text model comparison
GPT-5.6 Luna vs Mercury 2.5
GPT-5.6 Luna and Mercury 2.5 are both current text models, from OpenAI and Inception. Both cost $0.20 per 1M input tokens. GPT-5.6 Luna has the larger context window, 1,050,000 vs 260,000 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 | GPT-5.6 Luna | Mercury 2.5 |
|---|---|---|
| Price per 1M input tokens | $0.20 | $0.20 |
| Price per 1M output tokens | $1.20 | $0.75 (better) |
| Cost of 10M input and 2M output tokens | $4.40 | $3.50 (better) |
| Arena Text | 1452 Elo (#34 of 49) | Not measured |
| GPQA Diamond | 91.6% (#20 of 40) | Not measured |
| FrontierMath Tiers 1-3 (v2) | 82.1% (#12 of 40) | Not measured |
| SimpleQA Verified | 41% (#27 of 36) | Not measured |
| Provider | OpenAI | Inception |
| Release date | July 9, 2026 | September 8, 2026 |
| Access | API only | API only |
| Context window | 1,050,000 tokens | 260,000 tokens |
| Max output | 128,000 tokens | 65,536 tokens |
| Input | text, image | text |
| Output | text | text |
When to choose each
GPT-5.6 Luna
Best for
- High-volume API evaluation with published low token prices
- Subagents and batch reasoning where cost per call dominates
Watch out for
- Not in the pinned LiveBench snapshot; its independent scores here come from Epoch AI's own GPQA Diamond, FrontierMath and SimpleQA Verified runs
Mercury 2.5
Best for
- Latency-critical agent loops and voice agents
- High-throughput, low-cost text generation
Watch out for
- Inception publishes no benchmark scores for it, and no independent score is recorded here
- The recorded rates are list prices; an 80% launch discount was running with no published end date
GPT-5.6 Luna vs Mercury 2.5 FAQ
Which is cheaper, GPT-5.6 Luna or Mercury 2.5?
Both cost $0.20 per 1M input tokens. For 10M input and 2M output tokens, GPT-5.6 Luna costs $4.40 and Mercury 2.5 $3.50 at standard rates.
Which has the larger context window, GPT-5.6 Luna or Mercury 2.5?
GPT-5.6 Luna has the larger context window, 1,050,000 vs 260,000 tokens.
Related comparisons
Production evaluation
Choosing between GPT-5.6 Luna and Mercury 2.5?
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