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Link to Issue or Description of Change

1. Link to an existing issue (if applicable):

• Closes: N/A
• Related: N/A

2. Or, if no issue exists, describe the change:

Problem:
Workflows and workflow-specific node types (JoinNode, FunctionNode, ToolNode) defined in YAML config files could not be loaded or executed because:

1. The class resolution utilities lacked support for identifying and loading the Workflow class and workflow-specific nodes.
2. References to nested sub-agents and sub-nodes within workflow configuration files were parsed as raw strings rather than recursively resolved and loaded.

Solution:

1. Implemented the Workflow.from_config method to instantiate declarative workflow graphs from configuration inputs.
2. Added resolution support for Workflow, JoinNode, FunctionNode, and ToolNode in _resolve_node_class.
3. Implemented path-aware recursive resolution of nested sub-agent and node .yaml configurations during parsing.

Testing Plan

Unit Tests:

• I have added or updated unit tests for my change.
• All unit tests pass locally.

Summary of configuration-related test execution results:

• Agent configuration tests: uv run pytest tests/unittests/agents/test_agent_config.py
36 passed

Manual End-to-End (E2E) Tests:
Verified the correctness of workflow config loading by instantiating complex multi-agent graphs from declarative configurations in test_agent_config.py.

Checklist

• I have read the CONTRIBUTING.md document.
• I have performed a self-review of my own code.
• I have commented my code, particularly in hard-to-understand areas.
• I have added tests that prove my fix is effective or that my feature works.
• New and existing unit tests pass locally with my changes.
• I have manually tested my changes end-to-end.
• Any dependent changes have been merged and published in downstream modules.

Additional context

N/A