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Changelog

All notable changes to FlowEngine are documented here.

For the full changelog, see CHANGELOG.md in the repository.

Version History

[Unreleased]

[0.2.0] - Graph Execution, Checkpoints, and Hooks

Added

  • Graph-Based DAG Execution
  • New flow.type: "graph" with topological ordering (Kahn's algorithm)
  • GraphNodeConfig and GraphEdgeConfig schema models
  • GraphExecutor class for DAG-based flow execution

  • Cycle detection, unreachable node skipping, and per-node error handling

  • Port-Based Output Routing

  • Components signal active output ports via set_output_port(context, port)
  • Graph edges route conditionally based on matching port names

  • FlowContext.set_port(), get_active_port(), clear_port() methods

  • Async Component Support

  • BaseComponent.process_async() with automatic sync fallback

  • BaseComponent.is_async detection property

  • Execution Checkpoints (Suspend/Resume)

  • FlowContext.suspend(node_id, reason) for mid-execution pausing
  • Checkpoint dataclass with JSON serialization
  • CheckpointStore abstraction with InMemoryCheckpointStore

  • FlowEngine.resume(checkpoint_id, resume_data) for flow continuation

  • Step Lifecycle Hooks

  • ExecutionHook Protocol: on_node_start, on_node_complete, on_node_error, on_node_skipped, on_flow_suspended
  • Fault-tolerant — broken hooks never break flow execution
  • Multiple hooks supported simultaneously

Changed

  • FlowEngine accepts checkpoint_store and hooks parameters
  • FlowDefinition.type accepts "graph" alongside "sequential" and "conditional"
  • ExecutionMetadata includes suspension and completed_nodes state
  • Context serialization includes all new metadata fields

[0.1.0] - Initial Release

Added

  • Core Engine
  • FlowEngine class for flow orchestration
  • BaseComponent abstract class for components
  • FlowContext for data passing between components
  • DotDict for attribute-style dictionary access

  • ExecutionMetadata for timing and error tracking

  • Configuration

  • YAML-based flow configuration
  • ConfigLoader for loading and validating configs
  • Pydantic models for type-safe configuration

  • ComponentRegistry for dynamic component loading

  • Flow Types

  • Sequential flows (all matching steps run)

  • Conditional flows (first-match branching)

  • Condition Evaluation

  • Safe Python expression evaluation
  • AST-based security validation

  • Support for comparisons, logical operators, membership

  • Timeout Handling

  • Cooperative timeout mode with check_deadline()
  • Hard async timeout mode with asyncio
  • Hard process timeout mode with process isolation

  • Strict deadline enforcement option

  • Error Handling

  • fail_fast flow-level setting
  • Per-step on_error handling (fail, skip, continue)
  • Condition error handling modes

  • Comprehensive exception hierarchy

  • Contrib Components

  • LoggingComponent for debugging

  • HTTPComponent for API calls (optional)

  • Context Serialization

  • Full JSON serialization/deserialization
  • Round-trip context restore

Versioning

FlowEngine follows Semantic Versioning:

  • MAJOR: Incompatible API changes
  • MINOR: New functionality, backwards compatible
  • PATCH: Bug fixes, backwards compatible

Migration Guides

Migration guides for major version upgrades will be added here as new versions are released.