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Head-to-head comparison

GPT-5.6 Luna vs Grok 4.6

GPT-5.6 Luna (OpenAI) and Grok 4.6 (xAI) compared on the ModelCap Index, API price, context window, provider availability, weight access and every public benchmark board they share. Figures are the same ones shown on the live rankings; nothing here is a hidden score.

Snapshot as of 17 August 2026

As of 17 August 2026, Grok 4.6 holds the stronger ModelCap Index position (#10 vs #17); GPT-5.6 Luna is 5× cheaper per output token ($1.20/1M vs $6.00/1M); and GPT-5.6 Luna offers the longer context window (1M vs 500K tokens).

Which should you choose?

Choose GPT-5.6 Luna if…

  • API cost matters — $1.20/1M output tokens against $6.00/1M, about 5× cheaper.
  • your workload is prompt-heavy — input tokens cost $0.20/1M against $2.00/1M.
  • you need the longer context window — 1M tokens against 500K.
  • you want provider choice — 3 listed API providers against 1.

Choose Grok 4.6 if…

  • you want the stronger overall ModelCap Index position — #10 against #17 (74.4 vs 68.0 points).
  • Arena coding is your yardstick — 1512 against 1498.
  • ARC-AGI-2 is your yardstick — 67.1% against 59.5%.
  • ARC-AGI-3 is your yardstick — 2.1% against 0.2%.
  • Artificial Analysis Intelligence Index is your yardstick — 60.9 against 52.3.
  • you want the more recently listed model — Grok 4.6 was listed 12 August 2026, GPT-5.6 Luna 9 July 2026.

GPT-5.6 Luna vs Grok 4.6: specs, pricing and context

Specification comparison of GPT-5.6 Luna and Grok 4.6
FieldGPT-5.6 LunaOpenAIGrok 4.6xAI
ModelCap Index position#17#10
Index score68.074.4
EvidenceMeasuredMeasured
Input price / 1M tokens$0.20$2.00
Output price / 1M tokens$1.20$6.00
Context window1M tokens500K tokens
Max output tokens128K—
API providers listed31
Weight accessAPI onlyAPI only
Input modalitiesFile, Image, TextText, Image, File
First listed9 July 202612 August 2026
PublisherOpenAIxAI

Evidence: 6 public benchmark observations across 6 boards · 5 public benchmark observations across 5 boards. Prices are the lowest listed API offer per million tokens observed on the OpenRouter catalogue.

Benchmark scores: GPT-5.6 Luna vs Grok 4.6

Public benchmark boards where GPT-5.6 Luna or Grok 4.6 has a published result
BoardGPT-5.6 LunaGrok 4.6Leads
Arena codingArena (LMArena)14981489–1508X-High15121485–1538HighGrok 4.6
LMArena AgentLMArena4.3%2.4%–6.2%X-High—Only one result
ARC-AGI-2ARC Prize Foundation59.5%Max67.1%X-HighGrok 4.6
ARC-AGI-3ARC Prize Foundation0.2%Max2.1%X-HighGrok 4.6
Artificial Analysis Intelligence IndexArtificial Analysis52.3intelligence-index60.9intelligence-indexGrok 4.6

Scores are the sources' own published figures for each model's best evaluated configuration; ModelCap never re-runs a benchmark.

Want a different pairing? Open the interactive comparison tool to swap either model for any current ranked language model.

GPT-5.6 Luna vs Grok 4.6: common questions

Is GPT-5.6 Luna better than Grok 4.6?

Grok 4.6 ranks higher on the ModelCap Index as of 17 August 2026: #10 against #17. That is a capability ranking built from public benchmark evidence with published uncertainty; whether it is "better" for you also depends on price, context and where you can run it.

Is GPT-5.6 Luna cheaper than Grok 4.6?

GPT-5.6 Luna is cheaper on output tokens: $1.20/1M against $6.00/1M. Input tokens are $0.20/1M for GPT-5.6 Luna and $2.00/1M for Grok 4.6. Prices are the lowest listed API offer ModelCap observed, in USD per million tokens.

Which has the bigger context window, GPT-5.6 Luna or Grok 4.6?

GPT-5.6 Luna has the larger context window: 1M tokens against 500K.

Which is better for coding, GPT-5.6 Luna or Grok 4.6?

Arena coding: GPT-5.6 Luna 1498, Grok 4.6 1512 — Grok 4.6 leads.

Are GPT-5.6 Luna and Grok 4.6 open-weight models?

GPT-5.6 Luna: API only. Grok 4.6: API only. Open weights mean the checkpoint can be downloaded and self-hosted under its licence; API-only models are available solely through hosted endpoints.

Where can I run GPT-5.6 Luna and Grok 4.6?

ModelCap currently lists 3 API providers for GPT-5.6 Luna and 1 for Grok 4.6, from the OpenRouter catalogue snapshot the site serves; each model page lists the providers and their prices.

How current is this GPT-5.6 Luna vs Grok 4.6 comparison?

Every figure comes from the sealed ModelCap dataset published 17 August 2026; the page re-renders within a minute of each data refresh, and the ModelCap Index positions are the same ones shown on the live rankings.

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