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CONTRIBUTING.md

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+# Contributing to rust-rpxy
+
+Thank you for your interest in contributing to rust-rpxy!
+This project is maintained primarily based on the code owner's personal interests.
+It is not backed by any commercial contract or SLA. Contributions are therefore handled on a **best-effort basis**.
+
+---
+
+## Ways to contribute
+
+### 1. Reporting issues
+
+- Use the appropriate Issue template (Bug, Feature request, or Question).
+- For questions, please also consider using **GitHub Discussions** instead of Issues.
+- Please provide as much detail as possible (logs, configs, environment) to make the report useful.
+
+### 2. Suggesting new features
+
+- Feature requests should explain **why** the feature is needed and what alternatives exist.
+- Unclear or vague requests may be closed without action.
+- Features that introduce compatibility problems or are outside the project scope are unlikely to be accepted.
+- If the feature is critical for your environment, please consider:
+  - Implementing it in your own fork, or
+  - Sponsoring its development.
+
+### 3. Submitting code (Pull Requests)
+
+- Contributions are welcome! Please:
+  - Ensure code is formatted with `cargo fmt`.
+  - Run tests with `cargo test` and confirm they pass.
+  - Keep commits clean and focused.
+- Large changes should be discussed in an Issue or Discussion before a PR is submitted.
+
+### 4. Documentation improvements
+
+- Fixing typos, clarifying explanations, and improving examples are always appreciated.
+
+### 5. Security reports
+
+- Do **not** open public Issues for security vulnerabilities.
+- Please report them via [GitHub's Private vulnerability reporting](../../security/advisories/new).
+- Reports are handled confidentially and on a best-effort basis.
+
+---
+
+## Code of Conduct
+
+Be respectful and constructive.
+Aggressive, entitled, or hostile communication may result in your Issue or PR being closed without further discussion.
+
+---
+
+## Final notes
+
+- This project exists because of personal research and interests of the maintainer.
+- Time and resources are limited. Contributions that come with clear motivation, good context, or sponsorship are far more likely to be accepted.
+- Thank you for understanding and for supporting rust-rpxy!