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Vercel Chat SDK Adds Callback URLs to Automate Human Approval Workflows

Vercel, the frontend cloud and AI infrastructure platform, updated its Chat SDK—a library for building cross-platform bots—with a callbackUrl prop for buttons and modals. This integrates with the Workflow SDK to enable human-in-the-loop interactions within chat interfaces like Slack and Microsoft Teams.
Supported platforms
Slack, Microsoft Teams
Required SDKs
Chat SDK, Workflow SDK
UI components
Buttons, Modals
Implementation
callbackUrl prop
Availability
General availability

Building reliable agents requires safety checkpoints for high-stakes actions. This update builds on the Vercel Workflows feature and follows the release of Vercel Chat SDK's standardized toolset by moving orchestration logic into the infrastructure layer. It mirrors OpenRouter's human-in-the-loop tools by standardizing how autonomous systems request permission.

You can implement these flows by passing a workflow webhook URL to the callbackUrl prop inside a <Card> component. The SDK handles the event payload and resumes the workflow once the user responds. This is available now for all developers using the Chat SDK with official adapters for Slack and Teams.

View the full update on vercel.com
Sam Altman
Sam Altman
@sama
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Still wondering? A few quick answers below.

Developers can now add a callbackUrl prop to buttons and modals within the Chat SDK. When a user interacts with these UI elements in a chat platform, the event payload is sent to the specified URL. This mechanism allows an external system to receive user input and trigger subsequent logic automatically.

You can implement human in the loop by using the Workflow SDK to create a webhook that pauses a running execution. By passing this webhook URL to a Chat SDK button via the callbackUrl prop, the workflow remains suspended until a human clicks the button, which sends the signal to resume.

The callbackUrl prop is supported for buttons on most platforms that have an official Chat SDK adapter. For modal components, the functionality is currently available specifically for Slack and Microsoft Teams. This allows developers to collect form data or approvals directly within those enterprise messaging environments.

The Vercel Chat SDK is a TypeScript library designed for building AI-powered chatbots and agents that function across multiple platforms like Slack, Teams, and Discord from a single codebase. It provides specialized components like cards and buttons to create interactive interfaces that go beyond simple text-based chat.

Yes, the Chat SDK supports callback URLs for modals on Slack and Microsoft Teams. When a user submits a form or interacts with a button inside a modal, the resulting form data and event payload are sent to the designated callback endpoint, which can then resume a paused workflow.

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