Enum ProviderEvent 

#[non_exhaustive]
pub enum ProviderEvent {
    Start {
        partial: Arc<AssistantMessage>,
    },
    TextStart {
        content_index: usize,
        partial: Arc<AssistantMessage>,
    },
    TextDelta {
        content_index: usize,
        delta: String,
        partial: Arc<AssistantMessage>,
    },
    TextEnd {
        content_index: usize,
        content: String,
        partial: Arc<AssistantMessage>,
    },
    ThinkingStart {
        content_index: usize,
        partial: Arc<AssistantMessage>,
    },
    ThinkingDelta {
        content_index: usize,
        delta: String,
        partial: Arc<AssistantMessage>,
    },
    ThinkingEnd {
        content_index: usize,
        content: String,
        partial: Arc<AssistantMessage>,
    },
    ToolCallStart {
        content_index: usize,
        tool_call_id: Option<String>,
        tool_name: Option<String>,
        partial: Arc<AssistantMessage>,
    },
    ToolCallDelta {
        content_index: usize,
        delta: String,
        partial: Arc<AssistantMessage>,
    },
    ToolCallEnd {
        content_index: usize,
        tool_call: ToolCall,
        partial: Arc<AssistantMessage>,
    },
    ImageStart {
        content_index: usize,
        mime_type: String,
        partial: Arc<AssistantMessage>,
    },
    ImageDelta {
        content_index: usize,
        delta: String,
        partial: Arc<AssistantMessage>,
    },
    ImageEnd {
        content_index: usize,
        data: String,
        mime_type: String,
        partial: Arc<AssistantMessage>,
    },
    Done {
        reason: StopReason,
        message: AssistantMessage,
    },
    Error {
        reason: StopReason,
        error: AssistantMessage,
    },
}

Stable since 0.63.0

Streaming events emitted by providers

Note: We use crate::AssistantMessage directly to avoid type alias conflicts

Variants (Non-exhaustive)

Non-exhaustive enums could have additional variants added in future. Therefore, when matching against variants of non-exhaustive enums, an extra wildcard arm must be added to account for any future variants.

Start

Stream started with partial assistant message.

Fields

partial: Arc<AssistantMessage>

Partial assistant message state.

TextStart

Text content block started.

Fields

content_index: usize

Index of the content block in the message.

partial: Arc<AssistantMessage>

Partial assistant message state.

TextDelta

Incremental text delta received.

Fields

content_index: usize

Index of the content block in the message.

delta: String

The text delta to append.

partial: Arc<AssistantMessage>

Partial assistant message state.

TextEnd

Text content block finished.

Fields

content_index: usize

Index of the content block in the message.

content: String

The complete text content.

partial: Arc<AssistantMessage>

Partial assistant message state.

ThinkingStart

Thinking content block started.

Fields

content_index: usize

Index of the content block in the message.

partial: Arc<AssistantMessage>

Partial assistant message state.

ThinkingDelta

Incremental thinking delta received.

Fields

content_index: usize

Index of the content block in the message.

delta: String

The thinking text delta to append.

partial: Arc<AssistantMessage>

Partial assistant message state.

ThinkingEnd

Thinking content block finished.

Fields

content_index: usize

Index of the content block in the message.

content: String

The complete thinking content.

partial: Arc<AssistantMessage>

Partial assistant message state.

ToolCallStart

Tool call block started.

Fields

content_index: usize

Index of the content block in the message.

tool_call_id: Option<String>

The tool call ID from the provider, if available at start time. Providers that only surface the ID later (in deltas/end) leave this None.

tool_name: Option<String>

The tool name, if available at start time.

partial: Arc<AssistantMessage>

Partial assistant message state.

ToolCallDelta

Tool call delta received (partial JSON arguments).

Fields

content_index: usize

Index of the content block in the message.

delta: String

The delta string to append to tool arguments.

partial: Arc<AssistantMessage>

Partial assistant message state.

ToolCallEnd

Tool call block finished.

Fields

content_index: usize

Index of the content block in the message.

tool_call: ToolCall

The complete tool call with resolved arguments.

partial: Arc<AssistantMessage>

Partial assistant message state.

ImageStart

Image content block started (incremental image streaming, e.g. Gemini).

Mirrors omp’s AssistantMessageEvent::image_start. Without this event family, providers that stream images incrementally (Gemini) cannot represent image output — see P0-D in the omp-realignment design.

Fields

content_index: usize

Index of the content block in the message.

mime_type: String

MIME type of the incoming image (e.g. image/png).

partial: Arc<AssistantMessage>

Partial assistant message state.

ImageDelta

Incremental image delta received (base64-encoded chunk).

Fields

content_index: usize

Index of the content block in the message.

delta: String

Base64-encoded image bytes delta to append.

partial: Arc<AssistantMessage>

Partial assistant message state.

ImageEnd

Image content block finished.

Fields

content_index: usize

Index of the content block in the message.

data: String

The complete base64-encoded image data.

mime_type: String

MIME type of the image.

partial: Arc<AssistantMessage>

Partial assistant message state.

Done

Stream completed successfully.

Fields

reason: StopReason

Why the model stopped generating.

message: AssistantMessage

The final assistant message.

Error

Stream ended with an error.

Fields

reason: StopReason

The stop reason at time of error.

error: AssistantMessage

Error details in assistant message form.

Implementations

impl ProviderEvent

pub fn partial(&self) -> Option<&AssistantMessage>

Extract the partial assistant message if present

pub fn is_done(&self) -> bool

Check if this is a done event

pub fn is_error(&self) -> bool

Check if this is an error event

Trait Implementations

impl Clone for ProviderEvent

fn clone(&self) -> ProviderEvent

Returns a duplicate of the value.

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

Performs copy-assignment from source.

impl Debug for ProviderEvent

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

Formats the value using the given formatter.