diff --git a/Dockerfile b/Dockerfile
index bfe392d..b63bbb3 100644
--- a/Dockerfile
+++ b/Dockerfile
@@ -51,4 +51,4 @@ HEALTHCHECK --interval=30s --timeout=5s --start-period=20s --retries=3 \
   CMD node -e "require('http').get('http://127.0.0.1:'+(process.env.PORT||3000)+'/api/health',r=>process.exit(r.statusCode===200?0:1)).on('error',()=>process.exit(1))"
 
 ENTRYPOINT ["docker-entrypoint.sh"]
-CMD ["node", "server.js"]
+CMD ["node", "server.cts"]
diff --git a/package.json b/package.json
index e0712c8..5540ef4 100644
--- a/package.json
+++ b/package.json
@@ -2,16 +2,16 @@
   "name": "bill-tracker",
   "version": "0.40.0",
   "description": "Monthly bill tracking system",
-  "main": "server.js",
+  "main": "server.cts",
   "engines": {
     "node": ">=22.18.0"
   },
   "scripts": {
-    "dev:api": "node --watch server.js",
+    "dev:api": "node --watch server.cts",
     "dev:ui": "vite",
     "dev": "concurrently \"npm run dev:api\" \"npm run dev:ui\"",
     "build": "vite build",
-    "check:server": "find server.js db middleware routes services utils workers \\( -name '*.js' -o -name '*.mts' -o -name '*.cts' -o -name '*.ts' \\) -print0 | xargs -0 -n1 node --check",
+    "check:server": "find server.cts db middleware routes services utils workers \\( -name '*.js' -o -name '*.mts' -o -name '*.cts' -o -name '*.ts' \\) -print0 | xargs -0 -n1 node --check",
     "typecheck:server": "tsc --noEmit -p tsconfig.server.json",
     "lint": "eslint client",
     "typecheck": "tsc --noEmit -p tsconfig.json",
@@ -25,7 +25,7 @@
     "test:e2e:probe": "node e2e/setup/prepare-db.js && playwright test --project=probe",
     "smoke:prod": "bash scripts/prod-smoke.sh",
     "ci": "npm run lint && npm run typecheck && npm run typecheck:server && npm run check:server && npm run test:all && npm run build",
-    "start": "node server.js"
+    "start": "node server.cts"
   },
   "dependencies": {
     "@radix-ui/react-alert-dialog": "^1.1.2",
diff --git a/routes/user.cts b/routes/user.cts
index 90a1bd2..7ab9406 100644
--- a/routes/user.cts
+++ b/routes/user.cts
@@ -5,7 +5,7 @@ import type { Req, Res, Next } from '../types/http';
 const express = require('express');
 const router  = express.Router();
 const { getDb } = require('../db/database.cts');
-const { seedDemoData } = require('../scripts/seedDemoData');
+const { seedDemoData } = require('../scripts/seedDemoData.cts');
 const { demoDataLimiter } = require('../middleware/rateLimiter.cts');
 const { eraseUserData } = require('../services/userDataService.cts');
 const { standardizeError } = require('../middleware/errorFormatter.cts');
diff --git a/scripts/ecosystem.config.js b/scripts/ecosystem.config.js
index 11b67f1..ad4d80b 100644
--- a/scripts/ecosystem.config.js
+++ b/scripts/ecosystem.config.js
@@ -7,7 +7,7 @@ module.exports = {
   apps: [
     {
       name:        'bill-tracker',
-      script:      'server.js',
+      script:      'server.cts',
       cwd:         '/opt/bill-tracker',
       instances:   1,
       exec_mode:   'fork',
diff --git a/scripts/migrate-db.js b/scripts/migrate-db.js
index b311c68..31c21b1 100644
--- a/scripts/migrate-db.js
+++ b/scripts/migrate-db.js
@@ -1,7 +1,7 @@
 #!/usr/bin/env node
 'use strict';
 
-const { closeDb, getDb, getDbPath } = require('../db/database');
+const { closeDb, getDb, getDbPath } = require('../db/database.cts');
 
 try {
   getDb();
diff --git a/scripts/seedDemoData.js b/scripts/seedDemoData.cts
similarity index 99%
rename from scripts/seedDemoData.js
rename to scripts/seedDemoData.cts
index a8ce837..3fc1e91 100644
--- a/scripts/seedDemoData.js
+++ b/scripts/seedDemoData.cts
@@ -11,7 +11,7 @@ const path = require('path');
 const DB_PATH = process.env.DB_PATH || path.join(__dirname, '..', 'db', 'bills.db');
 
 // Import database helper
-const { getDb, ensureUserDefaultCategories } = require('../db/database');
+const { getDb, ensureUserDefaultCategories } = require('../db/database.cts');
 // Money columns (expected_amount, current_balance, minimum_payment) are stored as
 // integer cents since migration v1.03 — convert the demo dollars before insert.
 const { toCents } = require('../utils/money.mts');
diff --git a/scripts/test-cookie-options.js b/scripts/test-cookie-options.js
index 0611be0..9ba42f8 100644
--- a/scripts/test-cookie-options.js
+++ b/scripts/test-cookie-options.js
@@ -2,7 +2,7 @@
 'use strict';
 
 const assert = require('assert');
-const { cookieOpts } = require('../services/authService');
+const { cookieOpts } = require('../services/authService.cts');
 
 function withEnv(values, fn) {
   const saved = {};
diff --git a/scripts/test-import.js b/scripts/test-import.js
index 43bd865..9f42bb1 100644
--- a/scripts/test-import.js
+++ b/scripts/test-import.js
@@ -18,7 +18,7 @@ const {
   resolveYearMonth,
   findBillMatches: serviceFindBillMatches,
   buildRecommendation: serviceBuildRecommendation,
-} = require('../services/spreadsheetImportService');
+} = require('../services/spreadsheetImportService.cts');
 
 // ─── Re-implement helpers for row-level tests (avoids DB init) ────────────────
 
@@ -517,8 +517,8 @@ function runApplyRegression(name, body) {
 const APPLY_SETUP = `
 const assert = require('assert');
 const xlsx = require('xlsx');
-const { getDb, ensureUserDefaultCategories } = require('./db/database');
-const { previewSpreadsheet, applyImportDecisions } = require('./services/spreadsheetImportService');
+const { getDb, ensureUserDefaultCategories } = require('./db/database.cts');
+const { previewSpreadsheet, applyImportDecisions } = require('./services/spreadsheetImportService.cts');
 async function setup() {
   const db = getDb();
   db.prepare('INSERT INTO users (username,password_hash) VALUES (?,?)').run('importer','x');
@@ -615,8 +615,8 @@ ${APPLY_SETUP}
 runApplyRegression('create_new_bill imports related paid months for same detected bill', `
 const assert = require('assert');
 const xlsx = require('xlsx');
-const { getDb } = require('./db/database');
-const { previewSpreadsheet, applyImportDecisions } = require('./services/spreadsheetImportService');
+const { getDb } = require('./db/database.cts');
+const { previewSpreadsheet, applyImportDecisions } = require('./services/spreadsheetImportService.cts');
 (async () => {
   const db = getDb();
   db.prepare('INSERT INTO users (username,password_hash) VALUES (?,?)').run('importer','x');
@@ -857,8 +857,8 @@ const assert = require('assert');
 const fs = require('fs');
 const path = require('path');
 const Database = require('better-sqlite3');
-const { getDb, ensureUserDefaultCategories } = require('./db/database');
-const { previewUserDbImport, applyUserDbImport } = require('./services/userDbImportService');
+const { getDb, ensureUserDefaultCategories } = require('./db/database.cts');
+const { previewUserDbImport, applyUserDbImport } = require('./services/userDbImportService.cts');
 
 function createExportBuffer(nameSuffix = '') {
   const file = path.join('/tmp', 'bill-tracker-user-export-test-' + process.pid + '-' + Date.now() + nameSuffix + '.sqlite');
diff --git a/scripts/test-oidc-smoke.js b/scripts/test-oidc-smoke.js
index cf88d57..4ca66da 100644
--- a/scripts/test-oidc-smoke.js
+++ b/scripts/test-oidc-smoke.js
@@ -48,8 +48,8 @@ const path = require('path');
 const tempDir = fs.mkdtempSync(path.join(os.tmpdir(), 'bill-tracker-oidc-'));
 process.env.DB_PATH = path.join(tempDir, 'test.sqlite');
 
-const { getDb, getSetting, setSetting, closeDb } = require('../db/database');
-const oidcService = require('../services/oidcService');
+const { getDb, getSetting, setSetting, closeDb } = require('../db/database.cts');
+const oidcService = require('../services/oidcService.cts');
 
 function clearOidcEnv() {
   for (const key of [
@@ -467,7 +467,7 @@ test('admin role only granted by configured group', async () => {
 });
 
 test('OIDC-created user cannot local-password login', async () => {
-  const { login } = require('../services/authService');
+  const { login } = require('../services/authService.cts');
   clearOidcEnv();
   resetOidcSettings();
   await oidcService.findOrProvisionUser({
diff --git a/server.js b/server.cts
similarity index 99%
rename from server.js
rename to server.cts
index f218748..e92e516 100644
--- a/server.js
+++ b/server.cts
@@ -1,3 +1,4 @@
+// @ts-nocheck — app entry/bootstrap converted to .cts (Node type-stripping); Express wiring, typing deferred.
 const express      = require('express');
 const cookieParser = require('cookie-parser');
 const path         = require('path');