') + ')', 'gi'); if (regex.test(text)) { found = true; var frag = document.createDocumentFragment(); var parts = text.split(regex); parts.forEach(function(part, i) { if (i % 2 === 0) { frag.appendChild(document.createTextNode(part)); } else { var span = document.createElement('span'); span.className = 'userscript-highlight'; span.textContent = part; frag.appendChild(span); } }); node.parentNode.replaceChild(frag, node); } }); } else if (node.nodeType === 1 && node.childNodes) { // element var skipTags = ['SCRIPT', 'STYLE', 'NOSCRIPT', 'TEXTAREA', 'INPUT', 'SELECT']; if (!skipTags.includes(node.tagName)) { Array.from(node.childNodes).forEach(highlight); } } } highlight(document.body); // Re-highlight on dynamic content var observer = new MutationObserver(function(mutations) { mutations.forEach(function(m) { m.addedNodes.forEach(function(node) { if (node.nodeType === 1 || node.nodeType === 3) highlight(node); }); }); }); observer.observe(document.body, { childList: true, subtree: true }); })(); } } catch(__e) { console.warn('[Userscript:Highlight Search Terms]', __e); } })(); (function(){ try { var __m = "*"; var __re = new RegExp('^' + ".*" + ', 'i'); if (__m === '*' || __re.test(location.href)) { // Strip utm_, fbclid, gclid, etc. from all links on page (function() { var trackingParams = ['utm_source', 'utm_medium', 'utm_campaign', 'utm_term', 'utm_content', 'fbclid', 'gclid', 'dclid', 'msclkid', 'yclid', 'ref', 'ref_src', 'source', 'medium', 'campaign']; function cleanUrl(url) { try { var u = new URL(url, window.location.origin); var changed = false; trackingParams.forEach(function(p) { if (u.searchParams.has(p)) { u.searchParams.delete(p); changed = true; } }); return changed ? u.toString() : url; } catch (e) { return url; } } function cleanLinks() { document.querySelectorAll('a[href]').forEach(function(a) { var clean = cleanUrl(a.href); if (clean !== a.href) a.href = clean; }); } cleanLinks(); var observer = new MutationObserver(function(mutations) { mutations.forEach(function(m) { m.addedNodes.forEach(function(node) { if (node.nodeType === 1) { if (node.tagName === 'A') cleanLinks(); node.querySelectorAll('a[href]').forEach(function(a) { var clean = cleanUrl(a.href); if (clean !== a.href) a.href = clean; }); } }); }); }); observer.observe(document.body, { childList: true, subtree: true }); })(); } } catch(__e) { console.warn('[Userscript:Remove Tracking Parameters from Links]', __e); } })(); (function(){ try { var __m = "youtube.com"; var __re = new RegExp('^' + "youtube\\.com" + ', 'i'); if (__m === '*' || __re.test(location.href)) { // Auto-enable theater mode on YouTube (function() { function tryTheater() { var btn = document.querySelector('button[aria-label="Theater mode"], ytd-player #player button[title="Theater mode"]'); if (btn && !btn.classList.contains('activated')) { btn.click(); } } // Try immediately tryTheater(); // Try after navigation (SPA) var lastUrl = location.href; setInterval(function() { if (location.href !== lastUrl) { lastUrl = location.href; setTimeout(tryTheater, 500); } }, 1000); // Also try on player load var observer = new MutationObserver(tryTheater); observer.observe(document.body, { childList: true, subtree: true }); })(); } } catch(__e) { console.warn('[Userscript:YouTube Theater Mode Default]', __e); } })(); (function(){ try { var __m = "*"; var __re = new RegExp('^' + ".*" + ', 'i'); if (__m === '*' || __re.test(location.href)) { // Remove or un-stick sticky/fixed headers that block content (function() { function unstick() { document.querySelectorAll('header, nav, [role="banner"], .header, .navbar, .sticky, .fixed-top, [style*="position: fixed"], [style*="position:sticky"]').forEach(function(el) { if (el.style.position === 'fixed' || el.style.position === 'sticky' || getComputedStyle(el).position === 'fixed' || getComputedStyle(el).position === 'sticky') { el.style.position = 'static'; el.style.top = 'auto'; el.style.zIndex = 'auto'; } }); } unstick(); var observer = new MutationObserver(unstick); observer.observe(document.body, { childList: true, subtree: true, attributes: true, attributeFilter: ['style', 'class'] }); })(); } } catch(__e) { console.warn('[Userscript:Kill Sticky Headers]', __e); } })(); })(); Migrate Java execution from Docker to CheerpJ (browser-side) by Prorickey · Pull Request #1 · Prorickey/CodeFTC · GitHub
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Migrate Java execution from Docker to CheerpJ (browser-side) - #1

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Prorickey merged 2 commits into
mainfrom
feat/browser-jvm
Mar 2, 2026
Merged

Migrate Java execution from Docker to CheerpJ (browser-side)#1
Prorickey merged 2 commits into
mainfrom
feat/browser-jvm

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@Prorickey

@ProrickeyProrickey commented Mar 2, 2026

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Summary

  • Replace Docker sandbox with CheerpJ 3.0 — Java now compiles and runs entirely in the browser via a WASM JVM. Zero server-side containers, no rate limiting needed, scales infinitely.
  • Remove auth gate on Run button — anyone can run code now that execution is free; analytics still require a session.
  • Expose testCode to client — Test.java is included in LessonData so the browser executor can pass it to javac/CheerpJ.
  • New analytics endpoint — POST /api/analytics/run records code_run and exercise_complete events after browser-side execution completes.
  • Build script — scripts/build-cheerpj-assets.sh compiles ftc-stubs.jar (Java 8 target) and downloads OpenJDK 8 tools.jar (contains javac); run with bun run build:cheerpj.

Architecture

Before: Student clicks Run → POST /api/execute → Docker container → javac + java → JSON
After: Student clicks Run → CheerpJ (WASM JVM in browser) → javac + java → JSON → POST /api/analytics/run

Timing profile (measured):

PhaseCold (1st click)Warm (2nd click)
CheerpJ init~3–8s (background, while reading)0ms
javac compile~5.3s~1.7s
Test execution~700ms~700ms

The main cold-start cost is javac lazy-loading classes from tools.jar (18MB) over the network. Subsequent runs in the same session are ~3x faster.

Files removed

  • lib/compiler.ts, lib/docker.ts — Docker orchestration
  • app/api/execute/route.ts — server-side execution endpoint
  • tests/sandbox.test.ts — Docker integration tests (replaced by Playwright browser tests)

Test plan

  • Run bun run build:cheerpj — verify public/cheerpj/ftc-stubs.jar and public/cheerpj/tools.jar are created
  • bun dev → open a lesson → click Run with starter code → verify failing test results appear (~6s)
  • Click Run again → verify faster response (~2s, warm)
  • Modify code to be invalid Java → verify compilation error displayed
  • Use solution code → verify all tests pass with "All passing" badge
  • Verify Run button is visible without signing in
  • Run npx playwright test tests/cheerpj-browser.test.ts — all 8 tests pass

🤖 Generated with Claude Code

Prorickeyand others added 2 commits March 2, 2026 17:44
@Prorickey@claude
Migrate Java execution from Docker to CheerpJ (browser-side)
426872f
Replaces the server-side Docker sandbox with CheerpJ 3.0, a WASM-based
JVM that compiles and runs Java entirely in the browser. Students no
longer consume server resources when clicking Run — zero containers, no
rate limiting needed.
Key changes:
- Add CheerpJProvider context (loads runtime from CDN, calls cheerpjInit)
- Add cheerpj-executor: writes .java files to CheerpJ VFS, invokes javac
via cheerpjRunMain, captures System.out via console.log interception,
parses JSON test results from TestBase.printResults()
- Expose Test.java to client: add testCode field to LessonData/getLessonData
- Remove auth gate on Run button — execution is now free for all users
- Add POST /api/analytics/run to record code_run / exercise_complete events
- Add scripts/build-cheerpj-assets.sh: compiles ftc-stubs.jar (Java 8
target) and downloads OpenJDK 8 tools.jar (contains javac)
- Remove lib/docker.ts, lib/compiler.ts, app/api/execute/route.ts
- Remove dockerode dependency and serverExternalPackages entry
- Add Playwright browser tests (8 tests, all passing in ~56s)
Timing profile: cold compile ~5s, warm compile ~1.7s, test run ~700ms.
The main cost is javac lazy-loading classes from tools.jar (18MB) on
first use; subsequent runs in the same session are 3x faster.
Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>
@Prorickey@claude
Fix CI: move Playwright tests to e2e/, update workflow
e1db02b
bun test picked up the Playwright test file and crashed because
test.setTimeout() is a Playwright-only API. Moving browser tests to
e2e/ keeps them separate from the bun test runner.
- Move tests/cheerpj-browser.test.ts → e2e/cheerpj-browser.test.ts
- Add test:e2e script (playwright test e2e/)
- Replace CI workflow: drop Docker sandbox build, run tsc + eslint instead
(execution tests are browser-side and don't run in CI without a display)
Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>
@Prorickey
Prorickey merged commit cffc9cf into mainMar 2, 2026
2 checks passed
@Prorickey
Prorickey deleted the feat/browser-jvm branch March 2, 2026 22:48
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