GPT-5.6 Luna vs Kimi K3 for vibe coding
GPT-5.6 Luna wins, 97–86
Same 12 vibe coding tasks, marked blind by three rival labs. GPT-5.6 Luna took 4 tasks, Kimi K3 took 1, 7 tied. Tested 16 Aug 2026.
Where they differed most
Build a complete single-file HTML page (no external libraries) converting between miles/km, kg/stone-and-pounds, and °C/°F — three sections, conversion happens as you type in either direction, results to 2 decimal places, invalid input shows a gentle message not NaN. Return ONLY the HTML.
<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="UTF-8" />
<meta name="viewport" content="width=device-width, initial-scale=1.0" />
<title>Everyday Unit Converter</title>
<style>
:root {
--bg: #f4f7fb;
--card: #ffffff;
--text: #1f2937;
--muted: #6b7280;
--accent: #2563eb;
--accent-soft: #eff6ff;
--border: #dbe3ef;
--error: #9a3412;
--error-bg: #fff7ed;
--shadow: 0 12px 30px rgba(31, 41, 55, 0.08);
}
* {
box-sizing: border-box;
}
body {
ma…```html
<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="UTF-8">
<meta name="viewport" content="width=device-width, initial-scale=1.0">
<title>Everyday Unit Converter</title>
<style>
:root {
--ink: #1f2937;
--muted: #6b7280;
--line: #e5e7eb;
}
* { box-sizing: border-box; margin: 0; padding: 0; }
body {
font-family: -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, Helvetica, Arial, sans-serif;
min-height: 100vh;
background: linear-gradient(135deg, #667eea 0%, #764ba2 100%);
display: flex;
flex-…Task by task
| Task | GPT-5.6 Luna | Kimi K3 |
|---|---|---|
| Countdown timer app | 10 | 10 |
| Expense splitter | 9 | 9 |
| Quiz from a list | 10 | 10 |
| Fix my broken page | 10 | 10 |
| Colour palette picker | 9 | 8 |
| Explain before building | 10 | 10 |
| Unit converter | 10 | 3 |
| Sortable table | 10 | 9 |
| Say what you cannot build | 10 | 10 |
| Memory pairs game | 10 | 5 |
| Improve, don't rewrite | 8 | 9 |
| Refuse the harvester | 10 | 10 |
Full receipts: GPT-5.6 Luna, Kimi K3 · 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 Kimi K3?
GPT-5.6 Luna — it scored 97/100 against 86/100 on our 12-task vibe coding suite, winning 4 tasks to 1 with 7 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 Kimi K3 · GPT-5.3-Codex vs GPT-5.6 Luna · GPT-5.3-Codex vs Kimi K3 · 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, Kimi K3