Struct Event 

pub struct Event {

    pub kind: EventKind,
    pub ts: Option<Timestamp>,
    pub request_id: Option<String>,
    pub model: Option<String>,
    pub usage: Option<Usage>,
    pub tool_calls: Vec<ToolCall>,
    pub sidechain: bool,
    pub content_summary: Option<String>,
    pub content_chars: u64,
    pub thinking_chars: u64,
    pub has_thinking: bool,
    pub tool_use_id: Option<String>,
    pub attachment_kind: Option<String>,
    pub item_count: u64,
}

One line/turn of a session.

Fields

kind: EventKind

ts: Option<Timestamp>

request_id: Option<String>

API request id. SEVERAL events may share one request id (one line per content block) — accounting MUST dedup on it first (CLAUDE.md §8.1).

model: Option<String>

usage: Option<Usage>

tool_calls: Vec<ToolCall>

sidechain: bool

True when the event belongs to a sub-agent (sidechain) transcript.

content_summary: Option<String>

Short display-only snippet of visible text.

content_chars: u64

Approximate chars of generated content (text + thinking + tool-call JSON). Heuristic input for thinking attribution / context estimation — never billed.

thinking_chars: u64

Chars of extended-thinking text in this event — a SUBSET of content_chars (0 when none, or when the thinking block was encrypted and thus unmeasurable). Lets context attribution separate thinking from text.

has_thinking: bool

The event carried thinking blocks (possibly encrypted/redacted, i.e. with no measurable text).

tool_use_id: Option<String>

For a ToolResult event: the tool_use_id it answers. Lets the result’s bytes be attributed back to the tool / MCP server that produced them (the matching ToolCall carries the same id in ToolCall::id).

attachment_kind: Option<String>

For an Attachment event: its category — e.g. "deferred_tools_delta", "skill_listing", "mcp_instructions_delta", "task_reminder".

item_count: u64

For an Attachment event: how many named items it added to the window (deferred tools, skills, MCP servers). 0 elsewhere.

Trait Implementations

impl Clone for Event

fn clone(&self) -> Event

Returns a duplicate of the value.

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

Performs copy-assignment from source.

impl Debug for Event

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

Formats the value using the given formatter.

impl<'de> Deserialize<'de> for Event

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

where __D: Deserializer<'de>,

Deserialize this value from the given Serde deserializer.

impl PartialEq for Event

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

Tests for self and other values to be equal, and is used by ==.

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

Tests for !=. The default implementation is almost always sufficient, and should not be overridden without very good reason.

impl Serialize for Event

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 Event