better error traces

src/wf_core/runtime/scheduler.py

@@ -184,8 +184,26 @@ def resolve_no_ready_frames(run: RunState) -> RunStatus:
     ):
         return RunStatus.COMPLETED
     if any(frame.status == FrameStatus.BLOCKED for frame in run.frames.values()):
-        raise WorkflowExecutionError("run has no ready frames and is deadlocked")
+        raise WorkflowExecutionError(
-    raise WorkflowExecutionError("run has no ready frames")
+            "run has no ready frames and is deadlocked; "
+            f"{_scheduler_state_summary(run)}"
+        )
+    raise WorkflowExecutionError(
+        f"run has no ready frames; {_scheduler_state_summary(run)}"
+    )
+
+
+def _scheduler_state_summary(run: RunState) -> str:
+    """Return compact scheduler state for no-ready-frame diagnostics."""
+    frame_summary = ", ".join(
+        f"{frame.id}:{frame.status.value}@{frame.node_id}"
+        for frame in run.frames.values()
+    )
+    return (
+        f"ready_frame_ids={run.ready_frame_ids!r}; "
+        f"current_frame_id={run.current_frame_id!r}; "
+        f"frames=[{frame_summary}]"
+    )
 
 
 def _frame(run: RunState, frame_id: str) -> ExecutionFrame:

tests/core/test_scheduler.py

@@ -13,6 +13,7 @@ from wf_core.runtime.scheduler import (
     block_frame_on_children,
     enqueue_frame,
     select_next_frame,
+    resolve_no_ready_frames,
     wake_frame,
     wake_parent_if_children_complete,
 )
@@ -162,3 +163,17 @@ def test_resume_wakes_interrupted_frame_at_front() -> None:
     wake_frame(run, "waiting", front=True)
 
     assert run.ready_frame_ids == ["waiting", "sibling"]
+
+
+def test_deadlock_error_includes_ready_queue_and_frame_summary() -> None:
+    run = _run()
+    add_frame(run, ExecutionFrame(id="parent", kind="root", node_id="foreach"))
+    block_frame_on_children(run, "parent", ("missing_child",))
+
+    with pytest.raises(WorkflowExecutionError) as exc_info:
+        resolve_no_ready_frames(run)
+
+    message = str(exc_info.value)
+    assert "deadlocked" in message
+    assert "ready_frame_ids=[]" in message
+    assert "parent:blocked@foreach" in message