Support adding a prefix when extending graph

libs/core/langchain_core/runnables/base.py

@@ -2409,8 +2409,7 @@ def get_graph(self, config: Optional[RunnableConfig] = None) -> Graph:
                 step_graph.trim_first_node()
             if step is not self.last:
                 step_graph.trim_last_node()
-            graph.extend(step_graph)
-            step_first_node = step_graph.first_node()
+            step_first_node, _ = graph.extend(step_graph)
             if not step_first_node:
                 raise ValueError(f"Runnable {step} has no first node")
             if current_last_node:
@@ -3082,11 +3081,9 @@ def get_graph(self, config: Optional[RunnableConfig] = None) -> Graph:
             if not step_graph:
                 graph.add_edge(input_node, output_node)
             else:
-                graph.extend(step_graph)
-                step_first_node = step_graph.first_node()
+                step_first_node, step_last_node = graph.extend(step_graph)
                 if not step_first_node:
                     raise ValueError(f"Runnable {step} has no first node")
-                step_last_node = step_graph.last_node()
                 if not step_last_node:
                     raise ValueError(f"Runnable {step} has no last node")
                 graph.add_edge(input_node, step_first_node)
@@ -3779,11 +3776,9 @@ def get_graph(self, config: RunnableConfig | None = None) -> Graph:
                 if not dep_graph:
                     graph.add_edge(input_node, output_node)
                 else:
-                    graph.extend(dep_graph)
-                    dep_first_node = dep_graph.first_node()
+                    dep_first_node, dep_last_node = graph.extend(dep_graph)
                     if not dep_first_node:
                         raise ValueError(f"Runnable {dep} has no first node")
-                    dep_last_node = dep_graph.last_node()
                     if not dep_last_node:
                         raise ValueError(f"Runnable {dep} has no last node")
                     graph.add_edge(input_node, dep_first_node)

libs/core/langchain_core/runnables/graph.py

@@ -11,6 +11,7 @@
     List,
     NamedTuple,
     Optional,
+    Tuple,
     Type,
     TypedDict,
     Union,
@@ -236,11 +237,39 @@ def add_edge(
         self.edges.append(edge)
         return edge
 
-    def extend(self, graph: Graph) -> None:
+    def extend(
+        self, graph: Graph, *, prefix: str = ""
+    ) -> Tuple[Optional[Node], Optional[Node]]:
         """Add all nodes and edges from another graph.
         Note this doesn't check for duplicates, nor does it connect the graphs."""
-        self.nodes.update(graph.nodes)
-        self.edges.extend(graph.edges)
+        if all(is_uuid(node.id) for node in graph.nodes.values()):
+            prefix = ""
+
+        def prefixed(id: str) -> str:
+            return f"{prefix}:{id}" if prefix else id
+
+        # prefix each node
+        self.nodes.update(
+            {prefixed(k): Node(prefixed(k), v.data) for k, v in graph.nodes.items()}
+        )
+        # prefix each edge's source and target
+        self.edges.extend(
+            [
+                Edge(
+                    prefixed(edge.source),
+                    prefixed(edge.target),
+                    edge.data,
+                    edge.conditional,
+                )
+                for edge in graph.edges
+            ]
+        )
+        # return (prefixed) first and last nodes of the subgraph
+        first, last = graph.first_node(), graph.last_node()
+        return (
+            Node(prefixed(first.id), first.data) if first else None,
+            Node(prefixed(last.id), last.data) if last else None,
+        )
 
     def first_node(self) -> Optional[Node]:
         """Find the single node that is not a target of any edge.