Model comparison
GPT-5.5 Pro vs GPT-5.6 Luna
Head-to-head evidence from 5 shared benchmark results across 3 categories. Overall scores shown here use the public BenchAlign v5 ranking lane.
Public leaderboard positions: GPT-5.5 Pro #38 (Estimated); GPT-5.6 Luna #22 (Estimated). Intervals and evidence labels describe ranking uncertainty, not a guarantee for a specific workload.
Evidence parity. GPT-5.5 Pro and GPT-5.6 Luna share 5 comparable benchmark results. 3 of 8 categories are comparable. 2 results are unique to GPT-5.5 Pro; 36 to GPT-5.6 Luna.
Updated July 23, 2026- Shared results
- 5
- GPT-5.5 Pro only
- 2
- GPT-5.6 Luna only
- 36
- Comparable categories
- 3 / 8
Pick GPT-5.6 Luna if you want the stronger benchmark profile. GPT-5.5 Pro only becomes the better choice if agentic is the priority.
Confidence note. This is a partial-evidence comparison with 5 shared benchmark results across 3 evidence categories; 3 of 8 categories currently have scoreable aggregates for both models. Treat the verdict as directional until coverage is more balanced.
Why this result
GPT-5.6 Luna is clearly ahead on the BenchAlign aggregate, 67.17 to 63.69. The gap is large enough that you do not need to squint at the spreadsheet to see the difference.
GPT-5.6 Luna's sharpest advantage is in knowledge, where it averages 92.3 against 57.2. The single biggest benchmark swing on the page is FrontierMath v2 (Tiers 1-3), 51.000% to 78.600%. GPT-5.5 Pro does hit back in agentic, so the answer changes if that is the part of the workload you care about most.
GPT-5.5 Pro is also the more expensive model on tokens at $30.00 input / $180.00 output per 1M tokens, versus $1.00 input / $6.00 output per 1M tokens for GPT-5.6 Luna. That is roughly 30.0x on output cost alone.
Category breakdown
Exact category averages are shown below. Not measured means BenchLM does not have enough sourced public coverage for that model and category.
| Category | GPT-5.5 Pro | Δ | GPT-5.6 Luna |
|---|---|---|---|
| Knowledge | GPT-5.5 Pro57.2 | Margin→ 35.1 | GPT-5.6 Luna92.3 |
| Math | GPT-5.5 Pro48.1 | Margin→ 25.5 | GPT-5.6 Luna73.6 |
| Agentic | GPT-5.5 Pro90.1 | Margin← 6.0 | GPT-5.6 Luna84.1 |
| Coding | GPT-5.5 ProNot measured | MarginNo overlap | GPT-5.6 Luna62.7 |
| Multimodal | GPT-5.5 ProNot measured | MarginNo overlap | GPT-5.6 Luna78.4 |
Decisive benchmark drivers
The largest measured benchmark gaps in this matchup, with exact reported values.
More
- Source ↗
FrontierMath v2 (Tiers 1-3)
MathA 51.000%B 78.600%Winner: GPT-5.6 LunaΔ 27.6FrontierMath v2 (Tiers 1-3): GPT-5.5 Pro scored 51.000%; GPT-5.6 Luna scored 78.600%. GPT-5.6 Luna wins this benchmark. - Source ↗
FrontierMath v2 (Tier 4)
MathA 39.600%B 58.500%Winner: GPT-5.6 LunaΔ 18.9FrontierMath v2 (Tier 4): GPT-5.5 Pro scored 39.600%; GPT-5.6 Luna scored 58.500%. GPT-5.6 Luna wins this benchmark. - Source ↗
BrowseComp
AgenticA 90.1%B 83.3%Winner: GPT-5.5 ProΔ 6.8BrowseComp: GPT-5.5 Pro scored 90.1%; GPT-5.6 Luna scored 83.3%. GPT-5.5 Pro wins this benchmark.
Operational comparison
Runtime and commercial metrics are compared only when both models have a complete sourced value.
| Metric | GPT-5.5 Pro | GPT-5.6 Luna | Comparison |
|---|---|---|---|
| Input / output priceUSD per 1M tokens | GPT-5.5 Pro$30 input / $180 output | GPT-5.6 Luna$1 input / $6 output | GPT-5.6 Luna has the lower combined listed price. |
| Generation speedtokens per second | GPT-5.5 ProNot available | GPT-5.6 LunaNot available | A complete speed comparison is not available. |
| First-answer latencyseconds to first token | GPT-5.5 ProNot available | GPT-5.6 LunaNot available | A complete latency comparison is not available. |
| Context windowmaximum listed tokens | GPT-5.5 Pro1M | GPT-5.6 Luna1M | Listed context windows are equal. |
Benchmark Deep Dive
AgenticGPT-5.5 Pro wins15 benchmarks
| Benchmark | GPT-5.5 Pro | GPT-5.6 Luna | Result |
|---|---|---|---|
| BrowseCompSource | 90.1% | 83.3% | GPT-5.5 Pro leads |
| Terminal-Bench 2.0Source | — | 84.7% | Not comparable |
| OSWorld 2.0Source | — | 45.6% | Not comparable |
| CyberGymSource | — | 77.9% | Not comparable |
| ExploitGymSource | — | 12.4% | Not comparable |
| ToolathlonSource | — | 53.4% | Not comparable |
| AA Agentic IndexSource | — | 45.6% | Not comparable |
| GDPval-AASource | — | 54.2% | Not comparable |
| GDPval-AASource | — | 1584 | Not comparable |
| AA Harvey LABSource | — | 87.9% | Not comparable |
| AA ITBenchSource | — | 40.3% | Not comparable |
| AA Tau3 BankingSource | — | 27.2% | Not comparable |
| AA AutomationBenchSource | — | 42.2% | Not comparable |
| aaTerminalBench21Source | — | 80.9% | Not comparable |
| APEX-Agents-AASource | — | 35.8% | Not comparable |
Coding7 benchmarks
| Benchmark | GPT-5.5 Pro | GPT-5.6 Luna | Result |
|---|---|---|---|
| SWE-bench ProSource | — | 62.7% | Not comparable |
| Terminal-Bench 2.0Source | — | 84.7% | Not comparable |
| deepSweSource | — | 67.2% | Not comparable |
| FrontierCode 1.1 ExtendedSource | — | 55.1% | Not comparable |
| cursorBench32Source | — | 61.1% | Not comparable |
| AA Coding IndexSource | — | 71.5% | Not comparable |
| AA-SciCodeSource | — | 52.5% | Not comparable |
Reasoning3 benchmarks
KnowledgeGPT-5.6 Luna wins12 benchmarks
| Benchmark | GPT-5.5 Pro | GPT-5.6 Luna | Result |
|---|---|---|---|
| HLESource | 57.2% | — | Not comparable |
| HLE w/o toolsSource | 43.1% | — | Not comparable |
| GPQASource | — | 92.3% | Not comparable |
| GPQA-DSource | — | 92.3% | Not comparable |
| HealthBench ProfessionalSource | — | 55.7% | Not comparable |
| HealthBench HardSource | — | 32.0% | Not comparable |
| Artificial Analysis Intelligence IndexSource | — | 51.2% | Not comparable |
| AA-GPQA DiamondSource | — | 91.1% | Not comparable |
| AA-HLESource | — | 37.2% | Not comparable |
| AA-Omniscience IndexSource | — | -11.2% | Not comparable |
| AA-Omniscience AccuracySource | — | 41.5% | Not comparable |
| AA-Omniscience Hallucination RateSource | — | 90.1% | Not comparable |
MathGPT-5.6 Luna wins3 benchmarks
Frequently Asked Questions (4)
Which is better, GPT-5.5 Pro or GPT-5.6 Luna?
GPT-5.6 Luna is ahead on BenchLM's BenchAlign leaderboard, 67.17 to 63.69. The biggest single separator in this matchup is FrontierMath v2 (Tiers 1-3), where the scores are 51.000% and 78.600%.
Which is better for knowledge tasks, GPT-5.5 Pro or GPT-5.6 Luna?
GPT-5.6 Luna has the edge for knowledge tasks in this comparison, averaging 92.3 versus 57.2. GPT-5.5 Pro stays close enough that the answer can still flip depending on your workload.
Which is better for math, GPT-5.5 Pro or GPT-5.6 Luna?
GPT-5.6 Luna has the edge for math in this comparison, averaging 73.6 versus 48.1. Inside this category, FrontierMath v2 (Tiers 1-3) is the benchmark that creates the most daylight between them.
Which is better for agentic tasks, GPT-5.5 Pro or GPT-5.6 Luna?
GPT-5.5 Pro has the edge for agentic tasks in this comparison, averaging 90.1 versus 84.1. Inside this category, BrowseComp is the benchmark that creates the most daylight between them.
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