Struct AiSdkEncoder 

pub struct AiSdkEncoder { /* private fields */ }

Stateful encoder for AI SDK v6 UI Message Stream protocol.

Tracks text block lifecycle (open/close) across tool calls, ensuring text-start and text-end are always properly paired. This mirrors the pattern used by AG-UI encoders for AG-UI.

Text lifecycle rules

• TextDelta with text closed → prepend text-start, open text
• ToolCallStart with text open → prepend text-end, close text
• RunFinish with text open → prepend text-end before finish
• Error → terminal, no text-end needed

Implementations

impl AiSdkEncoder

pub fn new() -> Self

Create a new encoder.

The encoder is fully initialized when the first RunStart event arrives, which sets the message_id from the run ID.

pub fn message_id(&self) -> &str

Get the message ID.

pub fn on_agent_event(&mut self, ev: &AgentEvent) -> Vec<UIStreamEvent>

Convert an AgentEvent to UI stream events with proper text lifecycle.

Trait Implementations

impl Debug for AiSdkEncoder

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

Formats the value using the given formatter.

impl Default for AiSdkEncoder

fn default() -> Self

Returns the “default value” for a type.

impl Transcoder for AiSdkEncoder

type Input = AgentEvent

Input item type consumed by this transcoder.

type Output = UIStreamEvent

Output item type produced by this transcoder.

fn transcode(&mut self, item: &AgentEvent) -> Vec<UIStreamEvent>

Map one input item to zero or more output items.

fn prologue(&mut self) -> Vec<Self::Output>

Events emitted before the input stream starts.

fn epilogue(&mut self) -> Vec<Self::Output>

Events emitted after the input stream ends.