Compare / head-to-head
Claude Sonnet 5.5vs
Seed1.8
Claude Sonnet 5.5 and Seed1.8 do not yet share a public benchmark, so quality cannot be compared apples-to-apples. Seed1.8 is 5.3x cheaper per token. Claude Sonnet 5.5 has the larger context window (1M tokens).
Benchmarks from cited public sources; pricing from official pages; status from official provider feeds.
Shared benchmarks
0
no overlap yet
Cheaper per token
Seed1.8
5.3x cheaper, input + output
Larger context
Claude Sonnet 5.5
1M tokens
Providers
2 providers
Anthropic · ByteDance Seed
Claude Sonnet 5.5
Anthropic · released 2026-09-28
textvision
Quality
Benchmark matrix
0 shared · 29 only Claude Sonnet 5.5 · 16 only Seed1.8| Benchmark | Claude Sonnet 5.5 | Seed1.8 | Δ | Edge |
|---|---|---|---|---|
| Reported by both · 0 | ||||
| No public benchmark is reported for both models yet. | ||||
| Only Claude Sonnet 5.5 reports · 29 | ||||
| GPQA Diamond | 95.6% ↗epoch run | not reported | — | — |
| LMArena Elo | 1471 ↗ | not reported | — | — |
| APEX-Agents (Mercor) | 75.5% ↗ | not reported | — | — |
| Chartography (no tools) | 61.6% ↗ | not reported | — | — |
| CursorBench 4.0 | 55.5% ↗ | not reported | — | — |
| FrontierCode v1.1 (Main) | 46.2% ↗ | not reported | — | — |
| FrontierMath Tier 4 v2 (Epoch AI run) | 80.5% ↗epoch run | not reported | — | — |
| FrontierMath Tiers 1-3 v2 (Epoch AI run) | 88.8% ↗epoch run | not reported | — | — |
| FrontierSWE V2 (Proximal Labs) | 61.9% ↗ | not reported | — | — |
| Furniture Assembly (Epoch AI run) | 75% ↗epoch run | not reported | — | — |
| Humanity's Last Exam (with tools) | 64.5% ↗ | not reported | — | — |
| LiveBench Agentic Coding (LiveBench) | 56.3% ↗ | not reported | — | — |
| LiveBench Coding (LiveBench) | 91.4% ↗ | not reported | — | — |
| LiveBench Data Analysis (LiveBench) | 78.6% ↗ | not reported | — | — |
| LiveBench Instruction Following (LiveBench) | 70.5% ↗ | not reported | — | — |
| LiveBench Language (LiveBench) | 83.4% ↗ | not reported | — | — |
| LiveBench Mathematics (LiveBench) | 96.7% ↗ | not reported | — | — |
| LiveBench Reasoning (LiveBench) | 91.6% ↗ | not reported | — | — |
| LMArena Agent (LMArena) | 0.1252 ↗ | not reported | — | — |
| LMArena Vision (LMArena) | 1268.3 ↗ | not reported | — | — |
| LMArena WebDev (LMArena) | 1786.3 ↗ | not reported | — | — |
| Mystery Game Puzzles (Epoch AI run) | 65% ↗epoch run | not reported | — | — |
| OSWorld 2.1 (partial) | 80.1% ↗ | not reported | — | — |
| OTIS Mock AIME 2024-2025 (Epoch AI run) | 100% ↗epoch run | not reported | — | — |
| SAGE (Vals AI) | 51.8% ↗ | not reported | — | — |
| SimpleBench (SimpleBench) | 75.9% ↗ | not reported | — | — |
| SimpleQA Verified | 46.5% ↗epoch run | not reported | — | — |
| Terminal-Bench 4.0 | 70.6% ↗ | not reported | — | — |
| Terminal-Bench 4.0 (Vals AI) | 64.1% ↗ | not reported | — | — |
| Only Seed1.8 reports · 16 | ||||
| SWE-bench Verified | not reported | 72.9% ↗ | — | — |
| MMLU-Pro | not reported | 84.9% ↗ | — | — |
| AIME-25 | not reported | 94.3% ↗ | — | — |
| ARC-AGI-1 | not reported | 67.9% ↗ | — | — |
| BFCL-v4 | not reported | 57.2% ↗ | — | — |
| BrowseComp-en | not reported | 67.6% ↗ | — | — |
| GPQA-Diamond | not reported | 83.8% ↗ | — | — |
| HLE (text-only, agentic search) | not reported | 40.9% ↗ | — | — |
| LiveCodeBench(v6) | not reported | 79.5% ↗ | — | — |
| MM-BrowseComp | not reported | 46.3% ↗ | — | — |
| Multi-SWE-Bench | not reported | 42% ↗ | — | — |
| MultiChallenge | not reported | 66.7% ↗ | — | — |
| OSWorld-Verified (XLANG) | not reported | 61.9% ↗ | — | — |
| Terminal Bench 2.0 | not reported | 45.2% ↗ | — | — |
| WideSearch | not reported | 63.8% ↗ | — | — |
| τ2-Bench | not reported | 72% ↗ | — | — |
Scores tagged "epoch" or "matharena" are independent runs, used only where the lab has not published its own; ⚠ marks rows MathArena flags as released after the competition. Higher is better on every row. Δ is Claude Sonnet 5.5 minus Seed1.8 in the benchmark's own unit. "Not reported" means the lab has not published that figure; it is not a zero. ↗ opens the source.
Specs & pricing
Side by side
Official pricing pages and model cards| Spec | Claude Sonnet 5.5 | Seed1.8 | Edge |
|---|---|---|---|
| Context window | 1M tokens | 256K tokens | Claude Sonnet 5.5 |
| Max output | 128K tokens | 64K tokens | Claude Sonnet 5.5 |
| Input price / 1M | $2 ↗ | $0.25 ↗ | Seed1.8 |
| Output price / 1M | $10 ↗ | $2 ↗ | Seed1.8 |
| Cached input / 1M | $0.2 ↗ | $0.05 ↗ | Seed1.8 |
| Input + output / 1M Lower is cheaper. List prices; batch, tool and regional fees excluded. | $12 | $2.25 | Seed1.8 |
| Modalities | text · vision | text · vision · video | Seed1.8 |
| Released | 2026-09-28 | 2025-12-18 | — |
| Cited benchmark scores | 29 | 16 | — |
Reliability
Provider status
Live from /statusMore matchups
Claude Sonnet 5.5 vs …
Models sharing the most benchmarksMore matchups
Seed1.8 vs …
Models sharing the most benchmarksBuilt by Respan
Which one wins on your data?
Public benchmarks are a starting point. Run Claude Sonnet 5.5 and Seed1.8 on your own prompts with Respan evals, or route to either through one gateway key with automatic failover.