From 49770949daa7ca4ef4744a2f089100f8b872b869 Mon Sep 17 00:00:00 2001
From: dinos <dinospk1999@gmail.com>
Date: Sat, 11 Jul 2026 13:59:27 +0200
Subject: [PATCH] fix(langgraph): prefer executable in venv over path (#341)

---
 EvoScientist/langgraph_dev/manager.py | 16 ++++--
 tests/test_langgraph_manager.py       | 72 +++++++++++++++++++++++++++
 2 files changed, 83 insertions(+), 5 deletions(-)

diff --git a/EvoScientist/langgraph_dev/manager.py b/EvoScientist/langgraph_dev/manager.py
index b7539a4..69e5068 100644
--- a/EvoScientist/langgraph_dev/manager.py
+++ b/EvoScientist/langgraph_dev/manager.py
@@ -306,14 +306,19 @@ def is_async_subagents_available() -> bool:
 
 def _langgraph_exe() -> str | None:
     """Return the path to the langgraph CLI binary, or None if not found."""
+    import sys
+
+    executable_dir = os.path.dirname(sys.executable)
+    candidate_names = (
+        ["langgraph.exe", "langgraph"] if os.name == "nt" else ["langgraph"]
+    )
+    for candidate_name in candidate_names:
+        candidate = os.path.join(executable_dir, candidate_name)
+        if os.path.isfile(candidate) and os.access(candidate, os.X_OK):
+            return candidate
     found = shutil.which("langgraph")
     if found:
         return found
-    import sys as _sys
-
-    candidate = os.path.join(os.path.dirname(_sys.executable), "langgraph")
-    if os.path.isfile(candidate) and os.access(candidate, os.X_OK):
-        return candidate
     return None
 
 
@@ -709,6 +714,7 @@ def start_langgraph_dev(
     sub_env["EVOSCIENTIST_DEPLOY_MODE"] = "full" if deploy_mode else "stripped"
 
     try:
+        logger.info("Starting langgraph dev with CLI: %s", exe)
         proc = subprocess.Popen(
             [
                 exe,
diff --git a/tests/test_langgraph_manager.py b/tests/test_langgraph_manager.py
index 845064e..353013c 100644
--- a/tests/test_langgraph_manager.py
+++ b/tests/test_langgraph_manager.py
@@ -8,6 +8,7 @@ to be available.
 from __future__ import annotations
 
 import dataclasses
+import sys
 from types import SimpleNamespace
 from unittest.mock import MagicMock, patch
 
@@ -32,6 +33,77 @@ def reset_module_state():
     manager._LOG_OFFSET_AT_START = 0
 
 
+# =============================================================================
+# langgraph CLI resolution
+# =============================================================================
+
+
+class TestLanggraphCliResolution:
+    def _make_executable(self, path):
+        path.write_text("#!/bin/sh\n", encoding="utf-8")
+        path.chmod(0o755)
+
+    def test_prefers_current_python_environment_over_path(self, tmp_path, monkeypatch):
+        local_bin = tmp_path / "local" / "bin"
+        local_bin.mkdir(parents=True)
+        local_langgraph = local_bin / "langgraph"
+        self._make_executable(local_langgraph)
+
+        path_bin = tmp_path / "path" / "bin"
+        path_bin.mkdir(parents=True)
+        path_langgraph = path_bin / "langgraph"
+        self._make_executable(path_langgraph)
+
+        monkeypatch.setattr(sys, "executable", str(local_bin / "python"))
+        monkeypatch.setattr(
+            manager.shutil,
+            "which",
+            lambda command: str(path_langgraph) if command == "langgraph" else None,
+        )
+
+        assert manager._langgraph_exe() == str(local_langgraph)
+
+    def test_falls_back_to_path_when_environment_binary_missing(
+        self, tmp_path, monkeypatch
+    ):
+        path_bin = tmp_path / "path" / "bin"
+        path_bin.mkdir(parents=True)
+        path_langgraph = path_bin / "langgraph"
+        self._make_executable(path_langgraph)
+
+        monkeypatch.setattr(
+            sys, "executable", str(tmp_path / "local" / "bin" / "python")
+        )
+        monkeypatch.setattr(
+            manager.shutil,
+            "which",
+            lambda command: str(path_langgraph) if command == "langgraph" else None,
+        )
+
+        assert manager._langgraph_exe() == str(path_langgraph)
+
+    def test_checks_windows_suffix_next_to_current_python(self, tmp_path, monkeypatch):
+        scripts_dir = tmp_path / "Scripts"
+        scripts_dir.mkdir()
+        local_langgraph = scripts_dir / "langgraph.exe"
+        self._make_executable(local_langgraph)
+
+        path_bin = tmp_path / "path" / "bin"
+        path_bin.mkdir(parents=True)
+        path_langgraph = path_bin / "langgraph.exe"
+        self._make_executable(path_langgraph)
+
+        monkeypatch.setattr(sys, "executable", str(scripts_dir / "python.exe"))
+        monkeypatch.setattr(manager.os, "name", "nt", raising=False)
+        monkeypatch.setattr(
+            manager.shutil,
+            "which",
+            lambda command: str(path_langgraph) if command == "langgraph" else None,
+        )
+
+        assert manager._langgraph_exe() == str(local_langgraph)
+
+
 # =============================================================================
 # is_langgraph_dev_running
 # =============================================================================