So I'm particularly interested by the battery bypass of pixel phone. I use a pixel 10 pro with the latest experimental release@2025/01/05.

This feature has been documented to turn on when:

80% battery charge limiting is turned on;
==80% battery capacity is filed (not more/less !).

Some sources on this:
https://discuss.grapheneos.org/d/18159-new-battery-bypass-feature-in-gos
https://www.androidauthority.com/phones-with-bypass-charging-support-3509066/

In addition, you should need the following hardware to get battery bypass:

A PPS (a USB 3.0 PD extension) charger (>=45W);
The proper cable (that can deliver >=45W);

Some documentation:
https://uk.ugreen.com/blogs/charger/fast-charging-protocols
https://en.wikipedia.org/wiki/USB_hardware#USB_Power_Delivery

Also, I used a device to measure the power going through the cable. This allows me to check that PPS is a thing, and that once the 80% of the battery are reached, the phone continues drawing power through the cable, bypassing the battery.

Some tools to reproduce:
https://www.chargerlab.com/v-1-9-7-the-new-software-version-of-chargerlab-power-z-km003c/
https://www.amazon.it/dp/B0D95Y8L33

(Note, a first order way to know if you have a PPS capable charger is if amps and tension can modulate outside the fixed rates; 9V etc.).

Now, I plug my phone at around 20% capacity in the evening, let it go up to 80%. It draws ~ 25-27W up until 65% capacity. (Then the powers is reduced, going near zero if not restricting to 80%, this is standard procedure).
I used the BatteryBot Pro apps (com.darshancomputing.BatteryIndicatorPro https://github.com/darshan-/Battery-Indicator-Support/blob/master/SourceCode.md) or com.glgjing.hulk to monitor the phone's status. When the battery reaches 80%, the cable's tension stays at 9-9.1V@_0A in idle state.

I use the camera/video as a load (takes as much power as a game this thing...3.6-5.4W device total when running), to check if bypass works. And it does work but there is a few weird things.

Looking at the Battery Bot logs, or other battery status apps, I observe constant "No charging (AC)"/"Plugged In (AC)" status switches, this seems to happen at lock/unlock transitions, due to GOS' USB restriction policies (charge only when lock, etc.). I wonder if it can use bypass when locked then. I didn't have a battery draining app to run in the background (this status switch behavior does NOT happens when charging [0-80) even if I lock/unlock the phone);
Before engaging bypass, the battery got to 80% then dropped to 79% before charging again and getting in bypass state. The first 80-79% transition was evidently not under bypass.

The status switch concerns me a bit, but apart from that it seems to work.

I then unlocked charging (disabled the 80% limiter), it got to 88% quickly, I then enabled the feature back again. The phone then registered its charging status as "Unplugged", (it was plugged though). Unplugging/plugging the cable didn't change the status, nor did rebooting. I suppose this is to keep the battery @80%, which AFAIK is also good for long term storage.

PS:
I'm looking for a background, battery draining app to continue testing.