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GPT-5.6 Luna

by OpenAI · Released 2026

GPT-5.6 model optimized for cost-sensitive, high-volume workloads. Multimodal (text + vision), 1.05M context, reasoning, and tool calling at the lowest GPT-5.6 price.

OpenAI — gpt-5.6-luna logo
LLM Chat

GPT-5.6 Luna

Powered by OpenAI · Transformer (proprietary)

Context Window

1.05M

Parameters

Undisclosed

Max Output

128K

Category

LLM Chat

Overview

GPT-5.6 Luna is the fast, affordable tier of OpenAI's GPT-5.6 family, designed for cost-sensitive and high-volume workloads. It keeps the full 1,050,000 token context window (128K max output) and native vision while pricing well below Sol and Terra — the go-to GPT-5.6 model for real-time chat, summarization, classification, and large-scale automation.

Luna supports reasoning, structured outputs, function calling, and prompt caching, and accepts both text and image input. It trades some peak capability on the hardest tasks for markedly lower cost and fast responses.

Priced at $1.00 per million input tokens and $6.00 per million output tokens through CallMissed (long-context tier over 272K tokens), Luna is the value leader of the GPT-5.6 lineup.

Pricing

MetricPrice
Input /1M tokens₹100.0000
Output /1M tokens₹600.0000

1 credit = ₹1 = $0.01 USD. Prices shown from provider; CallMissed passes through with ~35% markup.

Key Highlights

  • Lowest-cost GPT-5.6 tier
  • Optimized for high-volume, cost-sensitive workloads
  • Native vision + 1.05M token context window
  • Reasoning and full tool calling

Technical Details

  • Context window: 1,050,000 tokens (128K max output)
  • Multimodal: accepts text and image input
  • Reasoning-capable for planning and multi-step tasks
  • Supports structured outputs, function calling, and prompt caching
  • Available via OpenAI API and CallMissed unified gateway

Strengths

  • Lowest GPT-5.6 price with the full 1.05M context window
  • Fast inference for real-time and high-volume workloads
  • Native vision at a cost-sensitive tier
  • Multimodal — combines text and image input

Limitations

  • Lower peak capability than Sol and Terra on complex tasks
  • Proprietary and closed-source — no self-hosting option

Use Cases

High-volume chatSummarization and classificationLarge-scale automationVision and document understanding

API Example

curl https://api.callmissed.com/v1/chat/completions \
  -H "Authorization: Bearer cm_YOUR_KEY" \
  -d '{"model": "gpt-5.6-luna", "messages": [{"role": "user", "content": "Classify these support tickets by intent"}]}'

Endpoint: POST /v1/chat/completions · Model ID: gpt-5.6-luna

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