Add start and end nodes to graph visualization and update edge generation

src/agents/extensions/visualization.py

@@ -4,6 +4,7 @@ import graphviz  # type: ignore
 
 from agents import Agent
 from agents.handoffs import Handoff
+from agents.tool import Tool
 
 
 def get_main_graph(agent: Agent) -> str:
@@ -41,6 +42,14 @@ def get_all_nodes(agent: Agent, parent: Optional[Agent] = None) -> str:
         str: The DOT format string representing the nodes.
     """
     parts = []
+
+    # Start and end the graph
+    parts.append(
+        f'"__start__" [label="__start__", shape=ellipse, style=filled, '
+        f"fillcolor=lightblue, width=0.5, height=0.3];"
+        f'"__end__" [label="__end__", shape=ellipse, style=filled, '
+        f"fillcolor=lightblue, width=0.5, height=0.3];"
+    )
     # Ensure parent agent node is colored
     if not parent:
         parts.append(
@@ -72,7 +81,7 @@ def get_all_nodes(agent: Agent, parent: Optional[Agent] = None) -> str:
     return "".join(parts)
 
 
-def get_all_edges(agent: Agent) -> str:
+def get_all_edges(agent: Agent, parent: Optional[Agent] = None) -> str:
     """
     Recursively generates the edges for the given agent and its handoffs in DOT format.
 
@@ -85,6 +94,11 @@ def get_all_edges(agent: Agent) -> str:
     """
     parts = []
 
+    if not parent:
+        parts.append(
+        f'"__start__" -> "{agent.name}";'
+        )
+
     for tool in agent.tools:
         parts.append(f"""
         "{agent.name}" -> "{tool.name}" [style=dotted, penwidth=1.5];
@@ -97,7 +111,12 @@ def get_all_edges(agent: Agent) -> str:
         if isinstance(handoff, Agent):
             parts.append(f"""
             "{agent.name}" -> "{handoff.name}";""")
-            parts.append(get_all_edges(handoff))
+            parts.append(get_all_edges(handoff, agent))
+
+    if not agent.handoffs and not isinstance(agent, Tool):
+        parts.append(
+        f'"{agent.name}" -> "__end__";'
+        )
 
     return "".join(parts)
 

tests/test_visualization.py

@@ -38,6 +38,14 @@ def test_get_main_graph(mock_agent):
     assert "graph [splines=true];" in result
     assert 'node [fontname="Arial"];' in result
     assert "edge [penwidth=1.5];" in result
+    assert (
+        '"__start__" [label="__start__", shape=ellipse, style=filled, '
+        "fillcolor=lightblue, width=0.5, height=0.3];" in result
+    )
+    assert (
+        '"__end__" [label="__end__", shape=ellipse, style=filled, '
+        "fillcolor=lightblue, width=0.5, height=0.3];" in result
+    )
     assert (
         '"Agent1" [label="Agent1", shape=box, style=filled, '
         "fillcolor=lightyellow, width=1.5, height=0.8];" in result
@@ -58,6 +66,14 @@ def test_get_main_graph(mock_agent):
 
 def test_get_all_nodes(mock_agent):
     result = get_all_nodes(mock_agent)
+    assert (
+        '"__start__" [label="__start__", shape=ellipse, style=filled, '
+        "fillcolor=lightblue, width=0.5, height=0.3];" in result
+    )
+    assert (
+        '"__end__" [label="__end__", shape=ellipse, style=filled, '
+        "fillcolor=lightblue, width=0.5, height=0.3];" in result
+    )
     assert (
         '"Agent1" [label="Agent1", shape=box, style=filled, '
         "fillcolor=lightyellow, width=1.5, height=0.8];" in result
@@ -78,6 +94,8 @@ def test_get_all_nodes(mock_agent):
 
 def test_get_all_edges(mock_agent):
     result = get_all_edges(mock_agent)
+    assert '"__start__" -> "Agent1";' in result
+    assert '"Agent1" -> "__end__";'
     assert '"Agent1" -> "Tool1" [style=dotted, penwidth=1.5];' in result
     assert '"Tool1" -> "Agent1" [style=dotted, penwidth=1.5];' in result
     assert '"Agent1" -> "Tool2" [style=dotted, penwidth=1.5];' in result
@@ -85,6 +103,7 @@ def test_get_all_edges(mock_agent):
     assert '"Agent1" -> "Handoff1";' in result
 
 
+
 def test_draw_graph(mock_agent):
     graph = draw_graph(mock_agent)
     assert isinstance(graph, graphviz.Source)
@@ -92,6 +111,14 @@ def test_draw_graph(mock_agent):
     assert "graph [splines=true];" in graph.source
     assert 'node [fontname="Arial"];' in graph.source
     assert "edge [penwidth=1.5];" in graph.source
+    assert (
+        '"__start__" [label="__start__", shape=ellipse, style=filled, '
+        "fillcolor=lightblue, width=0.5, height=0.3];" in graph.source
+    )
+    assert (
+        '"__end__" [label="__end__", shape=ellipse, style=filled, '
+        "fillcolor=lightblue, width=0.5, height=0.3];" in graph.source
+    )
     assert (
         '"Agent1" [label="Agent1", shape=box, style=filled, '
         "fillcolor=lightyellow, width=1.5, height=0.8];" in graph.source