Claude Opus 5.5 vs DeepSeek V4.1 Flash 1017.
Verdict by category, tale of the tape, shared benchmarks only, and cost at three workloads — all from the tracked data.
Verdict by category
| Category | Claude Opus 5.5 | DeepSeek V4.1 Flash 1017 | Winner |
|---|---|---|---|
| League Score | 96.8 | 81.4 | Claude Opus 5.5 |
| Coding (SWE-bench %) | — | — | — |
| Reasoning (GPQA %) | — | — | — |
| Context (tokens) | 1000000 | 1000000 | Draw |
| Speed (tok/s) | 75.6 | — | — |
| Price (blended $/1M) | $8.00 | $0.52 | DeepSeek V4.1 Flash 1017 (cheaper) |
Tale of the tape
| Spec | Claude Opus 5.5 | DeepSeek V4.1 Flash 1017 |
|---|---|---|
| Maker | Anthropic | DeepSeek |
| Released | Sep 22, 2026 | Oct 17, 2026 |
| League Score | 97 | 81 |
| Context | 1,000,000 tokens | 1,000,000 tokens |
| Max output | 128,000 | 384,000 |
| $/1M input | $4.00 | $0.30 |
| $/1M output | $20.00 | $1.20 |
| Weights | Closed | Open |
| Speed | 75.6 t/s | — |
Head-to-head benchmarks (shared only)
| Benchmark | Claude Opus 5.5 | DeepSeek V4.1 Flash 1017 |
|---|---|---|
| LiveBench overall | 86.5 | 79.2 |
Cost at three workloads
| Workload | Claude Opus 5.5 | DeepSeek V4.1 Flash 1017 |
|---|---|---|
| Light — 1M in / 250K out | $9.00 | $0.60 |
| Standard — 10M in / 2.5M out | $90.00 | $6.00 |
| Long-context — 50M in / 5M out | $300.00 | $21.00 |
The pick
Pick Claude Opus 5.5 if you want the higher overall League Score.
Pick DeepSeek V4.1 Flash 1017 if you want the lower running cost; you want downloadable weights / self-hosting.
All figures from the model database — sources and dates on each model page. Cost your own workload or compare a different pair.
Frequently asked questions
Which is better overall, Claude Opus 5.5 or DeepSeek V4.1 Flash 1017?
Claude Opus 5.5 leads on overall League Score, 97 to 81 — a gap of 15 points on a composite of sourced benchmarks. That is overall form, not every category: check the per-category verdicts before choosing.
Which is cheaper, Claude Opus 5.5 or DeepSeek V4.1 Flash 1017?
DeepSeek V4.1 Flash 1017 is cheaper: $0.52 vs $8.00 blended per 1M tokens (3:1 input/output mix) — about 15.2x less per token.
Which has the bigger context window, Claude Opus 5.5 or DeepSeek V4.1 Flash 1017?
Neither — both take 1M of context.
Are Claude Opus 5.5 and DeepSeek V4.1 Flash 1017 open source?
Claude Opus 5.5 is closed weights — API access only; DeepSeek V4.1 Flash 1017 is open weights — it can be downloaded and self-hosted.