[buffalobuffalo]

I don't see why the repo owner needs to do/approve this. All this requires is that the repo can be forked. I could see a product looking like this.

   -Define a CI-like pipeline that runs tests that will fail if the bug persists and succeed if the bug is fixed.
   -Allow bounty seekers to pass links to branches/repo forks that try to pass the tests.
   -The first one to pass the tests get the bounty released to them
   -As a courtesy, the system should probably offer the patched code as a PR to the original repo, even if they don't accept it.

[blep_]

This might work for libraries (with the addition of the obvious "and doesn't obviously game the system by special casing all the test inputs" rule, because as soon as you add financial incentives, someone will try that).

I'm not sure it works for end-user software; the set of people who can write working tests is usually smaller than the set of end users.

[klntsky]

The effort to set up a test suite is oftentimes significantly higher than simply fixing a bug or adding a feature.

[DomMac]

Rewards mechanism are set at the repo/organization level, only maintainers know what to merge and how to reward contributors. Many solutions can be explored to find common patterns.