GPT-5.6 Luna vs Grok 4.6
OpenAI · US | xAI · US · Updated June 2026
Quick verdict
Pick GPT-5.6 Luna for cheapest gpt-5.6 tier for high-volume drafting and automation or fast, affordable execution while keeping respectable coding. Pick Grok 4.6 for frontier-tier intelligence at a value price - artificial analysis intelligence index 61, tying gpt-5.6 sol or ranked #2 on artificial analysis's independent gdpval agentic test, behind only claude opus 5. On a tight budget at scale, GPT-5.6 Luna is the value pick.
GPT-5.6 Luna (OpenAI) and Grok 4.6 (xAI) are two of the models people most often weigh against each other in 2026. GPT-5.6 Luna is the budget, high-throughput GPT-5.6 tier — built for cheap, fast, large-volume work rather than deep long-context reasoning. Grok 4.6 is xAI's Grok 4.6 - frontier-level intelligence (AA Index 61, tying GPT-5.6 Sol) at a fraction of flagship pricing, and already in Cursor and Copilot. They diverge most on price and context window — each quantified below from the models' real specs.
Key differences at a glance
- ▸Price: GPT-5.6 Luna is about 2× cheaper on input ($1/$6 per 1M tokens vs $2/$6 per 1M tokens) — meaningful once you are processing millions of tokens a month.
- ▸Context window: GPT-5.6 Luna holds 2× more — 1M (~1,500 pages) vs 500K (~750 pages). But effective recall usually fades long before the advertised ceiling, so the bigger number only helps if the model reasons over it.
- ▸Recency: Grok 4.6 is the newer model by about 34 days (released August 12, 2026), usually meaning fresher training data and capabilities.
Side-by-side specs
| Spec | GPT-5.6 Luna | Grok 4.6 |
|---|---|---|
| Provider | OpenAI (US) | xAI (US) |
| Released | July 9, 2026 | August 12, 2026 |
| Context window | 1M (~1,500 pages) | 500K (~750 pages) |
| Price (in/out) | $1/$6 per 1M tokens | $2/$6 per 1M tokens |
| Open weight? | No — API only | No — API only |
| Modalities | text, image, code | text, image, code |
| SWE-Bench Verified | Not published | Not published |
| MRCR v2 @ 1M | Not published | Not published |
Who wins what
Cheapest GPT-5.6 tier for high-volume drafting and automation
GPT-5.6 Luna
At $1/$6 per 1M tokens it undercuts Grok 4.6 ($2/$6 per 1M tokens), and that gap compounds at volume.
Fast, affordable execution while keeping respectable coding
GPT-5.6 Luna
Grok 4.6 is comparatively weak here — coding gains (DeepSWE 65.9, APEX-Agents 57.5) are xAI's own numbers, not independently reproduced
Same 1M context and programmatic tool calling as its siblings
GPT-5.6 Luna
Its 1M window holds about 2× more than Grok 4.6's 500K in a single prompt.
Frontier-tier intelligence at a value price - Artificial Analysis Intelligence Index 61, tying GPT-5.6 Sol
Grok 4.6
XAI's Grok 4.6 - frontier-level intelligence (AA Index 61, tying GPT-5.6 Sol) at a fraction of flagship pricing, and already in Cursor and Copilot — and it is the newer of the two.
Ranked #2 on Artificial Analysis's independent GDPval agentic test, behind only Claude Opus 5
Grok 4.6
Grok 4.6 lists ranked #2 on Artificial Analysis's independent GDPval agentic test, behind only Claude Opus 5 among its strengths; GPT-5.6 Luna does not.
$2/$6 per million tokens - a fraction of Claude Opus 5 or GPT-5.6 Sol
Grok 4.6
Grok 4.6 lists $2/$6 per million tokens - a fraction of Claude Opus 5 or GPT-5.6 Sol among its strengths; GPT-5.6 Luna does not.
Lowest cost at scale
GPT-5.6 Luna
At $1/$6 per 1M tokens, it is the cheaper of the two — the gap dominates the bill on high-volume workloads.
Largest single-prompt input
GPT-5.6 Luna
Its 1M window is about 2× larger than Grok 4.6's 500K, fitting roughly 1,500 pages in one prompt.
Which should you pick?
A cost-sensitive startup shipping high volume
→ GPT-5.6 Luna
At $1/$6 per 1M tokens it undercuts Grok 4.6, and on millions of tokens that margin decides the monthly bill.
Someone analysing very long documents or codebases
→ GPT-5.6 Luna
Larger 1M window fits more in one prompt.
Anyone whose priority is cheapest gpt-5.6 tier for high-volume drafting and automation
→ GPT-5.6 Luna
It is specifically built for that.
Anyone whose priority is frontier-tier intelligence at a value price - artificial analysis intelligence index 61, tying gpt-5.6 sol
→ Grok 4.6
That is its strongest area.
GPT-5.6 Luna: where it fits
The budget, high-throughput GPT-5.6 tier — built for cheap, fast, large-volume work rather than deep long-context reasoning. Released July 9, 2026 by OpenAI, it is built for cheapest GPT-5.6 tier for high-volume drafting and automation, fast, affordable execution while keeping respectable coding, same 1M context and programmatic tool calling as its siblings, and high-throughput simple agentic jobs.
Its trade-offs are real: weak long-context recall deep in its 1M window (MRCR far below Sol), and lowest raw capability of the three GPT-5.6 tiers; no open weights. At $1 in / $6 out per million tokens, it sits in the budget price band.
Grok 4.6: where it fits
XAI's Grok 4.6 - frontier-level intelligence (AA Index 61, tying GPT-5.6 Sol) at a fraction of flagship pricing, and already in Cursor and Copilot. Released August 12, 2026 by xAI, it is built for frontier-tier intelligence at a value price - Artificial Analysis Intelligence Index 61, tying GPT-5.6 Sol, ranked #2 on Artificial Analysis's independent GDPval agentic test, behind only Claude Opus 5, $2/$6 per million tokens - a fraction of Claude Opus 5 or GPT-5.6 Sol, and 500K-token context; available same-day in Cursor and (two days later) GitHub Copilot.
Its trade-offs: coding gains (DeepSWE 65.9, APEX-Agents 57.5) are xAI's own numbers, not independently reproduced, parameter count is undisclosed, text and image input only - not a full multimodal model, and fast-moving target: xAI says Grok 4.7 is only weeks away. At $2 in / $6 out per million tokens, it sits in the mid price band.
The bottom line for this matchup
GPT-5.6 Luna and Grok 4.6 overlap enough that the right pick depends on your specific job. GPT-5.6 Luna costs less per token; GPT-5.6 Luna holds the larger context; and each leads in its own area — GPT-5.6 Luna for cheapest gpt-5.6 tier for high-volume drafting and automation, Grok 4.6 for frontier-tier intelligence at a value price - artificial analysis intelligence index 61, tying gpt-5.6 sol. Rather than crowning one, run the same hard task through both once and let the results decide.
Want both GPT-5.6 Luna and Grok 4.6 without two subscriptions? LumiChats gives you these plus 40+ models under one ₹69/day pass (about $1/day) — draft with one, cross-check with the other.
See pricingFrequently asked questions
Is GPT-5.6 Luna or Grok 4.6 better for coding?
Public SWE-Bench figures are not available for either model, so the honest test is your own repository — run an identical real bug through both. By design, GPT-5.6 Luna leans toward cheapest gpt-5.6 tier for high-volume drafting and automation while Grok 4.6 leans toward frontier-tier intelligence at a value price - artificial analysis intelligence index 61, tying gpt-5.6 sol, and that positioning usually predicts which feels better on your codebase.
Which is cheaper, GPT-5.6 Luna or Grok 4.6?
GPT-5.6 Luna is cheaper — $1/$6 per 1M tokens vs $2/$6 per 1M tokens, roughly 2× apart on input.
Which has the bigger context window?
GPT-5.6 Luna — 1M vs 500K, about 2× larger. Useful only if the model actually reasons over the full window, which not all do.
Can I use both GPT-5.6 Luna and Grok 4.6 together?
Yes — a multi-model platform like LumiChats gives you GPT-5.6 Luna, Grok 4.6 and 40+ others under one ₹69/day pass (about $1/day), so you can draft with one and cross-check with the other instead of buying two subscriptions.
Which is newer, GPT-5.6 Luna or Grok 4.6?
Grok 4.6 — released August 12, 2026, about 34 days after GPT-5.6 Luna.
Related comparisons
Specifications and benchmarks reflect publicly reported figures as of June 2026 and may change as providers release updates. Always verify on your own workload.