Opus 5: How to Review Generated Code

You ask Opus 5 to fix a date parser issue involving a timezone suffix. In just twenty seconds, it reports the job is done but the diff shows it has rewritten eleven files, renamed helpers, cleaned import blocks, and added a caching layer you never mentioned. All tests pass, but now you must decide whether to approve a change that was promised to be just one line. The problem lies in the reflexive approach of handing off the task to Opus 5 and then reviewing the result, which ends up costing you time and effort.

Anthropic documents this issue as the model's tendency to expand the scope of a task beyond what was explicitly requested. The solution involves three layers of defense: steering, reviewing, and deterministic gates. Steering aims to keep the model on track by providing clear instructions to avoid over-reach. For this specific scenario, write down the exact paths the task should touch, such as `src/dates/` and its associated tests.

Only modify files within this named set, and if a change would require editing files outside this set, explicitly state why before proceeding. Keep the changes minimal and focused on the original request.

Layer three implements a deterministic gate that serves as a hard filter. It checks if any change outside the named set occurs, and if so, refuses to make the edit. Steering and the gate work together to ensure that the model stays within the boundaries of the original task scope, preventing unwanted scope creep. By implementing these three layers of defense, you can reduce the risk of receiving unexpected changes from Opus 5 and maintain better control over the code review process.