GPT-5.6, Grok 4.5, and Claude Fable 5 Coding Build-Off Analysis

Frontier Models Maintain Lead in Complex Coding Tasks

Frontier models continue to significantly outperform open-weights alternatives on complex, novel coding tasks, though the gap closes on common patterns. In a large-scale build-off involving 12 models—including the new GPT-5.6 tiers (Sol, Terra, Luna), Claude Fable 5, and Meta's Muse Spark 1.1—GPT-5.6 Sol and Claude Fable 5 emerged as the top performers for high-complexity applications.

Task-Specific Performance Breakdown

3D Raycaster Maze

GPT-5.6 Sol delivered the most consistent and detailed results.

For the Doom-style raycaster task, GPT-5.6 Sol and GPT-5.6 Luna both achieved a 5/5 success rate for playability. GPT-5.6 Sol was noted for having the best overall detail and consistency. Grok 4.5 proved to be a viable, cost-effective alternative with a 5/5 success rate, while Muse Spark 1.1 showed high potential but lacked consistency, succeeding in only 2/5 attempts.

3D Rubik's Cube

Claude Fable 5 dominated the Rubik's Cube task with a perfect success rate.

Claude Fable 5 achieved a 5/5 success rate for "clean solves" (smooth animations without glitches or color changes). In contrast, Claude Opus 4.8 failed to produce a single flawless solve (0/5). GPT-5.6 Sol and Terra performed well (4/5), though GPT-5.6 Luna failed entirely (0/5), often breaking immediately upon scrambling.

Functional Calculator

Claude models showed the highest reliability for standard utility builds.

Both Claude Opus 4.8 and Claude Fable 5 achieved a 5/5 success rate. While GPT-5.6 Sol also hit 5/5, it was criticized for over-styling (attempting 3D renders), which occasionally degraded the user experience compared to the cleaner, more consistent output of the simpler GPT models and Grok 4.5.

Conway's Game of Life

Open-weights models are competitive on well-trodden coding patterns.

Unlike the 3D tasks, the Game of Life was simple enough for open-weights models like Qwen 3.7 Plus and GLM-5.2 to perform exceptionally well at a fraction of the cost of frontier models. This suggests that for tasks with abundant training data and existing open-source examples, the cost-to-performance ratio shifts heavily in favor of OSS models.

Speed, Cost, and Efficiency

Performance varies significantly across the GPT-5.6 tiers and open-weights models:

Latency: GPT-5.6 Luna is the fastest on short prompts, with response times around 1.0s. Qwen 3.7 Plus is also noted for being "absurdly cheap and fast."
Throughput: Qwen 3.7 Plus leads in tokens per second (204 tok/s), while DeepSeek V4 Pro and GLM-5.2 are the slowest.
Cost: Open-weights models (Qwen, GLM, DeepSeek) consistently offer the lowest cost per request.

SVG Rendering and Composition

Claude Fable 5 outperformed all other models in one-shot SVG generation, specifically in tasks requiring composition and likeness (e.g., caricatures of tech billionaires). GPT-5.6 models were described as "lackluster" in this category, producing more cartoony and less detailed results.

Community Insights and Critiques

Discussion among technical users highlighted several key points regarding the methodology and results:

Knowledge vs. Reasoning: Some critics argue that visual benchmarks may measure a model's ability to retrieve training data (knowledge) rather than its ability to reason through geometry and animation in latent space.
Benchmaxxing: The failure of certain models (like GLM-5.2) on novel tasks despite high benchmark scores suggests a trend of "benchmaxxing," where models are optimized for specific test sets rather than general capability.
Real-world Application: Some users noted that one-shotting random apps does not mirror professional software engineering workflows, which typically involve iterative development.

"The frontier still wins the hard tasks, and it is not particularly close on the complex ones... On a simple, well-trodden task like Game of Life, the OSS models hold their own."

Summary Table: Model Standouts

Model	Primary Strength	Notable Weakness
GPT-5.6 Sol	Complex 3D/Raycasting	Over-styling on simple tasks
Claude Fable 5	3D Logic (Cube) & SVG Art	Higher cost/latency
Grok 4.5	Price-to-Performance Ratio	Not as detailed as Sol
Qwen 3.7 Plus	Speed and Cost	Struggles with novel/complex work