Simon Willison (tweet, Hacker News):
This is the third in my annual series reviewing everything that happened in the LLM space over the past 12 months. For previous years see Stuff we figured out about AI in 2023 and Things we learned about LLMs in 2024.
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Every notable AI lab released at least one reasoning model in 2025. Some labs released hybrids that could be run in reasoning or non-reasoning modes. Many API models now include dials for increasing or decreasing the amount of reasoning applied to a given prompt.
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It turned out that the real unlock of reasoning was in driving tools. Reasoning models with access to tools can plan out multi-step tasks, execute on them and continue to reason about the results such that they can update their plans to better achieve the desired goal.
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Reasoning models are also exceptional at producing and debugging code. The reasoning trick means they can start with an error and step through many different layers of the codebase to find the root cause. I’ve found even the gnarliest of bugs can be diagnosed by a good reasoner with the ability to read and execute code against even large and complex codebases.
Previously:
Artificial Intelligence ChatGPT Claude Developer Tool Google Gemini/Bard LLaMA Programming
naruse (Hacker News):
Ruby Box is a new (experimental) feature to provide separation about definitions. Ruby Box is enabled when an environment variable RUBY_BOX=1 is specified. The class is Ruby::Box.
Definitions loaded in a box are isolated in the box. Ruby Box can isolate/separate monkey patches, changes of global/class variables, class/module definitions, and loaded native/ruby libraries from other boxes.
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ZJIT is a new just-in-time (JIT) compiler, which is developed as the next generation of YJIT. You need Rust 1.85.0 or newer to build Ruby with ZJIT support, and ZJIT is enabled when --zjit is specified.
We’re building a new compiler for Ruby because we want to both raise the performance ceiling (bigger compilation unit size and SSA IR) and encourage more outside contribution (by becoming a more traditional method compiler). See our blog post for more details.
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Ractor, Ruby’s parallel execution mechanism, has received several improvements. A new class, Ractor::Port, was introduced to address issues related to message sending and receiving (see our blog post).
Compiler Just-In-Time Compilation (JIT) Language Design Programming Ruby
