Grok 4.5, GPT-5.5, and Claude Coding Build-Off Comparison

A comprehensive build-off between Grok 4.5, GPT-5.5, Claude Opus 4.8, and Claude Fable 5 reveals that while Claude models lead in reliability for complex stateful tasks, Grok 4.5 dominates in throughput and cost-efficiency.

Coding Performance: Complex App Generation

Models were tested using three identical prompts requiring a single self-contained HTML file with no external libraries or network calls. Each model received one attempt, with a single retry permitted only if the app failed to render entirely.

3D Rubik's Cube (Complex State and Math)

Claude Opus 4.8 and Claude Fable 5 were the most reliable, both producing correctly colored 3D cubes with animated rotations and solve functionality on the first attempt. Grok 4.5 failed its first attempt (rendering a blank screen) but succeeded on its one allowed retry. GPT-5.5 performed the worst, rendering only a single dark face with minimal color.

Particle Gravity Sandbox (Visuals and Physics)

All four models successfully shipped a working sandbox. GPT-5.5 won on aesthetic quality, producing glowing neon attractors and dense, swirling colored trails. Grok 4.5 produced a clean orbital simulation with attractor rings, while Claude Fable 5 used soft glowing orbs and Claude Opus 4.8 created a dense, web-like particle field.

Breakout Game (General Game Logic)

All four models achieved a "dead heat," producing polished, playable brick-breaker games with scoring and lives on the first attempt. Grok 4.5 and GPT-5.5 were noted for having the strongest neon arcade aesthetics.

Performance Metrics: Speed and Cost

Testing conducted via a uniform provider path across three fixed prompts (coding, reasoning, and summarization) showed Grok 4.5 as the most efficient model for high-volume workloads.

Model	Median Latency	First Token	Throughput	Cost / Reply	Success Rate
Grok 4.5	2.8s	0.44s	110 tok/s	0.002¢	100%
GPT-5.5	2.0s	1.26s	53 tok/s	0.004¢	100%
Claude Opus 4.8	2.6s	1.16s	47 tok/s	0.004¢	100%
Claude Fable 5	6.3s	3.47s	0.47 tok/s	0.009¢	100%

Key Takeaways on Efficiency:

• Grok 4.5 achieved the fastest first-token response (under 0.5s) and the highest throughput (~110 tokens/second), making it roughly twice as fast as its competitors. It was also the cheapest model to run.
• GPT-5.5 was the fastest for short answers.
• Claude Fable 5 was the slowest and most expensive, reflecting its position as a high-intelligence tier model.

Spatial Imagination: SVG Generation

Models were tasked with creating a hand-authored SVG of a horse riding piggyback on an astronaut on the moon.

Claude Fable 5 produced the most creative and humorous result, adding dialogue to the scene. GPT-5.5 followed closely with a gleeful horse. Grok 4.5 produced a clean, readable scene. Claude Opus 4.8 succeeded visually but failed a technical correctness check, shipping a duplicate attribute that tripped strict SVG parsers.

Final Verdict

• Grok 4.5 is the optimal choice for high-volume code generation where latency and cost are primary constraints, offering the best "intelligence per unit of time and cost."
• Claude Opus 4.8 and Fable 5 are the most reliable for complex, stateful building tasks, though they come with higher latency and price points.
• GPT-5.5 excels in visual styling and responsiveness for short-form output.