Ben Thompson says agent differentiation isn't in the model — it's in the integration between harness and model. Claude Code got better not because of Opus 4.5 itself, but because the harness changed. Microsoft's Copilot Cowork also gave up on model-agnostic, acknowledging that agents need deep integration.
Probably right for now. But model capabilities are converging, and the tight fit between harness and model might only be a phase-specific advantage.