diff --git a/rsconnect/environment.py b/rsconnect/environment.py
index 85bd1037..9cd62663 100644
--- a/rsconnect/environment.py
+++ b/rsconnect/environment.py
@@ -116,7 +116,6 @@ def create_python_environment(
         requirements_file: typing.Optional[str] = "requirements.txt",
         python: typing.Optional[str] = None,
         override_python_version: typing.Optional[str] = None,
-        app_file: typing.Optional[str] = None,
         package_manager: typing.Optional[PackageInstaller] = None,
     ) -> "Environment":
         """Given a project directory and a Python executable, return Environment information.
@@ -128,14 +127,10 @@ def create_python_environment(
                                   capture the environment via pip freeze.
         :param python: the Python executable of the environment to use for inspection.
         :param override_python_version: the Python version required by  the project.
-        :param app_file: the main application file to use for inspection.
 
         :return: a tuple containing the Python executable of the environment and the Environment object.
         """
-        if app_file is None:
-            module_file = fake_module_file_from_directory(directory)
-        else:
-            module_file = app_file
+        module_file = fake_module_file_from_directory(directory)
 
         _warn_on_ignored_manifest(directory)
         _warn_if_environment_directory(directory)
diff --git a/rsconnect/main.py b/rsconnect/main.py
index 40b4f373..0d25a31b 100644
--- a/rsconnect/main.py
+++ b/rsconnect/main.py
@@ -2195,7 +2195,6 @@ def deploy_notebook(
     environment = Environment.create_python_environment(
         base_dir,
         requirements_file=requirements_file,
-        app_file=file,
         python=python,
         override_python_version=override_python_version,
         package_manager=package_installer,
@@ -3981,7 +3980,6 @@ def write_manifest_notebook(
             requirements_file=requirements_file,
             python=python,
             override_python_version=override_python_version,
-            app_file=file,
             package_manager=package_installer,
         )
     r_environment = None if exclude_renv else REnvironment.create(base_dir)
@@ -4104,7 +4102,7 @@ def write_manifest_voila(
     set_verbosity(verbose)
     output_params(ctx, locals().items())
     with cli_feedback("Checking arguments"):
-        base_dir = dirname(path)
+        base_dir = path if isdir(path) else dirname(path)
         manifest_path = join(base_dir, "manifest.json")
 
         if exists(manifest_path) and not overwrite:
@@ -4117,7 +4115,6 @@ def write_manifest_voila(
             requirements_file=requirements_file,
             override_python_version=override_python_version,
             python=python,
-            app_file=path,
             package_manager=package_installer,
         )
     r_environment = None if exclude_renv else REnvironment.create(base_dir)
diff --git a/tests/test_write_manifest_voila.py b/tests/test_write_manifest_voila.py
new file mode 100644
index 00000000..2227701d
--- /dev/null
+++ b/tests/test_write_manifest_voila.py
@@ -0,0 +1,57 @@
+import json
+from pathlib import Path
+
+import pytest
+from click.testing import CliRunner
+
+from rsconnect.bundle import file_checksum
+from rsconnect.main import cli
+
+
+@pytest.fixture
+def project(tmp_path: Path, monkeypatch: pytest.MonkeyPatch) -> Path:
+    monkeypatch.chdir(tmp_path)
+    project_dir = tmp_path / "proj"
+    project_dir.mkdir()
+    (project_dir / "report.ipynb").write_text('{"cells":[],"metadata":{},"nbformat":4,"nbformat_minor":5}')
+    (project_dir / "requirements.txt").write_text("voila\n")
+    return project_dir
+
+
+@pytest.mark.parametrize("path", ["proj", "proj/", "proj/report.ipynb"])
+@pytest.mark.parametrize("parent_requirements", [False, True])
+def test_write_manifest_voila_uses_project_requirements(project: Path, path: str, parent_requirements: bool):
+    if parent_requirements:
+        Path("requirements.txt").write_text("pandas\n")
+
+    result = CliRunner().invoke(cli, ["write-manifest", "voila", path])
+
+    assert result.exit_code == 0, result.output
+    manifest = json.loads((project / "manifest.json").read_text())
+    assert manifest["files"]["requirements.txt"]["checksum"] == file_checksum(project / "requirements.txt")
+
+
+def test_write_manifest_voila_checks_project_manifest_for_overwrite(project: Path):
+    manifest_path = project / "manifest.json"
+    manifest_path.write_text("{}")
+
+    result = CliRunner().invoke(cli, ["write-manifest", "voila", "proj"])
+
+    assert result.exit_code != 0
+    assert "manifest.json already exists" in result.output
+    assert manifest_path.read_text() == "{}"
+
+    result = CliRunner().invoke(cli, ["write-manifest", "voila", "--overwrite", "proj"])
+
+    assert result.exit_code == 0, result.output
+    assert json.loads(manifest_path.read_text())["metadata"]["appmode"] == "jupyter-voila"
+
+
+def test_write_manifest_voila_ignores_parent_manifest(project: Path):
+    Path("manifest.json").write_text("{}")
+
+    result = CliRunner().invoke(cli, ["write-manifest", "voila", "proj"])
+
+    assert result.exit_code == 0, result.output
+    assert (project / "manifest.json").exists()
+    assert Path("manifest.json").read_text() == "{}"