Use Middleware

Install the first-party middleware stack so kernel operations gain caching, parameter-file resolution, and glTF edge detection without any kernel changes. Middleware intercepts kernel operations inside the worker; call sites stay untouched.

Prerequisites

• Install @taucad/runtime
• Completed the Quick Start

Steps

1. Add the toolkit to defineRuntime

The @taucad/middleware toolkit's default preset installs the standard stack. The preset fixes execution order; middleware runs in onion-model order, first registered outermost:

// @ts-nocheck: the docs workspace does not install @taucad/middleware.
import { createRuntimeClient } from '@taucad/runtime';
import { defineRuntime } from '@taucad/runtime/worker';
import { replicad } from '@taucad/replicad';
import { esbuild } from '@taucad/esbuild';
import { fromMemoryFs } from '@taucad/runtime/filesystem';
import { inProcessTransport } from '@taucad/runtime/transport/in-process';
import { middleware } from '@taucad/middleware';

const runtime = defineRuntime({
  plugins: [replicad(), esbuild(), middleware()],
});

const client = createRuntimeClient({
  transport: inProcessTransport({ runtime, fileSystem: fromMemoryFs() }),
});

2. Know what each middleware does

The default preset installs four middleware, in order:

• parameterFileResolver() — merges persisted parameter-group values from .tau/parameters/<entry>.json over the request parameters.
• parameterUnits() — infers units for parameters whose schema does not declare one.
• geometryCache() — caches evaluate results as MessagePack binaries under .tau/cache/geometry/, skipping kernel computation when code and parameters are unchanged.
• gltfEdgeDetection() — adds edge primitives to glTF meshes for sharp-edge rendering.

3. Give caches a writable filesystem

Caches persist only when the filesystem is writable and durable. Use fromNodeFs in Node.js; with fromMemoryFs() the caches still run but do not survive the session:

// @ts-nocheck: the docs workspace does not install @taucad/middleware.
import { createRuntimeClient } from '@taucad/runtime';
import { fromNodeFs } from '@taucad/runtime/filesystem/node';
import { inProcessTransport } from '@taucad/runtime/transport/in-process';
import { defineRuntime } from '@taucad/runtime/worker';
import { replicad } from '@taucad/replicad';
import { esbuild } from '@taucad/esbuild';
import { middleware } from '@taucad/middleware';

const runtime = defineRuntime({
  plugins: [replicad(), esbuild(), middleware({ preset: 'cache' })],
});

const client = createRuntimeClient({
  transport: inProcessTransport({ runtime, fileSystem: fromNodeFs('/path/to/project') }),
});

The 'cache' preset shown here installs only geometryCache — pick it when your viewer needs no edge rendering or parameter files.

4. Render as usual

Middleware runs automatically inside the worker. document.export(target, request) and view subscriptions in Live Rendering need no changes; cached results flow through the same result shapes as fresh ones.

Related

• Middleware Model — How the onion model works
• Create Custom Middleware — Build your own middleware
• API Reference: Middleware — Middleware types and factories
• Set Up the Filesystem — Filesystem adapters for persistent caches