The chrome.proxy API Has No Independent Per-Tab Setting
Distinguish destination-based proxy selection from assigning a different proxy to each tab in one browser profile.
A proxy extension offering domain rules can send one website through proxy A and another through proxy B. That is destination-based selection, rather than a unique route attached to each tab.
Chrome’s proxy settings API supplies configuration with regular or incognito scope. It does not take a tabId for an independent proxy setting. PAC evaluation likewise receives destination information, not a browser tab identifier.
If two tabs request the same destination under the same policy, a domain rule cannot distinguish them. Changing the shared configuration can affect new requests from other tabs too; it does not move already established connections onto the new route.
For simultaneous different routes to the same website, choose separately configured browser profiles or another supported browser-context arrangement with independent proxy configuration. Incognito’s separate scope provides one particular separation, rather than an unlimited per-tab proxy interface.