docs: add contributing guide (abetlen#2229)

Author: abetlen

CHANGELOG.md

@@ -8,6 +8,7 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 ## [Unreleased]
 
 - feat: Update llama.cpp to ggml-org/llama.cpp@c0c7e147e
+- docs: add contributing guide by @abetlen in #2229
 - chore: Migrate llama.cpp submodule URL to ggml-org/llama.cpp by @shalinib-ibm in #2034
 - fix: Enable unified KV cache for embedding contexts to preserve full per-sequence context in batch embedding calls by @SanjanaB123 in #2217
 

CONTRIBUTING.md

@@ -0,0 +1,77 @@
+# Contributing
+
+Hello human and AI contributors, this document exists to help you understand the project and set some rules for contributions.
+
+## Contribution Workflow
+
+Before opening a pull request, search existing issues and PRs to avoid duplicate work.
+Keep each PR focused on one feature, bug fix, or vendor update.
+Avoid mixing unrelated Python changes, generated binding updates, documentation edits, and `vendor/llama.cpp` changes unless they are required for the same fix.
+
+Describe what changed, why it changed, and how it was tested.
+Link relevant issues, include any required build flags or hardware assumptions, and add a `CHANGELOG.md` entry for user-visible fixes or features (see `CHANGELOG.md` for examples).
+
+BREAKING CHANGES WILL ALMOST CERTAINLY BE REJECTED OR REFACTORED.
+
+## PR Titles and Changelog Entries
+
+Use PR titles in the form `<tag>: <title>`, with an optional scope when it adds clarity: `feat: add X`, `fix(server): handle Y`, `fix(ci): repair Z`, or `chore: bump version to N`.
+Prefer tags already used in the project history, such as `feat`, `fix`, `chore`, `ci`, `docs`, and `refactor`.
+
+Add changelog entries under `## [Unreleased]` using the PR title followed by `by @contributor in #1234`.
+
+```md
+- feat(server): add support for X by @contributor in #1234
+- fix(ci): repair Y wheel builds by @contributor in #1234
+```
+
+## Local Development
+
+Prerequisites: Python 3.8+, CMake 3.21+, a C/C++ compiler, and Git submodules.
+From a fresh checkout of the repository, initialize submodules and create a virtual environment:
+
+```bash
+git submodule update --init --recursive
+python3 -m venv .venv
+source .venv/bin/activate
+python -m pip install --upgrade pip
+make deps
+make build
+```
+
+Run tests and lint checks before submitting changes:
+
+```bash
+make test
+make lint
+```
+
+Use backend-specific build targets when validating native acceleration or backend-specific fixes, for example `make build.openblas`, `make build.cuda`, `make build.metal`, or `make build.vulkan`.
+
+## Testing Expectations
+
+Add or update tests for behavior changes or fixing regressions.
+The test suite uses pytest and lives under `tests/`; name files `test_*.py` and test functions `test_*`.
+
+For changes involving native backends, model behavior, performance, or platform compatibility, document the environment used for validation in the PR.
+If a change cannot be covered by automated tests, include a short manual validation recipe instead.
+
+## Code Style
+
+Python code is formatted with Ruff using an 88-character line length.
+Run `make format` to apply automatic fixes and `make lint` to check formatting and lint rules.
+
+Use 4-space indentation, `snake_case` for functions and variables, `PascalCase` for classes, and `UPPER_CASE` for constants.
+Follow existing patterns when touching ctypes bindings or server APIs, and avoid adding dependencies unless they are necessary for the feature or fix.
+
+## Documentation Style
+
+Write Markdown with one sentence or core idea per physical line to keep diffs focused and easier to review.
+Do not manually wrap lines at a fixed column width.
+Keep `README.md` focused on user-facing setup and usage; link to this guide for contribution workflow details rather than duplicating them.
+
+## Project Layout
+
+The Python package lives in `llama_cpp/`, with tests in `tests/` and examples in `examples/`.
+Documentation lives in `docs/` and is built with `mkdocs.yml`.
+The `vendor/llama.cpp/` directory is a Git submodule containing the upstream llama.cpp sources used by the bindings.

README.md

@@ -743,6 +743,7 @@ If you find any issues with the documentation, please open an issue or submit a
 ## Development
 
 This package is under active development and I welcome any contributions.
+See [CONTRIBUTING.md](CONTRIBUTING.md) for contribution workflow, PR title, changelog, testing, and style guidelines.
 
 To get started, clone the repository and install the package in editable / development mode: