Module models 

Structs

Capability

Schema declaration of a capability supported by a backend plugin.

CapabilityValue

A concrete capability value chosen by the client for a specific call.

FileCitation

A citation into a retrieved document, attached to a text message part.

LinkCitation

A citation into a web page, attached to a text message part. Shares the [N] index namespace with FileCitation.

LinkReference

A lightweight URL badge attached to a text message part (no quote/anchor).

Message

A message node in the immutable conversation tree.

MessagePart

A persisted, ordered fragment of a message body.

MessagePartInput

The wire / plugin shape of a message part before persistence: a type plus its typed content. Chat Engine assigns id and number on persist and returns a full MessagePart.

Session

A chat session: the top-level container that groups a conversation’s messages, tenant/user ownership, backend plugin binding, and lifecycle.

SessionType

A registered session type — pairs a human-readable name with the backend plugin instance that will process its sessions’ messages.

StreamingChunkEvent

A single text fragment appended to the assistant message in flight.

StreamingCitationEvent

Mid-stream citations/references attached to a part (StreamingEvent::Citation). Unlike the batch set carried on Complete, these arrive incrementally; they target the part at part_number.

StreamingCompleteEvent

Signals the assistant message is fully persisted and the stream is closing.

StreamingErrorEvent

Signals a mid-stream failure; the assistant message may be incomplete.

StreamingPartEvent

Emits a complete typed message part mid-stream (StreamingEvent::Part): images, videos, links, code, or an additional text part. The part is appended to the message document and persisted on finalize.

StreamingSessionMetaEvent

Session-scoped metadata patch (StreamingEvent::SessionMeta); shallow-merged into the owning session’s metadata while the message streams.

StreamingStartEvent

Opens a stream for a given assistant message.

StreamingStateEvent

Opaque assistant-message state patch (StreamingEvent::State); merged into the finalized message’s metadata under state.

StreamingStatusEvent

Transient progress indicator (StreamingEvent::Status). Streamed to the client for live feedback but not persisted with the finalized message.

StreamingToolEvent

Tool-invocation trace (StreamingEvent::Tool), e.g. a file search the plugin ran; appended to the finalized message’s metadata under tools.

TenantId

Tenant identifier. Opaque string from the auth token, used to scope all queries. Newtype distinguishes it from UserId at compile time so call sites cannot accidentally swap tenant and user arguments.

TextPositionAnchor

Per-marker source-location anchor, parallel to one entry in a citation’s text_positions. Forwarded verbatim from the plugin (see DESIGN cpt-cf-chat-engine-design-entity-citations).

UserId

End-user identifier (opaque string from the auth token). Newtype distinguishes it from TenantId at compile time.

VariantInfo

Summary of one variant at a given tree position — returned when listing variants for a message so clients can render navigation UI.

Enums

HealthStatus

Plugin health status returned by ChatEngineBackendPlugin::health_check.

LifecycleState

Lifecycle state of a session.

MemoryStrategy

Per-session memory strategy controlling how much conversation history is sent to the backend plugin on each call.

MessagePartType

Type discriminant for a MessagePart. The base set is fixed; plugin vendors extend it via GTS without forking Chat Engine core.

MessageRole

Message author role.

RetentionPolicy

Message retention policy — when messages in a session should be cleaned up.

StreamingEvent

NDJSON streaming event emitted by a plugin during response generation.