The AI arena is free today

Open Superagent

Claude Mythos 5.1 vs Phi 4 Reasoning Plus

Claude Mythos 5.1 leads the LLM Stats Score 45.1 to 15.1.

Anthropic · Microsoft · Updated for 2026

Which is better?

Claude Mythos 5.1 leads the overall LLM Stats Score 45.1 to 15.1, ranking #31 overall.

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 want the most recent training data — it shipped Sep 2026

Choose Phi 4 Reasoning Plus

  • you need open weights you can self-host or fine-tune

At a glance

The differences that matter most.

Claude Mythos 5.1
Anthropic
Phi 4 Reasoning Plus
Microsoft
Core performance indexes
LLM Stats Score
45.1
#31
15.1
#229
Reasoning
44.4
#34
15.5
#222
Coding
37.5
#17
5.7
#194
Cost, coverage & limits
Benchmark wins
—
—
Input price
$10.00 / M
— / M
Output price
$50.00 / M
— / M
Context window
1,000,000
—

Individual benchmarks

1 reported for Claude Mythos 5.1 · 11 for Phi 4 Reasoning Plus

No common benchmarks found

Claude Mythos 5.1 and Phi 4 Reasoning Plusdon'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

Context Window

Maximum input and output token capacity

Only Claude Mythos 5.1 specifies input context (1,000,000 tokens). Only Claude Mythos 5.1 specifies output context (128,000 tokens).

Anthropic
Claude Mythos 5.1
Input1,000,000 tokens
Output128,000 tokens
Microsoft
Phi 4 Reasoning Plus
Input- tokens
Output- tokens
Wed Sep 09 2026 • llm-stats.com

Input capabilities

Documented input modalities across available providers

Claude Mythos 5.1 supports multimodal inputs, whereas Phi 4 Reasoning Plus does not.

Claude Mythos 5.1 can handle both text and other forms of data like images, making it suitable for multimodal applications.

Claude Mythos 5.1

Text
Images
Audio
Video

Phi 4 Reasoning Plus

Text
Images
Audio
Video

License

Usage and distribution terms

Claude Mythos 5.1 is licensed under a proprietary license, while Phi 4 Reasoning Plus uses MIT.

License differences may affect how you can use these models in commercial or open-source projects.

Claude Mythos 5.1

Proprietary

Closed source

Phi 4 Reasoning Plus

MIT

Open weights

Release Timeline

When each model was launched

Claude Mythos 5.1 was released on 2026-09-01, while Phi 4 Reasoning Plus was released on 2025-04-30.

Claude Mythos 5.1 is 16 months newer than Phi 4 Reasoning Plus.

Claude Mythos 5.1

Sep 1, 2026

1 weeks ago

1.3yr newer
Phi 4 Reasoning Plus

Apr 30, 2025

1.4 years ago

Knowledge Cutoff

When training data ends

Phi 4 Reasoning Plus has a documented knowledge cutoff of 2025-03-01, while Claude Mythos 5.1's cutoff date is not specified.

We can confirm Phi 4 Reasoning Plus's training data extends to 2025-03-01, but cannot make a direct comparison without Claude Mythos 5.1's cutoff date.

Claude Mythos 5.1

—

Phi 4 Reasoning Plus

Mar 2025

Outputs Comparison

Notice missing or incorrect data?Start an Issue discussion→

Judge for yourself.

Run your own prompts against Claude Mythos 5.1 and Phi 4 Reasoning Plus side-by-side, then vote on the output you prefer.

Claude Mythos 5.1
✓ Preferred
Phi 4 Reasoning Plus
Open in Playground

FAQ

Common questions about Claude Mythos 5.1 vs Phi 4 Reasoning Plus.

Which is better, Claude Mythos 5.1 or Phi 4 Reasoning Plus?

Claude Mythos 5.1 leads the LLM Stats Score 45.1 to 15.1. Claude Mythos 5.1 is made by Anthropic and Phi 4 Reasoning Plus is made by Microsoft. 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 Phi 4 Reasoning Plus in benchmarks?

Claude Mythos 5.1 scores Terminal-Bench 4.0: 60.9%. Phi 4 Reasoning Plus scores FlenQA: 97.9%, HumanEval+: 92.3%, IFEval: 84.9%, OmniMath: 81.9%, AIME 2024: 81.3%.

What are the context window sizes for Claude Mythos 5.1 and Phi 4 Reasoning Plus?

Claude Mythos 5.1 supports 1.0M tokens and Phi 4 Reasoning Plus supports an unknown number of 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 Phi 4 Reasoning Plus?

Key differences include LLM Stats Score (45.1 vs 15.1), multimodal support (yes vs no), licensing (Proprietary vs MIT). See the full comparison above for benchmark-by-benchmark results.

Who makes Claude Mythos 5.1 and Phi 4 Reasoning Plus?

Claude Mythos 5.1 is developed by Anthropic and Phi 4 Reasoning Plus is developed by Microsoft.

Related comparisons