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Prompty

EngineCheckpoint

Portable durable checkpoint emitted after a committed model/tool round.

A resumed run rebuilt from a checkpoint MUST NOT duplicate a model or tool effect that the checkpoint already records as committed. Run identity is carried so delegated runs checkpoint independently under their own run.

Class Diagram

Section titled “Class Diagram”
---
title: EngineCheckpoint
config:
  look: handDrawn
  theme: colorful
  class:
    hideEmptyMembersBox: true
---
classDiagram
    class EngineCheckpoint {
        +string id
        +string sessionId
        +string turnId
        +string runId
        +string parentRunId
        +int32 delegationDepth
        +int32 iteration
        +int64 lastSequence
        +Message[] messages
        +int32 stablePrefixMessages
        +unknown inputs
        +string activeInvocationId
        +ModelToolRequest[] pendingToolRequests
        +ModelToolResult[] completedToolResults
        +int32 completedModelIterations
        +boolean reconciliationRequired
        +ModelReconciliationState modelReconciliation
        +unknown pendingOutput
        +boolean finalOutputReady
        +ModelInvocationResponse pendingModelResponse
        +boolean resumeSameIteration
        +boolean policyAppliedForIteration
        +InvocationContextState contextState
        +dictionary metadata
    }
    class Message {
        +string role
        +ContentPart[] parts
        +dictionary metadata
    }
    EngineCheckpoint *-- Message
    class ModelToolRequest {
        +string id
        +string name
        +unknown arguments
        +dictionary metadata
    }
    EngineCheckpoint *-- ModelToolRequest
    class ModelToolResult {
        +string requestId
        +string name
        +string outcome
        +unknown output
        +string errorKind
        +dictionary metadata
    }
    EngineCheckpoint *-- ModelToolResult
    class ModelReconciliationState {
        +string invocationId
        +ModelInvocationRequest request
        +int32 failedAttempt
        +string message
        +dictionary metadata
    }
    EngineCheckpoint *-- ModelReconciliationState
    class ModelInvocationResponse {
        +unknown output
        +InvocationUsage usage
        +Message[] assistantMessages
        +ModelToolRequest[] toolRequests
        +InvocationContextState nextContextState
        +dictionary metadata
    }
    EngineCheckpoint *-- ModelInvocationResponse

Yaml Example

Section titled “Yaml Example”
id: ckpt_abc123
sessionId: sess_abc123
turnId: turn_abc123
runId: run_abc123

Properties

Section titled “Properties”
Name Type Description
id string Stable unique identifier for this checkpoint
sessionId string Stable session identifier
turnId string Stable turn identifier
runId string Stable identifier of this engine run
parentRunId string Run identifier of the parent run when this run was delegated
delegationDepth int32 Zero-based delegation nesting depth; 0 for a top-level run
iteration int32 Zero-based model loop iteration captured by this checkpoint
lastSequence int64 Last committed event sequence included in this checkpoint
messages Message[] Canonical conversation messages at checkpoint time
stablePrefixMessages int32 Number of leading messages eligible for provider prefix-cache reuse
inputs unknown Turn inputs captured for deterministic resume
activeInvocationId string Active model invocation identifier, when one is in flight
pendingToolRequests ModelToolRequest[] Tool requests awaiting execution or commitment
completedToolResults ModelToolResult[] Tool results already executed in this round
completedModelIterations int32 Number of fully completed model iterations
reconciliationRequired boolean Whether the turn is blocked pending model outcome reconciliation
modelReconciliation ModelReconciliationState Typed provider state when model outcome reconciliation is required
pendingOutput unknown Final output pending commit, when computed
finalOutputReady boolean Whether the final output is ready to commit
pendingModelResponse ModelInvocationResponse Model response retained until all tool results form one conversation batch
resumeSameIteration boolean Resume this exact iteration because the checkpoint precedes an external model effect
policyAppliedForIteration boolean Whether the host policy rewrite is already durable for this iteration
contextState InvocationContextState Provider-context state carried by this checkpoint
metadata dictionary Opaque host-specific checkpoint metadata

Composed Types

Section titled “Composed Types”

The following types are composed within EngineCheckpoint: