How Sommelier handles your data

Sommelier encrypts workbook operations and conversations between the Excel task pane and the local bridge attached to your chosen agent. The relay does not hold the encryption secret.

What the relay can see

The relay sees an opaque connection ID, connection capability, endpoint role, IP addresses, timing and message sizes. It holds its rendezvous registry in memory and forwards encrypted frames. Cells, prompts, replies and tool results are decrypted only at the two endpoints.

What is stored on your device

The task pane stores authorized terminal names, connection secrets and the automatic reconnection preference in its browser storage. The bridge stores credentials in ~/.sommelier with owner-only file permissions on macOS and Linux. Chat, cell data and automatic write approval are not saved by this pairing feature. Choose Forget in Excel and run the bridge's forget --name NAME command to remove both local records.

Your agent and model provider

Your selected harness receives workbook data through bounded tool calls. Any further transfer to a model provider is controlled by that harness and its settings. The one-time setup contains a secret: if pasted into a model-backed chat, that harness may include it in its provider request or history.

Trust boundary

End-to-end encryption protects traffic from the relay, provided the task pane and bridge code are trusted. An operator able to replace those client files, a browser extension with access to the pane, or malware on an endpoint can bypass that protection. The application host must therefore be trusted or independently controlled. The protocol does not provide forward secrecy if a saved pairing secret is later stolen.

This page describes the application architecture. A public deployment still needs its operator's identity, contact details and applicable privacy terms.