRegistry, VideoRegistry, coverRect
reframe-video/compile executes the scene module in-process. Treat untrusted or model-authored source as code: bound it with a timeout and run it where a misbehaving module can’t do harm. True sandboxing is a separate concern.

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Load & validate a scene

import { loadScene, loadSceneFromCode, SceneLoadError } from "reframe-video/compile";

try {
  const compiled = await loadScene("scene.ts");        // bundle + validate → CompiledScene
  // or: await loadSceneFromCode(sourceString)          // no file on disk
} catch (err) {
  if (err instanceof SceneLoadError) {
    err.kind;     // "bundle" | "eval" | "validation" — which stage failed
    err.issues;   // ValidationIssue[] on a validation failure
  }
}
A ValidationIssue is structured, not prose — so a UI can point at the exact broken node: 
interface ValidationIssue {
  code: string;     // stable category, e.g. "unknown-blend", "duplicate-node-id"
  path: string;     // locator, e.g. "nodes.box", "timeline.beat(intro)[0]", "camera.zoom"
  message: string;  // the human-readable line
}
The CLI mirrors this: reframe compile --json returns { ok: false, error, kind, issues } on failure.

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Check determinism

import { checkDeterminism } from "reframe-video/compile";

const { deterministic, findings } = await checkDeterminism("scene.ts");
// compiles the source twice and diffs the IR; `findings` pins the first
// differing address when a Math.random() / Date leaked into a prop.
This is what reframe lint runs for the source-purity half of its gate.

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Render a frame

import { renderFrame } from "reframe-video/renderer";
import { compileScene, evaluate } from "reframe-video";

const ctx = canvas.getContext("2d")!;        // any Canvas 2D context
renderFrame(ctx, compiled, t);                // draw the scene at time t
renderFrame evaluates the compiled scene at t and paints the resulting DisplayList; pass an ImageRegistry / VideoRegistry to supply raster sources for image / video nodes. This is the same path the live browser preview uses.