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.
Standard Pricing
The token prices below are shown in USD per 1 million tokens; web search is billed in USD per use.
| Context | Input (USD / 1M Tokens) | Cache Write (USD / 1M Tokens) | Cache Read (USD / 1M Tokens) | Output (USD / 1M Tokens) | Web Search (USD / use) | Billing Notes |
|---|---|---|---|---|---|---|
| Short context | $0.20 | $0.25 | $0.02 | $1.20 | $0.01 | Standard GPT-5.6 Luna pricing |
Credits settlement: B.AI converts charges at 1 USD = 1,000,000 Credits and deducts Credits from the account balance.
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.