GPT-5.6 Terra vs GPT-6 Astra

GPT-6 Astra leads GPT-5.6 Terra on coding, 85.1 to 63.9 on the Vibe Coding Index, and GPT-5.6 Terra costs 4.2x less per output token ($12.00 vs $50.00 per million). Updated October 22, 2026; 105 benchmarks have a result for both.

Replace GPT-5.6 Terra Replace GPT-6 Astra

GPT-5.6 TerraOpenAI

Coding: 63.9
Overall: 68.1
Output $/M: $12.00

GPT-6 AstraOpenAI

Coding: 85.1
Overall: 83.0
Output $/M: $50.00

vs boards won of 105 shared, 1 tied

GPT-5.6 Terra or GPT-6 Astra: which to pick

Pick GPT-6 Astra for coding: it scores 85.1 on the Vibe Coding Index against 63.9 for GPT-5.6 Terra, though on 5 benchmarks against 6.

Pick GPT-5.6 Terra for output tokens 4.2x cheaper ($12.00 vs $50.00 per million) and work measured by CyberBench (Vals AI) or LMArena Text: software and IT, where it leads.

Model AGPT-5.6 TerraOpenAI63.9/1006 independent benchmarks$0.42 per solved task Model BGPT-6 AstraOpenAI85.1/1005 independent benchmarksNo cost per solved task

1052424

Shared results: 105
GPT-5.6 Terra only: 24
GPT-6 Astra only: 24
Like-for-like categories: 8 of 9

Only benchmarks that tested both models count toward a pick; a result only one model has is shown but not compared.

Which one for your work

Each card is decided by one number both models carry. Where only one has it, the card says so and makes no call.

Coding
Vibe Coding Index, six public coding benchmarks
GPT-6 Astra
GPT-6 Astra scores 85.1 against 63.9.
6 and 5 benchmarks behind the scores
Intelligence
AA Intelligence Index
GPT-6 Astra
GPT-6 Astra leads, 52.7 against 42.1.
Same board, both measured
Agentic work
AA Agentic Index
GPT-6 Astra
GPT-6 Astra leads, 51.0 against 43.2.
Same board, both measured
Reasoning
GPQA Diamond
No call
Only GPT-5.6 Terra has a GPQA Diamond result, 90.9%.
Directional only
Knowledge
MMLU Pro
No call
Only GPT-5.6 Terra has a MMLU Pro result, 86.7%.
Directional only
Web design
Design Arena: websites
GPT-6 Astra
GPT-6 Astra leads, 1336 against 1268.
Same board, both measured
General
Vals Index
No call
Only GPT-6 Astra has a Vals Index result, 65.0%.
Directional only
Long documents
Listed context window
No call
Both take 1.05M tokens.
Listed by OpenRouter
Everyday cost
1K input + 500 output tokens
GPT-5.6 Terra
GPT-5.6 Terra $0.0080, GPT-6 Astra $0.035 per turn.
List prices
Cost per solved task
One SWE-bench Verified task, solved
No call
Only GPT-5.6 Terra has the number, $0.42.
Directional only

At a glance

Coding index: GPT-5.6 Terra 63.9 from 6 benchmarks, GPT-6 Astra 85.1 from 5 benchmarks.
Widest category: Agentic work, 21.5 points apart on average over 17 shared benchmarks.
Widest single gap: Terminal-Bench-Science (Vals AI): GPT-5.6 Terra 10.0% against GPT-6 Astra 62.9%, 52.9 points apart on a 0 to 100 scale.
Output price: GPT-5.6 Terra $12.00 against GPT-6 Astra $50.00 per million output tokens, 4.2x apart.
Context window: Both take 1.05M tokens.

Benchmark by benchmark

First the score: boards each model leads, per category, where both have a result. Then every board, a category to a fold; bars are each result on a 0 to 100 scale, so compare the two in a row, not one row with another.

Boards won, where both have a result
Category	GPT-5.6 Terra	GPT-6 Astra	Ties
Coding	2	20
Intelligence	0	2
Agentic work	3	13	1 tie
Reasoning	3	10
Math	0	6
Knowledge	3	4
Web design	0	9
General	14	15
All shared boards	25	79	1 tie

CodingLike-for-likeSix of these boards feed the Vibe Coding Index220

Coding benchmarks for GPT-5.6 Terra and GPT-6 Astra
Benchmark	GPT-5.6 Terra	GPT-6 Astra	Leader
LiveBench coding	86.2%	93.7%	GPT-6 Astra
LMArena WebDev	1522	1774	GPT-6 Astra
AA Coding Index	76.7	76.9	GPT-6 Astra
LiveCodeBench (Vals AI)	85.9%	Not measured	Only GPT-5.6 Terra measured
SWE-bench Verified (Vals AI)	95.4%	Not measured	Only GPT-5.6 Terra measured
Terminal-Bench 4 (Vals AI)	22.7%	59.6%	GPT-6 Astra
Vibe Code Bench (Vals AI)	74.6%	89.6%	GPT-6 Astra
Code migration (Vals AI)	47.8%	67.7%	GPT-6 Astra
ProgramBench (Vals AI)	0.5%	5.5%	GPT-6 Astra
IOI (Vals AI)	87.6%	100.0%	GPT-6 Astra
Terminal-Bench 2.1 (Vals AI)	77.5%	87.3%	GPT-6 Astra
SWE-bench Multimodal (Vals AI)	Not measured	43.3%	Only GPT-6 Astra measured
Vibe Code Bench 1-100 (Vals AI)	14.8%	27.6%	GPT-6 Astra
SkillsBench (Vals AI)	58.9%	Not measured	Only GPT-5.6 Terra measured
CyberBench (Vals AI)	72.1%	41.1%	GPT-5.6 Terra
SciCode	55.0%	56.5%	GPT-6 Astra
Terminal-Bench Hard (Artificial Analysis run)	62.9%	Not measured	Only GPT-5.6 Terra measured
FrontierCode	41.3%	53.3%	GPT-6 Astra
FrontierSWE	Not measured	65.5%	Only GPT-6 Astra measured
GSO-Bench	Not measured	79.4%	Only GPT-6 Astra measured
WeirdML	78.3%	93.3%	GPT-6 Astra
MirrorCode	Not measured	46.7%	Only GPT-6 Astra measured
ALE-Bench	1951.4	2951.3	GPT-6 Astra
LMArena Text: coding	1485	1489	GPT-6 Astra
LMArena Text: software and IT	1482	1474	GPT-5.6 Terra
LMArena WebDev: React	1513	1798	GPT-6 Astra
LMArena WebDev: HTML	1526	1775	GPT-6 Astra
LMArena WebDev: from an image	1541	1726	GPT-6 Astra
SciCode	10.8%	12.3%	GPT-6 Astra
SWE-Bench Pro V2	92.4%	96.9%	GPT-6 Astra
SWE Atlas: Codebase QnA	Not measured	59.1%	Only GPT-6 Astra measured
SWE Atlas: Refactoring	Not measured	59.1%	Only GPT-6 Astra measured
SWE Atlas: Test Writing	Not measured	50.7%	Only GPT-6 Astra measured
Neither model has a result on the other 10 boards here

IntelligenceLike-for-likePublic boards, shown as published, kept out of the index02

Intelligence benchmarks for GPT-5.6 Terra and GPT-6 Astra
Benchmark	GPT-5.6 Terra	GPT-6 Astra	Leader
AA Intelligence Index	42.1	52.7	GPT-6 Astra
Epoch Capabilities Index	160.1	168.8	GPT-6 Astra

Agentic workLike-for-likePublic boards, shown as published, kept out of the index313

Agentic work benchmarks for GPT-5.6 Terra and GPT-6 Astra
Benchmark	GPT-5.6 Terra	GPT-6 Astra	Leader
AA Agentic Index	43.2	51.0	GPT-6 Astra
Design Arena: agents building web apps	1120	1374	GPT-6 Astra
Design Arena: agents building full-stack apps	1061	1357	GPT-6 Astra
Design Arena: agents building mobile apps	1110	1312	GPT-6 Astra
Design Arena: agents building Android apps	1060	Not measured	Only GPT-5.6 Terra measured
Design Arena: agents building Godot games	Not measured	1348	Only GPT-6 Astra measured
Design Arena: agents building games	1083	Not measured	Only GPT-5.6 Terra measured
Design Arena: HTML slides	1047	Not measured	Only GPT-5.6 Terra measured
Design Arena: PowerPoint slides	1104	1217	GPT-6 Astra
Design Arena: spreadsheets	Not measured	1378	Only GPT-6 Astra measured
LiveBench research	60.4%	85.2%	GPT-6 Astra
LiveBench browser	84.0%	84.0%	Tie
LiveBench long agentic	48.4%	82.4%	GPT-6 Astra
SREBench (Vals AI)	9.5%	56.9%	GPT-6 Astra
Finance Agent (Vals AI)	54.4%	53.5%	GPT-5.6 Terra
Tax Agent Bench (Vals AI)	30.0%	20.7%	GPT-5.6 Terra
Legal Research Bench (Vals AI)	41.4%	39.4%	GPT-5.6 Terra
Harvey's Legal Agent Benchmark (Vals AI)	Not measured	7.1%	Only GPT-6 Astra measured
Excel Modeling Benchmark (Vals AI)	66.2%	71.7%	GPT-6 Astra
BioMysteryBench (Vals AI)	Not measured	79.3%	Only GPT-6 Astra measured
Terminal-Bench-Science (Vals AI)	10.0%	62.9%	GPT-6 Astra
Vals Science Index	Not measured	65.1%	Only GPT-6 Astra measured
Time Horizon Index (Vals AI)	Not measured	90.5%	Only GPT-6 Astra measured
CUA-bench (Vals AI)	Not measured	19.2%	Only GPT-6 Astra measured
Robo-bench (Vals AI)	Not measured	23.3%	Only GPT-6 Astra measured
τ²-Bench Telecom	86.3%	Not measured	Only GPT-5.6 Terra measured
APEX-Agents	58.2%	64.7%	GPT-6 Astra
Remote Labor Index	Not measured	20.8%	Only GPT-6 Astra measured
BALROG	53.2%	68.3%	GPT-6 Astra
SpireClimb	Not measured	25.7%	Only GPT-6 Astra measured
Vending-Bench 2	$7,343	$15,515	GPT-6 Astra
Neither model has a result on the other 11 boards here

ReasoningLike-for-likePublic boards, shown as published, kept out of the index310

Reasoning benchmarks for GPT-5.6 Terra and GPT-6 Astra
Benchmark	GPT-5.6 Terra	GPT-6 Astra	Leader
GPQA Diamond	90.9%	Not measured	Only GPT-5.6 Terra measured
LiveBench reasoning	90.6%	92.7%	GPT-6 Astra
MysteryMechanism (Vals AI)	Not measured	53.1%	Only GPT-6 Astra measured
MMMU Pro (Vals AI)	86.5%	Not measured	Only GPT-5.6 Terra measured
GPQA Diamond (Artificial Analysis run)	92.5%	96.3%	GPT-6 Astra
Humanity's Last Exam (Artificial Analysis run)	42.9%	54.7%	GPT-6 Astra
GPQA Diamond (Epoch AI run)	93.3%	95.8%	GPT-6 Astra
ARC-AGI	96.5%	98.5%	GPT-6 Astra
ARC-AGI-2	83.9%	95.0%	GPT-6 Astra
SimpleBench	48.9%	Not measured	Only GPT-5.6 Terra measured
Chess puzzles	47.0%	74.0%	GPT-6 Astra
Mystery game puzzles	35.0%	84.0%	GPT-6 Astra
EBR-bench	Not measured	76.2%	Only GPT-6 Astra measured
LMArena Text: hard prompts	1469	1463	GPT-5.6 Terra
LMArena Text: expert	1496	1489	GPT-5.6 Terra
LMArena Text: hard prompts in English	1465	1464	GPT-5.6 Terra
LMArena Vision: diagrams	1295	1297	GPT-6 Astra
LMArena Vision: homework	1312	1337	GPT-6 Astra
Kagi LLM Benchmark	51.3%	Not measured	Only GPT-5.6 Terra measured
Humanity's Last Exam (Scale run)	Not measured	60.6%	Only GPT-6 Astra measured
Neither model has a result on the other 3 boards here

MathLike-for-likePublic boards, shown as published, kept out of the index06

Math benchmarks for GPT-5.6 Terra and GPT-6 Astra
Benchmark	GPT-5.6 Terra	GPT-6 Astra	Leader
OTIS Mock AIME	99.7%	100.0%	GPT-6 Astra
FrontierMath, tiers 1 to 3	86.0%	93.7%	GPT-6 Astra
FrontierMath, tier 4	70.7%	97.6%	GPT-6 Astra
ProofBench	74.0%	99.0%	GPT-6 Astra
LMArena Text: math	1465	1465	GPT-6 Astra
LMArena Text: mathematical work	1478	1484	GPT-6 Astra
MathArena	Not measured	81.9%	Only GPT-6 Astra measured
Neither model has a result on the other 7 boards here

KnowledgeLike-for-likePublic boards, shown as published, kept out of the index34

Knowledge benchmarks for GPT-5.6 Terra and GPT-6 Astra
Benchmark	GPT-5.6 Terra	GPT-6 Astra	Leader
MMLU Pro	86.7%	Not measured	Only GPT-5.6 Terra measured
LegalBench (Vals AI)	85.1%	Not measured	Only GPT-5.6 Terra measured
CorpFin (Vals AI)	65.3%	Not measured	Only GPT-5.6 Terra measured
TaxEval (Vals AI)	76.2%	Not measured	Only GPT-5.6 Terra measured
MortgageTax (Vals AI)	67.3%	Not measured	Only GPT-5.6 Terra measured
MedCode (Vals AI)	43.4%	48.5%	GPT-6 Astra
SimpleQA Verified	43.2%	75.6%	GPT-6 Astra
LMArena Text: science	1452	1451	GPT-5.6 Terra
LMArena Text: medicine and healthcare	1430	1425	GPT-5.6 Terra
LMArena Text: legal and government	1461	1462	GPT-6 Astra
LMArena Text: business and finance	1448	1439	GPT-5.6 Terra
FACTS Benchmark Suite	52.0%	75.7%	GPT-6 Astra
PRBench Finance	Not measured	47.5%	Only GPT-6 Astra measured
PRBench Legal	Not measured	48.4%	Only GPT-6 Astra measured
Neither model has a result on the other 6 boards here

Web designLike-for-likePublic boards, shown as published, kept out of the index09

Web design benchmarks for GPT-5.6 Terra and GPT-6 Astra
Benchmark	GPT-5.6 Terra	GPT-6 Astra	Leader
Design Arena: websites	1268	1336	GPT-6 Astra
Design Arena: UI components	1256	1394	GPT-6 Astra
Design Arena: game dev	1229	1480	GPT-6 Astra
Design Arena: data viz	1240	1334	GPT-6 Astra
Design Arena: 3D	1134	1500	GPT-6 Astra
Design Arena: all code categories	1240	1379	GPT-6 Astra
Design Arena: SVG	1219	1430	GPT-6 Astra
Design Arena: ASCII art	1178	1353	GPT-6 Astra
LiveBench design	76.0%	82.0%	GPT-6 Astra

GeneralLike-for-likePublic boards, shown as published, kept out of the index1415

General benchmarks for GPT-5.6 Terra and GPT-6 Astra
Benchmark	GPT-5.6 Terra	GPT-6 Astra	Leader
Vals Index	Not measured	65.0%	Only GPT-6 Astra measured
LiveBench data analysis	79.3%	83.0%	GPT-6 Astra
Public Benefits Bench (Vals AI)	62.4%	Not measured	Only GPT-5.6 Terra measured
SAGE (Vals AI)	47.0%	46.4%	GPT-5.6 Terra
MedScribe (Vals AI)	82.9%	87.9%	GPT-6 Astra
Vals Multimodal Index	65.1%	Not measured	Only GPT-5.6 Terra measured
IFBench	71.2%	Not measured	Only GPT-5.6 Terra measured
Long context reasoning (AA-LCR)	83.0%	80.7%	GPT-5.6 Terra
DTBench	93.3%	97.3%	GPT-6 Astra
LMCA	54.9%	64.4%	GPT-6 Astra
Surface Evolver Bench	83.8%	Not measured	Only GPT-5.6 Terra measured
Furniture assembly	54.2%	80.0%	GPT-6 Astra
LMArena Text	1448	1441	GPT-5.6 Terra
LMArena Text: instruction following	1456	1455	GPT-5.6 Terra
LMArena Text: creative writing	1413	1420	GPT-6 Astra
LMArena Vision	1271	1280	GPT-6 Astra
LMArena Text: English	1449	1447	GPT-5.6 Terra
LMArena Text: non-English	1441	1432	GPT-5.6 Terra
LMArena Text: Chinese	1514	1489	GPT-5.6 Terra
LMArena Text: German	1460	1459	GPT-5.6 Terra
LMArena Text: Japanese	1454	1405	GPT-5.6 Terra
LMArena Text: Korean	1427	1428	GPT-6 Astra
LMArena Text: French	1466	1432	GPT-5.6 Terra
LMArena Text: Spanish	1451	1422	GPT-5.6 Terra
LMArena Text: Russian	1452	1438	GPT-5.6 Terra
LMArena Text: Polish	1446	1422	GPT-5.6 Terra
LMArena Text: multi-turn	1453	1447	GPT-5.6 Terra
LMArena Text: longer queries	1454	1460	GPT-6 Astra
LMArena Text: writing and language	1431	1437	GPT-6 Astra
LMArena Text: entertainment and media	1418	1427	GPT-6 Astra
LMArena Vision: English	1272	1280	GPT-6 Astra
LMArena Vision: Chinese	1337	1361	GPT-6 Astra
LMArena Vision: reading text	1278	1292	GPT-6 Astra
LMArena Vision: humor	1236	Not measured	Only GPT-5.6 Terra measured
LMArena Vision: creative writing	1248	1286	GPT-6 Astra
LMArena Document	1472	Not measured	Only GPT-5.6 Terra measured
EQ-Bench 4	1234	Not measured	Only GPT-5.6 Terra measured
Neither model has a result on the other 11 boards here

Image generationNot comparablePublic boards, shown as published, kept out of the index0 boards, none shared

Image generation benchmarks for GPT-5.6 Terra and GPT-6 Astra
Benchmark	GPT-5.6 Terra	GPT-6 Astra	Leader
Neither model has a result on 5 boards here

What each workload costs

Three fixed token mixes at each model's listed price, so per-token rates become a bill.

Chat turn

1K input + 500 output tokens

GPT-5.6 Terra$0.0080Fits in one request

GPT-6 Astra$0.035Fits in one request

GPT-5.6 Terra costs less

Repository review

50K input + 3K output tokens

GPT-5.6 Terra$0.136Fits in one request

GPT-6 Astra$0.650Fits in one request

GPT-5.6 Terra costs less

Agent loop

200K input + 10K output tokens

GPT-5.6 Terra$0.520Fits in one request

GPT-6 Astra$2.50Fits in one request

GPT-5.6 Terra costs less

Listed OpenRouter rates, without cache or batch discounts. A workload that does not fit a model's context window would need splitting.

Specification differences

The leading value in a row is marked; a row with a missing value names no leader. Our two rows are marked in red.

Specifications of GPT-5.6 Terra and GPT-6 Astra
Specification	OpenAI GPT-5.6 Terra	OpenAI GPT-6 Astra
Maker	OpenAI	OpenAI
Weights	No public weights listed	No public weights listed
Released	July 9, 2026	September 4, 2026
Context window	1.05M	1.05M
Input $/Mtok	$2.00	$10.00
Output $/Mtok	$12.00	$50.00
Coding index	63.9	85.1
Independent measurements behind it	6	5
Cost per solved task	$0.42	Not computable
Source	OpenRouter listing	OpenRouter listing

Questions

Is GPT-5.6 Terra better than GPT-6 Astra for coding?

Pick GPT-6 Astra for coding: it scores 85.1 on the Vibe Coding Index against 63.9 for GPT-5.6 Terra, though on 5 benchmarks against 6. Pick GPT-5.6 Terra for output tokens 4.2x cheaper ($12.00 vs $50.00 per million) and work measured by CyberBench (Vals AI) or LMArena Text: software and IT, where it leads.

Which is cheaper, GPT-5.6 Terra or GPT-6 Astra?

GPT-5.6 Terra costs $2.00 per million input tokens and $12.00 per million output tokens; GPT-6 Astra costs $10.00 and $50.00. Cost per solved task is known for GPT-5.6 Terra only.

Which has the bigger context window, GPT-5.6 Terra or GPT-6 Astra?

Neither: both take 1.05M tokens.

How many benchmarks is the GPT-5.6 Terra vs GPT-6 Astra comparison based on?

105 benchmarks have a result for both models as of October 22, 2026. GPT-5.6 Terra's coding index rests on 6 independent benchmarks and GPT-6 Astra's on 5. Where only one model has a result, the page says so instead of naming a winner.

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GPT-5.6 Terra or GPT-6 Astra: which to pick

Which one for your work

Coding

Intelligence

Agentic work

Reasoning

Knowledge

Web design

General

Long documents

Everyday cost

Cost per solved task

At a glance

Benchmark by benchmark

What each workload costs

Chat turn

Repository review

Agent loop

Specification differences

Questions

Compare next