Claude Opus 5.5 vs DeepSeek V4.1 Flash

At a glance

• Capability index

  • Claude Opus 5.5166.8
  • DeepSeek V4.1 Flash155.6

  Claude Opus 5.5 is 11.3 points higher.

• Price per 1M tokens

  • Claude Opus 5.5$8.00
  • DeepSeek V4.1 Flash$0.464

  DeepSeek V4.1 Flash is 17 times cheaper.

• Context window

  • Claude Opus 5.51M tokens
  • DeepSeek V4.1 Flash1M tokens

  They take in about the same.

• Released

  • Claude Opus 5.5Sep 22, 2026
  • DeepSeek V4.1 FlashSep 10, 2026

  Claude Opus 5.5 is 12 days newer.

Where each scores higher

On the 21 tests both have taken, each on its own scale. A gap of a point or two can sit within a test’s margin of error.

1 more test has results for only one of them; the table below lists every result.

Everything side by side

Comparison of Claude Opus 5.5 vs DeepSeek V4.1 Flash

Measure	Claude Opus 5.5Anthropic	DeepSeek V4.1 FlashDeepSeek
Model
Maker	Anthropic	DeepSeek
Sold here by	Anthropic	engy
API model ID	claude-opus-5-5	deepseek-v4.1-flash
Released	Sep 22, 2026	Sep 10, 2026
Knowledge cutoff	Jun 2026	May 2025
Weights	Closed: hosted access only	Open: downloadable
Developer’s country	United States	China
Hosts selling it	40including Anthropic directly	80
Training compute	Not published	4.3 × 10²⁴ FLOPEpoch AI estimate
Test results
Capability index	166.8 (best of these models)#1 of 277	155.6#31 of 277
LiveBench overall	83.2% (best of these models)#2 of 70	81.1%#9 of 70
Arena text	1508 (best of these models)#3 of 415	1475#38 of 415
LiveBench coding	89.3% (best of these models)#2 of 70	80.0%#23 of 70
Arena WebDev	1811 (best of these models)#1 of 142	1619#24 of 142
Arena coding	1545 (best of these models)#8 of 410	1526#27 of 410
LiveBench mathematics	97.1% (best of these models)#1 of 70	93.3%#23 of 70
Mock AIME 2024–2025	100.0% (best of these models)#1 of 303	98.3%#24 of 303
FrontierMath Tiers 1–3	91.2% (best of these models)#3 of 117	67.4%#30 of 117
FrontierMath Tier 4	95.0% (best of these models)#6 of 73	26.8%#41 of 73
Arena math	1503 (best of these models)#14 of 400	1495#22 of 400
SimpleQA Verified	72.2% (best of these models)#5 of 90	42.9%#43 of 90
LiveBench agentic coding	71.7%#2 of 70	77.3% (best of these models)#1 of 70
CursorBench	57.8%#1 of 71	Not tested
LiveBench language	86.3% (best of these models)#10 of 70	81.2%#29 of 70
LiveBench instructions	67.0%#40 of 70	70.0% (best of these models)#32 of 70
Arena creative writing	1517 (best of these models)#1 of 413	1439#61 of 413
Arena instruction following	1518 (best of these models)#2 of 415	1477#24 of 415
LiveBench data analysis	80.3% (best of these models)#8 of 70	79.3%#18 of 70
LiveBench reasoning	92.2% (best of these models)#3 of 70	86.7%#32 of 70
GPQA Diamond	90.6% (best of these models)#41 of 323	89.8%#50 of 323
Chess puzzles	67.0% (best of these models)#4 of 243	48.0%#20 of 243
Arena hard prompts	1532 (best of these models)#3 of 415	1499#36 of 415
Price per million tokens
Input	$4.00	$0.04 (best of these models)
Output	$20.00	$0.08 (best of these models)
Blended, 3 input to 1 output	$8.00	$0.05 (best of these models)
Cached input	$0.20	$0.008 (best of these models)
Writing to the cache	$5.00	Not reported
The maker’s own price	This listing	Not sold directly
Limits
Context window	1M tokens (best of these models)	327.7K tokens
Max input	1M tokens	1M tokens
Max output	128K tokens (best of these models)	65.5K tokens
Features
Reads	images, PDFs and text	images and text
Produces	text	text
Reasoning	Yeseffort low, medium, high, xhigh, max; can be switched off	Yeseffort none, low, high, max; can be switched off; thinking budget can be set
Tool calling	Yes	Yes
Structured output	Yes, such as JSON	Yes, such as JSON
File attachments	Yes	Yes
Temperature setting	Fixed by the provider	Supported

Bold marks the better value in each row. Prices are each model’s own list price, or the middle price across hosts when the maker does not sell it, blended as three input tokens for every output token. Test results as published by LiveBench (Apache-2.0), Epoch AI (CC BY 4.0), Cursor CursorBench, compiled by Epoch AI (CC BY 4.0), Arena (CC BY 4.0); model details and prices from models.dev (MIT). Confirm pricing with the provider before use.