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.
- Input
- text image $5/M
- Output
- text $25/M
- Cache read
- $0.5/M
- Context
- 200K
- Knowledge cutoff
- 2025-05
Benchmarks
Vendor-published: Alibaba (Qwen) Anthropic ByteDance DeepSeek Google MiniMax Moonshot OpenAI Tencent Z.ai
Price in context
Where the price sits among 60 comparable models
The bar shows how this model’s price compares with every other model of the same kind on Synthorai. The cheapest and the most expensive are named at each end. These are base rates; batch, region and cache-write discounts are on the pricing page.
Specs & limits
Tokens
| Context window (vendor spec) | 200,000 |
|---|---|
| Max output (vendor spec) | 64,000 |
| Knowledge cutoff | 2025-05 |
| Training data through | 2025-08 knowledge cutoff 2025-05 |
Prompt caching
| How it caches | explicit (opt-in) |
|---|---|
| Min prefix | 4,096 provider default is 1,024 |
| Lifetime | 5m default, 1h option |
| Write cost | 1.25x (5m) / 2x (1h) |
Thinking
| Vendor control | thinking.type "enabled" + budget_tokens, plus output_config.effort |
|---|---|
| Accepted values | budget_tokens at least 1,024 and below max_tokens; effort low · medium · high (no xhigh, no max); "adaptive" returns 400 |
| Default | thinking off; effort high applied when the request sets nothing |
| Can be turned off | Yes |
| Thinking behaviour | The only extended-thinking-only model that supports effort, where effort shapes the whole response and budget_tokens sets reasoning depth, so set both; earlier turns' thinking blocks are kept in context and billed as input; interleaved thinking requires the interleaved-thinking-2025-05-14 beta header. |
| Parameter | reasoning_effort |
| Values | minimal · low · medium · high the gateway's parameter surface - the vendor mapping above applies |
Model
| Modalities | text + image → text |
|---|
- Legacy model
- introduced the effort parameter (public beta at launch)
- 200k context / 64k max output
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
- Anthropic introduced it as its most intelligent model combining maximum capability with practical performance, aimed at complex specialized tasks, professional software engineering, and advanced agents, with step-change improvements in vision, coding, and computer use.
- 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.
- It is also a hybrid in one revealing way: it is the only extended-thinking-only model that accepts the effort parameter, and Anthropic's guidance is to set both.
- Effort shapes the overall response while the thinking budget sets reasoning depth.
- Effort here covers low through max but not xhigh, which arrives with Opus 4.7.
- Requesting adaptive thinking returns an error, thinking is off unless enabled, and interleaved thinking requires a beta header.
- Unlike the Haiku tier, thinking blocks from previous turns are preserved in context and billed as input.
- Prompt caching needs a 4,096-token minimum prefix.
- 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.
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; 200K context with extended thinking; 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).
Related models
Compare
Every value on this page is transcribed from the vendor's own documentation, linked above, and carries the date it was checked. Prices are compared across the catalogue; specification values that vendors define differently are shown with the difference stated rather than charted. Nothing here is measured by us, and nothing is scored.