This migration is a high-impact, cross-module change with several independent breaking changes. Before editing, Claude must determine how the callback-based API is currently used, where the restructured User fields propagate, whether deprecated methods are wrapped or re-exported, and which downstream modules depend on the affected behavior. Plan mode is therefore the correct starting point because it allows Claude to inspect the repository, identify affected code paths, and produce an implementation strategy without modifying source files.

Anthropic recommends separating exploration and planning from implementation when the approach is uncertain, the change affects multiple files, or the developer is unfamiliar with the impacted code. Direct execution is better reserved for small, clearly scoped changes that can be described as a simple diff. ( https://code.claude.com/docs/en/best-practices )

Option A applies transformations before establishing whether every usage follows the same pattern. Option B turns the test suite into a reactive discovery mechanism and may miss untested behavior. Option D provides useful migration documentation but assumes all 45 files can be changed uniformly. The reliable sequence is exploration, impact mapping, migration planning, implementation, and verification against tests and type checks.

Official references/topics: Plan Mode; Explore–Plan–Implement Workflow; Multi-File Migration Planning; Verification.