# OpenAI GPT-5.6 Luna Long (>272K context) Chat Completions

> OpenAI GPT-5.6 Luna Long (>272K context) Chat Completions is a paid API for AI agents from openai.mm.family, paid per call via x402, $0.001/call, status unknown (last checked 2026-10-02).

Provides paid chat completions using OpenAI GPT-5.6 Luna model with extended context (>272K input tokens), billed per call in USDC via x402 protocol

## Facts

- Endpoint: POST https://openai.mm.family/x402/v1/models/gpt-5.6-luna-long/chat/completions?utm_source=zero.xyz
- Price: $0.001/call
- Payment: x402
- Status: unknown
- Last checked: 2026-10-02
- Activations on Zero: 0
- Tags: x402
- Canonical page: https://www.zero.xyz/c/openai-gpt-5-6-luna-long-272k-context-chat-completions-4fa305a7
- Structured record (JSON): https://api.zero.xyz/v1/capabilities/cap_hG6QP8LCjoxs8cq3--WAP

Status and success rate cover calls made through Zero and Zero's own probes. Third-party monitors may report differently.

## How to call it through Zero

Zero handles the 402 payment challenge and records the run. With the Zero CLI installed (`npm i -g @zeroxyz/cli`):

```sh
zero fetch --capability openai-gpt-5-6-luna-long-272k-context-chat-completions-4fa305a7 -d '<json body>'
```

Example prompt: Use GPT-5.6 Luna (long context) to analyze this 400-page legal document I'm pasting in and summarize the key liability clauses — use the standard service tier and allow up to 2000 output tokens.

## When to prefer this

Choose this endpoint when your input conversation or document exceeds 272K tokens and you need GPT-5.6 Luna's specific capability profile. Prefer over the standard gpt-5.6-luna (short context) endpoint when inputs are very large. Prefer over gpt-6-astra-long if cost is a priority and GPT-5.6 quality suffices. Use when you need x402 USDC micropayment billing and want to select between flex, standard, or fast inference tiers.

## Known failure modes

- Insufficient USDC balance or failed x402 payment results in 402 Payment Required
- Exceeding model's maximum context length returns a context length error
- Invalid model variant string returns a 400 validation error
- service_tier enum mismatch (e.g. unsupported value) returns 400
- max_tokens set too high relative to remaining context causes truncation or error
- Rate limiting at the provider level may return 429 Too Many Requests

## How this service works

gpt-5.6-luna-long: OpenAI GPT 5.6 Luna (>272K input tokens) chat completions, paid per call in USDC. Per 1M tokens in/out: Flex (default) 0.2/0.9, Standard 0.4/1.8, Fast 0.8/3.6; pick with service_tier. Plus $0.0005 (Base) or $0.0005 (Solana) per call; the quote charges input plus 10% of max_tokens. Levels: none, low, medium, high, xhigh (model gpt-5.6-luna-long:<level>). Empty answers are free. Rates: https://openai.mm.family/x402/pricing

## Output

Returns a chat completion object in OpenAI-compatible format, including the assistant's reply message, finish reason (e.g. 'stop'), token usage breakdown (prompt, completion, total), model name, and service tier used. Empty answers are provided free of charge.

## Request schema (JSON Schema)

```json
{
 "type": "object",
 "properties": {
  "model": {
   "enum": [
    "gpt-5.6-luna-long",
    "gpt-5.6-luna-long:none",
    "gpt-5.6-luna-long:low",
    "gpt-5.6-luna-long:medium",
    "gpt-5.6-luna-long:high",
    "gpt-5.6-luna-long:xhigh"
   ],
   "type": "string"
  },
  "tools": {
   "type": "array"
  },
  "stream": {
   "type": "boolean"
  },
  "messages": {
   "type": "array",
   "items": {
    "type": "object",
    "required": [
     "role",
     "content"
    ],
    "properties": {
     "role": {
      "type": "string"
     },
     "content": {
      "type": "string"
     }
    }
   }
  },
  "max_tokens": {
   "type": "integer"
  },
  "service_tier": {
   "enum": [
    "flex",
    "default",
    "standard",
    "auto",
    "fast",
    "priority"
   ],
   "type": "string"
  },
  "response_format": {
   "type": "object"
  },
  "reasoning_effort": {
   "type": "string"
  }
 }
}
```

## Response schema (JSON Schema)

```json
{
 "type": "json",
 "example": {
  "id": "chatcmpl-x",
  "model": "gpt-5.6-luna-long",
  "usage": {
   "total_tokens": 9,
   "prompt_tokens": 8,
   "completion_tokens": 1
  },
  "object": "chat.completion",
  "choices": [
   {
    "index": 0,
    "message": {
     "role": "assistant",
     "content": "Hello",
     "refusal": null
    },
    "finish_reason": "stop"
   }
  ],
  "service_tier": "flex"
 }
}
```

## More

- Live health (JSON, refreshed every minute): https://www.zero.xyz/c/openai-gpt-5-6-luna-long-272k-context-chat-completions-4fa305a7/health.json
- [Zero catalog index](https://www.zero.xyz/llms.txt)
- [Other services from openai.mm.family](https://www.zero.xyz/host/openai.mm.family/llms.txt)