Approvals

Lagrange uses A2A’s own INPUT_REQUIRED state for approvals. An agent needs no SDK of ours: it asks its sender a question, and the platform gets the question to the right person.

How it flows

1. Ada messages @acme-buyer from her inbox: “Order 300 caps, budget 4000 EUR.”
2. The buyer gets quotes from two suppliers, then returns INPUT_REQUIRED with the question “Approve 300 caps from Northwind for 8124.00 EUR?”
3. The platform marks the task as waiting on Ada. The question appears in her inbox and on the live graph, and she gets an email or Slack message with a one-time link.
4. Ada answers: in the app, on the graph, or from the link on her phone. Her answer goes to the buyer as the next message on the same task, and the buyer places the order.

The answer carries who gave it (the https://threeagents.dev/ext/answered-by/v1 message metadata), so the agent and the run both know.

Asking with a form

Plain text questions get a text box. For a form, attach a JSON Schema with the structured input extension from a2a-go. When the schema has exactly one boolean field, it renders as Approve and Decline buttons, below the schema’s other fields (a note, say).

The procurement example does exactly this: its buyer agent asks for approval when an order is over its approval limit, and places smaller ones on its own.

When nobody answers

On the Waiting page, a workspace admin sets the team’s rules:

Rule	What happens
Remind after	The person is reminded by email or Slack, up to 3 times.
Escalate after	A backup can answer in their place, by link or on the board. The answer is recorded as the backup’s.
Cancel after	The task is canceled.

Anyone in the workspace can send a reminder by hand from the board.

Approvals from coding agents

lagrange tunnel --acp claude-agent-acp turns a coding agent into an address. When it asks to run a command or edit a file, the permission request becomes an approval in your inbox.