Claude Code v2.1.201 removes mid-conversation system role harness reminders

In the latest v2.1.201 release, Claude Code adjusts Claude Sonnet 5 sessions by no longer using the system role to insert harness reminders mid-conversation. Earlier, the system role could be used to inject reminders about the harness (test framework or execution environment) during an ongoing session to steer model behavior. This change directly impacts developer experience during long sessions or iterative debugging. Removing mid-session reminders cuts unnecessary token usage and makes the dialogue smoother, preventing system messages from interrupting the user's train of thought. For scenarios requiring frequent prompt iterations (e.g., code refactoring or debugging), this adjustment lets the model focus better on the user's actual instructions.