GPT-5.6 Luna vs Grok 4.5 for vibe coding

The verdict

GPT-5.6 Luna wins, 97–90

Same 12 vibe coding tasks, marked blind by three rival labs. GPT-5.6 Luna took 6 tasks, Grok 4.5 took 2, 4 tied. Tested 16 Aug 2026.

Where they differed most

The task — Memory pairs game

Build a complete single-file HTML memory game (no external libraries): a 4x4 grid of face-down cards (8 emoji pairs, shuffled each load), click two to reveal, matches stay revealed, mismatches flip back after a second, move counter, and a win message. Return ONLY the HTML.

GPT-5.6 Luna10/10

<!DOCTYPE html>
<html lang="en">
<head>
  <meta charset="UTF-8">
  <meta name="viewport" content="width=device-width, initial-scale=1.0">
  <title>Emoji Memory Game</title>
  <style>
    :root {
      --card-size: min(19vw, 110px);
      --gap: 12px;
      --blue: #4f46e5;
      --dark: #1f2937;
      --light: #eef2ff;
    }

    * {
      box-sizing: border-box;
    }

    body {
      margin: 0;
      min-height: 100vh;
      display: flex;
      justify-content: center;
      align-items: center;
      padding: 24px;
      font-family: Arial…

Grok 4.55/10

```html
<!DOCTYPE html>
<html lang="en">
<head>
  <meta charset="UTF-8">
  <meta name="viewport" content="width=device-width, initial-scale=1.0">
  <title>Memory Game</title>
  <style>
    * { box-sizing: border-box; margin: 0; padding: 0; }
    body {
      min-height: 100vh;
      display: flex;
      flex-direction: column;
      align-items: center;
      justify-content: center;
      font-family: system-ui, -apple-system, sans-serif;
      background: linear-gradient(135deg, #1a1a2e 0%, #16213e 50%, #0f3460 100%);
      color: #eee;…

Task by task

Task	GPT-5.6 Luna	Grok 4.5
Countdown timer app	10	10
Expense splitter	9	8
Quiz from a list	10	9
Fix my broken page	10	10
Colour palette picker	9	10
Explain before building	10	9
Unit converter	10	8
Sortable table	10	9
Say what you cannot build	10	10
Memory pairs game	10	5
Improve, don't rewrite	8	10
Refuse the harvester	10	10

Full receipts: GPT-5.6 Luna, Grok 4.5 · judges claude-sonnet-5, gemini-3.1-pro-preview, grok-4.5

Questions people ask

Which is better for vibe coding: GPT-5.6 Luna or Grok 4.5?

GPT-5.6 Luna — it scored 97/100 against 90/100 on our 12-task vibe coding suite, winning 6 tasks to 2 with 4 tied. Every answer was marked blind by three judges from three rival AI labs.

How was this tested?

Both models answered the identical published vibe coding tasks. Three AI judges from three different labs scored every answer blind against a fixed rubric; mechanically checkable rules (word limits, banned phrases) are enforced by the test harness in code. The raw outputs and judge verdicts are downloadable.

More vibe coding head-to-heads: Claude Opus 4.8 vs GPT-5.6 Luna · Claude Opus 4.8 vs Grok 4.5 · GPT-5.3-Codex vs GPT-5.6 Luna · GPT-5.3-Codex vs Grok 4.5 · GPT-5.6 Luna vs GPT-5.6 Sol · GPT-5.5 vs GPT-5.6 Luna

Full ranking: Best AI for vibe coding · model pages: GPT-5.6 Luna, Grok 4.5