GPT-5.6 Luna vs Grok 4.5
At a Glance
| Compare |  GPT-5.6 LunaOpenAI | Grok 4.5xAI |
|---|---|---|
| Intelligence, Cost, and Efficiency | ||
| IntelligenceHigher is better · MM Intelligence v2.5 | #31 of 4652.7 score · 3/3 sources · complete | #25 of 4660.1 score · 3/3 sources · complete |
| CostLower is better · Published-token output estimate | #6 of 44$0.026 per LiveBench case | #15 of 44$0.063 per LiveBench case |
| EfficiencyHigher is better · MM Efficiency v1.5 | #4 of 3864.8 score · 3/3 sources · complete | #11 of 3859.2 score · 3/3 sources · complete |
| Pricing and Limits | ||
| Input priceFrom · USD / 1M tokens | $0.20Openai ↗ · Sep 3, 2026 | $2.00Xai ↗ · Sep 3, 2026 |
| Output priceFrom · USD / 1M tokens | $1.20Openai ↗ · Sep 3, 2026 | $6.00Xai ↗ · Sep 3, 2026 |
| Context windowMaximum documented tokens | 1,050K | 500K |
| Model facts checked | Aug 28, 2026View model evidence → | Sep 3, 2026View model evidence → |
Token prices are the lowest available sourced USD rates; input and output may use different providers. Cost ranking estimates output spend on LiveBench, not a full request bill. Ranking methodology →
Available Benchmarks
| Benchmark | GPT-5.6 Luna | Grok 4.5 |
|---|---|---|
| ARC-AGI-1verified-v1-ba05d69f6453 · verified_score · leader | 90.67100% of row best · percent · GPT-5.6 Luna 2026-07-30 (Max) | 87.1796% of row best · percent · Grok 4.5 (Medium) |
| ARC-AGI-2verified-v2-6c676fa3e9af · verified_score · leader | 59.58100% of row best · percent · GPT-5.6 Luna 2026-07-30 (Max) | 52.6488% of row best · percent · Grok 4.5 (Medium) |
| LMArena Agent Arenaagent-2026-09-15-d25aabda0010 · outcome_score · leader | -0.4497% of row best · score · GPT 5.6 Luna (xHigh); 95% CI [-1.27310649, 0.39719069]; sessions 29186; observations 2307801; rank 27 | 2.92100% of row best · score · Grok 4.5; 95% CI [1.93207740, 3.90928463]; sessions 38146; observations 1942877; rank 19 |
| LMArena Document Arenadocument-2026-09-13-d25aabda0010 · arena_rating · statistical tie | 1,456.92100% of row best · rating · gpt-5.6-luna-xhigh; 95% CI [1448.72029252, 1465.11301394]; votes 5766; rank 23 | 1,451.96100% of row best · rating · grok-4.5; 95% CI [1443.26182849, 1460.65626012]; votes 4965; rank 26 |
| LMArena Text Arenatext-2026-09-13-d25aabda0010 · arena_rating · leader | 1,429.8999% of row best · rating · gpt-5.6-luna-xhigh; 95% CI [1425.11549148, 1434.66063238]; votes 28547; rank 86 | 1,450.13100% of row best · rating · grok-4.5; 95% CI [1445.44268767, 1454.81726995]; votes 30103; rank 45 |
| LMArena Vision Arenavision-2026-09-13-d25aabda0010 · arena_rating · leader | 1,258.5398% of row best · rating · gpt-5.6-luna-xhigh; 95% CI [1250.17799393, 1266.87249678]; votes 7793; rank 48 | 1,288.54100% of row best · rating · grok-4.5; 95% CI [1280.47745270, 1296.60872281]; votes 8355; rank 24 |
| LiveBench2026-06-25 · overall · leader | 77.0596% of row best · percent · gpt-5.6-luna-max · 21,799 output tokens / case | 80.01100% of row best · percent · grok-4.5 · 10,517 output tokens / case |
| ToneBench2026-09-11-10-task-4ef099199c9c · overall_score · unverified | 84.47100% of row best · points · GPT-5.6 Luna (ultra) · 17,605 output tokens / case | 82.2397% of row best · points · Grok 4.5 · 2,688 output tokens / case |
| Overall ResultCounted from the protocol-matched rows above · 1 tie | 2 benchmark wins | 4 benchmark winsOverall lead |
Third-party benchmark Only like-for-like primary-publisher results are shown; raw scores, relative scores, configuration, and token spend remain visible.
Side-by-Side Facts
| Field | GPT-5.6 Luna | Grok 4.5 |
|---|---|---|
| Developer | OpenAI | xAI |
| Family | Gpt 5 6 | Grok 4 |
| Model | GPT-5.6 Luna | Grok 4.5 |
| Version | GPT-5.6 Luna | Grok 4.5 |
| Lifecycle | active | active |
| Released | Unknown | 2026-07-16 |
| Knowledge cutoff | 2026-02-16 | Unknown |
| Input modalities | Text, Image | Text, Image |
| Output modalities | Text | Text |
| Context window | 1,050K | 500K |
| Total parameters | Unknown | Unknown |
| Active parameters | Unknown | Unknown |
| License | Unknown | Unknown |
| Open weights | No | No |
| API available | Yes | Yes |
| Self-hostable | No | No |
| Provider access | Openai (Standard), Openrouter (Standard) | Xai (Standard) |
| Capabilities | chat, generation, reasoning, tools | chat, generation, reasoning, structured_outputs, tools |
GPT-5.6 Luna Capabilities
Grok 4.5 Capabilities
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Primary Evidence
Sources and Freshness
Questions
GPT-5.6 Luna vs Grok 4.5 FAQs
Is GPT-5.6 Luna or Grok 4.5 better for coding?+
This comparison does not currently contain a protocol-matched coding benchmark for both GPT-5.6 Luna and Grok 4.5, so Model Markets cannot name a coding leader from pricing, context size, or capability labels alone.
Which is cheaper, GPT-5.6 Luna or Grok 4.5?+
GPT-5.6 Luna is $0.20 and Grok 4.5 is $2.00 per million tokens, so GPT-5.6 Luna is cheaper on this metric. GPT-5.6 Luna is $1.20 and Grok 4.5 is $6.00 per million tokens, so GPT-5.6 Luna is cheaper on this metric.
Which has a larger context window, GPT-5.6 Luna or Grok 4.5?+
GPT-5.6 Luna has the larger sourced context window. GPT-5.6 Luna supports 1,050K and Grok 4.5 supports 500K.
Which performs better in benchmarks, GPT-5.6 Luna or Grok 4.5?+
Grok 4.5 leads the current overall benchmark count. The result uses 7 protocol-matched benchmarks from 3 publishers; it is not a universal quality score.
Can GPT-5.6 Luna or Grok 4.5 be self-hosted?+
Both models have the same recorded self-hosting status: unsupported. GPT-5.6 Luna is not marked open weight; Grok 4.5 is not marked open weight.
Can GPT-5.6 Luna and Grok 4.5 understand images?+
GPT-5.6 Luna is documented with image input; Grok 4.5 is documented with image input. This reflects supported input modalities, not vision quality.
Which can generate longer answers, GPT-5.6 Luna or Grok 4.5?+
Neither has a larger sourced maximum output. GPT-5.6 Luna is 128K and Grok 4.5 is —.
Do GPT-5.6 Luna and Grok 4.5 support reasoning and tool use?+
GPT-5.6 Luna: reasoning, tool calling, and image input. Grok 4.5: reasoning, tool calling, and image input. Feature support does not establish relative quality.
Which is available from more inference providers, GPT-5.6 Luna or Grok 4.5?+
GPT-5.6 Luna has 2 sourced provider routes; Grok 4.5 has 1, so GPT-5.6 Luna has broader tracked availability.
Which offers better value, GPT-5.6 Luna or Grok 4.5?+
There is no universal value winner. Compare the input and output prices above with the matched benchmark result for your workload: cheaper tokens can be offset by different quality, token usage, latency, or provider availability.