refactor: remove placeholder join step

src/wf_core/__init__.py

@@ -11,7 +11,6 @@ from .models import (
     InputPathBinding,
     InputValueBinding,
     InterruptNode,
-    JoinNode,
     JsonValue,
     LiteralExpression,
     NodeDef,
@@ -89,7 +88,6 @@ __all__ = [
     "InputValueBinding",
     "InterruptRequest",
     "InterruptRoute",
-    "JoinNode",
     "JsonValue",
     "LiteralExpression",
     "NodeDef",

src/wf_core/models/__init__.py

@@ -30,7 +30,6 @@ from wf_core.models.steps import (
     ForeachItemErrorPolicy,
     ForeachNode,
     InterruptNode,
-    JoinNode,
     NodeUse,
     Step,
     SubgraphNode,
@@ -54,7 +53,6 @@ __all__ = [
     "InputExpressionBinding",
     "InputPathBinding",
     "InputValueBinding",
-    "JoinNode",
     "JsonValue",
     "LiteralExpression",
     "LiteralOperand",

src/wf_core/models/steps.py

@@ -293,13 +293,6 @@ class ForeachNode(BaseModel):
         return GraphSourcePath("context", ("foreach", self.id, "index"))
 
 
-class JoinNode(BaseModel):
-    """Control-flow step that marks a branch or frame as joined."""
-
-    id: str
-    type: Literal["join"]
-
-
 class EndNode(BaseModel):
     """Explicit workflow terminal that sets the workflow-level outcome.
 
@@ -411,13 +404,7 @@ class InterruptNode(BaseModel):
 
 
 Step = Annotated[
-    NodeUse
-    | SubgraphNode
-    | ConditionNode
-    | ForeachNode
-    | JoinNode
-    | EndNode
-    | InterruptNode,
+    NodeUse | SubgraphNode | ConditionNode | ForeachNode | EndNode | InterruptNode,
     Field(discriminator="type"),
 ]
 """Discriminated union of all executable workflow graph steps."""

src/wf_core/runtime/ops/handlers.py

@@ -41,15 +41,6 @@ def handle_condition_step(
     )
 
 
-def handle_join_step() -> StepExecutionResult:
-    return StepExecutionResult(
-        outcome="done",
-        resolved_input={},
-        output={},
-        state_changes={},
-    )
-
-
 def handle_interrupt_step(
     run: RunState,
     step: InterruptNode,

src/wf_core/runtime/step.py

@@ -10,7 +10,6 @@ from wf_core.models.steps import (
     EndNode,
     ForeachNode,
     InterruptNode,
-    JoinNode,
     NodeUse,
     SubgraphNode,
 )
@@ -22,7 +21,6 @@ from wf_core.runtime.ops.foreach import step_foreach
 from wf_core.runtime.ops.handlers import (
     handle_condition_step,
     handle_interrupt_step,
-    handle_join_step,
 )
 from wf_core.runtime.ops.index import WorkflowIndex, build_workflow_index
 from wf_core.runtime.ops.merges import ReducerDefinition
@@ -149,8 +147,6 @@ def step_workflow(
             raise
     elif isinstance(step, ConditionNode):
         step_result = handle_condition_step(run, step)
-    elif isinstance(step, JoinNode):
-        step_result = handle_join_step()
     elif isinstance(step, EndNode):
         return complete_end_step(
             run=run,
@@ -264,8 +260,6 @@ async def step_workflow_async(
             raise
     elif isinstance(step, ConditionNode):
         step_result = handle_condition_step(run, step)
-    elif isinstance(step, JoinNode):
-        step_result = handle_join_step()
     elif isinstance(step, EndNode):
         return complete_end_step(
             run=run,

src/wf_core/validation/outcomes.py

@@ -19,8 +19,6 @@ def declared_outcomes_for_step(step: Step, node_defs: dict[str, NodeDef]) -> set
         if step.item_error.action in {"skip", "collect"}:
             outcomes.add("completed_with_errors")
         return outcomes
-    if step.type == "join":
-        return {"done"}
     if isinstance(step, EndNode):
         return set()
     if isinstance(step, InterruptNode):