Need to renew passport with TN

My CDN passport expires in December and the instructions say you have to send your current passport with the application -- but I still need to keep my TN. How do I do that? I've searched the Passport Canada site and no info re. keeping a work permit in the passport to be renewed. The site also says you cannot renew your passport at consulates -- only get forms. Bummer.

What have others done re this? Thanks in advance for your help.

Doesn't matter, just keep the I-94. The issued date and the stamp on the I-94 will be prior to the issued date of the passport so it's a simple explanation if it ever comes up.

USCIS don't really care about your passport, it's their paperwork they're interested in. You only need a passport/visa to cross the border. In the case of an actual visa, if you left and wanted to re-enter you would need to get the visa re-stamped in your new passport by the consulate using the original supporting paperwork, but with TN-1 all there is is the I-94 valid for multiple entries.

The thing that allows you to stay in the US is not your passport or any visas in it, it's the other paperwork which is the permit.

If you ask them nicely, the passport office will also give you back your old passport if you want. They'll cut the corner off, and stamp "cancelled" on the info page.