feat: add graph workflow fallback and retry metadata

backend/tests/domains/test_workflow_dispatch_service.py

@@ -220,6 +220,129 @@ async def test_dispatch_render_with_workflow_falls_back_when_workflow_runtime_pr
     assert runs == []
 
 
+@pytest.mark.asyncio
+async def test_dispatch_render_with_workflow_graph_mode_dispatches_supported_custom_workflow(
+    db,
+    admin_user,
+    monkeypatch,
+    tmp_path,
+):
+    _use_test_database(monkeypatch)
+    order_line = await _seed_renderable_order_line(db, admin_user, tmp_path)
+    workflow_definition = WorkflowDefinition(
+        name=f"Graph Workflow {uuid.uuid4().hex[:8]}",
+        output_type_id=order_line.output_type_id,
+        config={
+            "version": 1,
+            "ui": {"preset": "custom", "execution_mode": "graph"},
+            "nodes": [
+                {"id": "setup", "step": "order_line_setup", "params": {}},
+                {"id": "template", "step": "resolve_template", "params": {}},
+                {"id": "render", "step": "blender_still", "params": {"width": 1024, "height": 768}},
+            ],
+            "edges": [
+                {"from": "setup", "to": "template"},
+                {"from": "template", "to": "render"},
+            ],
+        },
+        is_active=True,
+    )
+    db.add(workflow_definition)
+    await db.flush()
+    output_type = await db.get(OutputType, order_line.output_type_id)
+    assert output_type is not None
+    output_type.workflow_definition_id = workflow_definition.id
+    await db.commit()
+
+    monkeypatch.setattr(
+        "app.tasks.celery_app.celery_app.send_task",
+        lambda task_name, args, kwargs: type("Result", (), {"id": "graph-task-1"})(),
+    )
+
+    result = dispatch_render_with_workflow(str(order_line.id))
+
+    await db.rollback()
+
+    run_result = await db.execute(
+        select(WorkflowRun)
+        .where(WorkflowRun.id == uuid.UUID(result["workflow_run_id"]))
+        .options(selectinload(WorkflowRun.node_results))
+    )
+    run = run_result.scalar_one()
+    node_results = {node_result.node_name: node_result for node_result in run.node_results}
+
+    assert result["backend"] == "workflow_graph"
+    assert result["execution_mode"] == "graph"
+    assert result["task_ids"] == ["graph-task-1"]
+    assert run.status == "pending"
+    assert node_results["setup"].status == "completed"
+    assert node_results["template"].status == "completed"
+    assert node_results["render"].status == "queued"
+
+
+@pytest.mark.asyncio
+async def test_dispatch_render_with_workflow_graph_mode_falls_back_to_legacy_on_graph_failure(
+    db,
+    admin_user,
+    monkeypatch,
+    tmp_path,
+):
+    _use_test_database(monkeypatch)
+    order_line = await _seed_renderable_order_line(db, admin_user, tmp_path)
+    workflow_definition = WorkflowDefinition(
+        name=f"Graph Workflow {uuid.uuid4().hex[:8]}",
+        output_type_id=order_line.output_type_id,
+        config={
+            "version": 1,
+            "ui": {"preset": "custom", "execution_mode": "graph"},
+            "nodes": [
+                {
+                    "id": "setup",
+                    "step": "order_line_setup",
+                    "params": {"failure_policy": {"fallback_to_legacy": True}},
+                },
+                {"id": "render", "step": "blender_still", "params": {"width": 1024, "height": 768}},
+            ],
+            "edges": [
+                {"from": "setup", "to": "render"},
+            ],
+        },
+        is_active=True,
+    )
+    db.add(workflow_definition)
+    await db.flush()
+    output_type = await db.get(OutputType, order_line.output_type_id)
+    assert output_type is not None
+    output_type.workflow_definition_id = workflow_definition.id
+    await db.commit()
+
+    monkeypatch.setattr(
+        "app.domains.rendering.workflow_graph_runtime.execute_graph_workflow",
+        lambda *_args, **_kwargs: (_ for _ in ()).throw(RuntimeError("graph dispatch exploded")),
+    )
+    monkeypatch.setattr(
+        "app.domains.rendering.dispatch_service._legacy_dispatch",
+        lambda order_line_id: {"backend": "legacy", "order_line_id": order_line_id},
+    )
+
+    result = dispatch_render_with_workflow(str(order_line.id))
+
+    await db.rollback()
+
+    runs = (
+        await db.execute(
+            select(WorkflowRun).options(selectinload(WorkflowRun.node_results)).order_by(WorkflowRun.created_at.desc())
+        )
+    ).scalars().all()
+    run = runs[0]
+
+    assert result["backend"] == "legacy"
+    assert result["fallback_from"] == "workflow_graph"
+    assert result["workflow_run_id"] == str(run.id)
+    assert run.status == "failed"
+    assert run.error_message == "graph dispatch exploded"
+
+
 @pytest.mark.asyncio
 async def test_workflow_dispatch_endpoint_returns_workflow_run_with_node_results(
     client,