Along these lines: agents will write mountains of super repetitive test code, seemingly uninterested in refactoring it (without explicit instruction) to reduce redundancies.

In any non-trivial integration test scenario, it's easy to end up several times the LoC in tests compared to actual shipped code.

Second problem: different models, agents, and harnesses seem to have different tendencies and they tend to avoid touching code that is not their own unless explicitly instructed. What I mean by this: it will happily duplicate some helper method from another test file rather than pulling it out and reusing it, seemingly avoiding coupling (good kind in this case since model level changes should be propagated atomically).

Tests are where I see agents just spew absolute mountains of code.