Open Weight LLMs Reveal Inconsistent Performance Across Hosted Providers

Aug 18, 2025
Simon Willison’s Weblog
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Summary

Open weight large language models reveal inconsistent performance across hosted providers, with those running the latest vLLM framework generally outperforming older versions, while conformance suites and compatibility tests aim to ensure consistent implementation.

Key Points

  • Open weight LLMs exhibit inconsistent performance across different hosted providers
  • Providers running the latest vLLM framework generally perform better than those using older versions
  • Conformance suites and compatibility tests help ensure consistent implementation across providers

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