.. SPDX-FileCopyrightText: Copyright (c) 2025-2026 NVIDIA CORPORATION & AFFILIATES. All rights reserved.
.. SPDX-License-Identifier: Apache-2.0

Environment Variables
=====================

Runtime Environment Variables
-----------------------------

- ``CUDA_PYTHON_CUDA_PER_THREAD_DEFAULT_STREAM`` : When set to 1, the default stream is the per-thread default stream. When set to 0, the default stream is the legacy default stream. This defaults to 0, for the legacy default stream. See `Stream Synchronization Behavior <https://docs.nvidia.com/cuda/cuda-runtime-api/stream-sync-behavior.html>`_ for an explanation of the legacy and per-thread default streams.

- ``CUDA_PYTHON_DISABLE_MAJOR_VERSION_WARNING`` : When set to 1, suppresses warnings about CUDA major version mismatches between ``cuda-bindings`` and the installed driver.


Build-Time Environment Variables
--------------------------------

- ``CUDA_PATH`` or ``CUDA_HOME``: Specifies the location of the CUDA Toolkit. If both are set, ``CUDA_PATH`` takes precedence.

  .. note::
     The ``CUDA_PATH`` > ``CUDA_HOME`` priority is determined by ``cuda-pathfinder``.
     Earlier versions of ``cuda-pathfinder`` (before 1.5.0) used the opposite order
     (``CUDA_HOME`` > ``CUDA_PATH``). See the
     `cuda-pathfinder 1.5.0 release notes <https://nvidia.github.io/cuda-python/cuda-pathfinder/latest/release/1.5.0-notes.html>`_
     for details and migration guidance.

- ``CUDA_PYTHON_PARALLEL_LEVEL`` (previously ``PARALLEL_LEVEL``) : int, sets the number of threads used in the compilation of extension modules. Not setting it or setting it to 0 would disable parallel builds.
