OpenAI Says Its Reworked Agent Harness Emits 54% Fewer Output Tokens Than Claude Fable 5, and Used GPT-5.6 to Rewrite Its Own Production Kernels for a 15% Lift

OpenAI (corroborated by The Next Web, Axios, SiliconANGLE, Engadget)·high signalXBlueskyLinkedInCopy link

Alongside the July 29 launch of ChatGPT for Academic Researchers — free GPT-5.6 Sol Pro for 10,000 researchers this summer scaling to 100,000 through 2027, backed by over $250 million — OpenAI disclosed efficiency work on the harness underlying Codex and ChatGPT Work. It claims 54 percent fewer output tokens than Claude Fable 5 on coding benchmarks, 80 percent cheaper operation on the lighter GPT-5.5 Luna, and a 15 percent efficiency gain after GPT-5.6 rewrote OpenAI's own production kernels via Codex. The two announcements are coupled: cheaper inference is what makes giving the model away at this scale viable.