Start an independent Codex Replay controller on an available loopback port. In both Codex Desktop and Codex CLI, prefer an available Codex in-app browser and otherwise use your system browser. Select one or more historical Claude threads, choose shared Codex models, and start their isolated implementations. Historical state and configuration are detected separately for each thread, with details available when needed. View finished comparisons individually or in aggregate while remaining threads continue. Available GPT-5.6 Sol, Terra, and Luna models are selected by default. Multiple replay sessions can run in parallel. Selection, execution, verification, evaluation, and results stay in the browser controller instead of a guided chat workflow.