GPT-5.6 Luna
Overview
GPT-5.6 Luna is OpenAI's cost-oriented GPT-5.6 tier, made generally available on July 9, 2026. In the API, its model ID is gpt-5.6-luna, and OpenAI positions it for efficient, high-volume workloads.
Key Features
- Cost-Oriented GPT-5.6 Tier: Designed for high-volume workloads where lower token cost and responsiveness are important.
- Expanded Reasoning Controls: Supports
none,low,medium,high,xhigh, andmaxreasoning effort; GPT-5.6 also supports Pro mode throughreasoning.mode: "pro". - Agentic Tooling: Supports Responses API workflows, functions, web search, file search, computer use, Programmatic Tool Calling, persisted reasoning, and multi-agent beta.
- Large Working Context: Supports a 1.05M-token context window and up to 128K output tokens, with a February 16, 2026 knowledge cutoff.
Best Use Cases
- High-Volume Assistance: Summarization, rewriting, classification, extraction, routing, and lightweight analysis.
- Responsive Product Features: User-facing assistants, workflow copilots, and routine automation with predictable cost constraints.
- First-Pass Technical Work: Initial issue triage, draft code review, test-case generation, and document analysis before escalating difficult cases to Terra or Sol.
Capabilities and Limitations
| Capability | Description |
|---|---|
| Reasoning | Supports none, low, medium, high, xhigh, and max; API Pro mode is enabled with reasoning.mode: "pro" rather than a separate Pro model slug. |
| Coding | Official benchmark examples include SWE-Bench Pro 62.7%, DeepSWE v1.1 67.2%, and Terminal-Bench 2.1 84.7%. |
| Creative Writing | General text generation is supported. |
| Multimodal | Text and image input with text output; GPT-5.6 preserves original image dimensions for original or auto detail. |
| Response Speed | Public API latency depends on reasoning effort, tools, and processing tier; Luna is positioned for efficient, high-volume use. |
| Context Window | 1.05M tokens. |
| Max Output | 128K tokens. |
| Tool Use | Functions, web search, file search, computer use, Programmatic Tool Calling, persisted reasoning, and multi-agent beta. |
| Multilingual | OpenAI API model documentation lists multilingual support across current models. |
Known Limitations
- Luna is positioned below Terra and Sol for capability, so complex reasoning, sensitive technical work, and quality-first workflows may need escalation.
- Higher reasoning efforts, Pro mode, multi-agent runs, and long-context use can increase latency and cost.
- Cyber and biology safeguards may refuse, block, or pause sensitive requests, including some legitimate dual-use work.
- Prompt cache writes are billed on GPT-5.6 models, so cache breakpoints should be monitored with
cache_write_tokensandcached_tokens.
Credits Usage
| Context | Input (Credits/Token) | Cache Write (Credits/Token) | Cache Read (Credits/Token) | Output (Credits/Token) | Web Search (Credits/Use) | Billing Notes |
|---|---|---|---|---|---|---|
| Short context | 1.00 | 1.25 | 0.10 | 6.00 | 10,000 | Standard GPT-5.6 Luna pricing |
| Long context (>272K input tokens) | 2.00 | 2.50 | 0.20 | 9.00 | 10,000 | Long-context pricing tier |
Pricing note
Prices shown in the documentation are B.AI standard reference prices for base billing purposes. B.AI may provide lower actual usage costs through top-up bonuses and account benefits. Specific prices, bonus Credits, and account benefits are subject to the platform display and final billing records.
- For GPT-5.6 models, cache writes are billed at 1.25x the uncached input rate; cache reads remain discounted at 0.1x input.