A unique identifier for the thought message.
OptionalcontentComplete replacement content for this thought message.
Optional_The _meta property is reserved by ACP to allow clients and agents to attach additional
metadata to their interactions. Omitted leaves the stored metadata unchanged; null
clears it. An object patches the stored metadata by top-level key: keys it omits are
unchanged, a key set to null is removed, and any other value replaces that key's
stored value without merging nested objects. Beyond this patch rule, implementations
MUST NOT make assumptions about values at these keys.
See protocol docs: Metadata Patches
An agent thought or reasoning message upsert.
Only [
AgentThought::message_id] is required.contenthas patch semantics: an omitted field leaves existing thought content unchanged,nullclears the value, and a concrete array replaces the previous value. For a newmessageId, omitted fields use client defaults.contentis replaced as a whole array; send[]ornullto clear it.Message updates and chunks are applied in the order they are received. When an
agent_thoughtupdate includescontent, that array replaces any content previously accumulated for the thought, including content from earlier chunks. Later chunks with the samemessageIdappend to the current content.