GPT-5.6 Luna vs Grok 4.5
GPT-5.6 Luna and Grok 4.5 are both current production-tier models. GPT-5.6 Luna has a 1.1M context window — about 2× the 500k of Grok 4.5. Grok 4.5 leads on coding, reasoning, general knowledge.
Specs side by side
| Metric | OpenAI GPT-5.6 Luna | xAI Grok 4.5 |
|---|---|---|
| Input price (per 1M) | $1 | $2 |
| Output price (per 1M) | $6 | $6 |
| Context window | 1.1M tokens | 500k tokens |
| Speed tier | fast | balanced |
| Open weights | No | No |
| EU region | Yes | No |
| Free tier | No | No |
| Prompt caching | Yes | Yes |
| Vision input | Yes | Yes |
| Extended thinking | Yes | Yes |
When to choose each
Choose GPT-5.6 Luna if…
- You need 1.1M context (2× more than Grok 4.5)
- EU data residency is required
- HIPAA eligibility is required
Choose Grok 4.5 if…
- Coding is central to your workload
- Reasoning is central to your workload
Benchmark delta
GPT-5.6 Luna leads on
GPT-5.6 Luna has no meaningful benchmark lead in this pair.
Grok 4.5 leads on
- Coding
- Reasoning
- General knowledge
- Tool use
FAQ — GPT-5.6 Luna vs Grok 4.5
GPT-5.6 Luna vs Grok 4.5 — which is better?
GPT-5.6 Luna and Grok 4.5 are both current production-tier models. GPT-5.6 Luna has a 1.1M context window — about 2× the 500k of Grok 4.5. Grok 4.5 leads on coding, reasoning, general knowledge. The right pick depends on your use case — see "When to choose each" above for a data-driven decision.
How does GPT-5.6 Luna pricing compare to Grok 4.5?
GPT-5.6 Luna costs $1 / $6 per 1M vs Grok 4.5 at $2 / $6 per 1M. Grok 4.5 is cheaper on input tokens by roughly 0%. Both support prompt caching, which reduces effective cost by 80-90% on repeat system prompts.
Does GPT-5.6 Luna or Grok 4.5 have the bigger context window?
GPT-5.6 Luna has a 1.1M-token context window — 2× the 500k context of Grok 4.5. Enough for entire codebases, books, or multi-document RAG.
Is there a free tier for GPT-5.6 Luna or Grok 4.5?
GPT-5.6 Luna: no — Low-cost at $1/$6 per 1M; starter credits only. Grok 4.5: no — X Premium / SuperGrok includes Grok web chat; API is paid.
Which is better for coding — GPT-5.6 Luna or Grok 4.5?
Grok 4.5 leads on coding benchmarks (GPT-5.6 Luna: 85/100, Grok 4.5: 94/100). For production coding agents also weigh tool-use performance — GPT-5.6 Luna scores 87, Grok 4.5 scores 92.