Struct Message 

pub struct Message {

    pub message_id: Uuid,
    pub session_id: Uuid,
    pub tenant_id: Option<TenantId>,
    pub user_id: Option<UserId>,
    pub parent_message_id: Option<Uuid>,
    pub variant_index: u32,
    pub is_active: bool,
    pub role: MessageRole,
    pub parts: Vec<MessagePart>,
    pub file_ids: Vec<Uuid>,
    pub metadata: Option<Value>,
    pub is_complete: bool,
    pub is_hidden_from_user: bool,
    pub is_hidden_from_backend: bool,
    pub created_at: OffsetDateTime,
    pub updated_at: OffsetDateTime,
}

A message node in the immutable conversation tree.

Messages form a DAG rooted at the session: each message (except the first) has a parent_message_id, and siblings sharing the same parent are variants differentiated by variant_index. Exactly one sibling per parent is is_active=true, which defines the current conversation path.

Fields

message_id: Uuid

Unique message identifier (primary key).

session_id: Uuid

Session this message belongs to.

tenant_id: Option<TenantId>

Owning tenant, denormalized from the parent session so message-scoped queries and sharding don’t require a join. When set, always equals the session’s tenant_id. None only for legacy rows persisted before the column existed (not yet backfilled).

user_id: Option<UserId>

Author of this specific message (not the session owner). Set to the authenticated user for user-role messages; None for assistant / system messages (machine-generated, no human author) and un-backfilled legacy rows. Enables author attribution in multi-user / shared sessions.

parent_message_id: Option<Uuid>

Parent message in the tree; None for the first (root) message.

variant_index: u32

Ordinal among siblings sharing the same parent_message_id within the same session. Starts at 0 and increments per recreate.

is_active: bool

True if this variant is currently on the active conversation path. Exactly one sibling per parent should be active.

role: MessageRole

Who produced the message: user / assistant / system.

parts: Vec<MessagePart>

Ordered, typed body fragments. The parts in number order form the message body (replaces the former single content blob). Empty only for a freshly-created assistant stub before its text part is persisted.

file_ids: Vec<Uuid>

External file UUIDs referenced by this message. Chat Engine forwards them opaquely — file content is never fetched by Chat Engine itself.

metadata: Option<Value>

Per-message metadata (model used, finish_reason, usage, etc.). Typed as JSON because it is plugin-defined.

is_complete: bool

true once the assistant finished streaming (or the message was persisted whole). User messages are always complete on creation.

is_hidden_from_user: bool

Hide this message from client UIs (e.g., system messages, internal summaries that should not appear in the transcript).

is_hidden_from_backend: bool

Exclude this message from the history sent to backend plugins (e.g., messages already covered by a newer summary).

created_at: OffsetDateTime

Creation timestamp (UTC).

updated_at: OffsetDateTime

Last-modified timestamp (UTC). Typically changes only when an assistant placeholder is filled in.

Trait Implementations

impl Clone for Message

fn clone(&self) -> Message

Returns a duplicate of the value.

fn clone_from(&mut self, source: &Self)

Performs copy-assignment from source.

impl Debug for Message

fn fmt(&self, f: &mut Formatter<'_>) -> Result<(), Error>

Formats the value using the given formatter.

impl<'de> Deserialize<'de> for Message

fn deserialize<__D>( __deserializer: __D, ) -> Result<Message, <__D as Deserializer<'de>>::Error>

where __D: Deserializer<'de>,

Deserialize this value from the given Serde deserializer.

impl Serialize for Message

fn serialize<__S>( &self, __serializer: __S, ) -> Result<<__S as Serializer>::Ok, <__S as Serializer>::Error>

where __S: Serializer,

Serialize this value into the given Serde serializer.