Claude Sonnet 5.5 vs GPT-6 Astra
Updated October 21, 2026. 94 benchmarks have a result for both. Coding is ranked on the Vibe Coding Index; every other board is shown as published.
Decision reading
Claude Sonnet 5.5 and GPT-6 Astra are level for coding, 88.9 against 88.7 on the Vibe Coding Index, so price and context decide.
Pick GPT-6 Astra when the context window is larger, 1.05M against 1M tokens, or when what matters is LMArena WebDev or IOI (Vals AI), where it leads. Pick Claude Sonnet 5.5 when output tokens cost 5.0x less, or when what matters is LiveBench coding or Terminal-Bench 4 (Vals AI), where it leads.
- Shared results
- 94
- Claude Sonnet 5.5 only
- 1
- GPT-6 Astra only
- 25
- 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
No call
Level: 88.9 against 88.7, inside 2 points.
2 benchmarks behind each score
Intelligence
AA Intelligence Index
Claude Sonnet 5.5
Claude Sonnet 5.5 leads, 56.0 against 52.7.
Same board, both measured
Agentic work
AA Agentic Index
No call
Only GPT-6 Astra has a AA Agentic Index result, 51.0.
Directional only
Web design
Design Arena: websites
GPT-6 Astra
GPT-6 Astra leads, 1337 against 1326.
Same board, both measured
General
Vals Index
Claude Sonnet 5.5
Claude Sonnet 5.5 leads, 70.8% against 65.0%.
Same board, both measured
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 5.5
Claude Sonnet 5.5 $0.0070, GPT-6 Astra $0.035 per turn.
List prices
At a glance
- Coding index
- Claude Sonnet 5.5 88.9 from 2 benchmarks, GPT-6 Astra 88.7 from 2 benchmarks.
- Widest category
- Agentic work, 10.6 points apart on average over 18 shared benchmarks.
- Widest single gap
- ALE-Bench: Claude Sonnet 5.5 1819.1 against GPT-6 Astra 2951.3, 37.7 points apart on a 0 to 100 scale.
- Output price
- Claude Sonnet 5.5 $10.00 against GPT-6 Astra $50.00 per million output tokens, 5.0x apart.
- Context window
- Claude Sonnet 5.5 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 5.5 | Bars | GPT-6 Astra | Ties |
|---|---|---|---|---|
| Coding | 12 | 7 | ||
| Intelligence | 1 | 1 | ||
| Agentic work | 7 | 10 | 1 tie | |
| Reasoning | 5 | 6 | ||
| Math | 3 | 2 | 1 tie | |
| Knowledge | 5 | 1 | ||
| Web design | 2 | 5 | ||
| General | 21 | 3 | 1 tie | |
| All shared boards | 56 | 35 | 3 ties |
CodingLike-for-likeFour of these boards feed the Vibe Coding Index127
| Benchmark | Claude Sonnet 5.5 | GPT-6 Astra | Leader |
|---|---|---|---|
| LiveBench coding | 94.7% | 93.7% | Claude Sonnet 5.5 |
| LMArena WebDev | 1768 | 1774 | GPT-6 Astra |
| AA Coding Index | Not measured | 76.9 | Only GPT-6 Astra measured |
| Terminal-Bench 4 (Vals AI) | 64.1% | 59.6% | Claude Sonnet 5.5 |
| Vibe Code Bench (Vals AI) | 92.4% | 89.6% | Claude Sonnet 5.5 |
| Code migration (Vals AI) | 69.8% | 67.7% | Claude Sonnet 5.5 |
| ProgramBench (Vals AI) | 6.5% | 5.5% | Claude Sonnet 5.5 |
| IOI (Vals AI) | 83.1% | 100.0% | GPT-6 Astra |
| Terminal-Bench 2.1 (Vals AI) | 83.2% | 87.3% | GPT-6 Astra |
| SWE-bench Multimodal (Vals AI) | 58.3% | 43.3% | Claude Sonnet 5.5 |
| Vibe Code Bench 1-100 (Vals AI) | Not measured | 27.6% | Only GPT-6 Astra measured |
| CyberBench (Vals AI) | 59.6% | 41.1% | Claude Sonnet 5.5 |
| SciCode | 61.0% | 56.5% | Claude Sonnet 5.5 |
| FrontierCode | 52.1% | 53.3% | GPT-6 Astra |
| FrontierSWE | 61.9% | 65.5% | GPT-6 Astra |
| GSO-Bench | Not measured | 79.4% | Only GPT-6 Astra measured |
| WeirdML | Not measured | 93.3% | Only GPT-6 Astra measured |
| MirrorCode | Not measured | 46.7% | Only GPT-6 Astra measured |
| ALE-Bench | 1819.1 | 2951.3 | GPT-6 Astra |
| LMArena Text: coding | 1513 | 1489 | Claude Sonnet 5.5 |
| LMArena Text: software and IT | 1504 | 1474 | Claude Sonnet 5.5 |
| LMArena WebDev: React | 1817 | 1798 | Claude Sonnet 5.5 |
| LMArena WebDev: HTML | 1741 | 1775 | GPT-6 Astra |
| LMArena WebDev: from an image | 1737 | 1726 | Claude Sonnet 5.5 |
| Neither model has a result on the other 14 boards here | |||
IntelligenceLike-for-likePublic boards, shown as published, kept out of the index11
| Benchmark | Claude Sonnet 5.5 | GPT-6 Astra | Leader |
|---|---|---|---|
| AA Intelligence Index | 56.0 | 52.7 | Claude Sonnet 5.5 |
| Epoch Capabilities Index | 166.2 | 168.8 | GPT-6 Astra |
Agentic workLike-for-likePublic boards, shown as published, kept out of the index710
| Benchmark | Claude Sonnet 5.5 | GPT-6 Astra | Leader |
|---|---|---|---|
| AA Agentic Index | Not measured | 51.0 | Only GPT-6 Astra measured |
| Design Arena: agents building web apps | 1303 | 1372 | GPT-6 Astra |
| Design Arena: agents building full-stack apps | Not measured | 1357 | Only GPT-6 Astra measured |
| Design Arena: agents building mobile apps | 1265 | 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 | 1245 | 1380 | GPT-6 Astra |
| LiveBench research | 83.6% | 85.2% | GPT-6 Astra |
| LiveBench browser | 84.0% | 84.0% | Tie |
| LiveBench long agentic | 78.8% | 82.4% | GPT-6 Astra |
| SREBench (Vals AI) | 30.1% | 56.9% | GPT-6 Astra |
| Finance Agent (Vals AI) | 58.1% | 53.5% | Claude Sonnet 5.5 |
| Tax Agent Bench (Vals AI) | 42.0% | 20.7% | Claude Sonnet 5.5 |
| Legal Research Bench (Vals AI) | 48.1% | 39.4% | Claude Sonnet 5.5 |
| Harvey's Legal Agent Benchmark (Vals AI) | 10.4% | 7.1% | Claude Sonnet 5.5 |
| Excel Modeling Benchmark (Vals AI) | 75.7% | 71.7% | Claude Sonnet 5.5 |
| BioMysteryBench (Vals AI) | 81.1% | 79.3% | Claude Sonnet 5.5 |
| Terminal-Bench-Science (Vals AI) | 47.1% | 62.9% | GPT-6 Astra |
| Vals Science Index | 59.1% | 65.1% | GPT-6 Astra |
| 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 | 75.5% | 64.7% | Claude Sonnet 5.5 |
| Remote Labor Index | Not measured | 20.8% | Only GPT-6 Astra measured |
| BALROG | Not measured | 68.3% | Only GPT-6 Astra measured |
| SpireClimb | 1.3% | 25.7% | GPT-6 Astra |
| Vending-Bench 2 | $11,165 | $15,515 | GPT-6 Astra |
| Neither model has a result on the other 12 boards here | |||
ReasoningLike-for-likePublic boards, shown as published, kept out of the index56
| Benchmark | Claude Sonnet 5.5 | GPT-6 Astra | Leader |
|---|---|---|---|
| LiveBench reasoning | 91.6% | 92.7% | GPT-6 Astra |
| MysteryMechanism (Vals AI) | 49.1% | 53.1% | GPT-6 Astra |
| GPQA Diamond (Artificial Analysis run) | Not measured | 96.3% | Only GPT-6 Astra measured |
| Humanity's Last Exam (Artificial Analysis run) | 55.0% | 54.7% | Claude Sonnet 5.5 |
| GPQA Diamond (Epoch AI run) | 95.6% | 95.8% | GPT-6 Astra |
| ARC-AGI | Not measured | 98.5% | Only GPT-6 Astra measured |
| ARC-AGI-2 | Not measured | 95.0% | Only GPT-6 Astra measured |
| Chess puzzles | 59.0% | 74.0% | GPT-6 Astra |
| Mystery game puzzles | 65.0% | 84.0% | GPT-6 Astra |
| EBR-bench | Not measured | 76.2% | Only GPT-6 Astra measured |
| LMArena Text: hard prompts | 1494 | 1463 | Claude Sonnet 5.5 |
| LMArena Text: expert | 1531 | 1489 | Claude Sonnet 5.5 |
| LMArena Text: hard prompts in English | 1502 | 1464 | Claude Sonnet 5.5 |
| LMArena Vision: diagrams | 1329 | 1297 | Claude Sonnet 5.5 |
| LMArena Vision: homework | 1331 | 1337 | GPT-6 Astra |
| Neither model has a result on the other 6 boards here | |||
MathLike-for-likePublic boards, shown as published, kept out of the index32
| Benchmark | Claude Sonnet 5.5 | GPT-6 Astra | Leader |
|---|---|---|---|
| OTIS Mock AIME | 100.0% | 100.0% | Tie |
| FrontierMath, tiers 1 to 3 | 88.8% | 93.7% | GPT-6 Astra |
| FrontierMath, tier 4 | 80.5% | 97.6% | GPT-6 Astra |
| ProofBench | 100.0% | 99.0% | Claude Sonnet 5.5 |
| LMArena Text: math | 1497 | 1465 | Claude Sonnet 5.5 |
| LMArena Text: mathematical work | 1510 | 1484 | Claude Sonnet 5.5 |
| Neither model has a result on the other 7 boards here | |||
KnowledgeLike-for-likePublic boards, shown as published, kept out of the index51
| Benchmark | Claude Sonnet 5.5 | GPT-6 Astra | Leader |
|---|---|---|---|
| MedCode (Vals AI) | 52.9% | 48.5% | Claude Sonnet 5.5 |
| SimpleQA Verified | 46.5% | 75.6% | GPT-6 Astra |
| LMArena Text: science | 1483 | 1451 | Claude Sonnet 5.5 |
| LMArena Text: medicine and healthcare | 1464 | 1425 | Claude Sonnet 5.5 |
| LMArena Text: legal and government | 1483 | 1462 | Claude Sonnet 5.5 |
| LMArena Text: business and finance | 1468 | 1439 | Claude Sonnet 5.5 |
| Neither model has a result on the other 11 boards here | |||
Web designLike-for-likePublic boards, shown as published, kept out of the index25
| Benchmark | Claude Sonnet 5.5 | GPT-6 Astra | Leader |
|---|---|---|---|
| Design Arena: websites | 1326 | 1337 | GPT-6 Astra |
| Design Arena: UI components | 1367 | 1394 | GPT-6 Astra |
| Design Arena: game dev | 1469 | 1474 | GPT-6 Astra |
| Design Arena: data viz | 1389 | 1335 | Claude Sonnet 5.5 |
| Design Arena: 3D | 1458 | 1501 | GPT-6 Astra |
| Design Arena: all code categories | 1364 | 1379 | GPT-6 Astra |
| Design Arena: SVG | Not measured | 1431 | Only GPT-6 Astra measured |
| Design Arena: ASCII art | Not measured | 1359 | Only GPT-6 Astra measured |
| LiveBench design | 85.0% | 82.0% | Claude Sonnet 5.5 |
GeneralLike-for-likePublic boards, shown as published, kept out of the index213
| Benchmark | Claude Sonnet 5.5 | GPT-6 Astra | Leader |
|---|---|---|---|
| Vals Index | 70.8% | 65.0% | Claude Sonnet 5.5 |
| LiveBench data analysis | 59.5% | 83.0% | GPT-6 Astra |
| Public Benefits Bench (Vals AI) | 67.2% | Not measured | Only Claude Sonnet 5.5 measured |
| SAGE (Vals AI) | 51.8% | 46.4% | Claude Sonnet 5.5 |
| MedScribe (Vals AI) | 91.1% | 87.9% | Claude Sonnet 5.5 |
| Long context reasoning (AA-LCR) | 82.7% | 80.7% | Claude Sonnet 5.5 |
| DTBench | 97.3% | 97.3% | Tie |
| LMCA | 68.3% | 64.4% | Claude Sonnet 5.5 |
| Furniture assembly | 75.0% | 80.0% | GPT-6 Astra |
| LMArena Text | 1473 | 1441 | Claude Sonnet 5.5 |
| LMArena Text: instruction following | 1492 | 1455 | Claude Sonnet 5.5 |
| LMArena Text: creative writing | 1467 | 1420 | Claude Sonnet 5.5 |
| LMArena Vision | 1287 | 1280 | Claude Sonnet 5.5 |
| LMArena Text: English | 1484 | 1447 | Claude Sonnet 5.5 |
| LMArena Text: non-English | 1456 | 1432 | Claude Sonnet 5.5 |
| LMArena Text: Chinese | 1535 | 1489 | Claude Sonnet 5.5 |
| LMArena Text: German | Not measured | 1459 | Only GPT-6 Astra measured |
| LMArena Text: Japanese | Not measured | 1405 | Only GPT-6 Astra measured |
| LMArena Text: Korean | Not measured | 1428 | Only GPT-6 Astra measured |
| LMArena Text: French | 1499 | 1432 | Claude Sonnet 5.5 |
| LMArena Text: Spanish | 1451 | 1422 | Claude Sonnet 5.5 |
| LMArena Text: Russian | 1454 | 1438 | Claude Sonnet 5.5 |
| LMArena Text: Polish | Not measured | 1422 | Only GPT-6 Astra measured |
| LMArena Text: multi-turn | 1465 | 1447 | Claude Sonnet 5.5 |
| LMArena Text: longer queries | 1495 | 1460 | Claude Sonnet 5.5 |
| LMArena Text: writing and language | 1474 | 1437 | Claude Sonnet 5.5 |
| LMArena Text: entertainment and media | 1461 | 1427 | Claude Sonnet 5.5 |
| LMArena Vision: English | 1289 | 1280 | Claude Sonnet 5.5 |
| LMArena Vision: Chinese | Not measured | 1361 | Only GPT-6 Astra measured |
| LMArena Vision: reading text | 1297 | 1292 | Claude Sonnet 5.5 |
| LMArena Vision: creative writing | 1242 | 1286 | GPT-6 Astra |
| 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 5.5 | 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 5.5 costs less
Repository review
50K input + 3K output tokens
Claude Sonnet 5.5 costs less
Agent loop
200K input + 10K output tokens
Claude Sonnet 5.5 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 5.5 | OpenAI GPT-6 Astra |
|---|---|---|
| Maker | Anthropic | OpenAI |
| Weights | No public weights listed | No public weights listed |
| Released | September 28, 2026 | September 4, 2026 |
| Context window | 1M | 1.05M |
| Input $/Mtok | $2.00 | $10.00 |
| Output $/Mtok | $10.00 | $50.00 |
| Coding index | 88.9 | 88.7 |
| Independent measurements behind it | 2 | 2 |
| Cost per solved task | Not computable | Not computable |
| Source | OpenRouter listing | OpenRouter listing |
Questions
Is Claude Sonnet 5.5 better than GPT-6 Astra for coding?
Claude Sonnet 5.5 and GPT-6 Astra are level for coding, 88.9 against 88.7 on the Vibe Coding Index, so price and context decide. Pick GPT-6 Astra when the context window is larger, 1.05M against 1M tokens, or when what matters is LMArena WebDev or IOI (Vals AI), where it leads. Pick Claude Sonnet 5.5 when output tokens cost 5.0x less, or when what matters is LiveBench coding or Terminal-Bench 4 (Vals AI), where it leads.
Which is cheaper, Claude Sonnet 5.5 or GPT-6 Astra?
Claude Sonnet 5.5 costs $2.00 per million input tokens and $10.00 per million output tokens; GPT-6 Astra costs $10.00 and $50.00. Cost per solved task is known for neither of them.
Which has the bigger context window, Claude Sonnet 5.5 or GPT-6 Astra?
GPT-6 Astra, with 1.05M tokens against 1M.
How many benchmarks is the Claude Sonnet 5.5 vs GPT-6 Astra comparison based on?
94 benchmarks have a result for both models as of October 21, 2026. Claude Sonnet 5.5'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.