A PAC URL Is Not an APT Proxy Configuration
APT has an external proxy-discovery hook, but handing it a browser PAC URL is not the same as providing a proxy endpoint.
Acquire::http::Proxy-Auto-Detect names an external command, not a PAC script URL. APT passes that command the URI it is about to contact.
| Command output | APT result |
|---|---|
| One proxy URI | Use the returned endpoint. |
DIRECT | Choose a direct connection. |
| No output | Leave the generic configuration in use. |
The transport contract does not make APT a browser PAC evaluator. A PAC URL is JavaScript route-selection data; a proxy URI is a forwarding service. A managed helper must translate the intended policy into the single result. Keep diagnostics off that standard-output result channel.
For a stable route, an approved explicit proxy with a few host-specific DIRECT entries can be simpler. APT documents host-specific proxy entries taking precedence over auto-detection for that host.
Keep authentication in an appropriate separate credential file where supported by the installed APT. Finding a route does not authenticate it. Inspect effective APT inputs rather than assume a desktop system-wide button translated every browser PAC condition.