text model comparison
GLM-5.3-Flash vs GPT-6 Luna
GLM-5.3-Flash and GPT-6 Luna are both current text models, from Z.ai and OpenAI. GPT-6 Luna is 33% cheaper per 1M input tokens than GLM-5.3-Flash, $0.10 vs $0.15. On Arena Text, GLM-5.3-Flash scores 1475 Elo and GPT-6 Luna 1443 Elo (Arena, measured October 8, 2026). GPT-6 Luna has the larger context window, 1,050,000 vs 1,000,000 tokens.
Data verified October 13, 2026 · Dataset 2026-10-13
Side by side
Standard-tier prices in effect today. The better value in each row is highlighted.
| Fact | GLM-5.3-Flash | GPT-6 Luna |
|---|---|---|
| Price per 1M input tokens | $0.15 | $0.10 (better) |
| Price per 1M output tokens | $0.50 | $0.50 |
| Cost of 10M input and 2M output tokens | $2.50 | $2 (better) |
| Arena Text | 1475 Elo (#21 of 49) (better) | 1443 Elo (#37 of 49) |
| GPQA Diamond | 90.2% (#27 of 40) | 90.5% (#25 of 40) (better) |
| FrontierMath Tiers 1-3 (v2) | 55.8% (#31 of 40) | 78.9% (#14 of 40) (better) |
| SimpleQA Verified | Not measured | 41.4% (#26 of 36) |
| Provider | Z.ai | OpenAI |
| Release date | August 26, 2026 | September 22, 2026 |
| Access | API and open weights | API only |
| Context window | 1,000,000 tokens | 1,050,000 tokens |
| Max output | 128,000 tokens | 128,000 tokens |
| Input | text, image, video | text, image |
| Output | text | text |
When to choose each
GLM-5.3-Flash
Best for
- Low-cost coding from screenshots or screen recordings
- Document and research agents on a budget
Watch out for
- Thinking cannot be disabled
- A faster GLM-5.3-FlashX is a separate model id at $0.37 input and $1.25 output per 1M tokens
GPT-6 Luna
Best for
- High-volume summarisation, extraction and routing
- Long-context budget work, where the 272k threshold is more forgiving than Haiku 5.5's 100k
Watch out for
- Prompts over 272,000 tokens are rebilled at $0.20 input and $0.75 output for the whole request
- A twentieth of GPT-6 Sol's price reflects a capability gap, not a discount on the same model
GLM-5.3-Flash vs GPT-6 Luna FAQ
Which is cheaper, GLM-5.3-Flash or GPT-6 Luna?
GPT-6 Luna is 33% cheaper per 1M input tokens than GLM-5.3-Flash, $0.10 vs $0.15. For 10M input and 2M output tokens, GLM-5.3-Flash costs $2.50 and GPT-6 Luna $2 at standard rates.
Which scores higher on independent benchmarks, GLM-5.3-Flash or GPT-6 Luna?
GLM-5.3-Flash leads on Arena Text, 1475 Elo to 1443 Elo; GPT-6 Luna leads on GPQA Diamond, 90.5% to 90.2%; GPT-6 Luna leads on FrontierMath Tiers 1-3 (v2), 78.9% to 55.8%. Scores are independent evaluations, not either vendor's launch figures.
Which has the larger context window, GLM-5.3-Flash or GPT-6 Luna?
GPT-6 Luna has the larger context window, 1,050,000 vs 1,000,000 tokens.
Can I run GLM-5.3-Flash or GPT-6 Luna myself?
GLM-5.3-Flash is released as open weights you can run yourself; GPT-6 Luna is available through its provider's API only.
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Production evaluation
Choosing between GLM-5.3-Flash and GPT-6 Luna?
Public benchmarks narrow the shortlist. We run both on your own tasks, data and cost limits, then build the routing and review controls to run the winner in production.
- A head-to-head evaluation on your real workload
- Routing between models by cost and difficulty