GPT 5.6 Soul vs Claude Fable 5: Is the Expensive One Worth It?

OpenAI just launched GPT 5.6, a new model family (Sol, Terra, and Luna), plus a new desktop app that combines chat, Work, and Codex in one place. The pitch: frontier-level output without treating every task like an unlimited-budget research project. So I put their flagship GPT 5.6 Soul up against Claude Fable 5, the model that's incredible at long, ambitious tasks but expensive to run. Same prompt, no starter code, no follow-up help, two builds each. First a convincing Flappy Bird clone, then a much less forgiving one: a full music production studio with a working transport bar, a 16-step sequencer, a mixer, animated meters, and a waveform. I score both on aesthetic, feel, and how many little product decisions each model held in its head. I also break down the part that matters more than the model itself: the harness. OpenAI's new Work is essentially their take on Claude Cowork, and Codex lines up against Claude Code. Chat is quietly being pushed to the side for quick, low-context questions while the whole industry moves toward longer workflows and finished deliverables. Thank you to our exclusive sponsor: PayPal Open, One Platform for All Business: http://paypalopen.com/ ⏱️ Timestamps: 0:00 — OpenAI drops GPT 5.6 and a new desktop app 0:28 — The matchup: GPT 5.6 Soul vs Claude Fable 5 1:05 — The new ChatGPT app: chat, Work, and Codex 1:24 — Sponsor: PayPal Open 1:40 — What Work actually is (and how it maps to Cowork) 2:41 — The test setup: same prompt, zero help 3:00 — Test 1: building Flappy Bird 4:30 — Flappy verdict 4:34 — Test 2: a real music production studio 5:26 — Fable's studio build 6:20 — GPT 5.6 Soul's studio build 6:50 — Final scorecard 7:01 — The real question: is Fable worth the price? 7:31 — Why the harness matters more than the model 8:03 — Takeaway (and don't forget Mythos) 8:19 — Which harness and model are you using? Subscribe to our Newsletter: https://thisweekinai.ai #GPT5.6 #ClaudeFable #OpenAI #Anthropic #Codex #ClaudeCowork #AImodels #ThisWeekInAI