An engineer asks the agent to migrate a legacy payments service off a deprecated HTTP client used in about 50 files, where retry and timeout handling differ between modules. In past attempts, the discovery phase filled the conversation with file contents, and by the time the agent designed the approach it was contradicting findings from early in the session. How should this task be run?

Answer: D — Use plan mode, delegating verbose discovery to the Explore subagent so only summaries return, then switch to direct execution to apply the planned migration.

A migration across about 50 files with behaviour that varies by module is a plan-mode task. The Explore subagent keeps verbose discovery output out of the main context and returns summaries, which prevents the degradation seen before. Planning first and then executing directly is the combination section 6 describes. (a) risks expensive rework when the variations show up late. (b) compacts only after the damage is done. (c) assumes the right design is known without exploring the code.