MODEL PROOF
GPT-5.6 Luna
TRADE-OFF
A stored alternative has an equal-or-higher score and an equal-or-lower price, with capability losses.
Base context tier shown; inspect the complete context ladder below.
GLM 5.3 Flash · Δ score 42 points · 47% lower measured price
- no file input
- Independent LMArena score
- 1,429.9 ± 4.77 · 28,547 votes
- Context window
- 1.05M
- Maximum output
- 128K
- Input modalities
- file, image, text
- Output modalities
- text
- Published input price
- $0.200 / 1M tokens
- Published output price
- $1.20 / 1M tokens
- Pricing kind
- fixed
- Context tiers
- Tiered by context
Inspect complete billing conditions and endpoint terms below.
Every price dimension · USD per million tokens
| Input | $0.200/M |
|---|---|
| Output | $1.20/M |
| Cached input | $0.020/M |
| Cache write | $0.250/M |
| Cache write 1h | Unknown/M |
| Reasoning | Unknown/M |
| Web search | $0.01/call |
| Batch discount | 50% |
The headline rate does not apply to a long-context workload.
Complete context ladder · 1 tier
| More than 272,000 tokens | $0.400/M in (2×) $1.80/M out $0.040/M cached input $0.500/M cache write |
|---|
Who sells it
The same weights, different shops. Cheapest is not like-for-like when serving precision differs.
7 provider offers · rates, limits and conditions
Rates are USD per million tokens. Endpoint terms can differ even when the quoted price and precision match. A listed parameter is a provider declaration, not a task-success test.
| Seller | Input | Output | Precision | Uptime (1d) |
|---|---|---|---|---|
| OpenAIopenai/flex Endpoint terms
| $0.100 | $0.600 | undeclared | 99.73% |
| Azureazure Endpoint terms
| $0.200 | $1.20 | undeclared | 97.52% |
| OpenAIopenai Endpoint terms
| $0.200 | $1.20 | undeclared | 99.99% |
| Azureazure/us Endpoint terms
| $0.220 | $1.32 | undeclared | 99.99% |
| Amazon Bedrockamazon-bedrock/us-east-1 Endpoint terms
| $0.220 | $1.32 | undeclared | 100.00% |
| Azureazure/eu Endpoint terms
| $0.220 | $1.32 | undeclared | 99.12% |
| OpenAIopenai/fast Endpoint terms
| $0.400 | $2.40 | undeclared | 99.99% |
Independent scores
| LMArena Elo | 1429.9xhigh |
|---|
LMArena Elo under CC BY 4.0. Absence of another board is not a score of zero.
Capability
| Context window | 1.1M |
|---|---|
| Max output | 128K |
| Input modes | file, image, text |
| Tool use | yes |
| Reasoning | optional |
| Knowledge cutoff | 2026-02-16 |
| Open weights | no |
Provenance
| Price source | openrouter.ai |
|---|---|
| Fetched | 2026-09-23 |
| Quality data | verified |
| Cross-checked | vendor page |
Our take
editorial — not a measurementLuna is a candidate for recurring extraction, retrieval and summarisation work. Evaluate it on your actual inputs and compare the selected-tier price with alternatives. The API model and a ChatGPT subscription are different products: a chat-plan placement or allowance does not establish this model’s capability or API entitlement.
Strengths
- Tools, structured outputs and cached-input pricing are listed
- The accepted table includes batch and context-tier information
Weaknesses
- Long prompts can select a different rate
- Low token prices do not establish acceptable task quality
Reach for it when
- High-volume extraction and summarisation evaluations
- Retrieval workflows with repeated context
Avoid it if
- It fails the quality threshold in your own evaluations
- You require downloadable weights
Sources: developers.openai.comchatgpt.com
GPT-5.6 Luna is a fast, cost-efficient model in OpenAI's GPT-5.6 series. It is suited for high-volume, latency-sensitive tasks such as chat, classification, and lightweight agentic workflows, providing capable reasoning for...
Questions this page answers
What does GPT-5.6 Luna cost?
$0.200/M in, $1.20/M out in this catalogue, as of the fetch date on this page. That is the API row, not a subscription.
Does GPT-5.6 Luna have an independent quality score?
GPT-5.6 Luna has an LMArena score in this catalogue.
What beats GPT-5.6 Luna?
GLM 5.3 Flash has an equal-or-higher measured score and an equal-or-lower price, with capability trade-offs.
Does this page use Artificial Analysis scores for GPT-5.6 Luna?
No. Artificial Analysis figures are not published here. Quality on this page is LMArena Elo where a score exists; otherwise the row is unrated.
MODEL MONUMENT
Save or share this proof
Badge
The verdict as one SVG, for a README or a docs page. It states this model's dominance status at the balanced workload on the LMArena lens, with the date it was computed, and it is rebuilt with the catalogue — so it changes when the verdict changes, including to one you would rather it did not.
[](https://undominated.ai/models/openai__gpt-5.6-luna/)<a href="https://undominated.ai/models/openai__gpt-5.6-luna/"><img src="https://undominated.ai/badge/openai__gpt-5.6-luna.svg" alt="GPT-5.6 Luna — Undominated.ai dominance verdict" height="36"></a>Direct file: https://undominated.ai/badge/openai__gpt-5.6-luna.svg — a static SVG, written by scripts/build-badges.mjs on every build, so the copy you embed is never
older than the last deploy.
