GPT-6 Luna logo

GPT-6 Luna

LLM

GPT-6 Luna is the fast, high-volume tier of OpenAI's GPT-6 family, released 22 September 2026 alongside Sol and priced 50% below its GPT-5.6 predecessor. It is built for repeatable work at scale: classification, extraction, labelling and short replies, with reasoning that can be switched off entirely for the lowest latency. Free and Go users get it in the desktop app.

How to use GPT-6 Luna

Set model to gpt-6-luna and reasoning_effort to none for the fastest, cheapest turns, or low when a field must be inferred. Use strict tools or json_schema output so results are machine-safe. Drop temperature and top_p when reasoning is on. Batch independent records and run them in parallel.

Best for

High-volume classification, extraction, tagging, routing and short-form generation; first tier in a two-tier setup where hard cases hand off to Sol or Astra; free-tier users who want GPT-6 behaviour in the desktop app.

How it behaves

Optimised for speed and volume. Supports reasoning_effort none, where all judgment must live in the instructions and the output should be a strict function call or JSON schema. Function calling on Chat Completions works only at none; use the Responses API for reasoning with tools. Follows instructions tightly and inherits the GPT-6 bias toward action.

Tips

Write the label boundaries into the system prompt and force a strict function call so the code can trust the output. Ask for a short evidence quote alongside every label as an audit trail. Keep effort at none or low for copy-and-extract work and escalate the uncertain cases to Sol.

Pricing

Included for Free and Go users in the ChatGPT desktop app, and in paid plans. API prices are 50% below GPT-5.6 promotional pricing; see the OpenAI pricing page for current per-token rates.

Prompts for GPT-6 Luna

See all 7

Bias Toward Action Operator Preamble

Generate an action-oriented assistant prompt focused on task completion and minimal clarification requests, outputting a structured report of actions and assumptions.

3

Concrete Draft Before Clarifying Questions

Generate a complete working draft before asking clarifying questions, ensuring assumptions are clearly marked.

2

Batch Extraction Schema for Repeatable Work

Generate structured JSON output for data extraction from specified document types, ensuring accurate field replication.

2

High-Volume Classification Run With No Reasoning

Generate consistent, high-volume labels for records without reasoning, using structured function calls.

1

User Instruction Precedence Over Loaded Skills

Defines instruction precedence for a workspace assistant in interactions within a specified workspace.

1

Plain Paragraph Output Policy

Generate clear and concise response templates through structured writing rules, ensuring clarity in discussions.

0