Enum StreamEvent 

#[non_exhaustive]
pub enum StreamEvent {
    TextDelta {
        text: String,
    },
    ToolCallStart {
        id: CallId,
        name: String,
    },
    ToolCallDelta {
        id: CallId,
        arguments_fragment: String,
    },
    ToolCallEnd {
        id: CallId,
    },
    Usage {
        usage: TokenUsage,
    },
    ResponseId {
        id: String,
    },
    Warning {
        warning: ResponseWarning,
    },
    Finish {
        reason: FinishReason,
    },
}

One increment of a streamed answer.

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.

TextDelta

More prose.

Fields

text: String

The fragment. Concatenated verbatim; adapters do not trim.

ToolCallStart

A tool call begins. Must precede any fragment for the same id.

Fields

id: CallId

Provider-assigned id.

name: String

Tool name.

ToolCallDelta

More argument bytes for a call already started.

Fields

id: CallId

Which call.

arguments_fragment: String

A fragment of the JSON arguments. Rarely valid JSON on its own.

ToolCallEnd

A tool call’s arguments are complete.

Fields

id: CallId

Which call.

Usage

Reported token usage. Providers send it once, at the end; a later report replaces an earlier one.

Fields

usage: TokenUsage

The counts.

ResponseId

The provider’s own response identifier, as soon as the wire reveals it.

Most vendors put it on the first frame — an OpenAI chunk’s id, an Anthropic message_start, a Gemini responseId — so the caller no longer has to seed it out of band to have it on the rebuilt response. A later identifier replaces an earlier one.

Fields

id: String

The identifier. For a support ticket; never a body, never a header.

Warning

Something the adapter wants the caller to know without failing the call.

The streamed path reports exactly what the whole path reports. Without this event an adapter that had to drop a stop sequence or a cache hint could say so in ModelResponse::warnings when called whole, and had nowhere to say it when called streamed — which made the same call honest one way and silent the other.

Fields

warning: ResponseWarning

What was given up.

Finish

Generation stopped. Exactly one per stream, and it must arrive.

Fields

reason: FinishReason

Why.

Implementations

impl StreamEvent

pub fn text(text: impl Into<String>) -> Self

A text delta.

pub fn tool_call_start(id: impl Into<CallId>, name: impl Into<String>) -> Self

A tool-call announcement.

pub fn tool_call_delta( id: impl Into<CallId>, fragment: impl Into<String>, ) -> Self

An argument fragment.

pub fn tool_call_end(id: impl Into<CallId>) -> Self

A tool-call terminator.

pub fn response_id(id: impl Into<String>) -> Self

The provider’s response identifier.

pub const fn warning(warning: ResponseWarning) -> Self

A warning the adapter wants carried into the rebuilt response.

pub const fn kind(&self) -> &'static str

Stable snake-case label.

pub const fn is_user_visible(&self) -> bool

Returns true for the events a UI may render directly (spec §18.5: only model-authored prose is streamed to the user).

Trait Implementations

impl Clone for StreamEvent

fn clone(&self) -> Self

Returns a duplicate of the value.

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

Performs copy-assignment from source.

impl Debug for StreamEvent

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

Formats the value using the given formatter.

impl<'de> Deserialize<'de> for StreamEvent

fn deserialize<__D>(__deserializer: __D) -> Result<Self, __D::Error>

where __D: Deserializer<'de>,

Deserialize this value from the given Serde deserializer.

impl Eq for StreamEvent

impl PartialEq for StreamEvent

fn eq(&self, other: &Self) -> bool

Equality operator ==.

fn ne(&self, other: &Rhs) -> bool

Inequality operator !=.

impl Serialize for StreamEvent

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

where __S: Serializer,

Serialize this value into the given Serde serializer.

impl StructuralPartialEq for StreamEvent