Claude Sonnet 4.5 vs GPT-6 Astra
Updated October 21, 2026. 67 benchmarks have a result for both. Coding is ranked on the Vibe Coding Index; every other board is shown as published.
Decision reading
Pick GPT-6 Astra for coding: it scores 88.7 on the Vibe Coding Index against 59.1 for Claude Sonnet 4.5.
Pick Claude Sonnet 4.5 when output tokens cost 3.3x less, or when what matters is LMArena Text: hard prompts in English or LMArena Text: medicine and healthcare, where it leads.
- Shared results
- 67
- Claude Sonnet 4.5 only
- 25
- GPT-6 Astra only
- 52
- Like-for-like categories
- 8 of 9
Shared results can support a head-to-head reading. Results only one model has describe coverage, not superiority.
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, four public coding benchmarks
GPT-6 Astra
GPT-6 Astra scores 88.7 against 59.1.
2 benchmarks behind each score
Intelligence
AA Intelligence Index
GPT-6 Astra
GPT-6 Astra leads, 52.7 against 20.7.
Same board, both measured
Agentic work
AA Agentic Index
GPT-6 Astra
GPT-6 Astra leads, 51.0 against 15.8.
Same board, both measured
Reasoning
GPQA Diamond
No call
Only Claude Sonnet 4.5 has a GPQA Diamond result, 81.6%.
Directional only
Math
AIME
No call
Only Claude Sonnet 4.5 has a AIME result, 88.2%.
Directional only
Knowledge
MMLU Pro
No call
Only Claude Sonnet 4.5 has a MMLU Pro result, 87.4%.
Directional only
Web design
Design Arena: websites
GPT-6 Astra
GPT-6 Astra leads, 1337 against 1190.
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
GPT-6 Astra
GPT-6 Astra takes 1.05M tokens against 1M.
Listed by OpenRouter
Everyday cost
1K input + 500 output tokens
Claude Sonnet 4.5
Claude Sonnet 4.5 $0.011, GPT-6 Astra $0.035 per turn.
List prices
Cost per solved task
One SWE-bench Verified task, solved
No call
Only Claude Sonnet 4.5 has the number, $1.16.
Directional only
At a glance
- Coding index
- Claude Sonnet 4.5 59.1 from 2 benchmarks, GPT-6 Astra 88.7 from 2 benchmarks.
- Widest category
- Math, 45.6 points apart on average over 6 shared benchmarks.
- Widest single gap
- FrontierMath, tier 4: Claude Sonnet 4.5 2.4% against GPT-6 Astra 97.6%, 95.2 points apart on a 0 to 100 scale.
- Output price
- Claude Sonnet 4.5 $15.00 against GPT-6 Astra $50.00 per million output tokens, 3.3x apart.
- Context window
- Claude Sonnet 4.5 takes 1M tokens, GPT-6 Astra 1.05M.
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.
| Category | Claude Sonnet 4.5 | Bars | GPT-6 Astra | Ties |
|---|---|---|---|---|
| Coding | 0 | 9 | ||
| Intelligence | 0 | 2 | ||
| Agentic work | 0 | 6 | ||
| Reasoning | 1 | 8 | ||
| Math | 0 | 6 | ||
| Knowledge | 2 | 4 | ||
| Web design | 0 | 8 | ||
| General | 10 | 11 | ||
| All shared boards | 13 | 54 |
CodingLike-for-likeFour of these boards feed the Vibe Coding Index09
| Benchmark | Claude Sonnet 4.5 | GPT-6 Astra | Leader |
|---|---|---|---|
| SWE-bench Verified | 74.8% | Not measured | Only Claude Sonnet 4.5 measured |
| SWE-bench Multilingual | 67.0% | Not measured | Only Claude Sonnet 4.5 measured |
| LiveBench coding | Not measured | 93.7% | Only GPT-6 Astra measured |
| LMArena WebDev | 1394 | 1774 | GPT-6 Astra |
| AA Coding Index | 52.1 | 76.9 | GPT-6 Astra |
| LiveCodeBench (Vals AI) | 73.0% | Not measured | Only Claude Sonnet 4.5 measured |
| SWE-bench Verified (Vals AI) | 70.0% | Not measured | Only Claude Sonnet 4.5 measured |
| Terminal-Bench 4 (Vals AI) | Not measured | 59.6% | Only GPT-6 Astra measured |
| Vibe Code Bench (Vals AI) | 22.6% | 89.6% | GPT-6 Astra |
| Code migration (Vals AI) | Not measured | 67.7% | Only GPT-6 Astra measured |
| ProgramBench (Vals AI) | Not measured | 5.5% | Only GPT-6 Astra measured |
| IOI (Vals AI) | Not measured | 100.0% | Only GPT-6 Astra measured |
| Terminal-Bench 2.1 (Vals AI) | Not measured | 87.3% | Only GPT-6 Astra measured |
| SWE-bench Multimodal (Vals AI) | Not measured | 43.3% | Only GPT-6 Astra measured |
| Vibe Code Bench 1-100 (Vals AI) | Not measured | 27.6% | Only GPT-6 Astra measured |
| CyberBench (Vals AI) | Not measured | 41.1% | Only GPT-6 Astra measured |
| SciCode | Not measured | 56.5% | Only GPT-6 Astra measured |
| Terminal-Bench | 46.5% | Not measured | Only Claude Sonnet 4.5 measured |
| FrontierCode | Not measured | 53.3% | Only GPT-6 Astra measured |
| FrontierSWE | Not measured | 65.5% | Only GPT-6 Astra measured |
| GSO-Bench | 14.7% | 79.4% | GPT-6 Astra |
| WeirdML | 47.7% | 93.3% | GPT-6 Astra |
| MirrorCode | Not measured | 46.7% | Only GPT-6 Astra measured |
| Cybench | 60.0% | Not measured | Only Claude Sonnet 4.5 measured |
| ALE-Bench | Not measured | 2951.3 | Only GPT-6 Astra measured |
| LMArena Text: coding | 1488 | 1489 | GPT-6 Astra |
| LMArena Text: software and IT | 1473 | 1474 | GPT-6 Astra |
| LMArena WebDev: React | 1386 | 1798 | GPT-6 Astra |
| LMArena WebDev: HTML | 1399 | 1775 | GPT-6 Astra |
| LMArena WebDev: from an image | Not measured | 1726 | Only GPT-6 Astra measured |
| Neither model has a result on the other 8 boards here | |||
IntelligenceLike-for-likePublic boards, shown as published, kept out of the index02
| Benchmark | Claude Sonnet 4.5 | GPT-6 Astra | Leader |
|---|---|---|---|
| AA Intelligence Index | 20.7 | 52.7 | GPT-6 Astra |
| Epoch Capabilities Index | 146.7 | 168.8 | GPT-6 Astra |
Agentic workLike-for-likePublic boards, shown as published, kept out of the index06
| Benchmark | Claude Sonnet 4.5 | GPT-6 Astra | Leader |
|---|---|---|---|
| AA Agentic Index | 15.8 | 51.0 | GPT-6 Astra |
| Design Arena: agents building web apps | 1060 | 1372 | GPT-6 Astra |
| Design Arena: agents building full-stack apps | 1050 | 1357 | GPT-6 Astra |
| Design Arena: agents building mobile apps | 1137 | 1312 | GPT-6 Astra |
| Design Arena: agents building Godot games | Not measured | 1348 | Only GPT-6 Astra measured |
| Design Arena: PowerPoint slides | Not measured | 1245 | Only GPT-6 Astra measured |
| Design Arena: spreadsheets | Not measured | 1380 | Only GPT-6 Astra measured |
| LiveBench research | Not measured | 85.2% | Only GPT-6 Astra measured |
| LiveBench browser | Not measured | 84.0% | Only GPT-6 Astra measured |
| LiveBench long agentic | Not measured | 82.4% | Only GPT-6 Astra measured |
| SREBench (Vals AI) | Not measured | 56.9% | Only GPT-6 Astra measured |
| Finance Agent (Vals AI) | Not measured | 53.5% | Only GPT-6 Astra measured |
| Tax Agent Bench (Vals AI) | Not measured | 20.7% | Only GPT-6 Astra measured |
| Legal Research Bench (Vals AI) | Not measured | 39.4% | Only GPT-6 Astra measured |
| Harvey's Legal Agent Benchmark (Vals AI) | Not measured | 7.1% | Only GPT-6 Astra measured |
| Excel Modeling Benchmark (Vals AI) | Not measured | 71.7% | Only GPT-6 Astra measured |
| BioMysteryBench (Vals AI) | Not measured | 79.3% | Only GPT-6 Astra measured |
| Terminal-Bench-Science (Vals AI) | Not measured | 62.9% | Only GPT-6 Astra measured |
| 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 |
| APEX-Agents | Not measured | 64.7% | Only GPT-6 Astra measured |
| METR time horizons | 67.4% | Not measured | Only Claude Sonnet 4.5 measured |
| Remote Labor Index | 2.1% | 20.8% | GPT-6 Astra |
| GDPval | 42.5% | Not measured | Only Claude Sonnet 4.5 measured |
| BALROG | Not measured | 68.3% | Only GPT-6 Astra measured |
| DeepResearch Bench | 52.6% | Not measured | Only Claude Sonnet 4.5 measured |
| OSWorld | 62.9% | Not measured | Only Claude Sonnet 4.5 measured |
| SpireClimb | Not measured | 25.7% | Only GPT-6 Astra measured |
| Vending-Bench 2 | $3,839 | $15,515 | GPT-6 Astra |
| Neither model has a result on the other 8 boards here | |||
ReasoningLike-for-likePublic boards, shown as published, kept out of the index18
| Benchmark | Claude Sonnet 4.5 | GPT-6 Astra | Leader |
|---|---|---|---|
| GPQA Diamond | 81.6% | Not measured | Only Claude Sonnet 4.5 measured |
| LiveBench reasoning | Not measured | 92.7% | Only GPT-6 Astra measured |
| MysteryMechanism (Vals AI) | Not measured | 53.1% | Only GPT-6 Astra measured |
| MMMU Pro (Vals AI) | 79.3% | Not measured | Only Claude Sonnet 4.5 measured |
| GPQA Diamond (Artificial Analysis run) | Not measured | 96.3% | Only GPT-6 Astra measured |
| Humanity's Last Exam (Artificial Analysis run) | Not measured | 54.7% | Only GPT-6 Astra measured |
| GPQA Diamond (Epoch AI run) | 82.3% | 95.8% | GPT-6 Astra |
| ARC-AGI | 63.7% | 98.5% | GPT-6 Astra |
| ARC-AGI-2 | 13.6% | 95.0% | GPT-6 Astra |
| SimpleBench | 54.3% | Not measured | Only Claude Sonnet 4.5 measured |
| Chess puzzles | 10.0% | 74.0% | GPT-6 Astra |
| Mystery game puzzles | 17.0% | 84.0% | GPT-6 Astra |
| EBR-bench | 2.4% | 76.2% | GPT-6 Astra |
| VPCT | 39.8% | Not measured | Only Claude Sonnet 4.5 measured |
| LMArena Text: hard prompts | 1462 | 1463 | GPT-6 Astra |
| LMArena Text: expert | 1483 | 1489 | GPT-6 Astra |
| LMArena Text: hard prompts in English | 1471 | 1464 | Claude Sonnet 4.5 |
| LMArena Vision: diagrams | Not measured | 1297 | Only GPT-6 Astra measured |
| LMArena Vision: homework | Not measured | 1337 | Only GPT-6 Astra measured |
| Neither model has a result on the other 2 boards here | |||
MathLike-for-likePublic boards, shown as published, kept out of the index06
| Benchmark | Claude Sonnet 4.5 | GPT-6 Astra | Leader |
|---|---|---|---|
| AIME | 88.2% | Not measured | Only Claude Sonnet 4.5 measured |
| MGSM (Vals AI) | 94.3% | Not measured | Only Claude Sonnet 4.5 measured |
| OTIS Mock AIME | 77.8% | 100.0% | GPT-6 Astra |
| FrontierMath, tiers 1 to 3 | 23.9% | 93.7% | GPT-6 Astra |
| FrontierMath, tier 4 | 2.4% | 97.6% | GPT-6 Astra |
| ProofBench | 19.0% | 99.0% | GPT-6 Astra |
| MATH level 5 | 97.7% | Not measured | Only Claude Sonnet 4.5 measured |
| LMArena Text: math | 1449 | 1465 | GPT-6 Astra |
| LMArena Text: mathematical work | 1462 | 1484 | GPT-6 Astra |
| Neither model has a result on the other 4 boards here | |||
KnowledgeLike-for-likePublic boards, shown as published, kept out of the index24
| Benchmark | Claude Sonnet 4.5 | GPT-6 Astra | Leader |
|---|---|---|---|
| MMLU Pro | 87.4% | Not measured | Only Claude Sonnet 4.5 measured |
| LegalBench (Vals AI) | 84.1% | Not measured | Only Claude Sonnet 4.5 measured |
| CaseLaw (Vals AI) | 62.2% | Not measured | Only Claude Sonnet 4.5 measured |
| CorpFin (Vals AI) | 62.0% | Not measured | Only Claude Sonnet 4.5 measured |
| TaxEval (Vals AI) | 73.3% | Not measured | Only Claude Sonnet 4.5 measured |
| MortgageTax (Vals AI) | 64.0% | Not measured | Only Claude Sonnet 4.5 measured |
| MedQA (Vals AI) | 94.7% | Not measured | Only Claude Sonnet 4.5 measured |
| MedCode (Vals AI) | 44.1% | 48.5% | GPT-6 Astra |
| SimpleQA Verified | 30.7% | 75.6% | GPT-6 Astra |
| LMArena Text: science | 1448 | 1451 | GPT-6 Astra |
| LMArena Text: medicine and healthcare | 1444 | 1425 | Claude Sonnet 4.5 |
| LMArena Text: legal and government | 1451 | 1462 | GPT-6 Astra |
| LMArena Text: business and finance | 1440 | 1439 | Claude Sonnet 4.5 |
| Neither model has a result on the other 4 boards here | |||
Web designLike-for-likePublic boards, shown as published, kept out of the index08
| Benchmark | Claude Sonnet 4.5 | GPT-6 Astra | Leader |
|---|---|---|---|
| Design Arena: websites | 1190 | 1337 | GPT-6 Astra |
| Design Arena: UI components | 1173 | 1394 | GPT-6 Astra |
| Design Arena: game dev | 1166 | 1474 | GPT-6 Astra |
| Design Arena: data viz | 1167 | 1335 | GPT-6 Astra |
| Design Arena: 3D | 1158 | 1501 | GPT-6 Astra |
| Design Arena: all code categories | 1183 | 1379 | GPT-6 Astra |
| Design Arena: SVG | 1114 | 1431 | GPT-6 Astra |
| Design Arena: ASCII art | 1204 | 1359 | GPT-6 Astra |
| LiveBench design | Not measured | 82.0% | Only GPT-6 Astra measured |
GeneralLike-for-likePublic boards, shown as published, kept out of the index1011
| Benchmark | Claude Sonnet 4.5 | GPT-6 Astra | Leader |
|---|---|---|---|
| Vals Index | Not measured | 65.0% | Only GPT-6 Astra measured |
| LiveBench data analysis | Not measured | 83.0% | Only GPT-6 Astra measured |
| SAGE (Vals AI) | 36.1% | 46.4% | GPT-6 Astra |
| MedScribe (Vals AI) | 84.5% | 87.9% | GPT-6 Astra |
| Long context reasoning (AA-LCR) | Not measured | 80.7% | Only GPT-6 Astra measured |
| DTBench | 83.2% | 97.3% | GPT-6 Astra |
| LMCA | 38.8% | 64.4% | GPT-6 Astra |
| Furniture assembly | Not measured | 80.0% | Only GPT-6 Astra measured |
| LMArena Text | 1438 | 1441 | GPT-6 Astra |
| LMArena Text: instruction following | 1459 | 1455 | Claude Sonnet 4.5 |
| LMArena Text: creative writing | 1442 | 1420 | Claude Sonnet 4.5 |
| LMArena Vision | Not measured | 1280 | Only GPT-6 Astra measured |
| LMArena Text: English | 1450 | 1447 | Claude Sonnet 4.5 |
| LMArena Text: non-English | 1425 | 1432 | GPT-6 Astra |
| LMArena Text: Chinese | 1460 | 1489 | GPT-6 Astra |
| LMArena Text: German | 1427 | 1459 | GPT-6 Astra |
| LMArena Text: Japanese | 1390 | 1405 | GPT-6 Astra |
| LMArena Text: Korean | 1402 | 1428 | GPT-6 Astra |
| LMArena Text: French | 1459 | 1432 | Claude Sonnet 4.5 |
| LMArena Text: Spanish | 1458 | 1422 | Claude Sonnet 4.5 |
| LMArena Text: Russian | 1437 | 1438 | GPT-6 Astra |
| LMArena Text: Polish | 1423 | 1422 | Claude Sonnet 4.5 |
| LMArena Text: multi-turn | 1465 | 1447 | Claude Sonnet 4.5 |
| LMArena Text: longer queries | 1475 | 1460 | Claude Sonnet 4.5 |
| LMArena Text: writing and language | 1442 | 1437 | Claude Sonnet 4.5 |
| LMArena Text: entertainment and media | 1428 | 1427 | Claude Sonnet 4.5 |
| LMArena Vision: English | Not measured | 1280 | Only GPT-6 Astra measured |
| LMArena Vision: Chinese | Not measured | 1361 | Only GPT-6 Astra measured |
| LMArena Vision: reading text | Not measured | 1292 | Only GPT-6 Astra measured |
| LMArena Vision: creative writing | Not measured | 1286 | Only GPT-6 Astra measured |
| LMArena Document | 1450 | Not measured | Only Claude Sonnet 4.5 measured |
| Neither model has a result on the other 15 boards here | |||
Image generationNot comparablePublic boards, shown as published, kept out of the index0 boards, none shared
| Benchmark | Claude Sonnet 4.5 | 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
Claude Sonnet 4.5 costs less
Repository review
50K input + 3K output tokens
Claude Sonnet 4.5 costs less
Agent loop
200K input + 10K output tokens
Claude Sonnet 4.5 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.
| Specification | Anthropic Claude Sonnet 4.5 | OpenAI GPT-6 Astra |
|---|---|---|
| Maker | Anthropic | OpenAI |
| Weights | No public weights listed | No public weights listed |
| Released | September 29, 2025 | September 4, 2026 |
| Context window | 1M | 1.05M |
| Input $/Mtok | $3.00 | $10.00 |
| Output $/Mtok | $15.00 | $50.00 |
| Coding index | 59.1 | 88.7 |
| Independent measurements behind it | 2 | 2 |
| Cost per solved task | $1.16 | Not computable |
| Source | OpenRouter listing | OpenRouter listing |
Questions
Is Claude Sonnet 4.5 better than GPT-6 Astra for coding?
Pick GPT-6 Astra for coding: it scores 88.7 on the Vibe Coding Index against 59.1 for Claude Sonnet 4.5. Pick Claude Sonnet 4.5 when output tokens cost 3.3x less, or when what matters is LMArena Text: hard prompts in English or LMArena Text: medicine and healthcare, where it leads.
Which is cheaper, Claude Sonnet 4.5 or GPT-6 Astra?
Claude Sonnet 4.5 costs $3.00 per million input tokens and $15.00 per million output tokens; GPT-6 Astra costs $10.00 and $50.00. Cost per solved task is known for Claude Sonnet 4.5 only.
Which has the bigger context window, Claude Sonnet 4.5 or GPT-6 Astra?
GPT-6 Astra, with 1.05M tokens against 1M.
How many benchmarks is the Claude Sonnet 4.5 vs GPT-6 Astra comparison based on?
67 benchmarks have a result for both models as of October 21, 2026. Claude Sonnet 4.5's coding index rests on 2 independent benchmarks and GPT-6 Astra's on 2. Where only one model has a result, the page says so instead of naming a winner.