ci: add conventional commit PR title linting (#23096)

Restore PR title validation that was removed in 828f33a when
cdr-bot was expected to handle it. That bot has since been disabled.

The new title job in contrib.yaml validates:
- Conventional commit format (type(scope): description)
- Type from the same set used by release notes generation
- Scope validity derived from the changed files in the PR diff
- All changed files fall under the declared scope

Uses actions/github-script (no third-party marketplace actions).

Also fixes feat(api) examples across docs (no api folder exists)
and consolidates commit rules into CONTRIBUTING.md as the single
source of truth.

.claude/docs/ARCHITECTURE.md

@@ -113,7 +113,7 @@ Coder emphasizes clear error handling, with specific patterns required:
 
 All tests should run in parallel using `t.Parallel()` to ensure efficient testing and expose potential race conditions. The codebase is rigorously linted with golangci-lint to maintain consistent code quality.
 
-Git contributions follow a standard format with commit messages structured as `type: <message>`, where type is one of `feat`, `fix`, or `chore`.
+Git contributions follow [Conventional Commits](https://www.conventionalcommits.org/en/v1.0.0/). See [CONTRIBUTING.md](docs/about/contributing/CONTRIBUTING.md#commit-messages) for full rules. PR titles are linted in CI.
 
 ## Development Workflow
 

.claude/docs/PR_STYLE_GUIDE.md

@@ -4,22 +4,13 @@ This guide documents the PR description style used in the Coder repository, base
 
 ## PR Title Format
 
-Follow [Conventional Commits 1.0.0](https://www.conventionalcommits.org/en/v1.0.0/) format:
+Format: `type(scope): description`. See [CONTRIBUTING.md](docs/about/contributing/CONTRIBUTING.md#commit-messages) for full rules. PR titles are linted in CI.
 
-```text
-type(scope): brief description
-```
+- Types: `feat`, `fix`, `docs`, `style`, `refactor`, `perf`, `test`, `build`, `ci`, `chore`, `revert`
+- Scopes must be a real path (directory or file stem) containing all changed files
+- Omit scope if changes span multiple top-level directories
 
-**Common types:**
-
-- `feat`: New features
-- `fix`: Bug fixes
-- `refactor`: Code refactoring without behavior change
-- `perf`: Performance improvements
-- `docs`: Documentation changes
-- `chore`: Dependency updates, tooling changes
-
-**Examples:**
+Examples:
 
 - `feat: add tracing to aibridge`
 - `fix: move contexts to appropriate locations`

.claude/docs/WORKFLOWS.md

@@ -136,9 +136,11 @@ Then make your changes and push normally. Don't use `git push --force` unless th
 
 ## Commit Style
 
-- Follow [Conventional Commits 1.0.0](https://www.conventionalcommits.org/en/v1.0.0/)
-- Format: `type(scope): message`
-- Types: `feat`, `fix`, `docs`, `style`, `refactor`, `test`, `chore`
+Format: `type(scope): message`. See [CONTRIBUTING.md](docs/about/contributing/CONTRIBUTING.md#commit-messages) for full rules. PR titles are linted in CI.
+
+- Types: `feat`, `fix`, `docs`, `style`, `refactor`, `perf`, `test`, `build`, `ci`, `chore`, `revert`
+- Scopes must be a real path (directory or file stem) containing all changed files
+- Omit scope if changes span multiple top-level directories
 - Keep message titles concise (~70 characters)
 - Use imperative, present tense in commit titles
 

.github/workflows/contrib.yaml

@@ -45,6 +45,109 @@ jobs:
           # Some users have signed a corporate CLA with Coder so are exempt from signing our community one.
           allowlist: "coryb,aaronlehmann,dependabot*,blink-so*,blinkagent*"
 
+  title:
+    runs-on: ubuntu-latest
+    if: ${{ github.event_name == 'pull_request_target' }}
+    steps:
+      - name: Validate PR title
+        uses: actions/github-script@ed597411d8f924073f98dfc5c65a23a2325f34cd # v8.0.0
+        with:
+          script: |
+            const { pull_request } = context.payload;
+            const title = pull_request.title;
+            const repo = { owner: context.repo.owner, repo: context.repo.repo };
+
+            const allowedTypes = [
+              "feat", "fix", "docs", "style", "refactor",
+              "perf", "test", "build", "ci", "chore", "revert",
+            ];
+            const expectedFormat = `"type(scope): description" or "type: description"`;
+            const guidelinesLink = `See: https://github.com/coder/coder/blob/main/docs/about/contributing/CONTRIBUTING.md#commit-messages`;
+            const scopeHint = (type) =>
+              `Use a broader scope or no scope (e.g., "${type}: ...") for cross-cutting changes.\n` +
+              guidelinesLink;
+
+            console.log("Title: %s", title);
+
+            // Parse conventional commit format: type(scope)!: description
+            const match = title.match(/^(\w+)(\(([^)]*)\))?(!)?\s*:\s*.+/);
+            if (!match) {
+              core.setFailed(
+                `PR title does not match conventional commit format.\n` +
+                `Expected: ${expectedFormat}\n` +
+                `Allowed types: ${allowedTypes.join(", ")}\n` +
+                guidelinesLink
+              );
+              return;
+            }
+
+            const type = match[1];
+            const scope = match[3]; // undefined if no parentheses
+
+            // Validate type.
+            if (!allowedTypes.includes(type)) {
+              core.setFailed(
+                `PR title has invalid type "${type}".\n` +
+                `Expected: ${expectedFormat}\n` +
+                `Allowed types: ${allowedTypes.join(", ")}\n` +
+                guidelinesLink
+              );
+              return;
+            }
+
+            // If no scope, we're done.
+            if (!scope) {
+              console.log("No scope provided, title is valid.");
+              return;
+            }
+
+            console.log("Scope: %s", scope);
+
+            // Fetch changed files.
+            const files = await github.paginate(github.rest.pulls.listFiles, {
+              ...repo,
+              pull_number: pull_request.number,
+              per_page: 100,
+            });
+            const changedPaths = files.map(f => f.filename);
+            console.log("Changed files: %d", changedPaths.length);
+
+            // Derive scope type from the changed files. The diff is the
+            // source of truth: if files exist under the scope, the path
+            // exists on the PR branch. No need for Contents API calls.
+            const isDir = changedPaths.some(f => f.startsWith(scope + "/"));
+            const isFile = changedPaths.some(f => f === scope);
+            const isStem = changedPaths.some(f => f.startsWith(scope + "."));
+
+            if (!isDir && !isFile && !isStem) {
+              core.setFailed(
+                `PR title scope "${scope}" does not match any files changed in this PR.\n` +
+                `Scopes must reference a path (directory or file stem) that contains changed files.\n` +
+                scopeHint(type)
+              );
+              return;
+            }
+
+            // Verify all changed files fall under the scope.
+            const outsideFiles = changedPaths.filter(f => {
+              if (isDir && f.startsWith(scope + "/")) return false;
+              if (f === scope) return false;
+              if (isStem && f.startsWith(scope + ".")) return false;
+              return true;
+            });
+
+            if (outsideFiles.length > 0) {
+              const listed = outsideFiles.map(f => "  - " + f).join("\n");
+              core.setFailed(
+                `PR title scope "${scope}" does not contain all changed files.\n` +
+                `Files outside scope:\n${listed}\n\n` +
+                scopeHint(type)
+              );
+              return;
+            }
+
+            console.log("PR title is valid.");
+
   release-labels:
     runs-on: ubuntu-latest
     permissions:

docs/about/contributing/CONTRIBUTING.md

@@ -247,8 +247,13 @@ characters long (no more than 72).
 
 Examples:
 
-- Good: `feat(api): add feature X`
-- Bad: `feat(api): added feature X` (past tense)
+- Good: `feat(coderd): add feature X`
+- Bad: `feat(coderd): added feature X` (past tense)
+
+Scopes must reference a real path in the repository (a directory or file stem)
+and must contain all changed files. For example, use `coderd/database` if all
+changes are within that directory. If changes span multiple top-level
+directories, omit the scope.
 
 A good rule of thumb for writing good commit messages is to recite:
 [If applied, this commit will ...](https://reflectoring.io/meaningful-commit-messages/).
@@ -263,7 +268,7 @@ to use the original commit title instead of the PR title.
 Breaking changes can be triggered in two ways:
 
 - Add `!` to the commit message title, e.g.
-  `feat(api)!: remove deprecated endpoint /test`
+  `feat(coderd)!: remove deprecated endpoint /test`
 - Add the
   [`release/breaking`](https://github.com/coder/coder/issues?q=sort%3Aupdated-desc+label%3Arelease%2Fbreaking)
   label to a PR that has, or will be, merged into `main`.

scripts/release.sh

@@ -19,7 +19,7 @@ new patch version will be created.
 
 To mark a release as containing breaking changes, the commit title should
 either contain a known prefix with an exclamation mark ("feat!:",
-"feat(api)!:") or the PR that was merged can be tagged with the
+"feat(coderd)!:") or the PR that was merged can be tagged with the
 "release/breaking" label.
 
 GitHub labels that affect release notes: