r/AI_Agents: Identical Prompts on Two Agent Instances Yield Divergent Code Changes — Same Model Weights, Different Refactoring Decisions

A developer running two instances of the same model with identical prompts on fresh checkouts of the same codebase found divergent outcomes: one instance refactored a shared utility outside its assigned scope while the other left it untouched. The post explicitly distinguishes this from test-suite non-determinism—the issue is divergent high-level decisions about what to touch—and opens discussion about whether concurrent multi-agent code ownership requires explicit file-level locking or serialization. Production builders in the comments confirm the pattern appears regularly in multi-agent CI/CD workflows.