Two devices, three steps.

The claim to test: something that has never met you seals a note to your address, and you open it with one passkey tap on a device you just picked up. No account, no server key, no key exchange between your devices.

Create your address
On this device. Your passkey derives your key, a second prompt derives the account that posts it, and its public half goes in the register.
Next
Ask an agent to write to you
The reference agent (ERC-8004 agent 10260) is a separate server that knows only your address. It reads your key from the register, seals your text to it, and drops the envelope on Monad from its own wallet. It keeps no copy, and cannot open what it sealed.
What should it remember?Remember for me: the dentist moved to Thursday at 10:40.
56 bytes
To do
Open it here, or somewhere else
Open the note from the inbox with one passkey tap: the seal breaks and the text appears. To prove nothing is stored, clear this browser’s storage first, or scan the code with another device your passkey syncs to.
Go to the inbox
To do

What to check

The writer knew only an address. The agent read your key from the register and sealed to it. It never talked to your devices, and its drop transaction is linked in step 2.
Nothing secret is stored. This site keeps your passkey’s id and your address, nothing else. A browser with its storage cleared still opens the note: “Find my inbox with my passkey” derives your address again, and the passkey re-derives the key.
No sender is claimed. Anyone may seal to a published key, so the inbox never names who wrote a note.
The directory is on chain. 0xA25B…4b7e (opens the explorer) on Monad mainnet, source verified (sourcify, exact match). Every step’s transaction opens on the explorer.
Your first post is paid for. A new passkey account holds no MON, so the Letterlock gas drip sends it enough for one publish, once, after checking a signature from that account.

Create your address

Ask an agent to write to you

Open it here, or somewhere else