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

Executive Summary

In a head-to-head "build-off" comparing Grok 4.5, GPT-5.5, Claude Opus 4.8, and Claude Fable 5, the results indicate a trade-off between reliability and efficiency. Claude models (Opus 4.8 and Fable 5) demonstrated the highest reliability for complex, stateful 3D tasks, while Grok 4.5 emerged as the leader in throughput, latency, and cost-effectiveness.

Coding Performance: Complex App Generation

To test the models, each was given three identical prompts to build self-contained HTML files without external libraries or network calls. Each model received one attempt, with a single retry allowed only if the app failed to render entirely.

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

Claude Opus 4.8 and Claude Fable 5 tied for the win, both producing correctly colored 3D cubes with animated rotations and solve functions on the first attempt. Grok 4.5 failed its first attempt (rendering a blank screen) but succeeded on the retry. GPT-5.5 failed the task, rendering only a single dark face instead of a full cube.

Particle Gravity Sandbox (Visuals and Physics)

All four models produced working sandboxes, with GPT-5.5 winning on aesthetic quality. GPT-5.5 created glowing neon attractors and dense colored trails, whereas Grok 4.5 focused on clean orbital rings and Fable 5 used soft glowing orbs. Claude Opus 4.8 provided strong physics but less visual polish.

Breakout Game (Standard Game Logic)

All four models achieved a "dead heat," producing ship-quality, playable brick-breaker games with scoring and lives on the first attempt. Grok 4.5 and GPT-5.5 leaned into a neon arcade aesthetic.

Operational Efficiency: Speed and Cost

Performance was measured using a harness of three fixed prompts across coding, reasoning, and summarization, capped at 400 output tokens.

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

Grok 4.5 is the most efficient model, delivering the fastest first-token response (0.44s) and roughly double the throughput of its competitors (~110 tok/s). It also provided the lowest cost per reply. Claude Fable 5 was the slowest and most expensive, representing the high-end cost of top-tier intelligence.

Spatial Imagination: SVG Generation

Models were asked to generate a single hand-authored SVG of a horse riding piggyback on an astronaut on the moon.

  • Claude Fable 5 won for creativity and humor, adding dialogue to the scene.
  • GPT-5.5 followed closely with a gleeful expression on the horse.
  • Grok 4.5 produced a clean, readable scene that followed the brief.
  • Claude Opus 4.8 succeeded visually but failed a strict SVG parser check due to a duplicate attribute in the raw code.

Final Verdict

  • Grok 4.5 is the optimal choice for high-volume code generation where latency and cost are primary constraints.
  • Claude Opus 4.8 and Fable 5 are the most reliable for complex, stateful architectural tasks.
  • GPT-5.5 provides a balance of speed for short answers and high-quality visual styling.

Sources

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