feat(langgraph): configurable recursion_limit for LangGraph agents

python/packages/kagent-langgraph/src/kagent/langgraph/_executor.py

@@ -6,6 +6,7 @@
 
 import asyncio
 import logging
+import os
 import uuid
 from datetime import UTC, datetime
 from typing import Any, override
@@ -25,9 +26,6 @@
     TaskStatusUpdateEvent,
     TextPart,
 )
-from langchain_core.runnables import RunnableConfig
-from pydantic import BaseModel
-
 from kagent.core.a2a import (
     KAGENT_HITL_DECISION_TYPE_DENY,
     TaskResultAggregator,
@@ -41,6 +39,9 @@
     clear_kagent_span_attributes,
     set_kagent_span_attributes,
 )
+from langchain_core.runnables import RunnableConfig
+from pydantic import BaseModel, Field
+
 from langgraph.graph.state import CompiledStateGraph
 from langgraph.types import Command
 
@@ -59,6 +60,14 @@ class LangGraphAgentExecutorConfig(BaseModel):
     # Whether to stream intermediate results
     enable_streaming: bool = True
 
+    # Maximum number of steps before LangGraph raises a recursion error.
+    # Configurable via LANGGRAPH_RECURSION_LIMIT env var. Default is 25 (LangGraph's default).
+    recursion_limit: int = Field(
+        default_factory=lambda: int(os.getenv("LANGGRAPH_RECURSION_LIMIT", "25")),
+        gt=0,
+        description="Maximum number of steps before LangGraph raises a recursion error",
+    )
+
 
 class LangGraphAgentExecutor(AgentExecutor):
     """An AgentExecutor that runs LangGraph workflows against A2A requests.
@@ -97,6 +106,7 @@ def _create_graph_config(self, context: RequestContext) -> RunnableConfig:
                 "thread_id": session_id,
                 "app_name": self.app_name,
             },
+            "recursion_limit": self._config.recursion_limit,
             "project_name": self.app_name,
             "run_name": "kagent-langgraph-exec",
             "tags": [
@@ -322,6 +332,7 @@ async def _handle_resume(
                 "thread_id": thread_id,  # Use thread from interrupted task!
                 "app_name": self.app_name,
             },
+            "recursion_limit": self._config.recursion_limit,
             "project_name": self.app_name,
             "run_name": "kagent-langgraph-resume",
             "tags": [

python/packages/kagent-langgraph/tests/test_executor_config.py

@@ -0,0 +1,58 @@
+"""Tests for LangGraphAgentExecutorConfig."""
+
+import os
+from unittest.mock import patch
+
+import pytest
+
+
+def test_recursion_limit_default():
+    """Test that default recursion_limit is 25 (LangGraph's default)."""
+    from kagent.langgraph._executor import LangGraphAgentExecutorConfig
+
+    with patch.dict(os.environ, {}, clear=False):
+        os.environ.pop("LANGGRAPH_RECURSION_LIMIT", None)
+        config = LangGraphAgentExecutorConfig()
+        assert config.recursion_limit == 25
+
+
+def test_recursion_limit_from_env_var():
+    """Test that LANGGRAPH_RECURSION_LIMIT env var is picked up at instance creation."""
+    import kagent.langgraph._executor as executor_mod
+
+    with patch.dict(os.environ, {"LANGGRAPH_RECURSION_LIMIT": "50"}):
+        config = executor_mod.LangGraphAgentExecutorConfig()
+        assert config.recursion_limit == 50
+
+
+def test_recursion_limit_explicit_override():
+    """Test that explicit config value overrides env var default."""
+    from kagent.langgraph._executor import LangGraphAgentExecutorConfig
+
+    config = LangGraphAgentExecutorConfig(recursion_limit=100)
+    assert config.recursion_limit == 100
+
+
+def test_recursion_limit_rejects_zero():
+    """Test that recursion_limit=0 is rejected by gt=0 validation."""
+    from kagent.langgraph._executor import LangGraphAgentExecutorConfig
+
+    with pytest.raises(Exception):
+        LangGraphAgentExecutorConfig(recursion_limit=0)
+
+
+def test_recursion_limit_rejects_negative():
+    """Test that negative recursion_limit is rejected by gt=0 validation."""
+    from kagent.langgraph._executor import LangGraphAgentExecutorConfig
+
+    with pytest.raises(Exception):
+        LangGraphAgentExecutorConfig(recursion_limit=-5)
+
+
+def test_recursion_limit_invalid_env_var():
+    """Test that a non-numeric LANGGRAPH_RECURSION_LIMIT env var raises an error."""
+    import kagent.langgraph._executor as executor_mod
+
+    with patch.dict(os.environ, {"LANGGRAPH_RECURSION_LIMIT": "abc"}):
+        with pytest.raises((ValueError, Exception)):
+            executor_mod.LangGraphAgentExecutorConfig()