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Claude Mythos 5.1 vs Seed 1.8

Claude Mythos 5.1 leads the LLM Stats Score 45.1 to 34.2. Seed 1.8 is 29.1x cheaper per token.

Anthropic · ByteDance · Updated for 2026

Which is better?

Claude Mythos 5.1 leads the overall LLM Stats Score 45.1 to 34.2, ranking #31 overall.

On price, Seed 1.8 is roughly 29.1x cheaper per token on a blended 3:1 input/output basis, which adds up quickly at production volume.

Claude Mythos 5.1 also accepts a larger context window (1,000,000 input tokens), making it the stronger choice for long documents and large codebases.

Based on current LLM Stats indexes, shared benchmarks, pricing, and model metadata for 2026.

Choose Claude Mythos 5.1

  • overall performance matters — it scores 45.1 and ranks #31 on LLM Stats
  • your work emphasizes reasoning and coding — it leads those capability indexes
  • you process long inputs — it offers a 1,000,000 token context window
  • you want the most recent training data — it shipped Sep 2026

Choose Seed 1.8

  • cost matters — it's about 29.1x cheaper per token

At a glance

The differences that matter most.

Claude Mythos 5.1
Anthropic
Seed 1.8
ByteDance
Core performance indexes
LLM Stats Score
45.1
#31
34.2
#91
Reasoning
44.4
#34
33.5
#93
Coding
37.5
#17
19.8
#99
Agents
34.5
#21
14.9
#86
Cost, coverage & limits
Benchmark wins
—
—
Input price
$10.00 / M
$0.25 / M
Output price
$50.00 / M
$2.00 / M
Context window
1,000,000
256,000

Individual benchmarks

1 reported for Claude Mythos 5.1 · 57 for Seed 1.8

No common benchmarks found

Claude Mythos 5.1 and Seed 1.8don't have any common benchmark datasets to compare. They may have been evaluated on different testing suites.

Human preference

Blind head-to-head votes and playground preference scores

Pricing Analysis

Price comparison per million tokens

Seed 1.8 costs less

For input processing, Claude Mythos 5.1 ($10.00/1M tokens) is 40.0x more expensive than Seed 1.8 ($0.25/1M tokens).

For output processing, Claude Mythos 5.1 ($50.00/1M tokens) is 25.0x more expensive than Seed 1.8 ($2.00/1M tokens).

In conclusion, Claude Mythos 5.1 is more expensive than Seed 1.8.*

* Using a 3:1 ratio of input to output tokens

Lowest available price from all providers
Wed Sep 09 2026 • llm-stats.com
Anthropic
Claude Mythos 5.1
Input tokens$10.00
Output tokens$50.00
Best providerAnthropic
ByteDance
Seed 1.8
Input tokens$0.25
Output tokens$2.00
Best providerDeepinfra
Notice missing or incorrect data?Start an Issue→

Context Window

Maximum input and output token capacity

Claude Mythos 5.1 accepts 1,000,000 input tokens compared to Seed 1.8's 256,000 tokens. Seed 1.8 can generate longer responses up to 256,000 tokens, while Claude Mythos 5.1 is limited to 128,000 tokens.

Anthropic
Claude Mythos 5.1
Input1,000,000 tokens
Output128,000 tokens
ByteDance
Seed 1.8
Input256,000 tokens
Output256,000 tokens
Wed Sep 09 2026 • llm-stats.com

Input capabilities

Documented input modalities across available providers

Both Claude Mythos 5.1 and Seed 1.8 support multimodal inputs.

They are both capable of processing various types of data, offering versatility in application.

Claude Mythos 5.1

Text
Images
Audio
Video

Seed 1.8

Text
Images
Audio
Video

License

Usage and distribution terms

Both models are licensed under proprietary licenses.

Both models have usage restrictions defined by their respective organizations.

Claude Mythos 5.1

Proprietary

Closed source

Seed 1.8

Proprietary

Closed source

Release Timeline

When each model was launched

Claude Mythos 5.1 was released on 2026-09-01, while Seed 1.8 was released on 2026-02-17.

Claude Mythos 5.1 is 7 months newer than Seed 1.8.

Claude Mythos 5.1

Sep 1, 2026

1 weeks ago

6mo newer
Seed 1.8

Feb 17, 2026

6 months ago

Knowledge Cutoff

When training data ends

Neither model specifies a knowledge cutoff date.

Unable to compare the recency of their training data.

No cutoff dates available

Provider Availability

Claude Mythos 5.1 is available from Anthropic. Seed 1.8 is available from DeepInfra.

Claude Mythos 5.1

anthropic logo
Anthropic
Input Price:Input: $10.00/1MOutput Price:Output: $50.00/1M

Seed 1.8

deepinfra logo
Deepinfra
Input Price:Input: $0.25/1MOutput Price:Output: $2.00/1M
* Prices shown are per million tokens

Outputs Comparison

Notice missing or incorrect data?Start an Issue discussion→

Judge for yourself.

Run your own prompts against Claude Mythos 5.1 and Seed 1.8 side-by-side, then vote on the output you prefer.

Claude Mythos 5.1
✓ Preferred
Seed 1.8
Open in Playground

FAQ

Common questions about Claude Mythos 5.1 vs Seed 1.8.

Which is better, Claude Mythos 5.1 or Seed 1.8?

Claude Mythos 5.1 leads the LLM Stats Score 45.1 to 34.2. Claude Mythos 5.1 is made by Anthropic and Seed 1.8 is made by ByteDance. The best choice depends on your use case — compare their capability indexes, individual benchmarks, pricing, and limits above.

How does Claude Mythos 5.1 compare to Seed 1.8 in benchmarks?

Claude Mythos 5.1 scores Terminal-Bench 4.0: 60.9%. Seed 1.8 scores CountBench: 96.3%, AIME 2025: 94.3%, VLMsAreBlind: 93.0%, MMLU: 92.3%, AI2D: 89.1%.

Is Claude Mythos 5.1 cheaper than Seed 1.8?

Seed 1.8 is 40.0x cheaper for input tokens. Claude Mythos 5.1 costs $10.00/M input and $50.00/M output via anthropic. Seed 1.8 costs $0.25/M input and $2.00/M output via deepinfra.

What are the context window sizes for Claude Mythos 5.1 and Seed 1.8?

Claude Mythos 5.1 supports 1.0M tokens and Seed 1.8 supports 256K tokens. A larger context window lets you process longer documents, conversations, or codebases in a single request.

What are the main differences between Claude Mythos 5.1 and Seed 1.8?

Key differences include LLM Stats Score (45.1 vs 34.2), context window (1.0M vs 256K), input pricing ($10.00 vs $0.25/M). See the full comparison above for benchmark-by-benchmark results.

Who makes Claude Mythos 5.1 and Seed 1.8?

Claude Mythos 5.1 is developed by Anthropic and Seed 1.8 is developed by ByteDance.

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