key-handover

name	key-handover
description	Hand off a Fast account's signing key from the user's wallet to your agent runtime using fast-cli's `authorize` commands. Use when the user wants to authorize you to sign on their behalf for a Fast account.

Key handover (fast-cli)

Setup

Check if fast-cli is installed:

fast --version

If it's not installed, ask the user to install it and wait for them to confirm — do not install it yourself. Show them this command:

npm install -g @fastxyz/cli

Flow

# 1. Generate the request.
fast authorize request --requester "my-agent" --json
# → { "auth_url": "...", "request_fingerprint": "123456", "request_expires_at": "..." }

If the user specified a particular authorize URL (e.g., a dev or staging environment), pass it via --url <URL>.

Show auth_url and the 6-digit request_fingerprint to the user. Tell them to open the URL in their Fast wallet, verify the fingerprint matches, approve, then paste back the encrypted handover code.

STOP and wait. Do not fabricate or guess the handover code. It can only come from the user after they approve in their wallet.

# 2. Once the user pastes the code, decrypt it.
fast authorize complete --message '<the code they pasted>' --json
# → { "private_key": "0x..." }

After success, confirm to the user that the key was received. Do not echo the private key back to them — they already have it in their wallet.