diff --git a/CONTRIBUTING.md b/CONTRIBUTING.md
new file mode 100644
index 000000000..49fe4f3b2
--- /dev/null
+++ b/CONTRIBUTING.md
@@ -0,0 +1,158 @@
+# Contributing to CCCC
+
+Contributions are welcome — bug reports, feature requests, code, and documentation.
+This page consolidates the conventions that are otherwise spread across the
+README, [SUPPORT.md](SUPPORT.md), [SECURITY.md](SECURITY.md), and
+[docs/guide/quality-gates.md](docs/guide/quality-gates.md).
+
+## Ways to Contribute
+
+- **Bug reports**: search [existing issues](https://github.com/ChesterRa/cccc/issues)
+  first, then open a new one. Include `cccc --version`, your OS, the exact
+  commands, and minimal reproduction steps. See [SUPPORT.md](SUPPORT.md) for the
+  full checklist and daemon-log guidance.
+- **Feature requests**: describe the problem, the proposed behavior, and the
+  operational impact on your multi-agent setup.
+- **Pull requests**: see the process below.
+- **Security issues**: report privately per [SECURITY.md](SECURITY.md). Never
+  open a public issue for a vulnerability.
+
+Runtime state lives under `CCCC_HOME` (default `~/.cccc/`) — never commit it,
+and do not paste tokens, credentials, or provider transcripts into issues.
+
+## Development Environment
+
+Source builds require:
+
+- Rust 1.88 (pinned in `rust-toolchain.toml`; `rustup` installs it automatically)
+- Node.js 24 with npm (CI pins 24.19.0)
+- Python 3.11+ — for release packaging and repository-contract checks only;
+  the product itself contains no Python implementation
+
+Build and run from source:
+
+```bash
+npm ci --prefix web
+npm -C web run build
+cargo run --locked --features standalone -p cccc --bin cccc -- --port 0
+```
+
+The frontend bundle is embedded into the Rust executable. After web-only
+changes, rebuild the executable (or rerun `npm -C web run build` before a Cargo
+build) to see them in the native binary.
+
+## Project Layout
+
+| Path | Contents |
+| --- | --- |
+| `crates/` | Rust workspace: contracts, core, runtime, client, daemon, web, MCP, CLI (see [docs/reference/architecture.md](docs/reference/architecture.md)) |
+| `web/` | React + TypeScript frontend (embedded into the binary) |
+| `docs/` | VitePress documentation site |
+| `scripts/`, `tests/` | Release packaging and repository-contract checks (Python) |
+
+## Quality Gates
+
+Run the checks selected by your changed files while developing:
+
+```bash
+scripts/quality_gate.sh fast
+```
+
+Inspect the selection without running it:
+
+```bash
+scripts/pre_commit_checks.sh --dry-run
+```
+
+Before handing off a broad change, run:
+
+```bash
+scripts/quality_gate.sh full
+```
+
+Useful individual commands:
+
+```bash
+cargo fmt --all --check
+cargo clippy --workspace --all-targets --locked -- -D warnings
+cargo test --workspace --locked
+npm -C web run check
+npm -C web test
+npm -C web run build
+uvx ruff check scripts tests
+uv run --no-project --with pytest --with pyyaml python -m pytest -q
+```
+
+Notes:
+
+- Combined daemon/Web process-lifecycle tests run with a single test thread to
+  avoid races; CI already does this, and `cargo test --workspace` locally
+  follows the same expectation for those binaries.
+- Local Cargo checks default to two build jobs to limit memory pressure.
+  Override with `CCCC_CARGO_JOBS=4` on larger machines.
+- Changes to account linkage, embedded workbenches, or Group connections must
+  also pass `python3 scripts/check_connect_browser.py`. See
+  [docs/guide/quality-gates.md](docs/guide/quality-gates.md) for its setup.
+- Repository-contract tests in `tests/` validate docs against code (for
+  example, the MCP architecture surface). Editing the MCP tool list, IPC
+  standards, or workflow contracts usually requires updating the matching
+  contract test in the same PR.
+
+## Code Constraints
+
+- `unsafe_code` is forbidden workspace-wide.
+- Clippy denies `unwrap_used`, `todo!`, and `dbg_macro` in product code.
+- File length is a review signal, not a goal in itself. Refactor when cohesion,
+  ownership, testing, or change risk provides concrete evidence.
+
+## Commit Messages
+
+Use [Conventional Commits](https://www.conventionalcommits.org/):
+`fix:`, `feat:`, `docs:`, `test:`, `perf:`, `refactor:`, `chore:`, optionally
+with a scope such as `fix(web):` or `fix(im):`. Commit messages in English or
+Chinese are both accepted — keep the subject line short and specific.
+
+## Pull Request Process
+
+1. Fork the repository and create a topic branch.
+2. Make the change, including tests and documentation updates where relevant.
+3. Run the impacted quality gates (at minimum
+   `scripts/quality_gate.sh fast`).
+4. Open the pull request with a clear description: what changed, why, and how
+   you verified it.
+5. Keep PRs focused — one logical change per PR makes review faster.
+
+CI runs these jobs on every PR:
+
+| Job | Responsibility |
+| --- | --- |
+| `quality` | Ruff plus release-tool, workflow, documentation, and packaging contract tests |
+| `web` | Frontend checks, TypeScript, all web tests, and the production bundle |
+| `package` | Native wheel/archive tooling and wheel layout checks |
+| `rust-linux` | Rust formatting, Clippy, workspace tests, Unix installer contracts |
+| `windows-smoke` | Native Windows process-lifecycle checks |
+| `ci-required` | Aggregate gate; fails when any required job fails or is skipped |
+
+Slower native-distribution checks run nightly and again on release artifacts;
+PRs only need to cover source correctness.
+
+## Documentation
+
+The docs site lives in `docs/` (VitePress). Preview locally:
+
+```bash
+npm ci --prefix docs
+npm run dev --prefix docs
+```
+
+New pages need an entry in `docs/.vitepress/config.ts` to appear in navigation.
+
+## Community
+
+- Telegram: [t.me/ccccpair](https://t.me/ccccpair)
+- Questions and troubleshooting: see [SUPPORT.md](SUPPORT.md)
+
+## License
+
+By contributing, you agree that your contributions are licensed under the
+[Apache-2.0 License](LICENSE).
diff --git a/README.ja.md b/README.ja.md
index d516be5bb..bbae8910f 100644
--- a/README.ja.md
+++ b/README.ja.md
@@ -614,6 +614,8 @@ Telegram コミュニティ: [t.me/ccccpair](https://t.me/ccccpair)
 3. 機能リクエスト：問題、提案する動作、運用への影響を記述
 4. ランタイム状態は `CCCC_HOME` に保持 — リポジトリにコミットしない
 
+開発環境・品質ゲート・PR プロセスの詳細は [CONTRIBUTING.md](CONTRIBUTING.md) を参照してください。
+
 ## License
 
 [Apache-2.0](LICENSE)
diff --git a/README.md b/README.md
index 666cf9724..66820c9e4 100644
--- a/README.md
+++ b/README.md
@@ -622,6 +622,8 @@ Contributions are welcome. Please:
 3. For features: describe the problem, proposed behavior, and operational impact
 4. Keep runtime state in `CCCC_HOME` — never commit it to the repo
 
+See [CONTRIBUTING.md](CONTRIBUTING.md) for development setup, quality gates, and the pull request process.
+
 ## License
 
 [Apache-2.0](LICENSE)
diff --git a/README.zh-CN.md b/README.zh-CN.md
index 218bfa27d..c7ba58f0e 100644
--- a/README.zh-CN.md
+++ b/README.zh-CN.md
@@ -606,6 +606,8 @@ Telegram 社区: [t.me/ccccpair](https://t.me/ccccpair)
 3. 功能建议：描述问题、期望行为和运维影响
 4. 运行时状态放在 `CCCC_HOME` — 不要提交到仓库
 
+开发环境、质量门与 PR 流程见 [CONTRIBUTING.md](CONTRIBUTING.md)。
+
 ## License
 
 [Apache-2.0](LICENSE)