Google: Gemini 3.8 Flash vs OpenAI: GPT-5.6 Luna
Side-by-side comparison of specs, pricing, benchmark scores, and task rankings. Updated 2026-10-19.
| Google: Gemini 3.8 Flash | OpenAI: GPT-5.6 Luna | |
|---|---|---|
| Vendor | openai | |
| Quality Score | 100 | 100 |
| Benchmark Score | 67.8 | - |
| Input Price | $0.82/M | $0.20/M |
| Output Price | $4.12/M | $1.20/M |
| Context Window | 1,048,576 | 1,050,000 |
| Max Output | 65,536 | 128,000 |
| Tool Calling | ✓ | ✓ |
| Structured Output | ✓ | ✓ |
| Reasoning Mode | ✓ | ✓ |
| Vision | ✓ | ✓ |
| Audio | ✓ | - |
| Benchmark Scores | ||
| ai_index | 67.5 | - |
The verdict
For a sample job of 1 million input tokens and 250,000 output tokens, GPT-5.6 Luna costs $0.50 and Gemini 3.8 Flash costs $1.86, so GPT-5.6 Luna is about 3.7 times cheaper for the same work.
Both take in a similar amount of text: 1,048,576 and 1,050,000 tokens, about 1,573 and 1,575 pages.
Only Gemini 3.8 Flash offers audio input and video input.
Across the 20 tasks where they differ, Gemini 3.8 Flash scores higher on 18 (SQL Generation, Code Review, Code Completion and others), GPT-5.6 Luna on 2 (JSON Extraction, Bulk Data Labeling).
Gemini 3.8 Flash was released in September 2026 and GPT-5.6 Luna in July 2026.
Pick Gemini 3.8 Flash if you need audio input, video input or the stronger all-round task scores; pick GPT-5.6 Luna if you need lower cost.
Costs use current list prices per million tokens; page counts assume about 0.75 words per token and 500 words per page.
Who wins by task?
| Task | Google: Gemini 3.8 Flash | OpenAI: GPT-5.6 Luna |
|---|---|---|
| SQL Generation | 141 | 133 |
| Code Review | 144 | 132 |
| Code Completion | 132 | 131 |
| Code Refactoring | 146 | 136 |
| Bug Fixing | 148 | 136 |
| Unit Test Generation | 132 | 124 |
| Code Documentation | 137 | 131 |
| Regex Writing | 125 | 119 |
| CI/CD Pipelines | 128 | 120 |
| Frontend Component Design | 130 | 122 |
| Data Analysis | 134 | 124 |
| CSV / Spreadsheet Cleanup | 136 | 133 |
| ETL Scripting | 137 | 128 |
| JSON Extraction | 131 | 131 |
| Bulk Data Labeling | 128 | 129 |
| OCR / Document Parsing | 134 | 131 |
| Table Extraction from PDFs | 134 | 131 |
| Long-Document Summarization | 148 | 137 |
| Short-Form Summarization | 126 | 123 |
| Blog Post Writing | 129 | 121 |
Scores reflect capability match + benchmark data + pricing for each task. Methodology →