The frequency should be a prime number (e.g., 97) for timestream reasons. This should be defined as a variable near the top, not a magic number in an if statement.

You need something like this during report deletion:

if (report->flags.bits.announcement)
    erase_from_vector(world->status.announcements, &df::report::id, report_id);

(Popups don't need to be handled because they're deleted upon viewing, even if someone was crazy enough to enable them for combat messages.)

Myk has a similar unfinished plugin. He ran into some kind of issue, but I don't remember specifics. Maybe it was the performance impact of unit.reports.log, which is less an issue at the frequency you're running?

You could probably delete the unit report logs as you're iterating them (by doing so in reverse order). I think DF itself leaves these stale entries lying around, which would be good to clean up so we can iterate less.

The frequency should be a prime number

Fixed

You need something like this during report deletion:

world->status.announcements does not contain sparring, combat and hunting reports

Myk has a similar unfinished plugin. He ran into some kind of issue, but I don't remember specifics. Maybe it was the performance impact of unit.reports.log, which is less an issue at the frequency you're running?

I set frequency to 1 (every tick) and still can't see any performance impact. Performance check says that one run takes less than 2 ms.
Myk proposition uses buckets and reinserts reports. I think my version is simpler: foreach unit, get sparring reports (or combat and hunting reports if enabled) and remove them from units and from world.status.reports

You could probably delete the unit report logs as you're iterating them

I accomplish this using log.clear();