Prompt
Help us plan our gradual transition by aligning it with the goals and resources below. [input] Goals and usage situations: You want to resolve any blockages in your gradual transition plan and decide on your next actions. Resources to review: Existing System and Previous Goals Conditions and Constraints: Please proceed based on the provided data, and mark any missing facts as requiring confirmation. Previous attempts and records: This is my first attempt. Please proceed from the parts that can be confirmed in the current data. [Key points to check in this topic] Divide coexistence, route switching, verification, and return into small units. [Results to be created this time] First determine responsibility, input/output, failure action, and contract with the existing caller. Compare two possible designs based on cost, complexity, and compatibility and choose small changes that are appropriate for your situation. Indicate items that need to be decided before implementation. [Working Principle] Give priority to facts confirmed in the current environment and provided code. Don't create APIs/files/tests that don't exist. Treat sensitive values as hidden examples and leave unexecuted tasks as unexecuted. If there is no input that will change the results, ask only the necessary questions first and proceed with the parts that can be confirmed with data. [Completion criteria] Ensure that the design meets requirements and accounts for changes to existing behavior. Distinguish between the basis for the outcome, remaining uncertainties, and next actions, and mark only what has actually been confirmed as complete.