Comparing tox 4 and Terminal Proxy Environments
Modern tox already passes standard proxy variables through. Inspect overrides and the process doing the download before copying old install-command workarounds.
tox 4's documented default pass-through includes http_proxy, https_proxy, no_proxy, and PIP_*. If pip works in a terminal but fails during tox setup, missing pass-through is only one possible explanation.
Compare the downloader's inputs
Inspect the endpoint and bypass values seen by the failing process, including explicit tox overrides and environment files. A project can replace a correct inherited value with an obsolete one. A custom name such as my_https_proxy needs an explicit mapping before a downloader can use it.
Identify the stage: environment creation, packaging, dependency installation, or a command inside the test environment. They can involve different processes and settings.
Compare Python and pip versions and persistent configuration as well. tox may create an environment with different certificate behavior, so a TLS trust failure is not sufficient evidence of a missing proxy variable.
Apply the required override
Use the installed tox version's supported environment configuration and normal secret mechanism. A pip wrapper is useful only if a necessary mapping cannot be expressed adequately there; it also needs correct argument forwarding, exit status, and platform behavior.
Keep the actual failed process's inputs in the report, with credentials removed. That provides a repeatable comparison when the project or tox version changes.