Approvals

Some tools shouldn't run until a person says yes: sending an email, issuing a refund, deleting a page. The AI SDK gives you the button: mark the tool, and the run pauses with an approval request.

What happens after the click is where it gets interesting.

Tomorrow. The user closes the laptop and approves the next morning, on their phone. If the paused run lived in a server's memory or a websocket, it's gone.

Twice. A double click, or the same card open in two tabs. The second click shouldn't send the email again.

Too late. A card in a tab left open since yesterday, from a conversation that has moved on. Approving it shouldn't restart an old answer.

From somewhere else. The approval arrives as a Slack button, or a subagent deep in a delegation needs one. The browser that started the run isn't involved at all.

Forged. The approval comes from the client. If the server trusts the client's copy of the paused message, a client can approve a refund it was never shown, with an amount of its choosing.

What Latch does

The pause lives in the conversation. A paused run is just its message, waiting for a decision. It survives restarts and deploys, and the decision can come from any device or channel, any time later.

Only the decision comes from the client. Latch takes which approval and yes or no, nothing else. The tool runs with the input the agent asked for, as stored.

Repeats and stale cards are ignored. A decision for an approval that's already handled, or that the conversation has moved past, does nothing.

Several at once. If one step asks for three approvals, the run waits until all three are answered, then runs exactly the approved ones and tells the agent which were declined.

Subagents ask in the parent chat. An approval needed by a subagent appears where the user actually is.

defineAgent({
  model,
  tools: { send_email, refund },
  toolApproval: { send_email: "user-approval", refund: "user-approval" },
});

// The client: the AI SDK's own approval flow, nothing custom.
const { addToolApprovalResponse } = useChat({
  transport,
  sendAutomaticallyWhen: lastAssistantMessageIsCompleteWithApprovalResponses,
});
<button onClick={() => addToolApprovalResponse({ id: part.approval.id, approved: true })}>Approve</button>;

Decisions from elsewhere, like a Slack button, go to runtime.applyApproval({ chatId, principal, decisions }).