GPT-5.5 Pro vs Grok 4 Heavy
GPT-5.5 Pro (2026) and Grok 4 Heavy (2025) are frontier reasoning models from OpenAI and xAI. GPT-5.5 Pro ships a 1.05m-token context window, while Grok 4 Heavy ships a 256k-token context window. On SWE-bench Pro, GPT-5.5 Pro leads by 18.8 pts. This comparison covers specs, pricing, API access, capabilities, benchmarks, input and output token costs, and production fit for coding and agent workloads.
GPT-5.5 Pro fits 4x more tokens; pick it for long-context work and Grok 4 Heavy for tighter calls.
Decision scorecard
Local evidence first| Signal | GPT-5.5 Pro | Grok 4 Heavy |
|---|---|---|
| Best for | reasoning-heavy apps, multimodal apps, and tool-calling agents | multimodal apps |
| Decision fit | Coding, RAG, and Agents | Coding, Long context, and Vision |
| Context window | 1.05m | 256k |
| Cheapest output | $180/1M tokens | - |
| Provider routes | 3 tracked | 0 tracked |
| Shared benchmarks | SWE-bench Pro leader | 1 shared |
Decision tradeoffs
- GPT-5.5 Pro holds a shared-benchmark lead on SWE-bench Pro, ahead by 18.8 points.
- GPT-5.5 Pro has the larger context window for long prompts, retrieval packs, or transcript analysis.
- GPT-5.5 Pro has broader tracked provider coverage for fallback and route flexibility.
- GPT-5.5 Pro uniquely exposes Reasoning, JSON / Tool use, and Structured outputs in local model data.
- Local decision data tags GPT-5.5 Pro for Coding, RAG, and Agents.
- Local decision data tags Grok 4 Heavy for Coding, Long context, and Vision.
Monthly cost at traffic
Estimate token spend from the cheapest tracked input and output route or tier on this page.
GPT-5.5 Pro
$69,000
Cheapest tracked route/tier: OpenAI API <=272K tokens (standard)
Grok 4 Heavy
Unavailable
No complete token price in local provider data
Cost delta unavailable until both models have sourced input and output token prices.
Switch friction
- No overlapping tracked provider route is sourced for GPT-5.5 Pro and Grok 4 Heavy; plan for SDK, billing, or endpoint changes.
- Check replacement coverage for Reasoning, JSON / Tool use, and Structured outputs before moving production traffic.
- No overlapping tracked provider route is sourced for Grok 4 Heavy and GPT-5.5 Pro; plan for SDK, billing, or endpoint changes.
- GPT-5.5 Pro adds Reasoning, JSON / Tool use, and Structured outputs in local capability data.
Specs
| Specification | ||
|---|---|---|
| Released | 2026-04-23 | 2025-07-09 |
| Context window | 1.05m | 256k |
| Parameters | — | — |
| Architecture | Decoder Only | - |
| License | Proprietary | Proprietary |
| Openness | Proprietary | Proprietary |
| Weights | Not released | Not released |
| Code | Unknown | Unknown |
| Commercial use | Commercial use: conditional | Commercial use: conditional |
| Knowledge cutoff | 2025-12 | 2024-11 |
Pricing and availability
| Pricing attribute | GPT-5.5 Pro | Grok 4 Heavy |
|---|---|---|
| Input price | $30/1M tokens | - |
| Output price | $180/1M tokens | - |
| Providers | - |
Capabilities
| Capability | GPT-5.5 Pro | Grok 4 Heavy |
|---|---|---|
| Vision | Yes | Yes |
| Multimodal | Yes | Yes |
| Reasoning | Yes | No |
| JSON / Tool use | Yes | No |
| Structured outputs | Yes | No |
| Code execution | Yes | No |
| IDE integration | No | No |
| Computer use | No | No |
| Parallel agents | No | No |
Benchmarks
| Benchmark | GPT-5.5 Pro | Grok 4 Heavy |
|---|---|---|
| SWE-bench Pro | 58.6 | 39.8 |
Continue comparing
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Last reviewed: 2026-07-09. Data sourced from public model cards and provider documentation.