Documentation Index

Fetch the complete documentation index at: https://agentclientprotocol.com/llms.txt Use this file to discover all available pages before exploring further.

Message IDs are stabilized

Announcement that optional Agent-generated message IDs are now part of the stable ACP v1 protocol.

Published: June 5, 2026

The Message ID RFD has moved to Completed and optional Agent-generated messageId fields are stabilized in ACP v1.

Agents can attach opaque, unique IDs to streamed message chunks. Chunks with the same ID belong to the same message, while a changed ID marks a new message, giving Clients a reliable boundary beyond changes in chunk type.

For the protocol documentation, see Message IDs.

Last updated Oct 08, 2026