docs(contributing): add Conventional Commits and Branches section

docs/extras/contributing_code.md

@@ -6,6 +6,7 @@ Here are the core requirements for any PR submitted to LiteLLM:
 
 - [ ] Sign the [Contributor License Agreement (CLA)](#contributor-license-agreement-cla)
 - [ ] Keep scope as isolated as possible — your changes should address **one specific problem** at a time
+- [ ] Follow the [Commit and Branch Conventions](#commit-and-branch-conventions) — PR titles are gated by CI
 
 ### Proxy (Backend) PRs
 
@@ -28,6 +29,86 @@ Before contributing code to LiteLLM, you must sign our [Contributor License Agre
 
 ---
 
+## Commit and Branch Conventions
+
+LiteLLM enforces two community specs:
+
+- **Commits** follow [Conventional Commits 1.0.0](https://www.conventionalcommits.org/en/v1.0.0/) — `<type>(<scope>)!: <description>`
+- **Branches** follow [Conventional Branches](https://conventional-branch.github.io/) — `<type>/<description>`
+
+Enforcement happens in two places: opt-in local git hooks in `.githooks/`, and a required CI check on the PR title (since squash-merge uses the PR title as the commit subject).
+
+### Commit message format
+
+```
+<type>(<optional scope>)!: <description>
+
+<optional body>
+
+<optional footer>
+```
+
+- `<type>` is one of: `feat`, `fix`, `docs`, `style`, `refactor`, `perf`, `test`, `build`, `ci`, `chore`, `revert`.
+- `<scope>` is optional and lowercase.
+- `!` before `:` marks a breaking change.
+- `<description>` is required and **must start with a lowercase letter** (digits and symbols are also fine; only `A–Z` is rejected).
+
+Examples:
+
+```
+feat(router): add weighted round-robin strategy
+fix(bedrock): decouple STS region from aws_region_name
+chore(deps): bump black to 26.3.1
+refactor!: drop Python 3.8 support
+```
+
+PR titles must follow the same format — squash-merge uses the PR title as the commit subject and the **Conventional PR Title** workflow validates it.
+
+### Branch naming
+
+Format: `<type>/<short-description>` where `<type>` is one of `feature`, `bugfix`, `hotfix`, `release`, `chore`.
+
+```
+feature/weighted-round-robin
+bugfix/streaming-empty-chunks
+chore/bump-black
+hotfix/auth-bypass
+release/v1.45.0
+```
+
+Branches always allowed (the `pre-push` hook bypasses them):
+
+- `main`
+- `litellm_internal_staging`
+- `dependabot/*`
+- `gh-readonly-queue/*`
+
+Tag pushes and branch deletions are also skipped.
+
+### Installing the hooks
+
+The hooks live in `.githooks/` and are opt-in. Run once per clone:
+
+```shell
+make install-hooks
+```
+
+This sets `core.hooksPath=.githooks` for the local repository. After that:
+
+- `git commit` runs `commit-msg`, which validates the subject line.
+- `git push` runs `pre-push`, which validates branch names.
+
+In a rare emergency you can bypass either hook per command:
+
+```shell
+git commit --no-verify -m "..."
+git push   --no-verify
+```
+
+To uninstall: `git config --unset core.hooksPath`.
+
+---
+
 ## Proxy (Backend)
 
 ### 1. Setting up your local dev environment