GPT-5.1 Series (API)

Access OpenAI's GPT-5.1 model family: GPT-5.1 (400K context), GPT-5.1-Chat (128K context), and GPT-5.1-Thinking (enhanced reasoning). All with built-in prompt caching.

Playground Not Available

This feature is currently only available for selected image and video generation models.

Build with GPT-5.1 API — Next-Gen Intelligence

Leverage the largest context window and most advanced reasoning from OpenAI. Perfect for complex analysis, code generation, and multi-step workflows.

What can GPT-5.1 API achieve?

Massive Context Analysis

Process up to 400K tokens in a single request. Analyze entire codebases, legal documents, or research papers without chunking.

Explore context capabilities

Advanced Reasoning

Tackle complex multi-step problems with GPT-5.1's enhanced reasoning engine. Ideal for research, coding, and decision support.

Test reasoning

Prompt Caching

Reduce costs by up to 90% with built-in prompt caching. Reuse system prompts and few-shot examples without reprocessing.

Learn about caching

Why developers choose GPT-5.1 API

GPT-5.1 represents OpenAI's cutting-edge capabilities, offering unmatched context length and reasoning for production applications.

Largest Context Window

400K tokens means you can process entire books, codebases, or conversation histories in one request.

Cost Efficient

Built-in prompt caching reduces repeated token costs by up to 90%, making large-scale deployments affordable.

State-of-the-Art Reasoning

Enhanced logical capabilities for complex tasks that require multi-step analysis and accurate conclusions.

How to integrate GPT-5.1 API

Start using GPT-5.1 through EvoLink's unified gateway in three steps.

Step 1 — Get Your API Key

Step 2 — Configure Your Client

Point your OpenAI SDK to EvoLink's endpoint and specify `gpt-5.1` as the model.

Step 3 — Start Building

Send your first request. Leverage the 400K context and prompt caching for your applications.

View API Docs

Core API Capabilities

Technical specifications for GPT-5.1 API

Capacity

400K Context

Process massive documents in a single request.

Efficiency

Prompt Caching

90% cost reduction on repeated tokens.

Intelligence

Advanced Reasoning

Multi-step problem solving capabilities.

Integration

Function Calling

Native support for tool use and structured outputs.

Reliability

JSON Mode

Guaranteed valid JSON responses for APIs.

Performance

Streaming

Real-time token streaming for responsive UIs.

GPT-5.1 Series Comparison

Choose the right variant for your needs

Model	Duration	Resolution	Price	Strength
GPT-5.1	N/A	400K Context	Premium	Largest context window, ideal for large documents and codebases.
GPT-5.1-Chat	N/A	128K Context	Standard	Cost-effective for general tasks with moderate context needs.
GPT-5.1-Thinking	N/A	400K Context	Premium	Enhanced chain-of-thought reasoning for complex problem solving.

GPT-5.1 API - FAQ

Everything you need to know about the product and billing.

GPT-5.1 supports a 400,000 token context window, making it ideal for processing large documents, entire codebases, or extensive conversation histories.

GPT-5.1 automatically caches your system prompts and few-shot examples. When you reuse the same prefix, you only pay ~10% of the normal input token cost.

Yes, GPT-5.1 is 100% compatible with the OpenAI SDK. Simply change the base URL to EvoLink's endpoint and use `gpt-5.1` as the model name.

GPT-5.1 offers 400K context for large documents. GPT-5.1-Chat has 128K context at lower cost. GPT-5.1-Thinking adds enhanced chain-of-thought reasoning for complex problems.

EvoLink offers competitive pricing with additional benefits like unified billing, smart routing, and no rate limit restrictions.