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Frontend SDK for embedding production-ready workflow editors.

Workflow Builder is an open-source SDK that gives you a ready-made workflow editor UI - canvas, nodes, edges, layout, and configuration panels - so you don't have to build workflow UX from scratch. It focuses exclusively on the frontend editor layer; execution, orchestration, and business logic stay fully under your control. The SDK outputs workflow definitions as JSON that your own backend executes.

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Try it live ->

Used in production by teams including Vercom, Athena Intelligence, Plura AI, and others.

🎉 Workflow Builder 2.0 is here.

A best-in-class SDK for embedding workflow editors, now paired with a dedicated reference backend and a fully modular plugin surface. Building products on top of a workflow editor has never been easier.

Starting with 2.0, this repository is the home of Workflow Builder. Previously we worked in a private monorepo and only partially mirrored changes here. From now on, every commit lands here directly.

See the CHANGELOG for everything that's changed since the last release.

Get started

Three onboarding paths. Pick one based on what you want to evaluate.

Goal	Path	Setup time	Docker
See the editor running in your browser	A. Try the demo	~2 min	no
Run the full reference stack (editor + execution + AI)	B. Run the full stack demo	~10 min	yes
Use the SDK inside your own React app	C. Embed the SDK	see docs	no

Want to skip the clone entirely? Try the live demo first.

Requirements

• Node 22.12.0 and pnpm 10.9.0. Both pinned in package.json. Use nvm, fnm, or corepack to match.
• Docker Desktop. Only required for Path B.

Works the same on macOS, Linux, and Windows. No platform-specific steps.

Preflight check

Run this once after cloning. It verifies Node, pnpm, Docker, port availability, and required .env files.

pnpm install
pnpm preflight

Expected output:

Workflow Builder preflight

✅ node                        22.12.0
✅ pnpm                        10.9.0
✅ docker                      running
✅ port_3001                   free (backend)
✅ port_4200                   free (demo)
✅ port_4201                   free (ai-studio)
✅ port_5432                   free (postgres)
✅ port_5433                   free (temporal-db)
✅ port_7233                   free (temporal)
✅ port_8233                   free (temporal-ui)
⚠️  apps/backend/.env           missing — copy from apps/backend/.env.example
⚠️  apps/execution-worker/.env  missing — copy from apps/execution-worker/.env.example

Ready to go. Pick a path in README.md "Get started".

The two .env warnings are expected on a fresh clone. They are only required for Path B and get created by pnpm setup:env in step 1 of that path. After that they switch to ✅ present.

Fix any red (❌) items before continuing. The script also has a --json mode for tooling: pnpm preflight --json.

Path A. Try the demo

UI only. No backend, no Docker. The fastest way to see the editor in action.

pnpm dev:demo

Expected output:

[1]   VITE vX.Y.Z  ready in NNN ms
[1]
[1]   ➜  Local:   http://localhost:4200/
[0] Found 0 errors. Watching for file changes.

Open http://localhost:4200. The editor loads with the default plugin set and a starter template. That's it.

Path B. Run the full stack demo

Full reference product: editor, Hono backend, Temporal worker, Postgres. The frontend on port 4201 is the AI Studio reference product (apps/ai-studio). Demonstrates end-to-end workflow execution.

1. Create .env files. First time only. Copies the .env.example templates into place; existing .env files are left untouched.

pnpm setup:env

2. Start infrastructure.

pnpm infra:up

Expected output (first run):

 Network backend_default            Created
 Volume "backend_temporal-db-data"  Created
 Volume "backend_app-db-data"       Created
 Container backend-app-db-1         Started
 Container backend-temporal-db-1    Started
 Container backend-temporal-1       Started
 Container backend-temporal-ui-1    Started

Verify: open http://localhost:8233 (Temporal UI). The default namespace appears.

3. Run migrations. First time, or after pulling schema changes.

pnpm -F backend db:migrate

Expected output:

> drizzle-kit migrate

Using 'postgres' driver for database querying
[✓] migrations applied successfully!

4. Start the stack.

pnpm dev:ai-studio

Expected output (three interleaved streams):

Temporal ready
[backend]    Backend running on http://127.0.0.1:3001
[worker]     Execution worker started on task queue: workflow-execution
[ai-studio]    VITE vX.Y.Z  ready in NNN ms
[ai-studio]    ➜  Local:   http://127.0.0.1:4201/

Open http://localhost:4201. Pick the "Sales Inquiry" template, click Play. The Temporal UI at http://localhost:8233 shows the running execution.

To stop: Ctrl+C, then pnpm infra:down.

Connect a real LLM (optional)

AI Studio works with stub responses out of the box. To use a real model, add to both apps/backend/.env and apps/execution-worker/.env:

OPENROUTER_API_KEY=sk-or-v1-...
AI_MODEL=anthropic/claude-3.5-haiku

If the key is missing the worker fails to start with OPENROUTER_API_KEY is required. If the model id is wrong the first AI node fails at runtime and the error surfaces in the UI log panel.

Path C. Embed the SDK

To build your own React app on top of @workflowbuilder/sdk, follow the React Component guide on the docs site. It covers installation, peer deduplication (for local-path builds until npm publish), usage, persistence strategies, theming, and the full API reference.

Troubleshooting

Symptom	Cause	Fix
EADDRINUSE on 3001, 4200, 4201, 5432, 5433, 7233, or 8233	Another process holds the port	pnpm preflight shows the conflict. Stop the other process or change the port
Temporal UI loads but the default namespace is missing	Migrations not run	pnpm -F backend db:migrate
Worker exits with OPENROUTER_API_KEY is required	Real LLM env var missing	Set it in apps/execution-worker/.env. Optional unless you want a real LLM call
pnpm dev:demo shows TypeScript errors but the dev server still starts	concurrently runs typecheck alongside Vite. TS errors are non-fatal	Fix the errors or ignore them temporarily
Vite acts up after a dependency change	Stale node_modules/.vite	rm -rf node_modules/.vite and rerun

For the full command reference, see the table in CLAUDE.md or the documentation site.

Key Features

• Plugin-first architecture - optional features can be added or removed without breaking the app
• Schema-driven properties panels - configure node inputs declaratively
• JSON-serializable workflows - plug into any backend; execution stays yours
• Design System Kit - theming and white-label support out of the box
• Configurable and extensible node system
• Visual workflow editor (nodes, edges, layout, validation)

Plugins

Workflow Builder uses a plugin-first architecture. Plugins are optional features that can be added or removed without breaking the app. For details on how the plugin system works, see the plugins guide.

Plugin	Description
Avoid Nodes Edges	Orthogonal edge routing using Web Workers and WASM
Copy Paste	Cut, copy, and paste operations for nodes and edges
Download PDF	Export diagrams to PDF
ELK Layout	Automatic node and edge arrangement using the ELK layout engine
Flow Runner	Example JSON parser that converts workflow diagrams into callable flow functions
Reshapable Edges	Manual reshaping of orthogonal edges using drag handles
Undo Redo	Local session history for undo/redo operations
Widgets	Optional node widgets displayed directly on the diagram

Typical Use Cases

Workflow Builder is commonly used to:

• embed workflow editors into B2B SaaS products
• build visual rule engines and configuration tools
• design AI agent and automation workflow platforms
• serve as a foundation for workflow-driven products and standalone apps

Repository Structure

Monorepo of Workflow Builder - a frontend-first SDK and foundation for building workflow-driven applications.

Using pnpm workspaces, Workflow Builder is split into runnable apps under apps/ and reusable libraries under packages/:

• packages/sdk - @workflowbuilder/sdk, the embeddable React library (public API, types, build)
• packages/types - @workflow-builder/types, shared TypeScript types used by the SDK and the bundled backend/worker
• packages/execution-core - Pure domain layer (ports, graph runner, node executors) shared by the bundled backend and worker
• apps/demo - Reference SPA that consumes the SDK with the full plugin set (also the source of truth for example node types, templates, and plugins)
• apps/docs - Documentation site
• apps/icons - Lazy-loadable, extensible icons consumed by the SDK

The repo also ships an example AI workflow execution backend used by the AI Studio plugin. This is not part of the frontend SDK — it is a reference implementation showing one way to pair the editor with an execution engine:

• backend - Hono HTTP server, workflow CRUD, SSE streaming; hexagonal — depends on WorkflowEnginePort
• execution-worker - Temporal worker executing workflow activities

Technical choices are documented in *.decision-log.md files that live alongside the code they relate to. See the decision logs list.

⚠️ Reference Backend — Local Development Only

The bundled execution backend (apps/backend, apps/execution-worker) is a reference implementation of the AI Studio plugin's execution layer. It has no authentication, no authorization, no user/tenant isolation, and no CORS restrictions. By default it binds only to 127.0.0.1 and the docker-compose stack does the same — nothing in the reference setup is reachable from the local network.

Do not expose this backend to the internet, a shared LAN, or any environment with untrusted users without first adding proper authn/authz. Anyone who can reach the port can read, modify, and execute every workflow.

For production deployments, see Workflow Builder Enterprise or build your own backend against WorkflowEnginePort.

License

Workflow Builder is available in two editions:

• Community Edition - Open source, Apache 2.0 licensed, this repository
• Enterprise Edition - Commercial license with long-term support, advanced features, and professional services. Learn more at workflowbuilder.io

Support

For companies that need end-to-end implementations or any other support, we offer professional consulting services.

Our team has delivered 170+ custom workflow tools across 20+ industries and brings 15+ years of experience building enterprise-class diagramming and automation tools. We can help with:

• backend execution engines
• custom integrations
• enterprise-grade customization and scaling
• accelerating time-to-market with proven architecture patterns

Talk to the team →