Struct Start 

pub(crate) struct Start {

    pub segment_id: String,
    pub agent_uid: String,
    pub definition_id: Option<String>,
    pub provider: String,
    pub config_dir: Option<String>,
    pub provider_session_id: Option<String>,
    pub cwd: String,
    pub channel: String,
    pub agentmux_version: String,
    pub block_id: String,
    pub zone: Option<String>,
    pub byte_start: Option<i64>,
    pub started_at_ms: i64,
    pub continuity_rung: Rung,
    pub predecessor_segment_id: Option<String>,
    pub lease_epoch: Option<u64>,
    pub identity_key: Option<String>,
    pub forked_from: Option<String>,
}

What is known about a segment when its process starts.

Fields

segment_id: String

agent_uid: String

definition_id: Option<String>

The block’s agentId: the transcript zone’s key, which differs from agent_uid for a template launch.

provider: String

config_dir: Option<String>

Where native resume would have to look (CLAUDE_CONFIG_DIR, …).

provider_session_id: Option<String>

Known up front on a resume; otherwise filled in by a session event.

cwd: String

channel: String

agentmux_version: String

block_id: String

zone: Option<String>

The global transcript zone this segment appends to, and its size then.

byte_start: Option<i64>

started_at_ms: i64

continuity_rung: Rung

predecessor_segment_id: Option<String>

lease_epoch: Option<u64>

The single-live-instance lease epoch this segment’s process held (SPEC_AGENT_SINGLE_LIVE_INSTANCE_2026_09_24 Phase 3). A change between consecutive segments is an ownership change — another instance, or a takeover — visible in the ledger. None: no lease (older build, no UID) or a record written before this field.

identity_key: Option<String>

The Anthropic identity config_dir was signed in as (account_email::identity_key_from_oauth_dir, SPEC_RESUME_GATE_AND_SAME_IDENTITY_CONTINUATION_2026_09_25.md §4.1). None: unknown, or a record written before this field.

forked_from: Option<String>

The session this spawn resumed with --fork-session after relocating it from another login of the same identity (spec §4.3). Its own id arrives in the segment’s session event.

Trait Implementations

impl Clone for Start

fn clone(&self) -> Start

Returns a duplicate of the value.

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

Performs copy-assignment from source.

impl Debug for Start

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

Formats the value using the given formatter.

impl<'de> Deserialize<'de> for Start

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

where __D: Deserializer<'de>,

Deserialize this value from the given Serde deserializer.

impl PartialEq for Start

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

Equality operator ==.

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

Inequality operator !=.

impl Serialize for Start

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 Start