fix(api): align graph protocols for response streaming

api/core/workflow/graph_engine/response_coordinator/session.py

@@ -10,10 +10,10 @@ from __future__ import annotations
 from dataclasses import dataclass
 
 from core.workflow.nodes.answer.answer_node import AnswerNode
-from core.workflow.nodes.base.node import Node
 from core.workflow.nodes.base.template import Template
 from core.workflow.nodes.end.end_node import EndNode
 from core.workflow.nodes.knowledge_index import KnowledgeIndexNode
+from core.workflow.runtime.graph_runtime_state import NodeProtocol
 
 
 @dataclass
@@ -29,7 +29,7 @@ class ResponseSession:
     index: int = 0  # Current position in the template segments
 
     @classmethod
-    def from_node(cls, node: Node) -> ResponseSession:
+    def from_node(cls, node: NodeProtocol) -> ResponseSession:
         """
         Create a ResponseSession from an AnswerNode or EndNode.
 

api/core/workflow/runtime/graph_runtime_state.py

@@ -12,6 +12,7 @@ from pydantic.json import pydantic_encoder
 
 from core.model_runtime.entities.llm_entities import LLMUsage
 from core.workflow.entities.pause_reason import PauseReason
+from core.workflow.enums import NodeExecutionType, NodeState, NodeType
 from core.workflow.runtime.variable_pool import VariablePool
 
 
@@ -103,14 +104,33 @@ class ResponseStreamCoordinatorProtocol(Protocol):
         ...
 
 
+class NodeProtocol(Protocol):
+    """Structural interface for graph nodes."""
+
+    id: str
+    state: NodeState
+    execution_type: NodeExecutionType
+    node_type: NodeType
+
+    def blocks_variable_output(self, variable_selectors: set[tuple[str, ...]]) -> bool: ...
+
+
+class EdgeProtocol(Protocol):
+    id: str
+    state: NodeState
+    tail: str
+    head: str
+    source_handle: str
+
+
 class GraphProtocol(Protocol):
     """Structural interface required from graph instances attached to the runtime state."""
 
-    nodes: Mapping[str, object]
-    edges: Mapping[str, object]
-    root_node: object
+    nodes: Mapping[str, NodeProtocol]
+    edges: Mapping[str, EdgeProtocol]
+    root_node: NodeProtocol
 
-    def get_outgoing_edges(self, node_id: str) -> Sequence[object]: ...
+    def get_outgoing_edges(self, node_id: str) -> Sequence[EdgeProtocol]: ...
 
 
 @dataclass(slots=True)