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A · closed · GPT-5.x

GPT-5.6 Luna

OpenAI

B · closed · GPT-5.x

GPT-5.6 Terra

OpenAI

2:15

overall capability wins (2 ties across 19 scored). GPT-5.6 Terra leads overall.

  • Reasoning1:5
  • Coding0:7
  • Arena0:1
  • Agents1:1
  • Tool use0:1
  • Composite indices0:2
  • Pricing3:0
  • Speed2:0

Verdict

GPT-5.6 Terra leads coding (widest gap: +7.1 on TermBench); GPT-5.6 Terra ranks higher on LMArena (+14 Elo); GPT-5.6 Luna is ~10.0x cheaper on a blended token basis than GPT-5.6 Terra.

  • GPT-5.6 Terra leads coding (widest gap: +7.1 on TermBench)
  • GPT-5.6 Terra ranks higher on LMArena (+14 Elo)
  • GPT-5.6 Luna is ~10.0x cheaper on a blended token basis than GPT-5.6 Terra

Cost for 1M in + 250K out

Illustrative chat workload at primary-provider list prices.

GPT-5.6 Luna
$0.50
GPT-5.6 Terra
$5

GPT-5.6 Luna is about 10.0x 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

Jul 9, 2026

Jul 9, 2026

Knowledge cutoff

-

-

API / provider

OpenAI

OpenAI

Modalities

text, image → text

text, image → text

Specs

Context window

1.1M

1.1M

tie

Max output

128K

128K

tie

Parameters

—

—

—

Pricing

Input $/1M

$0.20

$2

A +$1.80

Output $/1M

$1.20

$12

A +$10.80

Blended $/1M (3∶1)

$0.45

$4.50

A +$4.05

Speed

tok/s

195

135

A +60

TTFT (s)

0.2

0.3

A +0.10

Reasoning

MMLU-Pro

—

—

—

GPQA Diamond

91.1

92.5

B +1.4 pts

Humanity's Last Exam

39.5

42.9

B +3.4 pts

AIME 2025

—

—

—

MATH-500

—

—

—

Humanity's Last Exam (with tools)

—

—

—

AA-Omniscience Accuracy

42.7

46.8

B +4.1 pts

AA-LCR v1.1

83.7

83.0

A +0.7 pts

CritPt

20.6

30.0

B +9.4 pts

MMMU-Pro

78.6

80.7

B +2.1 pts

IFBench

—

71.2

—

Chartography

—

—

—

Chartography (With Tools)

—

—

—

Coding

SWE-bench Verified

—

—

—

SWE-bench Pro

62.7

63.4

B +0.7 pts

SWE-bench Multilingual

—

—

—

LiveCodeBench

—

—

—

Terminal-Bench 2.1

80.9

88.0

B +7.1 pts

Aider Polyglot

—

—

—

Terminal-Bench 3

14.3

20.8

B +6.5 pts

BigCodeBench

—

—

—

SciCode

53.6

55.0

B +1.4 pts

CursorBench

61.1

64.9

B +3.8 pts

SWE-Rebench

43.6

—

—

NL2Repo-Bench

—

—

—

DeepSWE

67.0

—

—

WebDev Arena

1,519

1,521

B +2 Elo

Terminal-Bench 4.0

17.3

21.5

B +4.2 pts

CursorBench 4.0

—

—

—

FrontierCode v1.1 (Main)

—

—

—

Arena

LMArena Elo

1,453

1,466

B +14 Elo

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.

GPT-5.6 Terra

Context
1.1M / 128K out
Parameters
—
Price
$2 / $12
Speed
135 tok/s · 0.3s TTFT
Modalities
text, image → text
License
Proprietary

Balanced GPT-5.6 mid-tier for everyday work; July 30, 2026 API cut brought Standard rates to $2/$12 (20% lower), with strong throughput for the price.

Benchmark charts

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

Reasoning & knowledge

GPQA: B +1.4HLE: B +3.4CritPt: B +9.4AA-LCR: A +0.7Omniscience Acc.: B +4.1MMMU-Pro: B +2.1

Coding

SWE-Pro: B +0.7TermBench: B +7.1TermBench 3: B +6.5TermBench 4: B +4.2SciCode: B +1.4CursorBench: B +3.8WebDev Elo: B +2

Tool use & function calling

τ³-Banking: B +9.1

Agents & computer use

TB-Science: B +5.3GDPval-AA: A +3

Arena

Arena Elo: B +14

Composite indices

AA Index: B +3.4AA Index v4.3: B +4.8

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