GPT-5.6 Pricing 2026: Sol, Terra, and Luna Costs Explained

Introduction

OpenAI's GPT-5.6 family brings three distinct tiers—Sol, Terra, and Luna—each optimised for different use cases and budgets. As developers and businesses look to integrate large language models, understanding the cost per million tokens is critical. This article breaks down the official pricing for each tier, compares them with Gemini API pricing, and shows how OneMux provides an OpenAI-compatible API that simplifies access to all three models with pay-as-you-go rates.

GPT-5.6 Pricing Tiers: Sol, Terra, and Luna

According to the eesel.ai blog, OpenAI’s direct API pricing for GPT-5.6 models is as follows:

Luna is the most affordable option, especially for output-heavy applications like summarisation, classification, or customer support. Terra offers a middle ground, while Sol delivers the highest capability at a premium.

How OneMux Prices GPT-5.6 Models

OneMux offers all three GPT-5.6 models—Sol, Terra, and Luna—through a single, OpenAI-compatible API. Our pricing is designed to be competitive and transparent, with no hidden fees or minimum commitments.

Note: OneMux prices are subject to change. Check our pricing page for the latest rates.

With OneMux, you get a unified input cost across tiers, simplifying budget planning. The output cost for Luna via OneMux ($12.50) is higher than OpenAI’s direct $6.00, but you gain the benefits of model routing, spend visibility, and consolidated billing.

Gemini API Pricing Comparison

Google’s Gemini API offers its own set of models at competitive rates. While exact pricing varies by model (e.g., Gemini 1.5 Pro, Flash), they typically range from $0.50 to $5.00 per million input tokens and $1.50 to $15.00 for output. By using OneMux, you can access both OpenAI and Gemini models through the same OpenAI-compatible API, making it easier to compare and switch providers based on cost and performance.

Why Use OneMux’s OpenAI-Compatible API?

OneMux is not just another API proxy. It’s a platform built for developers who need flexible AI model access without vendor lock-in. Key benefits:

• Unified API: Use one SDK for OpenAI, Gemini, and other leading models.
• Model Routing: Automatically route requests to the best-performing or cheapest model.
• Spend Visibility: Track costs per model, user, or project.
• Credit Top-Ups: Pay as you go with no upfront commitments.

See our model catalogue for the full list of supported models, including GPT-5.6 variants.

Getting Started with OneMux

To start using GPT-5.6 Luna or other models via OneMux, follow these steps:

1. Sign up at OneMux.
2. Obtain your API key from the dashboard.
3. Use the OpenAI SDK with your OneMux base URL:

import openai

client = openai.OpenAI(
    api_key="your-onemux-api-key",
    base_url="https://api.onemux.net/v1"
)

response = client.chat.completions.create(
    model="gpt-5.6-luna",
    messages=[{"role": "user", "content": "Hello, world!"}]
)

Check our quickstart guide for more examples.

FAQ

What is the cheapest GPT-5.6 model?

Directly from OpenAI, Luna is the cheapest at $1/1M input and $6/1M output. Through OneMux, all three models are priced equally at $1.50/1M input and $12.50/1M output.

Can I use GPT-5.6 Luna via OneMux with my existing OpenAI code?

Yes. OneMux's API is fully compatible with the OpenAI SDK. Just change the base URL and API key.

Does OneMux offer Gemini models?

Yes. OneMux provides access to Gemini models alongside OpenAI models through the same unified API.

Are there any hidden fees?

No. OneMux pricing is transparent. You pay only for tokens consumed, with no monthly minimums or setup fees.

How do I compare costs between OpenAI directly and OneMux?

Use the tables above. For Luna, direct OpenAI is cheaper for output. However, OneMux adds value through routing, visibility, and multi-provider access.

Conclusion

GPT-5.6 Sol, Terra, and Luna offer a range of capabilities and price points. Whether you need the raw power of Sol or the cost-efficiency of Luna, OneMux makes it easy to access these models through a single, OpenAI-compatible API. With competitive pricing, model routing, and spend management, OneMux is the practical choice for developers who want flexibility without complexity.

Sources

• eesel.ai blog: GPT-5.6 official pricing details.