Struct EventMetadata 

pub struct EventMetadata {
    pub uuid: String,
    pub parent_uuid: Option<String>,
    pub session_id: String,
    pub timestamp: DateTime<Utc>,
    pub is_sidechain: bool,
    pub user_type: Option<String>,
    pub cwd: Option<String>,
    pub version: Option<String>,
    pub git_branch: Option<String>,
    pub slug: Option<String>,
}

Common metadata present in most events

This structure captures the execution context for an event:

• Session identity: session_id links events to sessions
• Graph structure: parent_uuid forms conversation tree
• Execution context: cwd, git_branch track environment
• Timing: timestamp for chronological ordering

Links and Relationships

• uuid: Unique identifier for this event
• parent_uuid: Links to previous message (conversation chain)
• session_id: Groups events into sessions
• logical_parent_uuid: Used for compact boundaries to preserve logical flow

Frequency in Sessions

Present in ~95% of events (all except some system events)

Fields

uuid: String

Unique identifier for this event

UUIDs are used to build conversation graphs and link related events.

parent_uuid: Option<String>

Links to parent message in conversation chain

Forms a tree structure where:

• None = root message (session start)
• Some(uuid) = response to/result of another event

session_id: String

Session identifier (groups related events)

All events in a session file share the same session_id. Format: {uuid} (e.g., “7b1f4d79-4ab1-4d12-913d-e367cb3a5387”)

timestamp: DateTime<Utc>

Event timestamp (UTC)

Used for chronological ordering and session duration calculation.

is_sidechain: bool

Whether this event is part of a sidechain (branching conversation)

Sidechains occur when users:

• Undo/redo operations
• Branch from earlier conversation points

user_type: Option<String>

User type discriminator

• "external" = Human user input
• "internal" = Tool result or system message
• None = Not applicable (system events)

cwd: Option<String>

Current working directory when event occurred

Examples:

• Windows: "C:\\Users\\user\\project"
• Unix: "/home/user/project"

version: Option<String>

Claude Code version

Format: "2.1.19" or similar semver

git_branch: Option<String>

Git branch when event occurred

Useful for correlating sessions with code branches. Example: "main", "feature-xyz"

slug: Option<String>

Agent slug for delegated operations

Present in progress events when using agents. Examples: "rust-implementer", "research-agent"

Implementations

impl EventMetadata

pub fn is_user_prompt(&self) -> bool

Check if this is a human user prompt (vs tool result)

pub fn is_internal(&self) -> bool

Check if this is an internal message (tool result)

pub fn is_sidechain(&self) -> bool

Check if this is part of a sidechain

Trait Implementations

impl Clone for EventMetadata

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 EventMetadata

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

Formats the value using the given formatter.

impl<'de> Deserialize<'de> for EventMetadata

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

where __D: Deserializer<'de>,

Deserialize this value from the given Serde deserializer.

impl Serialize for EventMetadata

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

where __S: Serializer,

Serialize this value into the given Serde serializer.