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Good example. When the agent writes the fix and the test together, both come from its own reading of the bug. Would a test written from the bug report alone, by someone who never saw the fix, have hit that failing path? And would it run against the build that actually ships?

Exactly. A test written from the bug report alone would help avoid the agent's own assumptions. And it should reproduce the original failure before the fix, then pass on the actual release build. Otherwise, a green checkmark doesn't tell us much.

Red before the fix, green on the release build: that order is the evidence. Who would hold that test in between, so the agent fixing the bug never reads it? And could the customer who reported the bug check later that the test existed before the fix, without asking you?

Exactly. High coverage doesn't help much if the fixture misses the one path that actually matters. That's the tricky part to catch.