OpenAI-compatible chat completions, nano tier: gpt-6-luna (the default), gpt-5.6-luna, gpt-5-nano, gemini flash-lite, small llama/ministral/qwen, deepseek-chat - $0.003 per call in USDC over x402, priced for high-frequency agent loops. Same wire format as /v1/chat/completions with loop-sized caps (12k chars in, 768 tokens out). Streaming supported (stream: true). No API key, no signup.