Turns out most of the advice I was reading was written by people who don't own phones.
Somewhere around March my Pixel started throttling in the second half of every match. Frames would tank, inputs got mushy, and I'd lose games I had no business losing.
First thing I tried: taking the case off. Marginal improvement. Maybe 1-2 degrees.
Second thing: one of those little clip-on cooler fans. Actually worked, but it's loud and looks ridiculous on the couch. My girlfriend banned it from the living room after one weekend.
The real fix was boring — I capped the framerate at 60. My phone can hit 120 in Sideswipe but keeping it there means the SoC is boiling. At a locked 60 I get zero throttling for an entire ranked session. And honestly? I can't tell the difference in gameplay. My brain adjusted in about ten minutes.
The other unglamorous fix: don't charge while you play. I know, I know. Just don't.