I filed T13687 as a followup for preventing this particular sort of error (where a Phobject is incorrectly serialized directly).

That's very likely the same problem, and I think it should be fixed by updating to the current stable (rPf2a7db1 or newer).

I believe we may be hitting either the problem one of the above commit fixes, or suffering from a similar caused as side-effect from it.

...ideally this sort of thing should fail loudly at serialization time...

the (Show Details) would be a great first step for us - and cover our needs. Much like the logs for Herald Rules and other areas.

There are a few pieces here, since we have to thread the needle through many layers to get where we want to go.

Since this is at least a little bit of actual work, I'm just going to punt until we see an actual user request.

These have existed for a while and recently got support for customizing sub-object behaviors in 2018 Week 50 (Mid December) and are being extended to Projects in 2019 Week 5, so it looks like they're here to stay.

@amckinley, for general context on where I'm headed here:

It would be really nice to default newly added fields to hidden. Going through 20+ forms to hide the fields is tedious.

I also can't reproduce the original report in the general case: when I type text into the "Create Task" form, click a notification to navigate away, then press "Back", my text is recovered. This is true whether Quicksand is enabled or not.

That wouldn't actually address the original problem here (accidentally setting your computer on fire and losing work) but would address the issue in T12731.

A possible attack on this is via whatever future abuse system we ultimately might build (T10215).