LLM Comparison
GPT-6 Luna vs Leanstral 1.5
Side-by-side specs, pricing & capabilities · Updated September 2026
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2/6 models| Organization | ||
| OpenTools Score | ||
| Family | GPT-6 | Leanstral |
| Status | Current | Current |
| Release Date | Sep 2026 | Jun 2026 |
| Context Window | 1.1M tokens | 256K tokens |
| Input Price | $0.10/M tokens | Free |
| Output Price | $0.50/M tokens | Free |
| Pricing Notes | OpenAI standard API, USD per million tokens for prompts up to 272K input tokens: $0.10 input, $0.01 cached input, $0.125 cache writes, $0.50 output. Above 272K input tokens, the full request costs 2x input/cache and 1.5x output. Batch/Flex cost 50% of Standard; Fast costs 2x; regional processing adds 10% where available. Reasoning output tokens are charged at output rates. | Mistral model card lists Leanstral 1.5 price as $0. Changelog says the Labs endpoint is scheduled to retire on 2026-09-30. |
| Capabilities | textvisionreasoningcodingtool-uselong-contextcontext-caching | textreasoningcodingformal-verificationtool-usestructured-output |
| Training Cutoff | 2026-05-18 | — |
| Max Output | 128K tokens | 128K tokens |
| API Identifier | gpt-6-luna | labs-leanstral-1-5 |
| Benchmarks | ||
| Artificial Analysis Intelligence Index v4.3.2 | 37.2559686869738artificial-analysis | — |
| miniF2F | — | 100mistral |
| PutnamBench | — | 587mistral |
| FLTEval pass@8 | — | 43.2mistral |
| View GPT-6 Luna | View Leanstral 1.5 | |
Cost Calculator
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| Model | Input | Output | Total / mo | vs Best |
|---|---|---|---|---|
| Leanstral 1.5Cheapest | $0.00 | $0.00 | $0.00 | — |
| GPT-6 Luna | $0.10 | $0.25 | $0.35 | +0% |
OpenAI
GPT-6 Luna
GPT-6 Luna is OpenAI's efficient reasoning model for focused, high-volume tasks. It accepts text and images, produces text, supports a 1,050,000-token context window and 128,000 output tokens, and is available through the Responses and Chat Completions APIs under the exact gpt-6-luna identifier.
Mistral AI
Leanstral 1.5
Leanstral 1.5 is Mistral AI free Lean 4 formal proof-engineering model for automated theorem proving, autoformalization, and real-world code verification. Official Mistral docs list it as a Labs model with 119B total parameters, 6.5B active parameters, a 256k context window, 128k max output, $0 pricing, and the labs-leanstral-1-5 API identifier.
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