Open Layer: Establishing a Universal Open Standard for LLM Inference I/O

The Open Layer project is dedicated to solving the fragmentation problem of large language model (LLM) APIs. By defining unified inference input/output specifications, combined with its core architecture of specification layer, SDK layer, adapter layer, and conformance test suite, it helps developers seamlessly switch between different model providers and promotes the construction of a more open and interoperable AI ecosystem.

The current LLM ecosystem faces the problem of API fragmentation: although many providers claim to support "OpenAI-compatible" APIs, the actual compatibility of modern features is insufficient. For example, there are three different ways to name the thinking token field—wrapped in tags, the reasoning_content field, and the reasoning field—making cross-provider migration difficult, and developers need to write specialized client code for each provider.

Open Layer proposes a formal complete contract specification for inference I/O, covering 6 core aspects such as message format, thinking token, and streaming transmission, and verifies its feasibility through conformance tests. The core architecture is divided into three layers:

1. Specification layer: Defines the complete contract using Markdown and JSON Schema;
2. SDK layer: Provides an asynchronous httpx-based Python SDK, including typed data classes and adapter protocols;
3. Adapter layer: Implements adapters for providers like Nvidia NIM, DeepSeek, Groq, etc., to standardize differential responses.

Open Layer adopts a "specification-first" development approach; the specification includes JSON Schema that can be machine-verified. The project has 66 conformance test suites, supports tag parameterization, and covers 12 models and 10 model families. Adapters serve as temporary bridges to standardize responses at the client layer, with the goal of promoting native adoption of the specification by providers.

Nvidia NIM tests found: 4/12 models reject unknown request fields, 5/12 models have non-empty selection results in streaming usage statistics, there are 3 modes for thinking tokens, and invalid model errors return plain text. After adapter standardization, 12/12 models passed the tests. For developers: True portability, reduced integration costs, unified error handling; For providers: Reduced user migration costs, ecosystem compatibility, clear functional boundaries.

Open Layer is currently in the v0.1 phase, supporting three major providers: Nvidia NIM, DeepSeek, and Groq. It provides a Python SDK, adapters, test suites, and A/B demonstration tools. In the future, it is expected to become the de facto standard in the LLM inference field, similar to how HTTP/REST is for Web APIs.