Claude Opus 4.5 vs InternLM 2.5 20B

Compare Claude Opus 4.5 and InternLM 2.5 20B: pricing, performance, context window, latency, and best use cases. Side-by-side comparison on XALEN.

Updated 2026-05-21 · By Abhishek Raj · Our methodology

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Feature Claude Opus 4.5 InternLM 2.5 20B
CategoryFrontierOpen Source
Parameters~2.5T20B
Context Window200K256K
Input Price$0.15/1M tokens$0.02/1M tokens
Output Price$0.75/1M tokens$0.04/1M tokens
Latency~900ms~180ms

Choose Claude Opus 4.5 when:

  • ✓ Creative writing
  • ✓ Complex analysis
  • ✓ Research
Key Strengths:

Superior creativity, Nuanced reasoning, Complex analysis

Choose InternLM 2.5 20B when:

  • ✓ Long context tasks
  • ✓ Research
  • ✓ Multilingual
Key Strengths:

256K context, Strong reasoning, Good multilingual

Verdict: Claude Opus 4.5 vs InternLM 2.5 20B

For cost efficiency, InternLM 2.5 20B wins at $0.02/1M input tokens. For speed, InternLM 2.5 20B is faster at ~180ms. Claude Opus 4.5 excels at Creative writing while InternLM 2.5 20B is better for Long context tasks. Both are available on XALEN through a single API — try them in the Playground to see which fits your workload.

Detailed Analysis

Pricing Comparison

Claude Opus 4.5 costs $0.15/1M input tokens and $0.75/1M output tokens. InternLM 2.5 20B costs $0.02 input and $0.04 output. InternLM 2.5 20B is 7.5x cheaper on input tokens. XALEN offers batch processing at 50% discount on both models.

Performance & Context

Claude Opus 4.5 has a 200K context window with ~900ms latency. InternLM 2.5 20B offers 256K context at ~180ms. InternLM 2.5 20B has the larger context window.

Best For

Claude Opus 4.5 (Frontier) is optimized for: Creative writing, Complex analysis, Research. InternLM 2.5 20B (Open Source) works best for: Long context tasks, Research, Multilingual.

Try Both on XALEN

Both models are available through XALEN's OpenAI-compatible API. Switch between them by changing the model parameter:

from xalen import XALEN

client = XALEN(api_key="xln_test_YOUR_KEY")

# Use Claude Opus 4.5
response_a = client.chat.completions.create(
    model="claude-opus-4-5",
    messages=[{"role": "user", "content": "Your question here"}]
)

# Use InternLM 2.5 20B
response_b = client.chat.completions.create(
    model="internlm-2-5-20b",
    messages=[{"role": "user", "content": "Your question here"}]
)

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Get API Key Try in Playground

Frequently Asked Questions

Which is better, Claude Opus 4.5 or InternLM 2.5 20B?

Claude Opus 4.5 (Frontier, ~2.5T) offers Superior creativity. InternLM 2.5 20B (Open Source, 20B) offers 256K context. Choose Claude Opus 4.5 for Creative writing or InternLM 2.5 20B for Long context tasks.

How much does Claude Opus 4.5 cost vs InternLM 2.5 20B?

Claude Opus 4.5: $0.15/1M input, $0.75/1M output. InternLM 2.5 20B: $0.02/1M input, $0.04/1M output. Both available on XALEN with batch processing at 50% discount.

Can I use both models on XALEN?

Yes. XALEN provides 200+ models through a single OpenAI-compatible API. Switch between Claude Opus 4.5 and InternLM 2.5 20B by changing the model parameter. No code changes needed.

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Last updated: 2026-05-21. Pricing and specifications may change. Check pricing page for latest rates.