HITL sdk

A unified TypeScript SDK for human-in-the-loop approval in your mission ciritcal agentic workflows.

Installation

npm install @hitl-sdk/hitl

Install the workflow engine resolver for your platforms:

# for vercel's workflow sdk
npm install @hitl-sdk/resolver-workflow-sdk

# for inngest
npm install @hitl-sdk/resolver-inngest

# for temporal
npm install @hitl-sdk/resolver-temporal

Install channel adapters for the platforms:

# adapter for vercel's chat sdk
npm install @hitl-sdk/adapter-chat-sdk

# adapter for LINE Messaging API
npm install @hitl-sdk/adapter-line @line/bot-sdk

Usage

import { field, actions, isResolved } from "@hitl-sdk/hitl";
import { waitForHuman, notify } from "@/lib/hitl-client";

export async function handleInboundLead(input: { email: string; }) {
  "use workflow";

  const report = await researchAgent({ email: input.email });
  const draft = await emailWriterAgent({ email: input.email, report });

  const approval = await waitForHuman({
    message: `I wrote email to: ${input.email}. Review the email. I'll send it if you approve.`,
    actions: actions()
      .approve({
        label: "Review and send",
        fields: {
          subject: field.textField({ label: "Subject", default: draft.subject }),
          body: field.textArea({ label: "Body", default: draft.body }),
        },
      })
      .deny({
        label: "Reject",
        fields: { reason: field.textArea({ label: "Reason" }) },
      })
      .build(),
    timeout: "72h",
  });
  if (!isResolved(approval, "approve")) {
    await notify({ after: approval, message: "Rejected." });
    return;
  }

  await notify({ after: approval, message: `I'm sending email to ${input.email}...` });

  const { subject, body } = approval.feedbacks;
  await sendEmail({ to: input.email, subject, body });

  await notify({ after: approval, message: `Done.` });
}

Supported workflow engines

• Vercel Workflow SDK: @hitl-sdk/resolver-workflow-sdk
• Inngest: @hitl-sdk/resolver-inngest
• Temporal: @hitl-sdk/resolver-temporal

Supported backends for persistence

Approval state is in-memory by default. For persistence across restarts and replicas, pass a State implementation when constructing Hitl:

• Postgres: @hitl-sdk/state-pg
• SQLite (Node 22.13+): @hitl-sdk/state-sqlite
• Redis: @hitl-sdk/state-ioredis

Supported chat channels

Use @hitl-sdk/adapter-chat-sdk with the Vercel Chat SDK. One Hitl adapter covers every Chat SDK platform — install chat plus the @chat-adapter/* packages you need:

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

• Discord: @chat-adapter/discord
• Google Chat: @chat-adapter/gchat
• GitHub: @chat-adapter/github
• Linear: @chat-adapter/linear
• Messenger: @chat-adapter/messenger
• Slack: @chat-adapter/slack
• Microsoft Teams: @chat-adapter/teams
• Telegram: @chat-adapter/telegram
• Twilio: @chat-adapter/twilio
• Web: @chat-adapter/web
• WhatsApp: @chat-adapter/whatsapp

See the Chat SDK packages for the full, up-to-date list.

For LINE Official Accounts, use @hitl-sdk/adapter-line with @line/bot-sdk instead of the Chat SDK adapter. See packages/adapter-line/README.md.