SessionStartPayload

Payload for “session_start” events.

Class Diagram

---
title: SessionStartPayload
config:
  look: handDrawn
  theme: colorful
  class:
    hideEmptyMembersBox: true
---
classDiagram
    class SessionStartPayload {
        +string sessionId
        +string schemaVersion
        +string producer
        +string runtime
        +string promptyVersion
        +string startTime
        +string selectedModel
        +string reasoningEffort
        +HarnessContext context
    }
    class HarnessContext {
        +string cwd
        +string gitRoot
        +dictionary metadata
    }
    SessionStartPayload *-- HarnessContext

Yaml Example

sessionId: sess_abc123
schemaVersion: "1"
producer: prompty-agent
runtime: typescript
promptyVersion: 2.0.0
startTime: 2026-06-09T20:00:00Z
selectedModel: gpt-4o-mini
reasoningEffort: medium

Properties

Name	Type	Description
sessionId	string	Stable session identifier
schemaVersion	string	Session event schema version
producer	string	Producer that started the session
runtime	string	Runtime that produced the session
promptyVersion	string	Prompty library version
startTime	string	ISO 8601 UTC timestamp when the session started
selectedModel	string	Selected model identifier, when known
reasoningEffort	string	Selected reasoning effort or equivalent model setting, when known
context	HarnessContext	Repository and execution context

Composed Types

The following types are composed within SessionStartPayload:

• HarnessContext