GPT-5.6 Luna
Provider list prices: no platform markup, pay-as-you-go. These are official list prices. Logged-in customers may see effective prices including workspace discounts on /console/pricing. Effective input at a 70% cache-hit rate:$0.37/M. Automatic prefix caching once a prompt passes the minimum length, with no code changes; cached reads are discounted (up to 90% on current models) and there is no write fee. Fastest, most affordable GPT-5.6 tier, designed for cost-sensitive high-volume workloads (successor to the nano tier); keeps the family's full 1.05M context / 128k max output; cached input at 10% of list with 1.25x cache writes; prompts over 272k input tokens billed at 2x input / 1.5x output.
Use GPT-5.6 Luna in 30 seconds
OpenAI-compatible: swap the base_url, keep your SDK. POST /v1/chat/completions
from openai import OpenAI
client = OpenAI(
base_url="https://synthorai.io/v1",
api_key="sk-syn-...",
)
resp = client.chat.completions.create(
model="gpt-5.6-luna",
messages=[{"role": "user", "content": "Summarize this diff"}],
)
print(resp.choices[0].message.content)import OpenAI from "openai";
const client = new OpenAI({
baseURL: "https://synthorai.io/v1",
apiKey: "sk-syn-...",
});
const resp = await client.chat.completions.create({
model: "gpt-5.6-luna",
messages: [{ role: "user", content: "Summarize this diff" }],
});
console.log(resp.choices[0].message.content);curl https://synthorai.io/v1/chat/completions \
-H "Authorization: Bearer sk-syn-..." \
-H "Content-Type: application/json" \
-d '{
"model": "gpt-5.6-luna",
"messages": [{"role": "user", "content": "Hello"}]
}'package main
import (
"context"
"fmt"
"github.com/openai/openai-go/v3"
"github.com/openai/openai-go/v3/option"
)
func main() {
client := openai.NewClient(
option.WithBaseURL("https://synthorai.io/v1"),
option.WithAPIKey("sk-syn-..."),
)
resp, _ := client.Chat.Completions.New(context.TODO(), openai.ChatCompletionNewParams{
Model: "gpt-5.6-luna",
Messages: []openai.ChatCompletionMessageParamUnion{
openai.UserMessage("Summarize this diff"),
},
})
fmt.Println(resp.Choices[0].Message.Content)
}import com.openai.client.OpenAIClient;
import com.openai.client.okhttp.OpenAIOkHttpClient;
import com.openai.models.chat.completions.*;
OpenAIClient client = OpenAIOkHttpClient.builder()
.baseUrl("https://synthorai.io/v1")
.apiKey("sk-syn-...")
.build();
ChatCompletion resp = client.chat().completions().create(
ChatCompletionCreateParams.builder()
.model("gpt-5.6-luna")
.addUserMessage("Summarize this diff")
.build());
System.out.println(resp.choices().get(0).message().content().orElse(""));About GPT-5.6 Luna
GPT-5.6 Luna is the fastest, most affordable member of OpenAI's GPT-5.6 family, designed for cost-sensitive, high-volume workloads such as summarization, drafting, and routine automation, succeeding the nano tier of earlier GPT-5 generations.
- It keeps the family's full 1,050,000-token context window (vendor spec) and 128K max output tokens, takes image input, supports reasoning tokens, and reaches the hosted tool set including web search, file search, code interpreter, and computer use, with a February 2026 knowledge cutoff.
- Cached input is billed at a tenth of the list input price, which suits pipelines that reuse long prompts.
- Synthorai serves GPT-5.6 Luna through the same OpenAI-compatible chat completions endpoint as every GPT model.
Specs & limits
| Max output (vendor spec) | 128,000 |
| Modalities | text + image → text |
| Features | reasoning · vision · code · tools · caching |
| Notable | Fastest, most affordable GPT-5.6 tier, designed for cost-sensitive high-volume workloads (successor to the nano tier); keeps the family's full 1.05M context / 128k max output; cached input at 10% of list with 1.25x cache writes; prompts over 272k input tokens billed at 2x input / 1.5x output. |
| Prompt caching | automatic · min 1,024-token prefix · TTL 5–10m, up to 1h |
FAQ
Is the GPT-5.6 Luna API free to try?
Yes: new accounts get 10 trial calls and up to $1 in free credit, no card required. At $1/M input tokens, that credit alone covers roughly 125 requests of ~8K tokens against GPT-5.6 Luna.
What is GPT-5.6 Luna best at?
Fastest, most affordable GPT-5.6 tier, plus keeps the family's full 1,050,000-token context and cached input at a tenth of the list price. See the About section for the full picture from the vendor's own release notes.
How much does GPT-5.6 Luna cost?
GPT-5.6 Luna costs $1 per million input tokens and $6 per million output tokens on Synthorai. That is the provider's list price, with no platform markup. Cached input tokens bill at $0.1/M.
Does GPT-5.6 Luna support prompt caching?
Yes, automatically: OpenAI-served prompts cache with no code changes. Cached input tokens bill at $0.1/M vs $1/M uncached; prompts need a 1,024-token stable prefix to cache (TTL 5–10m, up to 1h). Prompt caching guide →
How do I get access to GPT-5.6 Luna?
Point your existing OpenAI SDK at base_url="https://synthorai.io/v1", set model="gpt-5.6-luna", and you're done. One API key covers every model on the gateway.
What is GPT-5.6 Luna's knowledge cutoff?
GPT-5.6 Luna's knowledge cutoff is 2026-02, per the vendor's official documentation (as of 2026-07-10).