OpenAI: GPT-5.6 Luna Pro vs Google: Gemma 4 31B
Side-by-side comparison of specs, pricing, benchmark scores, and task rankings. Updated 2026-11-07.
| OpenAI: GPT-5.6 Luna Pro | Google: Gemma 4 31B | |
|---|---|---|
| Vendor | openai | |
| Quality Score | 100 | 100 |
| Benchmark Score | - | 53.7 |
| Input Price | $0.20/M | $0.20/M |
| Output Price | $1.20/M | $0.40/M |
| Context Window | 1,050,000 | 262,144 |
| Max Output | 128,000 | 16,384 |
| Tool Calling | ✓ | ✓ |
| Structured Output | ✓ | ✓ |
| Reasoning Mode | ✓ | ✓ |
| Vision | ✓ | ✓ |
| Audio | - | - |
| Benchmark Scores | ||
| ai_index | - | 48.4 |
| ai_index_agentic | - | 23.8 |
| ai_index_coding | - | 71.7 |
| eqbench | - | 57.5 |
The verdict
For a sample job of 1 million input tokens and 250,000 output tokens, Gemma 4 31B costs $0.30 and GPT-5.6 Luna Pro costs $0.50, so Gemma 4 31B is about 1.7 times cheaper for the same work.
GPT-5.6 Luna Pro reads up to 1,050,000 tokens at once, roughly 1,575 pages of text, against about 393 pages for Gemma 4 31B.
Only Gemma 4 31B offers video input.
Across the 20 tasks where they differ, Gemma 4 31B on 20 (SQL Generation, Code Review, Code Completion and others).
GPT-5.6 Luna Pro was released in July 2026 and Gemma 4 31B in April 2026.
Pick GPT-5.6 Luna Pro if you need long documents; pick Gemma 4 31B if you need lower cost, video input or the stronger all-round task scores.
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 | OpenAI: GPT-5.6 Luna Pro | Google: Gemma 4 31B |
|---|---|---|
| SQL Generation | 133 | 156 |
| Code Review | 132 | 152 |
| Code Completion | 131 | 131 |
| Code Refactoring | 136 | 151 |
| Bug Fixing | 136 | 160 |
| Unit Test Generation | 124 | 143 |
| Code Documentation | 131 | 137 |
| Regex Writing | 119 | 131 |
| CI/CD Pipelines | 120 | 135 |
| Frontend Component Design | 122 | 138 |
| Data Analysis | 124 | 152 |
| CSV / Spreadsheet Cleanup | 133 | 145 |
| ETL Scripting | 128 | 143 |
| JSON Extraction | 131 | 143 |
| Bulk Data Labeling | 129 | 133 |
| OCR / Document Parsing | 131 | 140 |
| Table Extraction from PDFs | 131 | 140 |
| Long-Document Summarization | 137 | 149 |
| Short-Form Summarization | 123 | 129 |
| Blog Post Writing | 121 | 133 |
Scores reflect capability match + benchmark data + pricing for each task. Methodology →