Hey man. Nixpack always looks for requirements.txt in the root. To use a different file, either symlink your file to root as requirements.txt or disable the default install phase by adding skip = true under [phases.setup] and keep your custom install command.

Yes, even if you set skip = true under [phases.install], Nixpacks will still handle the setup phase, which includes creating the virtual environment and setting up Python based on your nixPkgs.

So no, you don’t need to rewrite the whole build process. Just skip the default install phase and provide your custom pip install command. Everything else (like venv creation) still works as expected from the setup phase.

To solve your issue cleanly, where nixpacks insists on using requirements.txt in the root but you want to use a custom location (requirements/production.txt), here's the recommended solution:

# nixpacks.toml

[variables]
# This variable is not used by nixpacks automatically; safe to remove or ignore
# BPREQUIREMENTSTXT_PATH = "requirements/production.txt"

[phases.setup]
nixPkgs = ["python312"]

[phases.install]
# ⛔ Skip default install behavior that looks for requirements.txt in root
skip = true
cmd = ["pip install -r requirements/production.txt"]

[start]
cmd = "./entrypoint.sh"

• Setting skip = true in [phases.install]prevents the default logic, which always looks for requirements.txt in the root.

• Your custom cmd still runs inside the virtual environment created by the setup phase — so you still get the automatic Python setup, virtual environment, and all default system dependencies.

Don’t rely on BPREQUIREMENTSTXT_PATH

That variable is used by the internal build plan generator, but is not currently configurable via nixpacks.toml. It’s ignored unless you patch the internals or fork Nixpacks.