I'm observing that when pants runs the ruff lint it isn't copying the referenced configuration to the sandbox.

pants -ldebug --keep-sandboxes=on_failure lint --check-only=ruff src/python/integration_test.py

Inside the sandbox:

$ tree .
.
├── __ruff_tool -> /private/var/folders/kw/qhf2k3js3nvgf7t8_1g46skm0000gq/T/immutable_inputsD7a0FO/.tmpYizkXQ/93d14855a9913f378328369f6e46db5b8600f0d37baf4f55e8630cb510f36020
├── __run.sh
├── reports
└── src
    └── python
        └── integration_test.py

# pants.toml
[ruff]
config = ".ruff.toml"
version = "0.8.6"