GPT-5.5 vs Grok 4.3
GPT-5.5 and Grok 4.3 are frontier reasoning models with 1M-class context windows, vision input, tool calling, and structured outputs. GPT-5.5 has the stronger sourced coding and research benchmark set; Grok 4.3 is the cheaper xAI route with $1.25/M input and $2.50/M output pricing.
Pick GPT-5.5 when benchmark-backed coding, terminal-agent, research, code-execution, or computer-use quality matters most. Pick Grok 4.3 when high-volume tool-calling or long-context workloads need much lower token cost, and verify Azure Foundry separately because that route is preview, custom-priced, and capped at 200K context.
Decision scorecard
Local evidence first| Signal | GPT-5.5 | Grok 4.3 |
|---|---|---|
| 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 | RAG, Agents, and Long context |
| Context window | 1.05m | 1m |
| Cheapest output | $30/1M tokens | $2.50/1M tokens |
| Provider routes | 3 tracked | 4 tracked |
| Shared benchmarks | Google-Proof Q&A leader | 1 rows |
Decision tradeoffs
- GPT-5.5 leads the largest shared benchmark signal on Google-Proof Q&A by 3.5 points.
- GPT-5.5 has the larger context window for long prompts, retrieval packs, or transcript analysis.
- GPT-5.5 uniquely exposes Code execution in local model data.
- Local decision data tags GPT-5.5 for Coding, RAG, and Agents.
- Grok 4.3 has the lower cheapest tracked output price at $2.50/1M tokens.
- Grok 4.3 has broader tracked provider coverage for fallback and procurement flexibility.
- Local decision data tags Grok 4.3 for RAG, Agents, and Long context.
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 4.3
$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 and Vercel AI Gateway; start route-level A/B tests there.
- Grok 4.3 is $27.50/1M tokens lower on cheapest tracked output pricing before cache, batch, or negotiated discounts.
- Check replacement coverage for Code execution before moving production traffic.
- Provider overlap exists on OpenRouter and Vercel AI Gateway; 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.
- GPT-5.5 adds Code execution in local capability data.
Specs
Pricing and availability
| Pricing attribute | GPT-5.5 | Grok 4.3 |
|---|---|---|
| Input price |
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| Output price |
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| Providers |
Capabilities
| Capability | GPT-5.5 | Grok 4.3 |
|---|---|---|
| Vision | Yes | Yes |
| Multimodal | Yes | Yes |
| Reasoning | Yes | Yes |
| Function calling | Yes | Yes |
| Tool use | Yes | Yes |
| Structured outputs | Yes | Yes |
| Code execution | Yes | No |
| IDE integration | No | No |
| Computer use | No | No |
| Parallel agents | No | No |
Benchmarks
| Benchmark | GPT-5.5 | Grok 4.3 |
|---|---|---|
| Google-Proof Q&A | 93.6 | 90.1 |
Deep dive
The benchmark split is asymmetric. GPT-5.5 has official rows for GPQA Diamond, SWE-Bench Pro, HumanEval, MMLU-Pro, IFEval, Terminal-Bench 2.0, and other launch metrics, while Grok 4.3 currently has a sparse official benchmark surface in the seed, centered on GPQA Diamond at 90.1. Treat the missing Grok coding rows as unavailable evidence, not as a zero score.
For coding and terminal agents, GPT-5.5 has the clearer sourced signal: SWE-Bench Verified and SWE-Bench Pro rows, HumanEval 94.2, and Terminal-Bench 2.0 at 82.7. Grok 4.3 may still be worth testing for tool loops because xAI documents function calling, structured outputs, configurable reasoning, and chain-of-thought summaries, but the page should not infer SWE-Bench or HumanEval performance without official rows.
Cost points toward Grok 4.3. The tracked xAI API row lists $1.25/M input, $2.50/M output, and $0.20/M cache-read tokens. GPT-5.5 standard OpenAI pricing is $5/M input and $30/M output, with batch/flex pricing at half rate and a long-context surcharge above 272K input tokens. For output-heavy agents, that gap can dominate the benchmark advantage.
Provider context changes the decision. Both models have OpenRouter and Vercel AI Gateway routes in the seed, and GPT-5.5 has a direct OpenAI API row. Grok 4.3 also has Microsoft Azure Foundry preview coverage, but that route is custom-priced, limited to 200K input tokens, and capped at 8,192 output tokens, so do not treat it as equivalent to the 1M-token xAI API route.
The practical selection rule is workload shape. Start with GPT-5.5 for quality-sensitive coding agents, research workflows, native code execution, computer use, and benchmark-backed stakeholder arguments. Start with Grok 4.3 for cost-constrained long-context analysis or tool-calling systems where you can run your own acceptance prompts and tolerate thinner public benchmark coverage.
FAQ
Is Grok 4.3 cheaper than GPT-5.5?
Yes. Grok 4.3 lists $1.25/M input and $2.50/M output on the xAI API, while GPT-5.5 standard pricing lists $5/M input and $30/M output. GPT-5.5 batch or flex pricing narrows the gap, but Grok 4.3 remains cheaper on the tracked standard token rows.
Which model has stronger coding evidence?
GPT-5.5 has the stronger sourced coding evidence because the seed includes SWE-Bench Verified, SWE-Bench Pro, HumanEval, and Terminal-Bench rows. Grok 4.3 is documented for tool calling and reasoning, but the current official-source datapack did not find comparable Grok 4.3 SWE-Bench or HumanEval rows.
Does GPT-5.5 have API access?
Yes. The corrected seed and provider rows treat GPT-5.5 as available through the OpenAI API, with tracked OpenAI, OpenRouter, and Vercel AI Gateway routes. The old model description that said API access was coming soon is stale.
Can I use Grok 4.3 on Azure Foundry?
Yes, but read it as a preview enterprise route rather than the same product surface as xAI's direct API. The tracked Azure Foundry row uses custom pricing, a 200K context limit, and an 8,192-token output cap for Grok 4.3.
Which model should I test first?
Test GPT-5.5 first for benchmark-sensitive coding, research, code execution, computer use, and terminal-agent quality. Test Grok 4.3 first when token cost is the gating constraint and the workload can be validated with your own prompts despite sparse public coding benchmarks.
Continue comparing
Last reviewed: 2026-06-03. Data sourced from public model cards and provider documentation.