diff --git a/.github/scripts/ciScript.js b/.github/scripts/ciScript.js
new file mode 100644
index 00000000..810a91fb
--- /dev/null
+++ b/.github/scripts/ciScript.js
@@ -0,0 +1,83 @@
+module.exports = async ({ github, context, core }) => {
+  const owner = context.repo.owner;
+  const repo = context.repo.repo;
+  const pr = context.payload.pull_request;
+  const prNumber = pr.number;
+  const prState = pr.state;
+
+  const backendFiles = [];
+  const mobileFiles = [];
+  const webFiles = [];
+
+  try {
+    if (prState === 'closed') {
+      console.log(`PR state is: ${prState}`);
+      return {
+        backendChanged: false,
+        mobileChanged: false,
+        webChanged: false
+      };
+    }
+
+    const changedFiles = await github.paginate(
+      github.rest.pulls.listFiles,
+      {
+        owner,
+        repo,
+        pull_number: prNumber
+      }
+    );
+
+    changedFiles.forEach((file) => {
+      const fileName = file.filename;
+
+      if (fileName.startsWith('apps/backend/')) {
+        backendFiles.push(fileName);
+      } else if (fileName.startsWith('apps/mobile/')) {
+        mobileFiles.push(fileName);
+      } else if (fileName.startsWith('apps/web/')) {
+        webFiles.push(fileName);
+      }
+    });
+
+  console.log({
+    backendFiles,
+    mobileFiles,
+    webFiles
+  });
+
+  core.setOutput(
+    "backendFiles",
+    backendFiles
+      .map(file => file.replace("apps/backend/", ""))
+      .join(" ")
+  )
+
+  core.setOutput(
+    "mobileFiles",
+    mobileFiles
+      .map(file => file.replace("apps/mobile/", ""))
+      .join(" ")
+  )
+
+  core.setOutput(
+    "webFiles",
+    webFiles
+      .map(file => file.replace("apps/web/", ""))
+      .join(" ")
+  )
+
+  core.setOutput("backendChanged", backendFiles.length > 0)
+  core.setOutput("mobileChanged", mobileFiles.length > 0)
+  core.setOutput("webChanged", webFiles.length > 0)
+
+  } catch (error) {
+    console.error(error);
+
+    return {
+      backendChanged: false,
+      mobileChanged: false,
+      webChanged: false
+    };
+  }
+};
\ No newline at end of file
diff --git a/.github/scripts/commentResults.js b/.github/scripts/commentResults.js
new file mode 100644
index 00000000..50cd1395
--- /dev/null
+++ b/.github/scripts/commentResults.js
@@ -0,0 +1,101 @@
+module.exports = async ({
+  github,
+  context,
+  backend,
+  mobile,
+  web,
+  backendLint,
+  backendTest,
+  backendTypecheck,
+  mobileLint,
+  mobileTest,
+  webCheck,
+  webBuild
+}) => {
+  const owner = context.repo.owner;
+  const repo = context.repo.repo;
+  const prNumber = context.payload.pull_request.number;
+
+  const emoji = (status) => {
+    if (status === 'success') return '✅';
+    if (status === 'failure') return '❌';
+    if (status === 'skipped') return '⏭️';
+    return '⚪';
+  };
+
+  const label = (status) => {
+    if (!status) return '⚪ unknown';
+    return `${emoji(status)} ${status}`;
+  };
+
+  const anyFailure = [
+    backend,
+    mobile,
+    web
+  ].includes('failure');
+
+  const title = anyFailure
+    ? '❌ Some checks failed'
+    : '✅ CI completed';
+
+  const timestamp = new Date().toUTCString();
+
+  const body = `## CI Results — ${title}
+
+### 🖥️ Backend (${label(backend)})
+| Check | Status |
+|---|---|
+| Lint | ${label(backendLint)} |
+| Test | ${label(backendTest)} |
+| Typecheck | ${label(backendTypecheck)} |
+
+### 📱 Mobile (${label(mobile)})
+| Check | Status |
+|---|---|
+| Lint | ${label(mobileLint)} |
+| Test | ${label(mobileTest)} |
+
+### 🌐 Web (${label(web)})
+| Check | Status |
+|---|---|
+| Check | ${label(webCheck)} |
+| Build | ${label(webBuild)} |
+
+---
+🕐 Last updated: \`${timestamp}\``;
+
+  const COMMENT_MARKER = '## CI Results —';
+
+  try {
+    const comments = await github.paginate(
+      github.rest.issues.listComments,
+      {
+        owner,
+        repo,
+        issue_number: prNumber
+      }
+    );
+
+    const existing = comments.find(
+      c => c.body && c.body.startsWith(COMMENT_MARKER)
+    );
+
+    if (existing) {
+      await github.rest.issues.updateComment({
+        owner,
+        repo,
+        comment_id: existing.id,
+        body
+      });
+    } else {
+      await github.rest.issues.createComment({
+        owner,
+        repo,
+        issue_number: prNumber,
+        body
+      });
+    }
+  } catch (err) {
+    console.error(err);
+  }
+};
\ No newline at end of file
diff --git a/.github/workflows/ci.yml b/.github/workflows/ci.yml
new file mode 100644
index 00000000..25f71019
--- /dev/null
+++ b/.github/workflows/ci.yml
@@ -0,0 +1,134 @@
+name: CI
+
+on:
+  pull_request_target:
+    types: [opened, synchronize, reopened]
+
+permissions:
+  pull-requests: write
+
+jobs:
+  detect-changes:
+    runs-on: ubuntu-latest
+
+    outputs:
+      backendChanged: ${{ steps.detect.outputs.backendChanged }}
+      mobileChanged: ${{ steps.detect.outputs.mobileChanged }}
+      webChanged: ${{ steps.detect.outputs.webChanged }}
+      backendFiles: ${{ steps.detect.outputs.backendFiles }}
+      mobileFiles: ${{ steps.detect.outputs.mobileFiles }}
+      webFiles: ${{ steps.detect.outputs.webFiles }}
+
+    steps:
+      - uses: actions/checkout@de0fac2e4500dabe0009e67214ff5f5447ce83dd
+
+      - name: Detect changed files
+        id: detect
+        uses: actions/github-script@3a2844b7e9c422d3c10d287c895573f7108da1b3
+        with:
+          github-token: ${{ secrets.GITHUB_TOKEN }}
+          script: |
+            const script = require('./.github/scripts/ciScript.js');
+            return await script({ github, context, core });
+
+  backend-ci:
+    needs: detect-changes
+    if: needs.detect-changes.outputs.backendChanged == 'true'
+    runs-on: ubuntu-latest
+
+    steps:
+      - uses: actions/checkout@de0fac2e4500dabe0009e67214ff5f5447ce83dd
+
+      - uses: actions/setup-node@48b55a011bda9f5d6aeb4c2d9c7362e8dae4041e
+        with:
+          node-version: 22
+
+      - uses: pnpm/action-setup@v6.0.8
+
+      - run: pnpm install
+
+      - name: Backend lint
+        id: backend_lint
+        run: cd apps/backend && pnpm eslint ${{ needs.detect-changes.outputs.backendFiles }}
+
+      - name: Backend test
+        id: backend_test
+        run: cd apps/backend && pnpm test ${{ needs.detect-changes.outputs.backendFiles }}
+
+      - name: Backend typecheck
+        id: backend_typecheck
+        run: cd apps/backend && pnpm typecheck ${{ needs.detect-changes.outputs.backendFiles }}
+
+  web-ci:
+    needs: detect-changes
+    if: needs.detect-changes.outputs.webChanged == 'true'
+    runs-on: ubuntu-latest
+
+    steps:
+      - uses: actions/checkout@de0fac2e4500dabe0009e67214ff5f5447ce83dd
+
+      - uses: actions/setup-node@48b55a011bda9f5d6aeb4c2d9c7362e8dae4041e
+        with:
+          node-version: 22
+
+      - uses: pnpm/action-setup@v6.0.8
+
+      - run: pnpm install
+
+      - name: Web check
+        id: web_check
+        run: cd apps/web && pnpm check
+
+      - name: Web build
+        id: web_build
+        run: cd apps/web && pnpm build
+
+  mobile-ci:
+    needs: detect-changes
+    if: needs.detect-changes.outputs.mobileChanged == 'true'
+    runs-on: ubuntu-latest
+
+    steps:
+      - uses: actions/checkout@de0fac2e4500dabe0009e67214ff5f5447ce83dd
+
+      - uses: actions/setup-node@48b55a011bda9f5d6aeb4c2d9c7362e8dae4041e
+        with:
+          node-version: 22
+
+      - uses: pnpm/action-setup@v6.0.8
+
+      - run: pnpm install
+
+      - name: Mobile lint
+        id: mobile_lint
+        run: cd apps/mobile && pnpm eslint ${{ needs.detect-changes.outputs.mobileFiles }}
+
+      - name: Mobile test
+        id: mobile_test
+        run: cd apps/mobile && pnpm test
+
+  comment-results:
+    needs:
+      - backend-ci
+      - web-ci
+      - mobile-ci
+    if: always()
+    runs-on: ubuntu-latest
+
+    steps:
+      - uses: actions/checkout@de0fac2e4500dabe0009e67214ff5f5447ce83dd
+
+      - name: Comment results
+        uses: actions/github-script@3a2844b7e9c422d3c10d287c895573f7108da1b3
+        with:
+          github-token: ${{ secrets.GITHUB_TOKEN }}
+          script: |
+            const script = require('./.github/scripts/commentResults.js');
+
+            await script({
+              github,
+              context,
+              backend: '${{ needs.backend-ci.result }}',
+              web: '${{ needs.web-ci.result }}',
+              mobile: '${{ needs.mobile-ci.result }}'
+            });
\ No newline at end of file
diff --git a/apps/backend/package.json b/apps/backend/package.json
index 5406427f..8bc19bf8 100644
--- a/apps/backend/package.json
+++ b/apps/backend/package.json
@@ -14,7 +14,8 @@
     "db:migrate": "prisma migrate dev",
     "db:deploy": "prisma migrate deploy",
     "db:seed": "tsx prisma/seed.ts",
-    "db:studio": "prisma studio"
+    "db:studio": "prisma studio",
+    "typecheck": "tsc --noEmit"
   },
   "dependencies": {
     "@devcard/shared": "workspace:*",