The Claude Opus 4.5 API runs our coding agent end to end — multi-file edits, tool use, long-horizon planning. The 5% RouterBase discount is pure margin.
The Claude Opus 4.5 API is Anthropic's flagship model for coding, agentic workflows, and complex reasoning — a 200K-token context window, extended thinking, vision, tool use, and prompt caching. The Claude Opus 4.5 API is OpenAI-compatible: point any existing SDK at RouterBase and swap the model name to claude-opus-4-5. Input at $4.50 / 1M tokens, output at $22.50 / 1M tokens, cache reads at $0.45 / 1M tokens — 5% below the standard rate, all through one REST endpoint.
Input
Claude Opus 4.5
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Claude Opus 4.5 API: Chat
Use the Claude Opus 4.5 API to run Anthropic's flagship model for coding and agentic workflows with a 200K-token context window.
The Claude Opus 4.5 API is Anthropic's most capable model for coding, agentic workflows, and complex reasoning — a 200K-token context window, extended thinking, vision, tool use, and built-in prompt caching. Routed through RouterBase, the Claude Opus 4.5 API is fully OpenAI-compatible: point any existing SDK at RouterBase's base URL, swap the model name to claude-opus-4-5, and your first call goes through immediately.
Pricing is $4.50 / 1M input tokens, $22.50 / 1M output tokens, and $0.45 / 1M cached-input reads — 5% below the standard rate. One RouterBase key — no Anthropic-specific SDK or separate credentials required.
Six reasons teams ship on the Claude Opus 4.5 API
From extended thinking to prompt caching — what makes the Claude Opus 4.5 API stand out.
200K-token context
Accepts up to 200,000 tokens per request — large codebases, document chains, or long conversation histories fit in a single Claude Opus 4.5 API call without chunking or retrieval glue.
Coding & agentic workflows
Claude Opus 4.5 is Anthropic's flagship for coding and multi-step agents — strong tool use, reliable long-horizon planning, and the model teams reach for on their hardest engineering tasks.
Extended thinking
Enable extended thinking to let the Claude Opus 4.5 API reason step-by-step before answering, allocating extra compute to difficult sub-problems — higher accuracy on complex analysis, planning, and math.
Prompt caching
Cache repeated prefixes with the Claude Opus 4.5 API. Cache reads cost $0.45 / 1M tokens — up to 90% savings on workloads with stable system prompts, few-shot examples, or reference documents.
OpenAI-compatible endpoint
The Claude Opus 4.5 API speaks the OpenAI chat-completions wire format. Any Python, Node, Go, or Rust SDK that works with OpenAI works here — just update the base URL and model name.
One key for 200+ models
The same RouterBase key that calls the Claude Opus 4.5 API also routes to GPT-5, Gemini 3.5 Flash, Sora 2, and 200+ other models — no per-provider credential management.
Quickstart
Get started with the Claude Opus 4.5 API in 3 steps
From sign-up to your first response in under 5 minutes.
Create a RouterBase API key
Sign up and generate an API key — one key reaches the Claude Opus 4.5 API and every other model in the catalog.
Send your first message
Point any OpenAI-compatible SDK at routerbase.com/v1 and set the model to claude-opus-4-5. The response follows the standard chat-completions schema — streaming and vision supported.
Inspect usage
Every response includes a detailed token breakdown — input, output, and cache-read tokens — so cost and cache-hit rate are visible on every call.
Pay only for what you use
RouterBase passes through partner-tier pricing. Compared against the model's official published API rate.
What teams build with the Claude Opus 4.5 API
Real production loads running on the Claude Opus 4.5 API and the RouterBase model catalog.
We switched our agent stack to the Claude Opus 4.5 API with a two-line change. Zero regression on our eval suite.
Prompt caching cut our monthly bill sharply — the system prompt is 40K tokens and hits the cache every time. RouterBase made the switch painless.
Extended thinking on the Claude Opus 4.5 API solved planning tasks our previous model couldn't touch. Accuracy jumped on our internal benchmark.
200K tokens of context means I can throw whole modules at it. The Claude Opus 4.5 API just handles the codebase.
RouterBase puts the Claude Opus 4.5 API and 200+ other models behind one key. Our team stopped filing requests for new provider accounts.
Vision and tool use on the Claude Opus 4.5 API let our agent read screenshots and call functions in one loop — same SDK, one model field.
We migrated 42 services to the Claude Opus 4.5 API over a weekend. The only PR comment was 'wait, that's all?'.
At $4.50 / 1M input minus 5%, plus cache-read pricing, the Claude Opus 4.5 API saves us six figures per quarter. The ROI math was instant.
Frequently Asked Questions
Common questions about the Claude Opus 4.5 API.
It is RouterBase's pass-through to Anthropic's Opus 4.5 model — a 200K-token context chat endpoint with extended thinking, vision, tool use, and prompt caching, served via an OpenAI-compatible REST interface.