feat(exec): add path prepend config

tests/tools/test_exec_env.py

@@ -45,6 +45,28 @@ async def test_exec_path_append_preserves_system_path():
     assert "Exit code: 0" in result
 
 
+@_UNIX_ONLY
+@pytest.mark.asyncio
+async def test_exec_path_prepend_takes_lookup_precedence(tmp_path):
+    """pathPrepend should win over pathAppend for executable lookup."""
+    preferred = tmp_path / "preferred"
+    fallback = tmp_path / "fallback"
+    preferred.mkdir()
+    fallback.mkdir()
+    preferred_tool = preferred / "pathprobe"
+    fallback_tool = fallback / "pathprobe"
+    preferred_tool.write_text("#!/bin/sh\necho preferred\n", encoding="utf-8")
+    fallback_tool.write_text("#!/bin/sh\necho fallback\n", encoding="utf-8")
+    preferred_tool.chmod(0o755)
+    fallback_tool.chmod(0o755)
+
+    tool = ExecTool(path_prepend=str(preferred), path_append=str(fallback))
+    result = await tool.execute(command="pathprobe")
+
+    assert "preferred" in result
+    assert "fallback" not in result
+
+
 @_UNIX_ONLY
 @pytest.mark.asyncio
 async def test_exec_allowed_env_keys_passthrough(monkeypatch):

tests/tools/test_exec_platform.py

@@ -202,6 +202,65 @@ class TestPathAppendPlatform:
         assert captured_env["NANOBOT_PATH_APPEND"] == "/opt/bin; echo INJECTED"
         assert "INJECTED" not in captured_cmd
 
+    @pytest.mark.asyncio
+    async def test_unix_path_prepend_uses_env_var_in_fixed_export(self):
+        """On Unix, path_prepend must not be interpolated into shell source."""
+        mock_proc = AsyncMock()
+        mock_proc.communicate.return_value = (b"ok", b"")
+        mock_proc.returncode = 0
+
+        captured_cmd = None
+        captured_env = {}
+
+        async def capture_spawn(cmd, cwd, env, shell_program=None, login=True, *, stdin=None):
+            nonlocal captured_cmd
+            captured_cmd = cmd
+            captured_env.update(env)
+            return mock_proc
+
+        with (
+            patch("nanobot.agent.tools.shell._IS_WINDOWS", False),
+            patch("nanobot.agent.tools.shell.os.pathsep", ":"),
+            patch.object(ExecTool, "_spawn", side_effect=capture_spawn),
+            patch.object(ExecTool, "_guard_command", return_value=None),
+        ):
+            tool = ExecTool(path_prepend="/venv/bin; echo INJECTED")
+            await tool.execute(command="python --version")
+
+        assert captured_cmd == 'export PATH="$NANOBOT_PATH_PREPEND:$PATH"; python --version'
+        assert captured_env["NANOBOT_PATH_PREPEND"] == "/venv/bin; echo INJECTED"
+        assert "INJECTED" not in captured_cmd
+
+    @pytest.mark.asyncio
+    async def test_unix_path_prepend_and_append_order(self):
+        mock_proc = AsyncMock()
+        mock_proc.communicate.return_value = (b"ok", b"")
+        mock_proc.returncode = 0
+
+        captured_cmd = None
+        captured_env = {}
+
+        async def capture_spawn(cmd, cwd, env, shell_program=None, login=True, *, stdin=None):
+            nonlocal captured_cmd
+            captured_cmd = cmd
+            captured_env.update(env)
+            return mock_proc
+
+        with (
+            patch("nanobot.agent.tools.shell._IS_WINDOWS", False),
+            patch("nanobot.agent.tools.shell.os.pathsep", ":"),
+            patch.object(ExecTool, "_spawn", side_effect=capture_spawn),
+            patch.object(ExecTool, "_guard_command", return_value=None),
+        ):
+            tool = ExecTool(path_prepend="/venv/bin", path_append="/usr/sbin")
+            await tool.execute(command="python --version")
+
+        assert captured_cmd == (
+            'export PATH="$NANOBOT_PATH_PREPEND:$PATH:$NANOBOT_PATH_APPEND"; python --version'
+        )
+        assert captured_env["NANOBOT_PATH_PREPEND"] == "/venv/bin"
+        assert captured_env["NANOBOT_PATH_APPEND"] == "/usr/sbin"
+
     @pytest.mark.asyncio
     async def test_windows_modifies_env(self):
         """On Windows, path_append is appended to PATH in the env dict."""
@@ -226,6 +285,32 @@ class TestPathAppendPlatform:
 
         assert captured_env["PATH"].endswith(r";C:\tools\bin")
 
+    @pytest.mark.asyncio
+    async def test_windows_path_prepend_and_append_order(self):
+        mock_proc = AsyncMock()
+        mock_proc.communicate.return_value = (b"ok", b"")
+        mock_proc.returncode = 0
+
+        captured_env = {}
+
+        async def capture_spawn(cmd, cwd, env, shell_program=None, login=True, *, stdin=None):
+            captured_env.update(env)
+            return mock_proc
+
+        with (
+            patch("nanobot.agent.tools.shell._IS_WINDOWS", True),
+            patch("nanobot.agent.tools.shell.os.pathsep", ";"),
+            patch.object(ExecTool, "_build_env", return_value={"PATH": r"C:\Windows\System32"}),
+            patch.object(ExecTool, "_spawn", side_effect=capture_spawn),
+            patch.object(ExecTool, "_guard_command", return_value=None),
+        ):
+            tool = ExecTool(path_prepend=r"C:\venv\Scripts", path_append=r"C:\tools\bin")
+            await tool.execute(command="python --version")
+
+        assert captured_env["PATH"] == (
+            r"C:\venv\Scripts;C:\Windows\System32;C:\tools\bin"
+        )
+
 
 # ---------------------------------------------------------------------------
 # sandbox

tests/tools/test_tool_loader.py

@@ -244,6 +244,7 @@ def test_exec_tool_create():
     mock_config.exec.enable = True
     mock_config.exec.timeout = 120
     mock_config.exec.sandbox = ""
+    mock_config.exec.path_prepend = "/venv/bin"
     mock_config.exec.path_append = ""
     mock_config.exec.allowed_env_keys = []
     mock_config.exec.allow_patterns = []
@@ -252,6 +253,7 @@ def test_exec_tool_create():
     ctx = ToolContext(config=mock_config, workspace="/tmp")
     tool = ExecTool.create(ctx)
     assert isinstance(tool, ExecTool)
+    assert tool.path_prepend == "/venv/bin"
 
 
 def test_web_tools_config_cls():
@@ -360,7 +362,7 @@ def test_config_round_trip():
     config_dict = {
         "tools": {
             "web": {"enable": True, "search": {"provider": "brave", "api_key": "test"}},
-            "exec": {"enable": False, "timeout": 120},
+            "exec": {"enable": False, "timeout": 120, "pathPrepend": "/venv/bin"},
             "my": {"allowSet": True},
             "imageGeneration": {"enabled": True, "provider": "openrouter"},
         }
@@ -370,8 +372,10 @@ def test_config_round_trip():
 
     assert dumped["tools"]["my"]["allowSet"] is True
     assert dumped["tools"]["imageGeneration"]["enabled"] is True
+    assert dumped["tools"]["exec"]["pathPrepend"] == "/venv/bin"
     assert config.tools.exec.enable is False
     assert config.tools.exec.timeout == 120
+    assert config.tools.exec.path_prepend == "/venv/bin"
     assert config.tools.web.search.provider == "brave"
 
 
@@ -382,6 +386,7 @@ def test_config_defaults():
     config = Config.model_validate({})
     assert config.tools.exec.enable is True
     assert config.tools.exec.timeout == 60
+    assert config.tools.exec.path_prepend == ""
     assert config.tools.web.enable is True
     assert config.tools.web.search.provider == "duckduckgo"
     assert config.tools.my.enable is True
@@ -403,6 +408,7 @@ def test_loader_registers_same_tools_as_old_hardcoded():
     mock_config.exec.enable = True
     mock_config.exec.timeout = 60
     mock_config.exec.sandbox = ""
+    mock_config.exec.path_prepend = ""
     mock_config.exec.path_append = ""
     mock_config.exec.allowed_env_keys = []
     mock_config.exec.allow_patterns = []