diff --git a/docs/CHANGELOG.md b/docs/CHANGELOG.md
index ac4920d0..2ed5d4a0 100644
--- a/docs/CHANGELOG.md
+++ b/docs/CHANGELOG.md
@@ -13,6 +13,8 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
   dependencies installed by connect to run the deployed content
 - `rsconnect content venv` command recreates a local python environment
   equal to the one used by connect to run the content.
+- Added `--requirements-file` option on deploy and write-manifest commands to
+  supply an explicit requirements file instead of detecting the environment.
 
 
 ## [1.28.2] - 2025-12-05
diff --git a/rsconnect/actions.py b/rsconnect/actions.py
index bb8b65a5..a16e7359 100644
--- a/rsconnect/actions.py
+++ b/rsconnect/actions.py
@@ -382,8 +382,8 @@ def deploy_app(
 
     environment = Environment.create_python_environment(
         directory,  # pyright: ignore
-        force_generate,
-        python,
+        requirements_file="requirements.txt" if not force_generate else None,
+        python=python,
     )
 
     # At this point, kwargs has a lot of things, but we can need to prune it down to just the things that
diff --git a/rsconnect/environment.py b/rsconnect/environment.py
index 270a0620..d2d2ca31 100644
--- a/rsconnect/environment.py
+++ b/rsconnect/environment.py
@@ -114,7 +114,7 @@ def from_dict(
     def create_python_environment(
         cls,
         directory: str,
-        force_generate: bool = False,
+        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,
@@ -125,8 +125,8 @@ def create_python_environment(
         If no Python executable is provided, the current system Python executable is used.
 
         :param directory: the project directory to inspect.
-        :param force_generate: force generating "requirements.txt" to snapshot the environment
-                               packages even if it already exists.
+        :param requirements_file: requirements file name relative to the project directory. If None,
+                                  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.
@@ -138,9 +138,8 @@ def create_python_environment(
         else:
             module_file = app_file
 
-        # click.secho('    Deploying %s to server "%s"' % (directory, connect_server.url))
         _warn_on_ignored_manifest(directory)
-        _warn_if_no_requirements_file(directory)
+        _warn_if_no_requirements_file(directory, requirements_file)
         _warn_if_environment_directory(directory)
 
         python_version_requirement = pyproject.detect_python_version_requirement(directory)
@@ -163,7 +162,7 @@ def create_python_environment(
             python_version_requirement = f"=={override_python_version}"
 
         # with cli_feedback("Inspecting Python environment"):
-        environment = cls._get_python_env_info(module_file, python, force_generate)
+        environment = cls._get_python_env_info(module_file, python, requirements_file=requirements_file)
         environment.python_version_requirement = python_version_requirement
 
         if override_python_version:
@@ -181,14 +180,17 @@ def create_python_environment(
             # Derive allow_uv from selection
             environment.package_manager_allow_uv = selected_package_manager is PackageInstaller.UV
 
-        if force_generate:
+        if requirements_file is None:
             _warn_on_ignored_requirements(directory, environment.filename)
 
         return environment
 
     @classmethod
     def _get_python_env_info(
-        cls, file_name: str, python: typing.Optional[str], force_generate: bool = False
+        cls,
+        file_name: str,
+        python: typing.Optional[str],
+        requirements_file: typing.Optional[str] = "requirements.txt",
     ) -> "Environment":
         """
         Gathers the python and environment information relating to the specified file
@@ -196,14 +198,13 @@ def _get_python_env_info(
 
         :param file_name: the primary file being deployed.
         :param python: the optional name of a Python executable.
-        :param force_generate: force generating "requirements.txt" or "environment.yml",
-        even if it already exists.
+        :param requirements_file: which requirements file to read. If None, generate via pip freeze.
         :return: information about the version of Python in use plus some environmental
         stuff.
         """
         python = which_python(python)
         logger.debug("Python: %s" % python)
-        environment = cls._inspect_environment(python, os.path.dirname(file_name), force_generate=force_generate)
+        environment = cls._inspect_environment(python, os.path.dirname(file_name), requirements_file=requirements_file)
         if environment.error:
             raise RSConnectException(environment.error)
         logger.debug("Python: %s" % python)
@@ -215,7 +216,7 @@ def _inspect_environment(
         cls,
         python: str,
         directory: str,
-        force_generate: bool = False,
+        requirements_file: typing.Optional[str] = "requirements.txt",
         check_output: typing.Callable[..., bytes] = subprocess.check_output,
     ) -> "Environment":
         """Run the environment inspector using the specified python binary.
@@ -223,13 +224,8 @@ def _inspect_environment(
         Returns a dictionary of information about the environment,
         or containing an "error" field if an error occurred.
         """
-        flags: typing.List[str] = []
-        if force_generate:
-            flags.append("f")
-
         args = [python, "-m", "rsconnect.subprocesses.inspect_environment"]
-        if flags:
-            args.append("-" + "".join(flags))
+        args.extend(["--requirements-file", requirements_file or "none"])
         args.append(directory)
 
         try:
@@ -321,17 +317,28 @@ def _warn_on_ignored_manifest(directory: str) -> None:
         )
 
 
-def _warn_if_no_requirements_file(directory: str) -> None:
+def _warn_if_no_requirements_file(directory: str, requirements_file: typing.Optional[str]) -> None:
     """
-    Checks for the existence of a file called requirements.txt in the given directory.
-    If it's not there, a warning will be printed.
+    Check that a requirements file exists, and that it lives inside the deployment directory.
 
     :param directory: the directory to check in.
+    :param requirements_file: the name of the requirements file, or None to skip the check.
     """
-    if not os.path.exists(os.path.join(directory, "requirements.txt")):
+    if requirements_file is None:
+        return
+
+    directory_path = pathlib.Path(directory)
+    requirements_file_path = directory_path / pathlib.Path(requirements_file)
+    if directory_path not in requirements_file_path.parents:
+        click.secho(
+            "    Warning: The requirements file '%s' is outside of the deployment directory.\n" % requirements_file,
+            fg="red",
+        )
+
+    if not requirements_file_path.exists():
         click.secho(
             "    Warning: Capturing the environment using 'pip freeze'.\n"
-            "             Consider creating a requirements.txt file instead.",
+            "             Consider creating a %s file instead." % requirements_file,
             fg="yellow",
         )
 
diff --git a/rsconnect/main.py b/rsconnect/main.py
index 5ba24c59..2bab7e17 100644
--- a/rsconnect/main.py
+++ b/rsconnect/main.py
@@ -1018,6 +1018,16 @@ def _warn_on_ignored_requirements(directory: str, requirements_file_name: str):
     is_flag=True,
     help='Force generating "requirements.txt", even if it already exists.',
 )
+@click.option(
+    "--requirements-file",
+    "-r",
+    type=click.Path(exists=True, dir_okay=False),
+    default="requirements.txt",
+    help=(
+        "Path to requirements file to record in the manifest instead of detecting the environment. "
+        "Must be inside the notebook directory. Use 'none' to capture via pip freeze."
+    ),
+)
 @click.option(
     "--package-installer",
     type=click.Choice(PackageInstaller),
@@ -1050,6 +1060,7 @@ def deploy_notebook(
     python: Optional[str],
     override_python_version: Optional[str],
     force_generate: bool,
+    requirements_file: Optional[str],
     verbose: int,
     file: str,
     extra_files: tuple[str, ...],
@@ -1073,18 +1084,16 @@ def deploy_notebook(
     app_mode = AppModes.JUPYTER_NOTEBOOK if not static else AppModes.STATIC
 
     base_dir = dirname(file)
+    requirements_file = resolve_requirements_file(base_dir, requirements_file, force_generate)
     environment = Environment.create_python_environment(
         base_dir,
+        requirements_file=requirements_file,
         app_file=file,
-        force_generate=force_generate,
         python=python,
         override_python_version=override_python_version,
         package_manager=package_installer,
     )
 
-    if force_generate:
-        _warn_on_ignored_requirements(base_dir, environment.filename)
-
     ce = RSConnectExecutor(
         ctx=ctx,
         name=name,
@@ -1179,6 +1188,16 @@ def deploy_notebook(
     is_flag=True,
     help='Force generating "requirements.txt", even if it already exists.',
 )
+@click.option(
+    "--requirements-file",
+    "-r",
+    type=click.Path(exists=True, dir_okay=False),
+    default="requirements.txt",
+    help=(
+        "Path to requirements file to record in the manifest instead of detecting the environment. "
+        "Must be inside the notebook directory. Use 'none' to capture via pip freeze."
+    ),
+)
 @click.option(
     "--package-installer",
     type=click.Choice(PackageInstaller),
@@ -1199,6 +1218,7 @@ def deploy_voila(
     python: Optional[str],
     override_python_version: Optional[str],
     force_generate: bool,
+    requirements_file: Optional[str],
     extra_files: tuple[str, ...],
     exclude: tuple[str, ...],
     image: Optional[str],
@@ -1225,11 +1245,13 @@ def deploy_voila(
     set_verbosity(verbose)
     output_params(ctx, locals().items())
     app_mode = AppModes.JUPYTER_VOILA
+    base_dir = path if isdir(path) else dirname(path)
+    requirements_file = resolve_requirements_file(base_dir, requirements_file, force_generate)
     environment = Environment.create_python_environment(
-        path if isdir(path) else dirname(path),
-        force_generate,
-        python,
-        override_python_version,
+        base_dir,
+        requirements_file=requirements_file,
+        python=python,
+        override_python_version=override_python_version,
         package_manager=package_installer,
     )
 
@@ -1256,7 +1278,7 @@ def deploy_voila(
         entrypoint,
         extra_files,
         exclude,
-        force_generate,
+        requirements_file is None,
         environment,
         image=image,
         env_management_py=env_management_py,
@@ -1400,6 +1422,16 @@ def deploy_manifest(
     is_flag=True,
     help='Force generating "requirements.txt", even if it already exists.',
 )
+@click.option(
+    "--requirements-file",
+    "-r",
+    type=click.Path(exists=True, dir_okay=False),
+    default="requirements.txt",
+    help=(
+        "Path to requirements file to record in the manifest instead of detecting the environment. "
+        "Must be inside the project directory. Use 'none' to capture via pip freeze."
+    ),
+)
 @click.option(
     "--package-installer",
     type=click.Choice(PackageInstaller),
@@ -1429,6 +1461,7 @@ def deploy_quarto(
     python: Optional[str],
     override_python_version: Optional[str],
     force_generate: bool,
+    requirements_file: Optional[str],
     verbose: int,
     file_or_directory: str,
     extra_files: Sequence[str],
@@ -1459,9 +1492,12 @@ def deploy_quarto(
 
     environment = None
     if "jupyter" in engines:
+        requirements_file = resolve_requirements_file(base_dir, requirements_file, force_generate)
         with cli_feedback("Inspecting Python environment"):
             environment = Environment.create_python_environment(
-                base_dir, force_generate=force_generate, override_python_version=override_python_version
+                base_dir,
+                requirements_file=requirements_file,
+                override_python_version=override_python_version,
             )
 
     ce = RSConnectExecutor(
@@ -1713,6 +1749,19 @@ def deploy_html(
         ce.verify_deployment()
 
 
+def resolve_requirements_file(directory: str, requirements_file: Optional[str], force_generate: bool) -> Optional[str]:
+    """
+    Determine which requirements file to use.
+
+    Returns None when pip freeze should be used (force_generate=True), otherwise returns
+    the provided path or the default "requirements.txt".
+    """
+    if force_generate:
+        _warn_on_ignored_requirements(directory, requirements_file or "requirements.txt")
+        return None
+    return requirements_file or "requirements.txt"
+
+
 def generate_deploy_python(app_mode: AppMode, alias: str, min_version: str, desc: Optional[str] = None):
     if desc is None:
         desc = app_mode.desc()
@@ -1772,6 +1821,15 @@ def generate_deploy_python(app_mode: AppMode, alias: str, min_version: str, desc
         is_flag=True,
         help='Force generating "requirements.txt", even if it already exists.',
     )
+    @click.option(
+        "--requirements-file",
+        "-r",
+        type=click.Path(exists=True, dir_okay=False),
+        help=(
+            "Path to requirements file to record in the manifest instead of detecting the environment. "
+            "Must be inside the deployment directory. Use 'none' to capture via pip freeze."
+        ),
+    )
     @click.option(
         "--package-installer",
         type=click.Choice(PackageInstaller),
@@ -1804,6 +1862,7 @@ def deploy_app(
         python: Optional[str],
         override_python_version: Optional[str],
         force_generate: bool,
+        requirements_file: Optional[str],
         verbose: int,
         directory: str,
         extra_files: tuple[str, ...],
@@ -1823,10 +1882,11 @@ def deploy_app(
         set_verbosity(verbose)
         entrypoint = validate_entry_point(entrypoint, directory)
         extra_files_list = validate_extra_files(directory, extra_files)
+        requirements_file = resolve_requirements_file(directory, requirements_file, force_generate)
         environment = Environment.create_python_environment(
             directory,
-            force_generate,
-            python,
+            requirements_file=requirements_file,
+            python=python,
             override_python_version=override_python_version,
             package_manager=package_installer,
         )
@@ -1969,6 +2029,15 @@ def write_manifest():
     is_flag=True,
     help='Force generating "requirements.txt", even if it already exists.',
 )
+@click.option(
+    "--requirements-file",
+    "-r",
+    type=click.Path(exists=True, dir_okay=False),
+    help=(
+        "Path to requirements file to record in the manifest instead of detecting the environment. "
+        "Must be inside the notebook directory. Use 'none' to capture via pip freeze."
+    ),
+)
 @click.option(
     "--package-installer",
     type=click.Choice(PackageInstaller),
@@ -2001,6 +2070,7 @@ def write_manifest_notebook(
     hide_all_input: Optional[bool] = None,
     hide_tagged_input: Optional[bool] = None,
     package_installer: Optional[PackageInstaller] = None,
+    requirements_file: Optional[str] = None,
 ):
     set_verbosity(verbose)
     output_params(ctx, locals().items())
@@ -2013,16 +2083,18 @@ def write_manifest_notebook(
         if exists(manifest_path) and not overwrite:
             raise RSConnectException("manifest.json already exists. Use --overwrite to overwrite.")
 
+    requirements_file = resolve_requirements_file(base_dir, requirements_file, force_generate)
     with cli_feedback("Inspecting Python environment"):
         environment = Environment.create_python_environment(
             base_dir,
-            force_generate=force_generate,
+            requirements_file=requirements_file,
             python=python,
             override_python_version=override_python_version,
             app_file=file,
             package_manager=package_installer,
         )
 
+    generate_env = requirements_file is None
     with cli_feedback("Creating manifest.json"):
         environment_file_exists = write_notebook_manifest_json(
             file,
@@ -2036,7 +2108,7 @@ def write_manifest_notebook(
             env_management_r,
         )
 
-    if environment_file_exists and not force_generate:
+    if environment_file_exists and not generate_env:
         click.secho(
             "    Warning: %s already exists and will not be overwritten." % environment.filename,
             fg="yellow",
@@ -2074,6 +2146,15 @@ def write_manifest_notebook(
     is_flag=True,
     help='Force generating "requirements.txt", even if it already exists.',
 )
+@click.option(
+    "--requirements-file",
+    "-r",
+    type=click.Path(exists=True, dir_okay=False),
+    help=(
+        "Path to requirements file to record in the manifest instead of detecting the environment. "
+        "Must be inside the notebook directory. Use 'none' to capture via pip freeze."
+    ),
+)
 @click.option(
     "--package-installer",
     type=click.Choice(PackageInstaller),
@@ -2122,6 +2203,7 @@ def write_manifest_voila(
     env_management_r: Optional[bool],
     multi_notebook: bool,
     package_installer: Optional[PackageInstaller] = None,
+    requirements_file: Optional[str] = None,
 ):
     set_verbosity(verbose)
     output_params(ctx, locals().items())
@@ -2132,10 +2214,11 @@ def write_manifest_voila(
         if exists(manifest_path) and not overwrite:
             raise RSConnectException("manifest.json already exists. Use --overwrite to overwrite.")
 
+    requirements_file = resolve_requirements_file(base_dir, requirements_file, force_generate)
     with cli_feedback("Inspecting Python environment"):
         environment = Environment.create_python_environment(
             base_dir,
-            force_generate=force_generate,
+            requirements_file=requirements_file,
             override_python_version=override_python_version,
             python=python,
             app_file=path,
@@ -2143,8 +2226,8 @@ def write_manifest_voila(
         )
 
     environment_file_exists = exists(join(base_dir, environment.filename))
-
-    if environment_file_exists and not force_generate:
+    generate_env = requirements_file is None
+    if environment_file_exists and not generate_env:
         click.secho(
             "    Warning: %s already exists and will not be overwritten." % environment.filename,
             fg="yellow",
@@ -2160,7 +2243,7 @@ def write_manifest_voila(
             environment,
             extra_files,
             exclude,
-            force_generate,
+            generate_env,
             image,
             env_management_py,
             env_management_r,
@@ -2216,6 +2299,15 @@ def write_manifest_voila(
     is_flag=True,
     help='Force generating "requirements.txt", even if it already exists.',
 )
+@click.option(
+    "--requirements-file",
+    "-r",
+    type=click.Path(exists=True, dir_okay=False),
+    help=(
+        "Path to requirements file to record in the manifest instead of detecting the environment. "
+        "Must be inside the project directory."
+    ),
+)
 @click.option(
     "--package-installer",
     type=click.Choice(PackageInstaller),
@@ -2246,6 +2338,7 @@ def write_manifest_quarto(
     env_management_py: Optional[bool],
     env_management_r: Optional[bool],
     package_installer: Optional[PackageInstaller],
+    requirements_file: Optional[str],
 ):
     set_verbosity(verbose)
     output_params(ctx, locals().items())
@@ -2265,20 +2358,27 @@ def write_manifest_quarto(
         logger.debug("Quarto: %s" % quarto)
         inspect = quarto_inspect(quarto, file_or_directory)
         engines = validate_quarto_engines(inspect)
+        if requirements_file and "jupyter" not in engines:
+            raise RSConnectException(
+                "--requirements-file is only supported for Quarto content using the Jupyter engine."
+            )
 
     environment = None
+    generate_env = False
     if "jupyter" in engines:
+        requirements_file = resolve_requirements_file(base_dir, requirements_file, force_generate)
+        generate_env = requirements_file is None
         with cli_feedback("Inspecting Python environment"):
             environment = Environment.create_python_environment(
                 base_dir,
-                force_generate=force_generate,
+                requirements_file=requirements_file,
                 override_python_version=override_python_version,
                 python=python,
                 package_manager=package_installer,
             )
 
         environment_file_exists = exists(join(base_dir, environment.filename))
-        if environment_file_exists and not force_generate:
+        if environment_file_exists and not generate_env:
             click.secho(
                 "    Warning: %s already exists and will not be overwritten." % environment.filename,
                 fg="yellow",
@@ -2414,6 +2514,15 @@ def generate_write_manifest_python(app_mode: AppMode, alias: str, desc: Optional
         is_flag=True,
         help='Force generating "requirements.txt", even if it already exists.',
     )
+    @click.option(
+        "--requirements-file",
+        "-r",
+        type=click.Path(exists=True, dir_okay=False),
+        help=(
+            "Path to requirements file to record in the manifest instead of detecting the environment. "
+            "Must be inside the application directory. Use 'none' to capture via pip freeze."
+        ),
+    )
     @click.option(
         "--package-installer",
         type=click.Choice(PackageInstaller),
@@ -2446,7 +2555,9 @@ def manifest_writer(
         env_management_py: Optional[bool],
         env_management_r: Optional[bool],
         package_installer: Optional[PackageInstaller],
+        requirements_file: Optional[str],
     ):
+        resolved_requirements_file = resolve_requirements_file(directory, requirements_file, force_generate)
         _write_framework_manifest(
             ctx,
             overwrite,
@@ -2454,7 +2565,6 @@ def manifest_writer(
             exclude,
             python,
             override_python_version,
-            force_generate,
             verbose,
             directory,
             extra_files,
@@ -2463,6 +2573,7 @@ def manifest_writer(
             env_management_py,
             env_management_r,
             package_installer=package_installer,
+            requirements_file=resolved_requirements_file,
         )
 
     return manifest_writer
@@ -2487,7 +2598,6 @@ def _write_framework_manifest(
     exclude: tuple[str, ...],
     python: Optional[str],
     override_python_version: Optional[str],
-    force_generate: bool,
     verbose: int,
     directory: str,
     extra_files: tuple[str, ...],
@@ -2496,6 +2606,7 @@ def _write_framework_manifest(
     env_management_py: Optional[bool],
     env_management_r: Optional[bool],
     package_installer: Optional[PackageInstaller] = None,
+    requirements_file: Optional[str] = None,
 ):
     """
     A common function for writing manifests for APIs as well as Dash, Streamlit, Bokeh, and Panel apps.
@@ -2506,8 +2617,6 @@ def _write_framework_manifest(
                     the deploy.
     :param python: a path to the Python executable to use.
     :param override_python_version: Python version number Connect should use instead of the locally-installed version
-    :param force_generate: a flag to force the generation of manifest and
-                           requirements file.
     :param verbose: a flag to produce more (debugging) output.
     :param directory: the directory of the thing to deploy.
     :param extra_files: any extra files that should be included.
@@ -2528,10 +2637,11 @@ def _write_framework_manifest(
         if exists(manifest_path) and not overwrite:
             raise RSConnectException("manifest.json already exists. Use --overwrite to overwrite.")
 
+    resolved_requirements_file = resolve_requirements_file(directory, requirements_file, False)
     with cli_feedback("Inspecting Python environment"):
         environment = Environment.create_python_environment(
             directory,
-            force_generate=force_generate,
+            requirements_file=resolved_requirements_file,
             override_python_version=override_python_version,
             python=python,
         )
@@ -2554,7 +2664,8 @@ def _write_framework_manifest(
             env_management_r,
         )
 
-    if environment_file_exists and not force_generate:
+    generate_env = resolved_requirements_file is None
+    if environment_file_exists and not generate_env:
         click.secho(
             "    Warning: %s already exists and will not be overwritten." % environment.filename,
             fg="yellow",
diff --git a/rsconnect/subprocesses/inspect_environment.py b/rsconnect/subprocesses/inspect_environment.py
index 97b2c9a4..92af5452 100644
--- a/rsconnect/subprocesses/inspect_environment.py
+++ b/rsconnect/subprocesses/inspect_environment.py
@@ -8,6 +8,7 @@
 """
 from __future__ import annotations
 
+import argparse
 import datetime
 import json
 import locale
@@ -60,21 +61,21 @@ class EnvironmentException(Exception):
     pass
 
 
-def detect_environment(dirname: str, force_generate: bool = False) -> EnvironmentData:
+def detect_environment(dirname: str, requirements_file: Optional[str] = "requirements.txt") -> EnvironmentData:
     """Determine the python dependencies in the environment.
 
     `pip freeze` will be used to introspect the environment.
 
     :param: dirname Directory name
-    :param: force_generate Force the generation of an environment
+    :param: requirements_file The requirements file to read. If None, generate using pip freeze.
     :return: a dictionary containing the package spec filename and contents if successful,
     or a dictionary containing `error` on failure.
     """
 
-    if force_generate:
+    if requirements_file is None:
         result = pip_freeze()
     else:
-        result = output_file(dirname, "requirements.txt", "pip") or pip_freeze()
+        result = output_file(dirname, requirements_file, "pip") or pip_freeze()
 
     if result is not None:
         result["python"] = get_python_version()
@@ -206,17 +207,24 @@ def main():
     Run `detect_environment` and dump the result as JSON.
     """
     try:
-        if len(sys.argv) < 2:
-            raise EnvironmentException("Usage: %s [-fc] DIRECTORY" % sys.argv[0])
-        # directory is always the last argument
-        directory = sys.argv[len(sys.argv) - 1]
-        flags = ""
-        force_generate = False
-        if len(sys.argv) > 2:
-            flags = sys.argv[1]
-        if "f" in flags:
-            force_generate = True
-        envinfo = detect_environment(directory, force_generate)._asdict()
+        parser = argparse.ArgumentParser(
+            description="Inspect python environment and return dependency metadata.", add_help=True
+        )
+        parser.add_argument(
+            "-r",
+            "--requirements-file",
+            dest="requirements_file",
+            default="requirements.txt",
+            help="Requirements file name (relative to the directory). Use 'none' to capture via pip freeze.",
+        )
+        parser.add_argument("directory", help="Directory to inspect.")
+        args = parser.parse_args()
+
+        requirements_file = args.requirements_file
+        if requirements_file.lower() == "none":
+            requirements_file = None
+
+        envinfo = detect_environment(args.directory, requirements_file=requirements_file)._asdict()
         if "contents" in envinfo:
             keepers = list(map(strip_ref, envinfo["contents"].split("\n")))
             keepers = [line for line in keepers if not exclude(line)]
diff --git a/tests/test_environment.py b/tests/test_environment.py
index 9d883315..0495fc90 100644
--- a/tests/test_environment.py
+++ b/tests/test_environment.py
@@ -2,6 +2,7 @@
 import sys
 import os
 import tempfile
+import shutil
 import subprocess
 from unittest import TestCase
 from unittest import mock
@@ -59,6 +60,23 @@ def test_file(self):
         )
         self.assertEqual(expected, result)
 
+    def test_requirements_override(self):
+        with tempfile.TemporaryDirectory() as tmpdir:
+            project_dir = os.path.join(tmpdir, "project")
+            shutil.copytree(get_dir("pip1"), project_dir)
+            os.makedirs(os.path.join(project_dir, "alt"), exist_ok=True)
+            custom_requirements = os.path.join(project_dir, "alt", "custom.txt")
+            with open(custom_requirements, "w") as f:
+                f.write("foo==1.0\nbar>=2.0\nrsconnect==0.1\n")
+
+            result = Environment.create_python_environment(
+                project_dir, requirements_file=os.path.join("alt", "custom.txt")
+            )
+
+            assert result.filename.endswith("custom.txt")
+            assert result.contents == "foo==1.0\nbar>=2.0\n"
+            assert result.source == "file"
+
     def test_pip_freeze(self):
         result = Environment.create_python_environment(get_dir("pip2"))
 
@@ -175,7 +193,7 @@ def test_inspect_environment_catches_type_error():
     (
         "file_name",
         "python",
-        "force_generate",
+        "requirements_file",
         "expected_python",
         "expected_environment",
     ),
@@ -183,7 +201,7 @@ def test_inspect_environment_catches_type_error():
         pytest.param(
             "path/to/file.py",
             sys.executable,
-            False,
+            "requirements.txt",
             sys.executable,
             Environment.from_dict(
                 dict(
@@ -203,7 +221,7 @@ def test_inspect_environment_catches_type_error():
         pytest.param(
             "another/file.py",
             os.path.basename(sys.executable),
-            False,
+            "requirements.txt",
             sys.executable,
             Environment.from_dict(
                 dict(
@@ -223,7 +241,7 @@ def test_inspect_environment_catches_type_error():
         pytest.param(
             "will/the/files/never/stop.py",
             "argh.py",
-            False,
+            "requirements.txt",
             "unused",
             Environment.from_dict(
                 dict(
@@ -245,7 +263,7 @@ def test_get_python_env_info(
     monkeypatch,
     file_name,
     python,
-    force_generate,
+    requirements_file,
     expected_python,
     expected_environment,
 ):
@@ -255,7 +273,7 @@ def fake_which_python(python, env=os.environ):
     def fake_inspect_environment(
         python,
         directory,
-        force_generate=False,
+        requirements_file="requirements.txt",
         check_output=subprocess.check_output,
     ):
         return expected_environment
@@ -266,9 +284,9 @@ def fake_inspect_environment(
 
     if expected_environment.error is not None:
         with pytest.raises(RSConnectException):
-            _ = Environment._get_python_env_info(file_name, python, force_generate=force_generate)
+            _ = Environment._get_python_env_info(file_name, python, requirements_file=requirements_file)
     else:
-        environment = Environment._get_python_env_info(file_name, python, force_generate=force_generate)
+        environment = Environment._get_python_env_info(file_name, python, requirements_file=requirements_file)
 
         assert environment.python_interpreter == expected_python
         assert environment == expected_environment
diff --git a/tests/testdata/stock-api-fastapi/main.py b/tests/testdata/stock-api-fastapi/main.py
index c69f2ca1..867f027a 100644
--- a/tests/testdata/stock-api-fastapi/main.py
+++ b/tests/testdata/stock-api-fastapi/main.py
@@ -1,6 +1,6 @@
 # -*- coding: utf-8 -*-
 import os
-from datetime import date
+from datetime import date  # noqa: F401
 from typing import List
 
 import numpy as np