OpenAI: GPT-5.6 Luna vs SpaceXAI: Grok 4.5
Side-by-side comparison of specs, pricing, benchmark scores, and task rankings. Updated 2026-10-09.
| OpenAI: GPT-5.6 Luna | SpaceXAI: Grok 4.5 | |
|---|---|---|
| Vendor | openai | x-ai |
| Quality Score | 100 | 100 |
| Benchmark Score | 62.3 | 65.0 |
| Input Price | $0.20/M | $2.00/M |
| Output Price | $1.20/M | $6.00/M |
| Context Window | 1,050,000 | 500,000 |
| Max Output | 128,000 | 450,000 |
| Tool Calling | ✓ | ✓ |
| Structured Output | ✓ | ✓ |
| Reasoning Mode | ✓ | ✓ |
| Vision | ✓ | ✓ |
| Audio | - | - |
| Benchmark Scores | ||
| ai_index | 61.6 | 64.0 |
The verdict
For a sample job of 1 million input tokens and 250,000 output tokens, GPT-5.6 Luna costs $0.50 and Grok 4.5 costs $3.50, so GPT-5.6 Luna is about 7.0 times cheaper for the same work.
GPT-5.6 Luna reads up to 1,050,000 tokens at once, roughly 1,575 pages of text, against about 750 pages for Grok 4.5.
On our blended benchmark score Grok 4.5 leads 65.0 to 62.3.
Across the 20 tasks where they differ, GPT-5.6 Luna scores higher on 10 (SQL Generation, Code Completion, Code Documentation and others), Grok 4.5 on 10 (Code Review, Code Refactoring, Bug Fixing and others).
Pick GPT-5.6 Luna if you need lower cost or long documents; pick Grok 4.5 if you need benchmark performance.
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 | SpaceXAI: Grok 4.5 |
|---|---|---|
| SQL Generation | 141 | 140 |
| Code Review | 143 | 144 |
| Code Completion | 133 | 119 |
| Code Refactoring | 145 | 146 |
| Bug Fixing | 147 | 148 |
| Unit Test Generation | 131 | 131 |
| Code Documentation | 137 | 136 |
| Regex Writing | 125 | 124 |
| CI/CD Pipelines | 127 | 127 |
| Frontend Component Design | 129 | 129 |
| Data Analysis | 133 | 133 |
| CSV / Spreadsheet Cleanup | 136 | 135 |
| ETL Scripting | 136 | 137 |
| JSON Extraction | 131 | 122 |
| Bulk Data Labeling | 129 | 119 |
| OCR / Document Parsing | 134 | 134 |
| Table Extraction from PDFs | 134 | 134 |
| Long-Document Summarization | 147 | 147 |
| Short-Form Summarization | 126 | 117 |
| Blog Post Writing | 129 | 128 |
Scores reflect capability match + benchmark data + pricing for each task. Methodology →