Install

Install the core SDK, then add one package per axis. You do not need every package. Compose only what your stack uses.

Core

terminal

npm i @hitl-sdk/hitl

@hitl-sdk/hitl provides the server, inbox API, field builders, and the internal HTTP API.

Workflow resolver (pick one)

Engine	Package	Docs
Workflow SDK	`@hitl-sdk/resolver-workflow-sdk` + `workflow`	Workflow SDK
Temporal	`@hitl-sdk/resolver-temporal` + `@temporalio/client` + `@temporalio/workflow`	Temporal
Inngest	`@hitl-sdk/resolver-inngest` + `inngest`	Inngest

terminal

# Workflow SDK (default)
npm i @hitl-sdk/resolver-workflow-sdk workflow

# Temporal
npm i @hitl-sdk/resolver-temporal @temporalio/client @temporalio/workflow

# Inngest
npm i @hitl-sdk/resolver-inngest inngest

# Workflow SDK (default)
npm i @hitl-sdk/resolver-workflow-sdk workflow

# Temporal
npm i @hitl-sdk/resolver-temporal @temporalio/client @temporalio/workflow

# Inngest
npm i @hitl-sdk/resolver-inngest inngest

If you use Vercel Workflow SDK, configure its world (runtime storage and queues) separately from Hitl's state backend below.

State backend (pick one)

In-memory is the default when you omit state. Use a persistent backend for production or multi-replica deploys.

Backend	Package	When to use
in-memory	built into `@hitl-sdk/hitl`	Local dev, single process
SQLite	`@hitl-sdk/state-sqlite`	Local dev, small deploys, Node 22.13+
Postgres	`@hitl-sdk/state-pg` + `pg`	Production, existing Postgres
Redis	`@hitl-sdk/state-ioredis` + `ioredis`	Production, existing Redis

terminal

npm i @hitl-sdk/state-sqlite
# or
npm i @hitl-sdk/state-pg pg
# or
npm i @hitl-sdk/state-ioredis ioredis

npm i @hitl-sdk/state-sqlite
# or
npm i @hitl-sdk/state-pg pg
# or
npm i @hitl-sdk/state-ioredis ioredis

See State docs for setup and migrations.

Delivery (optional add-on)

The web inbox is always included. No extra package required. Add the Chat SDK adapter only when you need Slack, Teams, Discord, or other chat platforms:

terminal

npm i @hitl-sdk/adapter-chat-sdk chat @chat-adapter/slack

Install @chat-adapter/* packages for each platform you use. See Chat SDK adapter.

Choose your stack

Use this table to jump to the detailed doc for each axis of your stack.

Your choice	Covers	Doc
Workflow SDK	`workflowResolver` + workflow client	workflow-engines/workflow-sdk
Temporal	`temporalResolver` + activity-backed client	workflow-engines/temporal
Inngest	`inngestResolver` + `step.invoke` wiring	workflow-engines/inngest
SQLite	`state` in `new Hitl()`	state/sqlite
Postgres	`state` in `new Hitl()`	state/postgres
Redis	`state` in `new Hitl()`	state/redis
Web inbox only	Built-in `hitl.inbox` (default)	channels/web-inbox
Slack / Teams / …	Channel adapters in `new Hitl()`	channels/chat-sdk
Next.js	Internal API route mounting	host-integration#nextjs
Express / Hono / …	Internal API route mounting	host-integration

Recommended default for new projects: Workflow SDK + SQLite + web inbox + Next.js, same as the Quickstart.

Environment variables

Variable	Where	Purpose
`HITL_SECRET`	Server	Bearer token for the internal workflow → server API
`HITL_URL`	Workflow / Inngest runtime	Base URL for hitl HTTP calls (when not inferred)
`HITL_POSTGRES_URL`	Server	Postgres connection for `@hitl-sdk/state-pg`
`REDIS_URL`	Server	Redis connection for `@hitl-sdk/state-ioredis`
`TEMPORAL_ADDRESS`	Server	Temporal frontend for `@hitl-sdk/resolver-temporal`

Without HITL_SECRET, the internal API is open in development and a warning is logged once.