GPT-5.5-Pro vs Grok 4 Heavy
OpenAI GPT-5.5-Pro | SpaceXAI Grok 4 Heavy | |
|---|---|---|
| Overview | ||
| Company | OpenAI | SpaceXAI |
| Release date | Apr 23 2026 | Jul 9 2025 |
| Access | Proprietary | Proprietary |
| Benchmarks | ||
Nonsense detection BullshitBench v2Given a confidently-worded but nonsensical prompt, does the AI spot that it makes no sense and push back — instead of playing along and inventing an answer? The score is how often it clearly called out the nonsense. Higher is better. | 36% | — |
Next.js coding Next.js EvalsVercel's open eval of how well AI coding agents build and migrate real Next.js apps — measured as the share of tasks the agent completes successfully. Higher is better. | 83% | — |
Web browsing BrowseCompCan the AI browse the web and track down hard-to-find answers? Higher is better. | 90.1% | — |
Multidisciplinary reasoning Humanity's Last Exam · with toolsHumanity's Last Exam — extremely hard expert questions across many subjects. “With tools” means the AI is allowed to search the web or run code while answering. Higher is better. | 57.2% | — |
Advanced math FrontierMath · Tier 1–3Very hard, research-level math problems. Tiers 1–3 are the (still extremely difficult) lower tiers. Higher is better. | 52.4% | — |
Advanced math FrontierMath · Tier 4Very hard, research-level math problems. Tier 4 is the hardest — close to what professional research mathematicians tackle. Higher is better. | 39.6% | — |
Knowledge work GDPval (win/tie rate)How often the AI's work matches or beats a human expert's on real knowledge-work tasks. Higher is better. | 82.3% | — |
| Timeline | ||
| Release gap | Grok 4 Heavy shipped 288 days before GPT-5.5-Pro | |
Which is better: GPT-5.5-Pro or Grok 4 Heavy?
GPT-5.5-Pro and Grok 4 Heavy don't publish scores on any of the same benchmarks, so there's no direct head-to-head comparison. Grok 4 Heavy shipped 288 days before GPT-5.5-Pro, so benchmark comparisons should account for the intervening progress.
Published specifications for these two models are limited — see each model page for the latest details.
Direct benchmark comparisons are unavailable — GPT-5.5-Pro and Grok 4 Heavy don't publish scores on any of the same benchmarks.
Frequently asked questions
GPT-5.5-Pro was released by OpenAI on Apr 23 2026.
Grok 4 Heavy was released by SpaceXAI on Jul 9 2025.
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