diff --git a/.github/workflows/lint-commit.yml b/.github/workflows/lint-commit.yml
new file mode 100644
index 00000000000..210a08a771e
--- /dev/null
+++ b/.github/workflows/lint-commit.yml
@@ -0,0 +1,28 @@
+on:
+  push:
+    branches: [main]
+  pull_request:
+    # By default, CI will trigger on opened/synchronize/reopened event types.
+    # https://docs.github.com/en/actions/writing-workflows/choosing-when-your-workflow-runs/events-that-trigger-workflows#pull_request
+    # Note: To re-run `lint-commits` after fixing the PR title, close-and-reopen the PR.
+    branches: [main, feature/*]
+
+# Cancel old jobs when a pull request is updated.
+concurrency:
+  group: ${{ github.head_ref || github.run_id }}
+  cancel-in-progress: true
+
+jobs:
+  lint-commits:
+    # Note: To re-run `lint-commits` after fixing the PR title, close-and-reopen the PR.
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v4
+        with:
+          fetch-depth: 1
+      - uses: actions/setup-node@v4
+        with:
+          node-version: '20'
+      - name: Check PR title
+        run: |
+          node "$GITHUB_WORKSPACE/.github/workflows/lintcommit.js"
diff --git a/.github/workflows/lintcommit.js b/.github/workflows/lintcommit.js
new file mode 100644
index 00000000000..299657f0a1c
--- /dev/null
+++ b/.github/workflows/lintcommit.js
@@ -0,0 +1,213 @@
+// Copyright 2025 Amazon.com, Inc. or its affiliates. All Rights Reserved.
+// SPDX-License-Identifier: Apache-2.0
+
+// Checks that a PR title conforms to our custom flavor of "conventional commits"
+// (https://www.conventionalcommits.org/).
+//
+// To run self-tests, simply run this script:
+//
+//     node lintcommit.js test
+//
+// TODO: "PR must describe Problem in a concise way, and Solution".
+// TODO: this script intentionally avoids github APIs so that it is locally-debuggable, but if those
+// are needed, use actions/github-script as described in: https://github.com/actions/github-script?tab=readme-ov-file#run-a-separate-file
+//
+
+const fs = require('fs')
+// This script intentionally avoids github APIs so that:
+//   1. it is locally-debuggable
+//   2. the CI job is fast ("npm install" is slow)
+// But if we still want to use github API, we can keep it fast by using `actions/github-script` as
+// described in: https://github.com/actions/github-script?tab=readme-ov-file#run-a-separate-file
+//
+// const core = require('@actions/core')
+// const github = require('@actions/github')
+
+const types = new Set([
+    'build',
+    // Don't allow "chore" because it's over-used.
+    // Instead, add a new type if absolutely needed (if the existing ones can't possibly apply).
+    // 'chore',
+    'ci',
+    'config',
+    'deps',
+    'docs',
+    'feat',
+    'fix',
+    'perf',
+    'refactor',
+    'revert',
+    'style',
+    'telemetry',
+    'test',
+    'types',
+])
+
+// TODO: Validate against this once we are satisfied with this list.
+const scopes = new Set([
+    'amazonq',
+    'core',
+    'explorer',
+    'lambda',
+    'logs',
+    'redshift',
+    'q-chat',
+    'q-featuredev',
+    'q-inlinechat',
+    'q-transform',
+    'sam',
+    's3',
+    'telemetry',
+    'toolkit',
+    'ui',
+])
+void scopes
+
+/**
+ * Checks that a pull request title, or commit message subject, follows the expected format:
+ *
+ *      type(scope): message
+ *
+ * Returns undefined if `title` is valid, else an error message.
+ */
+function validateTitle(title) {
+    const parts = title.split(':')
+    const subject = parts.slice(1).join(':').trim()
+
+    if (title.startsWith('Merge')) {
+        return undefined
+    }
+
+    if (parts.length < 2) {
+        return 'missing colon (:) char'
+    }
+
+    const typeScope = parts[0]
+
+    const [type, scope] = typeScope.split(/\(([^)]+)\)$/)
+
+    if (/\s+/.test(type)) {
+        return `type contains whitespace: "${type}"`
+    } else if (type === 'chore') {
+        return 'Do not use "chore" as a type. If the existing valid types are insufficent, add a new type to the `lintcommit.js` script.'
+    } else if (!types.has(type)) {
+        return `invalid type "${type}"`
+    } else if (!scope && typeScope.includes('(')) {
+        return `must be formatted like type(scope):`
+    } else if (!scope && ['feat', 'fix'].includes(type)) {
+        return `"${type}" type must include a scope (example: "${type}(amazonq)")`
+    } else if (scope && scope.length > 30) {
+        return 'invalid scope (must be <=30 chars)'
+    } else if (scope && /[^- a-z0-9]+/.test(scope)) {
+        return `invalid scope (must be lowercase, ascii only): "${scope}"`
+    } else if (subject.length === 0) {
+        return 'empty subject'
+    } else if (subject.length > 100) {
+        return 'invalid subject (must be <=100 chars)'
+    }
+
+    return undefined
+}
+
+function run() {
+    const eventData = JSON.parse(fs.readFileSync(process.env.GITHUB_EVENT_PATH, 'utf8'))
+    const pullRequest = eventData.pull_request
+
+    // console.log(eventData)
+
+    if (!pullRequest) {
+        console.info('No pull request found in the context')
+        return
+    }
+
+    const title = pullRequest.title
+
+    const failReason = validateTitle(title)
+    const msg = failReason
+        ? `
+Invalid pull request title: \`${title}\`
+
+* Problem: ${failReason}
+* Expected format: \`type(scope): subject...\`
+    * type: one of (${Array.from(types).join(', ')})
+    * scope: lowercase, <30 chars
+    * subject: must be <100 chars
+    * documentation: https://github.com/aws/aws-toolkit-vscode/blob/master/CONTRIBUTING.md#pull-request-title
+* Hint: *close and re-open the PR* to re-trigger CI (after fixing the PR title).
+`
+        : `Pull request title matches the [expected format](https://github.com/aws/aws-toolkit-vscode/blob/master/CONTRIBUTING.md#pull-request-title).`
+
+    if (process.env.GITHUB_STEP_SUMMARY) {
+        fs.appendFileSync(process.env.GITHUB_STEP_SUMMARY, msg)
+    }
+
+    if (failReason) {
+        console.error(msg)
+        process.exit(1)
+    } else {
+        console.info(msg)
+    }
+}
+
+function _test() {
+    const tests = {
+        ' foo(scope): bar': 'type contains whitespace: " foo"',
+        'build: update build process': undefined,
+        'chore: update dependencies':
+            'Do not use "chore" as a type. If the existing valid types are insufficent, add a new type to the `lintcommit.js` script.',
+        'ci: configure CI/CD': undefined,
+        'config: update configuration files': undefined,
+        'deps: bump the aws-sdk group across 1 directory with 5 updates': undefined,
+        'docs: update documentation': undefined,
+        'feat(foo): add new feature': undefined,
+        'feat(foo):': 'empty subject',
+        'feat foo):': 'type contains whitespace: "feat foo)"',
+        'feat(foo)): sujet': 'invalid type "feat(foo))"',
+        'feat(foo: sujet': 'invalid type "feat(foo"',
+        'feat(Q Foo Bar): bar': 'invalid scope (must be lowercase, ascii only): "Q Foo Bar"',
+        'feat(scope):': 'empty subject',
+        'feat(q foo bar): bar': undefined,
+        'feat(foo): x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x ':
+            'invalid subject (must be <=100 chars)',
+        'feat: foo': '"feat" type must include a scope (example: "feat(amazonq)")',
+        'fix: foo': '"fix" type must include a scope (example: "fix(amazonq)")',
+        'fix(a-b-c): resolve issue': undefined,
+        'foo (scope): bar': 'type contains whitespace: "foo "',
+        'invalid title': 'missing colon (:) char',
+        'perf: optimize performance': undefined,
+        'refactor: improve code structure': undefined,
+        'revert: feat: add new feature': undefined,
+        'style: format code': undefined,
+        'test: add new tests': undefined,
+        'types: add type definitions': undefined,
+        'Merge staging into feature/lambda-get-started': undefined,
+    }
+
+    let passed = 0
+    let failed = 0
+
+    for (const [title, expected] of Object.entries(tests)) {
+        const result = validateTitle(title)
+        if (result === expected) {
+            console.log(`✅ Test passed for "${title}"`)
+            passed++
+        } else {
+            console.log(`❌ Test failed for "${title}" (expected "${expected}", got "${result}")`)
+            failed++
+        }
+    }
+
+    console.log(`\n${passed} tests passed, ${failed} tests failed`)
+}
+
+function main() {
+    const mode = process.argv[2]
+
+    if (mode === 'test') {
+        _test()
+    } else {
+        run()
+    }
+}
+
+main()