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, when 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, complex, complex, complex, complex, complex, complex, complex, complex, complex, complex, complex, complex, complex, complex, complex, complex, complex, complex, complex, complex, complex, complex, complex, complex, complex, complex, complex, complex, complex, complex, complex, complex, complex, complex, complex, complex, complex, complex, complex, complex, complex, complex, complex, complex, complex, complex, complex, complex, complex, complex, complex, complex, complex, complex, complex, complex, complex, complex, complex, complex, complex, complex, complex, complex, complex, complex, complex, complex, complex, complex, complex, complex, complex, complex, complex, complex, complex, complex, complex, complex, complex, complex, complex, complex, complex, complex, complex, complex, complex, complex, complex, complex, complex, complex, complex, complex, complex, complex, complex, complex, complex, complex, complex,x, complex, complex, complex, complex, complex, complex, complex, complex, complex, complex, complex, complex, complex, complex, complex, complex, complex, complex, complex, complex, complex, complex, complex, complex, complex, complex, complex, complex, complex, complex, complex, complex, complex, complex, complex, complex, complex, complex, complex, complex, complex, complex, complex, complex, complex, complex, complex, complex, complex, complex, complex, complex, complex, complex, complex, complex, complex, complex, complex, complex, complex, complex, complex, complex, complex, complex, complex, complex, complex, complex, complex, complex, complex, complex, complex, complex, complex, complex,

• GPT-5.5 excels in visual styling and responsiveness for short-form output.