Claude Fable 5.1 Is INSANE – Hands-On With the BEST Model Yet!

Summary
YouTuber and developer Bijan Bowen reviews Anthropic's Claude Fable 5.1 model across coding, CAD, and 3D web development benchmarks. He tests the model via Claude's web interface, Claude Code CLI, and Cursor, evaluating its outputs on games, 3D graphics, OpenSCAD CAD modeling, and browser interfaces while examining pricing and credit usage.

What is shown

• [00:09] Overview of the Claude Fable 5.1 launch popup, Anthropic blog post, release details, pricing, and system safeguards.
• [01:45] Analysis of official benchmark tables (Terminal-Bench 4.0, OSWorld, Humanity's Last Exam) and scientific research use cases (15-PGDH protein design, Venus elevation map).
• [05:16] Browser OS ("Aurora OS"): Web UI test producing a complete multi-app desktop environment containing window management, a custom system bus ("Aurora Link"), and 3D games (Blocktown GTA clone and Voidrunner space shooter).
• [11:51] C++ Skateboarding Game: Tested via Claude Code CLI; compiles a single-file C++ game (NYC Block Skate) using OpenGL/GLFW, with subsequent autonomous bug-fixing [15:10] for ollie mechanics, collision bailing, and urban NPC interactions.
• [17:20] Seinfeld Apartment 3D Model: Prompted via Claude.ai chat to generate a Three.js interactive walkthrough and dollhouse view [19:23] of Jerry Seinfeld's apartment.
• [19:48] OpenSCAD Engine Model: Prompted inside Cursor to create a 3D-printable model of an RB26 twin-turbo engine fitted for an N20 micro motor, verified in OpenSCAD [20:31] and sliced in Ultimaker Cura [21:34].
• [23:57] Interactive Watch Website ("Slappis"): Generates an interactive luxury watch promotional site featuring Three.js rendering and an exploded view assembly slider [25:03].
• [26:21] C++ Rally Game ("Alpine Rally '97"): A first-person retro rally racer in C++ with terrain physics, procedural engine audio, working gauges, and rear-view mirrors [27:27].
• [28:36] Subway FPS Game ("Ashworth St"): Generated via Claude Code using "Ultracode" mode; generates an extensive architectural design spec (DESIGN.md) [29:48], followed by a complete Three.js zombie shooter featuring arriving subway trains [31:30], multiple weapons, bullet decals, dynamic lighting, and escalating waves [33:50].
• [34:57] Review of usage statistics and billing dashboard showing token consumption and credit costs.

Claims & numbers

• The presenter says Claude Fable 5.1 costs $10 per million input tokens and $50 per million output tokens, matching Fable 5.
• The presenter says typical workloads cost an estimated 25% less than Fable 5 due to improved prompt caching.
• The presenter states that on internal internal benchmarks presented by Anthropic, Fable 5.1 scores 55.9% on Agentic Coding (Terminal-Bench 4.0), 52.6% on Agentic scientific research, 77.9% on Computer use (OSWorld 2.0), and 41.7% on Multidisciplinary reasoning (Humanity's Last Exam).
• The presenter states Anthropic claims Fable 5.1 reduced false-positive refusal rates by 60% compared to previous safeguard implementations.
• The presenter shows that on DeepSWE v1.1, Fable 5.1 is reported to have scored an average of 67.4% over five trials.
• The presenter notes that his Claude Max subscription plan costs $200 per month (Max 20x tier).
• The presenter reports spending $156.59 in additional usage credits during this single evaluation session.
• The presenter notes that the C++ skateboarding game took approximately 1 hour and 10 minutes to write, compile, and headlessly verify during its initial run, followed by a sub-3-minute bugfix run.
• The presenter states the C++ rally game took 40–50 minutes to complete, and the Subway FPS project ran for over 3.5 hours in Claude Code Ultracode mode (including over 2 hours spent solely writing the design specification).

Notable quotes

• [01:04] "Fable 5.1 will cost an estimated 25% less than Fable 5 for typical workloads, wherever usage is billed by token."
• [29:36] "Don't use Ultracode. After two hours, it has not written a single piece of the game. It's still doing the design workflow."
• [32:07] "This is sick. Adding in the train thing where the train comes in for the next wave and then has them spawn in, that is a very..."

Assessment
This is an authentic third-party technical review and real-time capability demonstration by an independent software developer. The creator runs unedited live code outputs, compiles and plays generated games on camera, and provides transparent criticism regarding slow agentic workflows ("Ultracode"), minor graphical bugs, and high token costs.

Described by gemini-3.8-flash on 2026-09-29 from the video's audio and frames.