GPT-5.5 vs Grok 4
GPT-5.5 (2026) and Grok 4 (2025) are frontier-tier reasoning models from OpenAI and xAI. GPT-5.5 ships a 1.05m-token context window, while Grok 4 ships a 256k-token context window. On MMLU PRO, GPT-5.5 leads by 1.1 pts. On pricing, GPT-5.5 ranges from $5 to $8/1M input tokens by tier; Grok 4 costs $1.25/1M input tokens. 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 fits 4x more tokens; pick it for long-context work and Grok 4 for tighter calls.
Decision scorecard
Local evidence first| Signal | GPT-5.5 | Grok 4 |
|---|---|---|
| Best for | reasoning-heavy apps, multimodal apps, and tool-calling agents | reasoning-heavy apps, multimodal apps, and tool-calling agents |
| Decision fit | Coding, RAG, and Agents | Coding, RAG, and Agents |
| Context window | 1.05m | 256k |
| Cheapest output | $30/1M tokens | $2.50/1M tokens |
| Provider routes | 4 tracked | 4 tracked |
| Shared benchmarks | MMLU PRO leader | 7 shared |
Decision tradeoffs
- GPT-5.5 holds a shared-benchmark lead on MMLU PRO, ahead by 1.1 points.
- GPT-5.5 has the larger context window for long prompts, retrieval packs, or transcript analysis.
- Local decision data tags GPT-5.5 for Coding, RAG, and Agents.
- Grok 4 holds a shared-benchmark lead on AIME 2025, ahead by 10.5 points.
- Grok 4 has the lower cheapest tracked output price at $2.50/1M tokens.
- Local decision data tags Grok 4 for Coding, RAG, and Agents.
Monthly cost at traffic
Estimate token spend from the cheapest tracked input and output route or tier on this page.
GPT-5.5
$11,500
Cheapest tracked route/tier: OpenAI API 0-272K input tokens
Grok 4
$1,625
Cheapest tracked route/tier: xAI Console
Estimated monthly gap: $9,875. Batch, cache, alternate speed tiers, and negotiated pricing are excluded from this local estimate.
Switch friction
- Provider overlap exists on OpenRouter; start route-level A/B tests there.
- Grok 4 is $27.50/1M tokens lower on cheapest tracked output pricing before cache, batch, or negotiated discounts.
- Provider overlap exists on OpenRouter; start route-level A/B tests there.
- GPT-5.5 is $27.50/1M tokens higher on cheapest tracked output pricing, so quality gains need to justify the spend.
Specs
| Specification | ||
|---|---|---|
| Released | 2026-04-23 | 2025-07-09 |
| Context window | 1.05m | 256k |
| Parameters | — | — |
| Architecture | Decoder Only | 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 | - |
Pricing and availability
| Pricing attribute | GPT-5.5 | Grok 4 |
|---|---|---|
| Input price |
| $1.25/1M tokens |
| Output price |
| $2.50/1M tokens |
| Providers |
Capabilities
| Capability | GPT-5.5 | Grok 4 |
|---|---|---|
| Vision | Yes | Yes |
| Multimodal | Yes | Yes |
| Reasoning | Yes | Yes |
| JSON / Tool use | Yes | Yes |
| Structured outputs | Yes | Yes |
| Code execution | Yes | Yes |
| IDE integration | No | No |
| Computer use | No | No |
| Parallel agents | No | No |
Benchmarks
| Benchmark | GPT-5.5 | Grok 4 |
|---|---|---|
| MMLU PRO | 88.1 | 87.0 |
| SWE-bench Verified | 82.6 | 76.7 |
| Google-Proof Q&A | 93.6 | 87.5 |
| AIME 2025 | 81.2 | 91.7 |
| Humanity's Last Exam | 41.4 | 25.4 |
| ARC-AGI-2 | 85.0 | 15.9 |
| Aider Polyglot | 88.0 | 79.6 |
Continue comparing
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Last reviewed: 2026-07-10. Data sourced from public model cards and provider documentation.