.NET: Python: [Bug]: Declarative SetValue with variable: builds fine but never writes the value #9427

Observed Behavior

A SetValue action that uses variable: instead of path: passes build() validation, then does nothing at run time. The target variable stays unset and there is no error or warning.

The builder accepts variable on purpose. ACTION_ALTERNATE_FIELDS has "SetValue.path": ["variable"] (_declarative_builder.py:99) and test_setvalue_accepts_alternate_variable_field checks that this builds. But SetValueExecutor only reads path (_executors_basic.py:56), so the write is skipped.

Expected Behavior

SetValue with variable: Local.b (or variable: {path: Local.b}) sets Local.b, same as path: Local.b does. SetVariable already reads both shapes through _get_variable_path.

Steps to Reproduce

1. Build a workflow with kind: SetValue, variable: Local.b, value: from variable.
2. Run it.
3. Read Local.b. It is None.

Minimal Reproduction

No API keys or PowerFx needed. It reads the state from the last checkpoint.

"""Repro: declarative SetValue with `variable:` builds fine but writes nothing.

Runs the real workflow (no PowerFx, no API keys) and reads the declarative
state from the last checkpoint.
"""

import asyncio

import agent_framework_declarative
from agent_framework import InMemoryCheckpointStorage
from agent_framework_declarative._workflows._declarative_base import DECLARATIVE_STATE_KEY
from agent_framework_declarative._workflows._factory import WorkflowFactory

print("agent_framework_declarative from:", agent_framework_declarative.__file__)

YAML = """
kind: Workflow
name: setvalue_variable
actions:
  - kind: SetValue
    id: with_path
    path: Local.a
    value: from path
  - kind: SetValue
    id: with_variable
    variable: Local.b
    value: from variable
  - kind: SetValue
    id: with_nested_variable
    variable:
      path: Local.c
    value: from nested variable
"""


async def main() -> None:
    storage = InMemoryCheckpointStorage()
    workflow = WorkflowFactory(checkpoint_storage=storage).create_workflow_from_yaml(YAML)
    await workflow.run({})
    checkpoints = await storage.list_checkpoints(workflow_name=workflow.name)
    last = max(checkpoints, key=lambda c: c.timestamp)
    local = last.state[DECLARATIVE_STATE_KEY]["Local"]
    print("Local.a =", repr(local.get("a")))
    print("Local.b =", repr(local.get("b")))
    print("Local.c =", repr(local.get("c")))


asyncio.run(main())

Output on main (cae4955):

agent_framework_declarative from: python/packages/declarative/agent_framework_declarative/__init__.py
Local.a = 'from path'
Local.b = None
Local.c = None

Local.a uses path: and works. Local.b and Local.c use variable: and are never set.

Error Messages and Stack Traces

None. That's the problem, it fails silently.

Package Versions

agent-framework-core 1.22.0, agent-framework-declarative 1.3.0 (main at cae4955)

Python Version

3.12.13

Operating System

macOS 26.6.2

Regression

No. The alias and the executor have been out of sync since the declarative runtime landed in #2815.

Additional Context

Root cause: python/packages/declarative/agent_framework_declarative/_workflows/_executors_basic.py:56

path = self._action_def.get("path")

Proposed fix, one line: path = self._action_def.get("path") or _get_variable_path(self._action_def). path still wins when both are set. I have it ready with a test and can open the PR.

The other choice would be to drop the variable alternate from the builder so this fails at build time. I went with honoring it, since the builder and its test already treat variable as valid, and .NET authors write variable: on SetVariable.

AI assistance: I used an AI assistant to help find and analyze this bug. I ran the repro and checked the output myself.

Acknowledgements

• I searched existing issues and did not find a duplicate.
• I personally verified this behavior and the reproduction details are authentic.
• I will wait for explicit maintainer agreement before starting implementation of a non-trivial change.