AnthropicText / ChatClaude Opus 5 API: Anthropic's most advanced Opus, one key away
Claude Opus 5 via the ApexApi gateway
Claude Opus 5 is Anthropic's most advanced Opus-tier model and a step change in coding and long-running agentic work. It handles multi-file features and large refactors end-to-end, orchestrates tools and subagents reliably, and reads dense documents, charts, and screenshots at high fidelity, with a 1M-token context window and thinking on by default. Call it through ApexApi's unified, OpenAI-compatible API.
Claude Opus 5 is served through ApexApi's unified, OpenAI-compatible API. One key, one format, with smart routing and automatic failover. Provider: Anthropic on Vertex (Claude).
Why Claude Opus 5
Step-change coding
Long-horizon projects in large codebases, from architecture to deployment, staying on track across extended, multi-stage work.
Agent orchestration
Plans deliberately, coordinates subagents and parallel tool calls, and drives long-running work forward with minimal oversight.
High-fidelity vision
Reads dense documents, charts, screenshots, and diagrams reliably. Strong for document extraction and computer use.
Specifications
- Modality
- chat
- Context window
- 1000K tokens
- Max output
- 128K tokens
- Streaming
- Yes
- Tool / function calling
- Yes
- Vision input
- Yes
Claude Opus 5: measured reliability
From real calls ApexApi made to Claude Opus 5 during health sweeps over the last 30 days. Our own measurements, not vendor claims.
- Success rate
- 100%
- Avg latency
- 4.4s
- Calls measured
- 1
- Last checked
- Jul 25
See how Claude Opus 5 compares against every model we serve on the model rankings.
Claude Opus 5 pricing
- A million tokens in and a million out costs $36.00 here, all-in.
- It runs 2× cheaper than Claude Fable 5, the pricier option from the same maker.
- It is one of 33 chat models here with a 1M-token context window.
Getting started with Claude Opus 5
OpenAI-compatible. Point your client at ApexApi, swap your key, and call it. No new SDK to learn.
from openai import OpenAI
client = OpenAI(
base_url="https://api.apexapi.dev/v1",
api_key="<YOUR_APEXAPI_KEY>",
)
response = client.chat.completions.create(
model="anthropic/claude-opus-5",
messages=[{"role": "user", "content": "Hello!"}],
)
print(response.choices[0].message.content)Claude Opus 5 use cases
What teams build with Claude Opus 5 on ApexApi.
Autonomous coding agents
Delegate complex, multi-file engineering work: features, refactors, reviews, and full-lifecycle runs.
Enterprise workflows
Multi-day projects end-to-end, with precise instruction following and professional-grade documents and analysis.
Document & data extraction
Dense filings, charts, and real-world imagery, parsed with the best vision in the Opus line.
Claude Opus 5 vs other models
How it compares, and on ApexApi you can switch between any of them with a single string change, same key, same endpoint.
Claude Opus 5 vs Claude Opus 4.8
Opus 4.8 is the prior Opus flagship at the same price; Opus 5 steps up coding, agentic orchestration, and vision. A/B them with one key on ApexApi.
Claude Opus 5 vs Claude Fable 5
Fable 5 is Anthropic's most capable (and pricier) model for the hardest reasoning; Opus 5 delivers near-flagship agentic coding at half the cost.
Learn more about Claude Fable 5 API →Claude Opus 5 vs GPT-5.5
GPT-5.5 is OpenAI's broad multimodal frontier; Opus 5 specializes in long-horizon coding and dependable agent runs.
Learn more about GPT-5.5 API →Claude Opus 5 API: FAQ
How do I use the Claude Opus 5 API?
Create an ApexApi key, then point your client at https://api.apexapi.dev/v1 and use the model slug. Send a request to /v1/chat/completions with the model slug. The API is OpenAI-compatible, so most OpenAI SDKs work by changing the base URL and key.
Is the Claude Opus 5 API OpenAI-compatible?
Yes. ApexApi exposes Claude Opus 5 through the same OpenAI-compatible interface used across the whole catalog. Swap the base URL and API key and keep your existing code.
How much does Claude Opus 5 cost on ApexApi?
Pay-per-use. See the live price in the Pricing section above. There's no subscription or minimum; you buy credits and pay only for what you call.
Can I switch from Claude Opus 5 to another model later?
Yes. Change a single string (the model slug) to call any other model in the catalog through the same endpoint and key. No re-integration.
Ready to build with Claude Opus 5?
One API key. Every major AI model. Pay only for what you use.
Get your API key, free to start