GPT-5.6 Luna vs GPT Realtime 2
GPT-5.6 Luna and GPT Realtime 2 are both current openai production-tier models. GPT-5.6 Luna is meaningfully cheaper at $1 / $6 per 1M. GPT-5.6 Luna has a 1.1M context window — about 8× the 128k of GPT Realtime 2. GPT-5.6 Luna leads on coding, reasoning, long-context retrieval.
Specs side by side
| Metric | OpenAI GPT-5.6 Luna | OpenAI GPT Realtime 2 |
|---|---|---|
| Input price (per 1M) | $1 | $4 |
| Output price (per 1M) | $6 | $24 |
| Context window | 1.1M tokens | 128k tokens |
| Speed tier | fast | ultra |
| Open weights | No | No |
| EU region | Yes | Yes |
| Free tier | No | No |
| Prompt caching | Yes | No |
| Vision input | Yes | No |
| Extended thinking | Yes | No |
When to choose each
Choose GPT-5.6 Luna if…
- Cost is a priority ($1 / $6 per 1M vs $4 / $24 per 1M)
- You need 1.1M context (8× more than GPT Realtime 2)
- HIPAA eligibility is required
- You need image input / vision
- Coding is central to your workload
- Reasoning is central to your workload
Choose GPT Realtime 2 if…
- You need realtime speech-to-speech
Benchmark delta
GPT-5.6 Luna leads on
- Coding
- Reasoning
- Long-context retrieval
GPT Realtime 2 leads on
GPT Realtime 2 has no meaningful benchmark lead in this pair.
FAQ — GPT-5.6 Luna vs GPT Realtime 2
GPT-5.6 Luna vs GPT Realtime 2 — which is better?
GPT-5.6 Luna and GPT Realtime 2 are both current openai production-tier models. GPT-5.6 Luna is meaningfully cheaper at $1 / $6 per 1M. GPT-5.6 Luna has a 1.1M context window — about 8× the 128k of GPT Realtime 2. GPT-5.6 Luna leads on coding, reasoning, long-context retrieval. 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 GPT Realtime 2?
GPT-5.6 Luna costs $1 / $6 per 1M vs GPT Realtime 2 at $4 / $24 per 1M. GPT-5.6 Luna is cheaper on output tokens by roughly 300%. Both support prompt caching, which reduces effective cost by 80-90% on repeat system prompts.
Does GPT-5.6 Luna or GPT Realtime 2 have the bigger context window?
GPT-5.6 Luna has a 1.1M-token context window — 8× the 128k context of GPT Realtime 2. Enough for entire codebases, books, or multi-document RAG.
Is there a free tier for GPT-5.6 Luna or GPT Realtime 2?
GPT-5.6 Luna: no — Low-cost at $1/$6 per 1M; starter credits only. GPT Realtime 2: no — Paid-only.
Which is better for coding — GPT-5.6 Luna or GPT Realtime 2?
GPT-5.6 Luna leads on coding benchmarks (GPT-5.6 Luna: 85/100, GPT Realtime 2: 78/100). For production coding agents also weigh tool-use performance — GPT-5.6 Luna scores 87, GPT Realtime 2 scores 84.