OpenAI: GPT-5.6 Luna Pro

openai/gpt-5.6-luna-pro

GPT-5.6 Luna Pro is the same underlying model as [GPT-5.6 Luna](https://openrouter.ai/openai/gpt-5.6-luna), served with `reasoning.mode` set to `pro` for higher-quality responses on complex tasks. **Cost note:** pro mode spends far more...

Modalities

In / out price

$0.2 / $1.2 per 1M

Context

1.05M

Released

Jul 9, 2026

Why use GPT-5.6 Luna Pro

Understands images
Reads PDFs and other files
Step-by-step reasoning mode
Tool and function calling (agent-ready)
Structured (JSON) outputs
Very long context: whole books or codebases in one prompt

Pricing

Input	$0.2 / 1M tokens
Output	$1.2 / 1M tokens
Cached input (read)	$0.020 / 1M tokens
Cache write	$0.25 / 1M tokens

List prices via OpenRouter, checked daily. Real cost depends on the provider and on reasoning tokens.

Cost calculator

Pick a task, set how often you run it, and compare what it costs on each model.

TaskInput tokens≈ 602 wordsOutput tokens≈ 1,504 wordsRuns per month

Input served from cache: 0%Repeated prompts (same instructions or document) are billed at the cheaper cache-read price where the model supports it.

Model	Per run	Per month	Per 1,000 runs
OpenAI: GPT-5.6 Luna Pro	$0.0026	$2.56	$2.56

Estimates from list prices via OpenRouter; real bills vary by provider and reasoning tokens.

Will it fit? Context window simulator

Each square is about one page (500 words). Colored squares are your content; grey squares are free space in the model's context window.

Your content

Novel (90,000 words)

Total: about 120,000 tokens (≈ 90,226 words). Token counts are estimates.

Models

Zoom (square size): 6pxZoom out to see a whole million-token window at once.