Enum StreamDelta 

#[non_exhaustive]
pub enum StreamDelta {
    TextDelta {
        delta: String,
        block_index: usize,
    },
    ThinkingDelta {
        delta: String,
        block_index: usize,
    },
    ToolUseStart {
        id: String,
        name: String,
        block_index: usize,
        thought_signature: Option<String>,
    },
    ToolInputDelta {
        id: String,
        delta: String,
        block_index: usize,
    },
    Usage(Usage),
    Done {
        stop_reason: Option<StopReason>,
    },
    SignatureDelta {
        delta: String,
        block_index: usize,
    },
    RedactedThinking {
        data: String,
        block_index: usize,
    },
    OpaqueReasoning {
        provider: String,
        data: Value,
        block_index: usize,
    },
    Error {
        message: String,
        kind: StreamErrorKind,
    },
}

Events yielded during streaming LLM responses.

Each variant represents a different type of event that can occur during a streaming response from an LLM provider.

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

A text delta for streaming text content.

Fields

delta: String

The text fragment to append

block_index: usize

Index of the content block being streamed

ThinkingDelta

A thinking delta for streaming thinking/reasoning content.

Fields

delta: String

The thinking fragment to append

block_index: usize

Index of the content block being streamed

ToolUseStart

Start of a tool use block (name and id are known).

Fields

id: String

Unique identifier for this tool call

name: String

Name of the tool being called

block_index: usize

Index of the content block

thought_signature: Option<String>

Optional thought signature (used by Gemini 3.x models)

ToolInputDelta

Incremental JSON for tool input (partial/incomplete JSON).

Fields

id: String

Tool call ID this delta belongs to

delta: String

JSON fragment to append

block_index: usize

Index of the content block

Usage(Usage)

Usage information (typically at stream end).

Done

Stream completed with stop reason.

Fields

stop_reason: Option<StopReason>

Why the stream ended

SignatureDelta

A signature delta for a thinking block.

Fields

delta: String

The signature fragment to append

block_index: usize

Index of the content block being streamed

RedactedThinking

A redacted thinking block received at content_block_start.

Fields

data: String

Opaque data payload

block_index: usize

Index of the content block

OpaqueReasoning

A complete provider-owned reasoning-state item.

Unlike text/thinking deltas this item is not user-visible and must not be interpreted. It is carried through the stream solely so agent history can replay it to the provider that owns it.

Fields

provider: String

Provider protocol that owns the payload.

data: Value

Exact provider response item to preserve.

block_index: usize

Index used to retain the provider’s output-item ordering.

Error

Error during streaming.

Fields

message: String

Error message

kind: StreamErrorKind

Categorization of the error so downstream consumers can map it back to the correct agent_sdk_foundation::llm::ChatOutcome variant or audit-record TurnAttemptOutcome without losing the rate-limit / server-error / invalid-request distinction.

Trait Implementations

impl Clone for StreamDelta

fn clone(&self) -> StreamDelta

Returns a duplicate of the value.

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

Performs copy-assignment from source.

impl Debug for StreamDelta

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

Formats the value using the given formatter.