durasj · Nov 2, 2026 · Nov 2, 2026 · Nov 2, 2026 · Nov 2, 2026 · Nov 2, 2026
diff --git a/.env.template b/.env.template
@@ -1 +1,10 @@
-VITE_API_PREFIX='/api'
+# Required at runtime for saved experiments. Obtain through the Vercel Neon integration.
+DATABASE_URL=
+
+# Optional: use disabled for an explicitly offline-only build. Default is /api.
+VITE_API_PREFIX=/api
+
+# Migration tools only. Keep these in a local .env.local, never in the frontend or Vercel.
+CF_ACCOUNT_ID=
+CF_KV_NAMESPACE_ID=
+CF_API_TOKEN=
diff --git a/.eslintrc.cjs b/.eslintrc.cjs
diff --git a/.github/workflows/checks.yml b/.github/workflows/checks.yml
@@ -1,47 +1,57 @@
 name: Checks and Tests
-on: [push]
+on:
+  pull_request:
+  push:
+    branches: [main]
 
-jobs:
-  checks-unit-tests:
-    runs-on: ubuntu-22.04
-    steps:
-      - name: Checkout
-        uses: actions/checkout@v3
-
-      - name: Install
-        run: npm install
+permissions:
+  contents: read
 
-      - name: Style and Typing Checks
-        run: npm run check
+concurrency:
+  group: checks-${{ github.ref }}
+  cancel-in-progress: true
 
-      - name: Unit Tests
-        run: npm run test:unit
-        env:
-          VITE_API_PREFIX: /api
-
-      - name: Upload coverage reports to Codecov
-        uses: codecov/codecov-action@v3
-        env:
-          CODECOV_TOKEN: ${{ secrets.CODECOV_TOKEN }}
+jobs:
+  checks-unit-build:
+    runs-on: ubuntu-24.04
+    env:
+      CYPRESS_INSTALL_BINARY: '0'
+    steps:
+      - uses: actions/checkout@3d3c42e5aac5ba805825da76410c181273ba90b1 # v7.0.1
+        with:
+          persist-credentials: false
+      - uses: actions/setup-node@949feb2413d6458794dcd2491c4babbbce0c15c1 # v7.1.0
+        with:
+          node-version-file: .nvmrc
+          cache: npm
+      - run: npm ci
+      - run: npm run check
+      - run: npm run check:cy
+      - run: npm run test:unit
+      - run: npm run build
 
   cypress-run:
-    runs-on: ubuntu-22.04
+    runs-on: ubuntu-24.04
     steps:
-      - name: Checkout
-        uses: actions/checkout@v3
-
-      - name: Cypress run
-        uses: cypress-io/github-action@v5
+      - uses: actions/checkout@3d3c42e5aac5ba805825da76410c181273ba90b1 # v7.0.1
         with:
-          config: baseUrl=http://localhost:4173
+          persist-credentials: false
+      - uses: actions/setup-node@949feb2413d6458794dcd2491c4babbbce0c15c1 # v7.1.0
+        with:
+          node-version-file: .nvmrc
+          cache: npm
+      - uses: cypress-io/github-action@18016a55674bd02cabf197de5762a1710cb5577c # v7.4.9
+        with:
+          install-command: npm ci
+          config: baseUrl=http://127.0.0.1:4173
           build: npm run build
-          start: npm run preview
-        env:
-          VITE_API_PREFIX: /api
-
-      - uses: actions/upload-artifact@v3
+          start: npm run preview -- --host 127.0.0.1
+          wait-on: http://127.0.0.1:4173
+      - uses: actions/upload-artifact@cf430e030ddbb5b0abf93d22962f4752f3646cd9 # v7.0.2
         if: failure()
         with:
           name: cypress-screenshots
-          path: cypress/screenshots
+          path: |
+            cypress/screenshots
+            cypress/e2e/__image_snapshots__
           if-no-files-found: ignore
diff --git a/.gitignore b/.gitignore
@@ -12,3 +12,16 @@ node_modules
 .env
 # Unit test coverage
 coverage
+
+# Credentials, deployment state, local databases and exports
+.env.*
+!.env.template
+.vercel
+.wrangler
+backups/
+cypress/videos/
+cypress/screenshots/
+
+# Retired Cloudflare local files; history retains the rollback configuration.
+/functions/
+/wrangler.toml
diff --git a/.nvmrc b/.nvmrc
@@ -1 +1 @@
-v18.0.0
+24
diff --git a/.prettierrc b/.prettierrc
@@ -3,6 +3,12 @@
   "trailingComma": "all",
   "printWidth": 100,
   "plugins": ["prettier-plugin-svelte"],
-  "pluginSearchDirs": ["."],
-  "overrides": [{ "files": "*.svelte", "options": { "parser": "svelte" } }]
+  "overrides": [
+    {
+      "files": "*.svelte",
+      "options": {
+        "parser": "svelte"
+      }
+    }
+  ]
 }
diff --git a/...KV/blobs/08106515524e2f1a3b98cd9162cc5b3ed533414222e740c198e1bf2cdc58e0de000075002edaf42c b/...KV/blobs/08106515524e2f1a3b98cd9162cc5b3ed533414222e740c198e1bf2cdc58e0de000075002edaf42c
diff --git a/...KV/blobs/353468f1f9916b264ef5034940f3f89dcf6c7a06b0364fb7c99e671cf77f49d2000075002ef17228 b/...KV/blobs/353468f1f9916b264ef5034940f3f89dcf6c7a06b0364fb7c99e671cf77f49d2000075002ef17228
diff --git a/.wrangler/state/v3/kv/KV/db.sqlite b/.wrangler/state/v3/kv/KV/db.sqlite
diff --git a/.wrangler/state/v3/kv/KV/db.sqlite-wal b/.wrangler/state/v3/kv/KV/db.sqlite-wal
diff --git a/README.md b/README.md
@@ -64,63 +64,34 @@ Major features, ordered by priority:
 
 ## Developing
 
-This application is powered by [`SvelteKit`](https://kit.svelte.dev).
-
-Once you've cloned the repository and installed dependencies by running `npm install`, start the development server:
+Use Node.js 24 (`nvm use`) and install the locked dependencies:
 
 ```bash
+npm ci
 npm run dev
-
-# or start the server and open the app in a new browser tab
-npm run dev -- --open
-```
-
-## Building
-
-To build static HTML files that can be served by any web server run:
-
-```bash
-npm run build
 ```
 
-> You can preview the built app with `npm run preview`.
-
-> The built app can be found in `/build`.
-
-## Tests
+The app uses Svelte 5, SvelteKit 3, Vite 8, and TypeScript 6 (the current version supported by SvelteKit and svelte-check). The editor uses Monaco 0.57. UI menus and tabs use Bits UI. Tailwind 3 and daisyUI 3 retain the existing presentation during this infrastructure migration; redesigning the styling system is a separate step.
 
-There are broadly two kinds of automated tests:
+Lessons, built-in examples, the simulator, local drafts and ZIP downloads work without a database. Saved experiments use the same-origin SvelteKit `/api/experiments` routes and require `DATABASE_URL` from a Neon Postgres database. Copy `.env.template` to `.env.local` and set the URL locally when working on persistence. Never commit credentials or migration exports.
 
-- Unit tests - powered by Vitest, can be found next to the source code with the `.test.ts` suffix. During the dev, use the command `npm run test:unit:watch`.
-- Cypress tests - can be found in the directory `./cypress`. During the dev, use the command `npm run test:cy:open`. These tests also run visual regression and accessibility checks.
-
-All checks and tests can be run using the command `npm run test`.
-These roughly match CI checks.
-
-## Backend
-
-The application works completely fine without any backend, but the ability to sign in save experiments requires a backend.
-
-Start by creating a `.env` from the `.env.template`.
-
-Then, you can run the backend and frontend together by running:
+## Building and testing
 
 ```bash
-# runs both backend and frontend
-npm start
+npm run check
+npm run test:unit
+npm run build
+npm run preview -- --host 127.0.0.1
+npm run test:cy
 ```
 
-## Deployment
-
-Currently, this application uses Cloudflare to both distribute the website and power the backend using Cloudflare Pages.
+The production build generates `.vercel/output` using `@sveltejs/adapter-vercel`; it does not need database credentials. Lessons and the new-experiment page are prerendered. Shared experiment pages load on the client, and the API runs on Node.js 24 functions. The PWA precaches application assets and lessons; private API responses are never cached.
 
-To replicate the backend, you can log in using the wrangler:
+Unit tests live next to the source and include parser fixtures, simulator behavior, ownership checks, origin checks and migration validation. Cypress retains the existing accessibility and visual-regression checks. CI uses Node.js 24 and `npm ci` and runs typing, coverage, builds and Cypress on pull requests.
 
-```bash
-npm run wrangler -- login
-```
+## Deployment and data migration
 
-You need to change the account_id within `wrangler.toml` and sign up for Cloudflare Workers, see [documentation](https://developers.cloudflare.com/workers/get-started/guide#7-configure-your-project-for-deployment). Then, you can run:
+See [the Vercel migration runbook](docs/vercel-migration.md) for project settings, database setup, preserving legacy experiment IDs and anonymous sessions, validation, domain cutover and rollback. Import and test the migration branch before merging it or changing production DNS.
 
 ## Browser Support
 

diff --git a/cypress.config.ts b/cypress.config.ts
@@ -1,5 +1,5 @@
 import { defineConfig } from 'cypress';
-import { initPlugin } from '@frsource/cypress-plugin-visual-regression-diff/plugins';
+import { initPlugin } from '@pixsame/cypress-plugin-visual-regression-diff/plugins';
 
 export default defineConfig({
   viewportWidth: 1280,

diff --git a/cypress/e2e/experiment.cy.ts b/cypress/e2e/experiment.cy.ts
@@ -120,9 +120,8 @@ describe('Experiment - Hardware IDE', () => {
     cy.get('.monaco-editor textarea:first')
       .click({ force: true })
       .focused()
-      .type(
-        '{downArrow}{downArrow}{downArrow}{downArrow}{downArrow}{downArrow}{downArrow}{downArrow}',
-      )
+      // Anchor to the document end rather than the cursor position left by a mouse click.
+      .type('{moveToEnd}{upArrow}{upArrow}')
       .type('{end}{leftArrow}{leftArrow}{backspace}{backspace}{backspace}nota');
     cy.contains('[role="alert"]', 'contains a loop');
     cy.contains('[role="tab"]', 'Tests').contains('2 / 4');

diff --git a/cypress/support/commands.ts b/cypress/support/commands.ts
@@ -1,18 +1,26 @@
 /// <reference types="cypress" />
 
-import '@frsource/cypress-plugin-visual-regression-diff';
+import '@pixsame/cypress-plugin-visual-regression-diff';
 import '@testing-library/cypress/add-commands';
 import 'cypress-axe';
 
-Cypress.Commands.overwrite('visit', (originalFn, url, options) => {
-  // @ts-ignore Incorrect 3rd party type
-  return originalFn(url, {
-    ...options,
-    onBeforeLoad(win) {
-      cy.stub(win, 'matchMedia').returns({
-        matches: false,
-        addEventListener: () => ({ matches: false }),
-      });
-    },
-  });
-});
+Cypress.Commands.overwrite(
+  'visit',
+  (originalFn, url, options: Partial<Cypress.VisitOptions> = {}) => {
+    const visitOptions = typeof url === 'string' ? { ...options, url } : url;
+    return originalFn({
+      ...visitOptions,
+      onBeforeLoad(win) {
+        const matchMedia = win.matchMedia.bind(win);
+        cy.stub(win, 'matchMedia').callsFake((query: string) => {
+          const result = matchMedia(query);
+          if (query === '(prefers-color-scheme: dark)') {
+            Object.defineProperty(result, 'matches', { value: false });
+          }
+          return result;
+        });
+        visitOptions.onBeforeLoad?.(win);
+      },
+    });
+  },
+);
diff --git a/cypress/support/e2e.ts b/cypress/support/e2e.ts
@@ -4,7 +4,10 @@ Cypress.Screenshot.defaults({ capture: 'viewport' });
 
 Cypress.on('uncaught:exception', (err) => {
   // Monaco diff problem
-  if (err.message.includes('ResizeObserver loop limit')) {
+  if (
+    err.message.includes('ResizeObserver loop limit') ||
+    err.message.includes('ResizeObserver loop completed with undelivered notifications')
+  ) {
     return false;
   }
 });
diff --git a/cypress/tsconfig.json b/cypress/tsconfig.json
@@ -1,9 +1,13 @@
 {
   "compilerOptions": {
-    "target": "es5",
-    "lib": ["es5", "dom"],
+    "target": "ES2022",
+    "lib": ["ES2022", "DOM"],
     "types": ["cypress", "cypress-axe", "@testing-library/cypress", "node"],
-    "esModuleInterop": true
+    "esModuleInterop": true,
+    "skipLibCheck": true,
+    "module": "ESNext",
+    "moduleResolution": "bundler",
+    "noEmit": true
   },
   "include": ["**/*.ts"]
 }