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Claude Opus 5.5 vs Phi 4 Reasoning Plus

Claude Opus 5.5 leads the LLM Stats Score 59.7 to 15.0.

Anthropic · Microsoft · Updated for 2026

Which is better?

Claude Opus 5.5 leads the overall LLM Stats Score 59.7 to 15.0, ranking #1 overall.

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

Choose Claude Opus 5.5

  • overall performance matters — it scores 59.7 and ranks #1 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 Opus 5.5
Anthropic
Phi 4 Reasoning Plus
Microsoft
Core performance indexes
LLM Stats Score
59.7
#1
15.0
#237
Reasoning
57.8
#1
15.4
#230
Coding
51.7
#1
5.7
#202
Cost, coverage & limits
Benchmark wins
—
—
Input price
$4.00 / M
— / M
Output price
$20.00 / M
— / M
Context window
1,000,000
—

Capability indexes

Additional strengths measured across groups of related public benchmarks

1 shared
Index
Claude Opus 5.5
Phi 4 Reasoning Plus
Math
42.5#5
18.3#183
Conservative TrueSkill rating · higher is betterHow scores work

Individual benchmarks

31 reported for Claude Opus 5.5 · 11 for Phi 4 Reasoning Plus

No common benchmarks found

Claude Opus 5.5 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 Opus 5.5 specifies input context (1,000,000 tokens). Only Claude Opus 5.5 specifies output context (128,000 tokens).

Anthropic
Claude Opus 5.5
Input1,000,000 tokens
Output128,000 tokens
Microsoft
Phi 4 Reasoning Plus
Input- tokens
Output- tokens
Tue Sep 22 2026 • llm-stats.com

Input capabilities

Documented input modalities across available providers

Claude Opus 5.5 supports multimodal inputs, whereas Phi 4 Reasoning Plus does not.

Claude Opus 5.5 can handle both text and other forms of data like images, making it suitable for multimodal applications.

Claude Opus 5.5

Text
Images
Audio
Video

Phi 4 Reasoning Plus

Text
Images
Audio
Video

License

Usage and distribution terms

Claude Opus 5.5 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 Opus 5.5

Proprietary

Closed source

Phi 4 Reasoning Plus

MIT

Open weights

Release Timeline

When each model was launched

Claude Opus 5.5 was released on 2026-09-22, while Phi 4 Reasoning Plus was released on 2025-04-30.

Claude Opus 5.5 is 17 months newer than Phi 4 Reasoning Plus.

Claude Opus 5.5

Sep 22, 2026

0 days ago

1.4yr newer
Phi 4 Reasoning Plus

Apr 30, 2025

1.4 years ago

Knowledge Cutoff

When training data ends

Claude Opus 5.5 has a knowledge cutoff of 2026-06-01, while Phi 4 Reasoning Plus has a cutoff of 2025-03-01.

Claude Opus 5.5 has more recent training data (up to 2026-06-01), making it potentially better informed about events through that date compared to Phi 4 Reasoning Plus (2025-03-01).

Claude Opus 5.5

Jun 2026

1.3 yr newer
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 Opus 5.5 and Phi 4 Reasoning Plus side-by-side, then vote on the output you prefer.

Claude Opus 5.5
✓ Preferred
Phi 4 Reasoning Plus
Open in Playground

FAQ

Common questions about Claude Opus 5.5 vs Phi 4 Reasoning Plus.

Which is better, Claude Opus 5.5 or Phi 4 Reasoning Plus?

Claude Opus 5.5 leads the LLM Stats Score 59.7 to 15.0. Claude Opus 5.5 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 Opus 5.5 compare to Phi 4 Reasoning Plus in benchmarks?

Claude Opus 5.5 scores BenchCAD (with Python tool): 96.2%, Global-MMLU: 94.3%, SWE-bench Multilingual: 93.9%, MILU: 93.1%, ArXivMath: 91.2%. 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 Opus 5.5 and Phi 4 Reasoning Plus?

Claude Opus 5.5 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 Opus 5.5 and Phi 4 Reasoning Plus?

Key differences include LLM Stats Score (59.7 vs 15.0), multimodal support (yes vs no), licensing (Proprietary vs MIT). See the full comparison above for benchmark-by-benchmark results.

Who makes Claude Opus 5.5 and Phi 4 Reasoning Plus?

Claude Opus 5.5 is developed by Anthropic and Phi 4 Reasoning Plus is developed by Microsoft.

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