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A · closed · GPT-5.x

GPT-5.4 Nano

OpenAI

B · closed · GPT-5.x

GPT-5.6 Luna

OpenAI

0:12

overall capability wins (1 ties across 13 scored). GPT-5.6 Luna leads overall.

  • Reasoning0:6
  • Coding0:3
  • Arena0:1
  • Tool use0:1
  • Composite indices0:2
  • Pricing0:2
  • Speed1:1
  • Specs0:1

Verdict

GPT-5.6 Luna leads coding (widest gap: +20.2 on TermBench); GPT-5.6 Luna ranks higher on LMArena (+50 Elo); GPT-5.6 Luna offers ~2.6x larger context (1.1M vs 400K).

  • GPT-5.6 Luna leads coding (widest gap: +20.2 on TermBench)
  • GPT-5.6 Luna ranks higher on LMArena (+50 Elo)
  • GPT-5.6 Luna offers ~2.6x larger context (1.1M vs 400K)

Cost for 1M in + 250K out

Illustrative chat workload at primary-provider list prices.

GPT-5.4 Nano
$0.51
GPT-5.6 Luna
$0.50

GPT-5.6 Luna is about 1.0x cheaper on this workload.

Price per 1M tokens

Full comparison

Organization

OpenAI

OpenAI

Family

GPT-5.x

GPT-5.x

License

Proprietary

Proprietary

Open weights

No

No

Release

Mar 17, 2026

Jul 9, 2026

Knowledge cutoff

-

-

API / provider

OpenAI

OpenAI

Modalities

text, image → text

text, image → text

Specs

Context window

400K

1.1M

B +650K

Max output

128K

128K

tie

Parameters

—

—

—

Pricing

Input $/1M

$0.20

$0.20

tie

Output $/1M

$1.25

$1.20

B +$0.05

Blended $/1M (3∶1)

$0.46

$0.45

B +$0.01

Speed

tok/s

180

195

B +15

TTFT (s)

0.18

0.2

A +0.02

Reasoning

MMLU-Pro

—

—

—

GPQA Diamond

81.7

91.1

B +9.4 pts

Humanity's Last Exam

28.3

39.5

B +11.2 pts

AIME 2025

—

—

—

MATH-500

—

—

—

Humanity's Last Exam (with tools)

—

—

—

AA-Omniscience Accuracy

25.7

42.7

B +17.0 pts

AA-LCR v1.1

76.7

83.7

B +7.0 pts

CritPt

9.3

20.6

B +11.3 pts

MMMU-Pro

65.4

78.6

B +13.2 pts

IFBench

75.9

—

—

Chartography

—

—

—

Chartography (With Tools)

—

—

—

Coding

SWE-bench Verified

—

—

—

SWE-bench Pro

52.4

62.7

B +10.3 pts

SWE-bench Multilingual

—

—

—

LiveCodeBench

—

—

—

Terminal-Bench 2.1

60.7

80.9

B +20.2 pts

Aider Polyglot

—

—

—

Terminal-Bench 3

—

14.3

—

BigCodeBench

—

—

—

SciCode

47.2

53.6

B +6.4 pts

CursorBench

—

61.1

—

SWE-Rebench

—

43.6

—

NL2Repo-Bench

—

—

—

DeepSWE

—

67.0

—

WebDev Arena

—

1,519

—

Terminal-Bench 4.0

—

17.3

—

CursorBench 4.0

—

—

—

FrontierCode v1.1 (Main)

—

—

—

Arena

LMArena Elo

1,402

1,453

B +50 Elo

GPT-5.4 Nano

Context
400K / 128K out
Parameters
—
Price
$0.20 / $1.25
Speed
180 tok/s · 0.18s TTFT
Modalities
text, image → text
License
Proprietary

Cheapest GPT-5.4 tier for high-volume classification and light assistants.

GPT-5.6 Luna

Context
1.1M / 128K out
Parameters
—
Price
$0.20 / $1.20
Speed
195 tok/s · 0.2s TTFT
Modalities
text, image → text
License
Proprietary

Fastest, cheapest GPT-5.6 tier for high-volume chat, classification, and light coding; July 30, 2026 API cut dropped Standard rates 80% to $0.20/$1.20.

Benchmark charts

Winner bars are emphasized. Per-benchmark deltas sit above each chart.

Reasoning & knowledge

GPQA: B +9.4HLE: B +11.2CritPt: B +11.3AA-LCR: B +7.0Omniscience Acc.: B +17.0MMMU-Pro: B +13.2

Coding

SWE-Pro: B +10.3TermBench: B +20.2SciCode: B +6.4

Tool use & function calling

τ³-Banking: B +3.7

Arena

Arena Elo: B +50

Composite indices

AA Index: B +22.2AA Index v4.3: B +16.3

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