Claude Opus 4.5
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:$1.85/M. Explicit cache_control breakpoints; cached reads bill at 0.1x the input price, cache writes carry a 1.25x (5-minute TTL) or 2x (1-hour TTL) surcharge; per-model minimum prefix sizes apply.
Use Claude Opus 4.5 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="claude-opus-4-5",
messages=[{"role": "user", "content": "Summarize this diff"}],
reasoning_effort="medium",
)
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: "claude-opus-4-5",
messages: [{ role: "user", content: "Summarize this diff" }],
reasoning_effort: "medium",
});
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": "claude-opus-4-5",
"messages": [{"role": "user", "content": "Hello"}],
"reasoning_effort": "medium"
}'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: "claude-opus-4-5",
Messages: []openai.ChatCompletionMessageParamUnion{
openai.UserMessage("Summarize this diff"),
},
ReasoningEffort: openai.ReasoningEffortMedium,
})
fmt.Println(resp.Choices[0].Message.Content)
}import com.openai.client.OpenAIClient;
import com.openai.client.okhttp.OpenAIOkHttpClient;
import com.openai.models.chat.completions.*;
import com.openai.models.ReasoningEffort;
OpenAIClient client = OpenAIOkHttpClient.builder()
.baseUrl("https://synthorai.io/v1")
.apiKey("sk-syn-...")
.build();
ChatCompletion resp = client.chat().completions().create(
ChatCompletionCreateParams.builder()
.model("claude-opus-4-5")
.addUserMessage("Summarize this diff")
.reasoningEffort(ReasoningEffort.MEDIUM)
.build());
System.out.println(resp.choices().get(0).message().content().orElse(""));About Claude Opus 4.5
Claude Opus 4.5 is a previous-generation Opus model, the release that repositioned Anthropic's top tier at $5/$25 per million tokens, down from Claude Opus 4.1's $15/$75.
- It supports a 200K-token context window, up to 64K output tokens, extended thinking, vision input, and Claude's tool-use and caching features, with moderate latency.
- Anthropic lists it as a legacy model and recommends migrating to newer Opus releases.
- For teams standardized on OpenAI SDKs, Synthorai serves Claude Opus 4.5 through its OpenAI-compatible chat API.
Specs & limits
| Max output (vendor spec) | 64,000 |
| Modalities | text + image → text |
| Features | tools · parallel_tool_calls · structured_output · streaming · vision · batch · caching · reasoning · computer_use |
| Training data through | 2025-08 (answers reliable to 2025-05) |
| Notable | Legacy model; introduced the effort parameter (public beta at launch); 200k context / 64k max output. |
| Prompt caching | explicit (opt-in) · min 4,096-token prefix · TTL 5m default, 1h option · writes 1.25x (5m) / 2x (1h) |
FAQ
Is the Claude Opus 4.5 API free to try?
Yes: new accounts get 10 trial calls and up to $1 in free credit, no card required. At $5/M input tokens, that credit alone covers roughly 24 requests of ~8K tokens against Claude Opus 4.5.
What is Claude Opus 4.5 best at?
Top tier repositioned at $5/$25 per million, plus 200K context with extended thinking and listed as legacy, migration to newer recommended. See the About section for the full picture from the vendor's own release notes.
How much does Claude Opus 4.5 cost?
Claude Opus 4.5 costs $5 per million input tokens and $25 per million output tokens on Synthorai. That is the provider's list price, with no platform markup. Cached input tokens bill at $0.5/M.
Does Claude Opus 4.5 support prompt caching?
Yes, via opt-in: mark stable prefixes with cache_control breakpoints. Cached input tokens bill at $0.5/M vs $5/M uncached; prompts need a 4,096-token stable prefix to cache (TTL 5m default, 1h option). Prompt caching guide →
How do I get access to Claude Opus 4.5?
Point your existing OpenAI SDK at base_url="https://synthorai.io/v1", set model="claude-opus-4-5", and you're done. One API key covers every model on the gateway.
What is Claude Opus 4.5's knowledge cutoff?
Claude Opus 4.5's knowledge cutoff is 2025-05, per the vendor's official documentation (as of 2026-07-09).