Z.ai: GLM 5.3 Flash vs OpenAI: GPT-5.6 Luna
Side-by-side comparison of specs, pricing, benchmark scores, and task rankings. Updated 2026-10-11.
| Z.ai: GLM 5.3 Flash | OpenAI: GPT-5.6 Luna | |
|---|---|---|
| Vendor | z-ai | openai |
| Quality Score | 100 | 100 |
| Benchmark Score | 70.6 | 62.3 |
| Input Price | $0.15/M | $0.20/M |
| Output Price | $0.50/M | $1.20/M |
| Context Window | 1,048,576 | 1,050,000 |
| Max Output | 943,717 | 128,000 |
| Tool Calling | ✓ | ✓ |
| Structured Output | ✓ | ✓ |
| Reasoning Mode | ✓ | ✓ |
| Vision | ✓ | ✓ |
| Audio | - | - |
| Benchmark Scores | ||
| ai_index | 69.0 | 61.6 |
The verdict
For a sample job of 1 million input tokens and 250,000 output tokens, GLM 5.3 Flash costs $0.28 and GPT-5.6 Luna costs $0.50, so GLM 5.3 Flash is about 1.8 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 GLM 5.3 Flash offers video input.
On our blended benchmark score GLM 5.3 Flash leads 70.6 to 62.3.
Across the 20 tasks where they differ, GLM 5.3 Flash scores higher on 20 (SQL Generation, Code Review, Code Completion and others).
GLM 5.3 Flash was released in August 2026 and GPT-5.6 Luna in July 2026.
Pick GLM 5.3 Flash if you need lower cost, video input, benchmark performance 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 | Z.ai: GLM 5.3 Flash | OpenAI: GPT-5.6 Luna |
|---|---|---|
| SQL Generation | 142 | 141 |
| Code Review | 145 | 143 |
| Code Completion | 133 | 133 |
| Code Refactoring | 147 | 145 |
| Bug Fixing | 149 | 147 |
| Unit Test Generation | 132 | 131 |
| Code Documentation | 138 | 137 |
| Regex Writing | 126 | 125 |
| CI/CD Pipelines | 128 | 127 |
| Frontend Component Design | 130 | 129 |
| Data Analysis | 134 | 133 |
| CSV / Spreadsheet Cleanup | 136 | 136 |
| ETL Scripting | 137 | 136 |
| JSON Extraction | 131 | 131 |
| Bulk Data Labeling | 129 | 129 |
| OCR / Document Parsing | 134 | 134 |
| Table Extraction from PDFs | 134 | 134 |
| Long-Document Summarization | 149 | 147 |
| Short-Form Summarization | 127 | 126 |
| Blog Post Writing | 130 | 129 |
Scores reflect capability match + benchmark data + pricing for each task. Methodology →