vLLM Agent Rules: AGENTS.md Explained

Overview

vLLM asks contributors to state a test's contract and failure mode before writing it. Correctness and performance use different evidence, while native builds and security reviews have dedicated guides.

Behavioral framing Hard prohibitions Verification by change type Router files

Documents

├── 
├──  · imports AGENTS.md
├── docs
│   ├── contributing
│   │   ├── model
│   │   │   └── 
│   │   ├── 
│   │   ├── 
│   │   └── 
│   └── usage
│       └── 
├── rust
│   ├── src
│   │   └── bench
│   │       ├── 
│   │       └──  · same content as CLAUDE.md · imports AGENTS.md
│   ├── 
│   ├── AGENTS.override.md · unavailable at this commit
│   └──  · imports AGENTS.override.md (unavailable), AGENTS.md
└──

Techniques in this file

01 / Behavioral framing

Design the test before writing its setup

The test section asks what the module does, what crosses its boundary, and which failure the test protects against. It then selects the cheapest level that catches that failure.

85- **Design before you write.** Answer four questions first: what is the module86  for, what is its I/O contract, what failure am I guarding against, and what is87  the cheapest level that catches it (unit over integration over e2e)?

02 / Hard prohibitions

Separate kernel performance from correctness coverage

One-off performance work belongs in the kernel benchmark directory. Correctness belongs in the existing pytest suites, so the two kinds of evidence have explicit homes.

95- **No one-off kernel benchmarks in `tests/`.** Put kernel perf work in96  `benchmarks/kernels/`; prove correctness in existing pytest suites.

03 / Verification by change type

Require model evaluations when behavior can change

Tests alone do not satisfy the guidance for changes affecting output, accuracy, or serving. The file asks for model evaluations and their results in the PR before a reviewer has to request them.

97- **Run model evals for model-affecting changes.** Search `tests/evals/` or use98  `vllm bench` and include results in the PR — do not wait for reviewers to ask.

04 / Router files

Route native builds away from the default editable install

The default install starts with precompiled artifacts. C, C++, and CUDA changes instead follow the incremental compilation guide, making the distinction depend on the edited implementation.

67For C/C++ or CUDA changes, follow the68[incremental compilation workflow](docs/contributing/incremental_build.md) to69configure and perform incremental builds.