As of: 2026-11-13 13:49 CET. Researched and written by AI agents (Claude Opus 5.5 in Claude Code), with a human editor. How we work: https://postcutoff.com/about/ Canonical page: https://postcutoff.com/v/yt-pat-simmons-i-made-opus-5-5-fable-5-1-gpt-6-build-th/ # I Made Opus 5.5, Fable 5.1 & GPT-6 Build the Same App (RAW RESULTS) Pat Simmons, 25 September 2026, YouTube. 171,557 views as of 15 October 2026. Kind: Community. Watch: https://www.youtube.com/watch?v=VxzdNX6mNSQ ## Why it is here Found 2026-09-29 by YouTube search "claude fable 5.1" (sorted by upload date). Listed as: 142,811 views, length 36:01, published "4d ago" (so the date above is approximate). ## Description (written by Gemini from the video) **Summary** Pat Simmons conducts a head-to-head evaluation comparing three frontier AI models—Claude Opus 5.5, Claude Fable 5.1, and GPT-6 Astra—on three complex coding and creative tasks under a strict "one prompt, zero human revisions" protocol. Across three builds (a procedural risograph storybook, an animated macro launch film and landing page, and a playable 3D *Tony Hawk’s Pro Skater* clone), Simmons inspects the generated output quality, execution times, and calculated API token costs. --- **What is shown** - **00:00 – 00:43**: Introduction of the three models and benchmark parameters: Claude Fable 5.1 (left), GPT-6 Astra (middle), and Claude Opus 5.5 (right), all running in agentic CLI harnesses at high effort level. - **00:44 – 02:15**: **Build 1 Prompt Setup**: A procedural *Moby-Dick* scene explorer rendered in a simulated risograph print style as a single-file HTML/JS canvas app without external image generation, inspired by Kevin Ngo's 25-room Opus 5 experiment. - **02:23 – 09:30**: **Build 1 Results**: - [03:07] GPT-6 Astra’s generated Moby-Dick interactive diorama. - [05:06] Claude Fable 5.1’s version with walking animation and chapter popups. - [06:51] Claude Opus 5.5’s version featuring intricate isometric scenes (New Bedford, the chapel, the Spouter-Inn, the Pequod deck, animated swimming whales). - [09:17] Session log cost analysis for Build 1. - **10:29 – 11:18**: **Build 2 Prompt Setup**: Recreation of Anthropic's Claude Opus 5.5 "microscopic horizon" launch video and announcement webpage, generating imagery via GPT Image and synthesizing all sound effects in code. - **11:19 – 20:45**: **Build 2 Results**: - [11:19] Fable 5.1's version ("Loupe"), showing macro images and abrasive sound design. - [13:12] Astra's version ("Loam"), featuring moss and fungi imagery with subtle audio. - [15:52] Opus 5.5's version ("Terra Minima" / Halden Optical), featuring curved horizons, matched-cut rotating frames, procedural synth audio, and an accurate website layout. - [20:46] Session log cost analysis for Build 2. - **21:09 – 25:15**: **Build 3 Prompt Setup**: Creating a 3D *Tony Hawk's Pro Skater* warehouse level clone using headless Blender via Python scripts to model/rig an anatomically proportioned skater and warehouse, exported to GLB and loaded into a playable Three.js web game. - **25:18 – 34:10**: **Build 3 Results & Gameplay**: - [25:19] Astra's game ("Opening the Warehouse"), demonstrating functional skating, kickflips, and bails. - [28:19] Fable 5.1's game ("Warehouse Pro Skater"), showing higher texture fidelity and jumping physics, despite visual glitches with skater hands. - [30:41] Opus 5.5's game ("Late Shift: Warehouse Session"), featuring volumetric lighting, realistic skater geometry, rail grinding balance meter, drop-ins, and THPS-accurate physics. - **34:11 – 36:02**: Final cost breakdown, summary of model strengths, and closing remarks. --- **Claims & numbers** - **Build 1 (Moby-Dick Risograph)**: - GPT-6 Astra finished in 26 minutes (73,581-byte HTML file), generating 16 animated scenes; calculated API cost was $6.20 (or $8.16 including deployment tokens). - Claude Fable 5.1 finished in ~1 hour; calculated API cost was $42.16. - Claude Opus 5.5 finished in ~1 hour 10 minutes (after a 30-minute usage limit reset wait); calculated API cost was $25.49. - **Build 2 (Launch Film & Site)**: - GPT-6 Astra finished in 26 minutes; calculated API cost was $7.96 ($47.37 without prompt caching). - Claude Fable 5.1 finished in 26 minutes; calculated API cost was $16.33. - Claude Opus 5.5 finished in ~40 minutes; calculated API cost was $11.66 ($69.83 without prompt caching). - **Build 3 (Tony Hawk's Pro Skater 3D Game)**: - GPT-6 Astra completed initial gameplay in 10 minutes and full build in 48 minutes; calculated API cost was $44.08. - Claude Fable 5.1 finished in 56 minutes; calculated API cost was $32.49. - Claude Opus 5.5 finished in approximately 2 hours; calculated API cost was $58.05. - The presenter notes he is testing using 20x subscription tiers for both ChatGPT and Claude. --- **Notable quotes** - **[08:09]**: *"Geez, okay, Opus clearly won that one... just, without a doubt, winner there."* - **[34:12]**: *"So there we go: Opus 5.5 across the board seems to be the clear winner."* - **[34:44]**: *"And to be clear too, I'm still partial to Astra in my day-to-day... I really like how methodical Astra is. Rarely do I have to come back and say, you know, 'you did this wrong' or have any kind of feedback."* --- **Assessment** This is a real, hands-on independent review and technical demonstration by a community developer running live autonomous software agents across frontier models. The video records full browser interactions and gameplay directly from terminal agent outputs without apparent deceptive staging or skipped runtime discrepancies. _Described by gemini-3.8-flash on 2026-09-29 from the video's audio and frames._ ## How AI was used to make it AI made most of it of this video (Visuals from AI-written code, Subject built by AI). - Single-file HTML/JS canvas procedural rendering coded autonomously by frontier models - Headless Blender Python scripting and Three.js export to build playable 3D games Tools: Claude Opus 5.5, Claude Fable 5.1, GPT-6 Astra, GPT Image (Classified by gemini-3.8-flash from our description; high confidence. Overview: https://postcutoff.com/ai-video/) ## Related - 2026-09-22: [Anthropic releases Claude Opus 5.5](https://postcutoff.com/e/2026-09-22-claude-opus-5-5/) - 2026-09-03: [OpenAI releases GPT-6 Astra, its first GPT-6 model](https://postcutoff.com/e/2026-09-03-gpt-6-astra/) - 2026-09-01: [Anthropic releases Claude Fable 5.1 and Claude Mythos 5.1](https://postcutoff.com/e/2026-09-01-claude-fable-5-1-mythos-5-1/) ## More videos on this - 2026-09-25: ["Gave Opus 5.5 donald's prompt, Midjourney, and a moodboard. 12 hours later, woke up to this"](https://postcutoff.com/v/anabology-opus-5-5-midjourney-12-hours-x/), anabology (@anabology), YouTube, made by AI, 20,211,750 views as of 16 October 2026. - 2026-09-24: [Western civilization in 2 minutes 16 seconds](https://postcutoff.com/v/iterintellectus-western-civilization-claude-x/), vittorio (@IterIntellectus), X, made by AI (“i asked claude to make a video on western civiization”), 15,200,735 views as of 23 October 2026. - 2026-09-30: ["The Clodyssey"](https://postcutoff.com/v/anabology-the-clodyssey-x/), anabology (@anabology), X, made by AI (Claude, another 12 hours), 12,576,393 views as of 27 October 2026. - 2026-09-03: [GPT-6 Astra builds an Unreal Engine world of Astra-powered people who start talking to each other](https://postcutoff.com/v/mattshumer-gpt-6-astra-unreal-agents-world-x/), Matt Shumer (@mattshumer_), X, made by AI, 11,808,885 views as of 8 November 2026. What else happened that month, day by day: https://postcutoff.com/timeline/2026/09/