Migrating a production AI agent from Claude Opus 4.8 to GPT-5.6 Sol: the three engineering costs behind the 2.2x benchmark
In the 48 hours after OpenAI’s 7/9 dual launch (GPT-5.6 and ChatGPT Work on the same day), the agent ecosystem started realigning along three visible axes. OpenAI temporarily lifted the 5-hour rate limit on Plus / Business / Pro. Codex weekly active users crossed 6 million. And one production agent — Ploy, who builds real marketing websites with an agent that plans across apps, reads and writes code, takes its own screenshots, and decides for itself when the build is done — migrated its core model from Claude Opus 4.8 to GPT-5.6 Sol and posted first-impression numbers that beat Opus 4.8 across the board: 2.17x faster wall-clock, 27% lower cost, 0.970 vs 0.936 on the visual score. ...