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Simon Willison quote, Dec 31, 2025

Independent developer and writer · Dec 31, 2025 · Post, 2025: The year in LLMs

This turns out to be the big unlock: the latest coding agents against the ~November 2025 frontier models are remarkably effective if you can give them an existing test suite to work against.

Primary source

Words found on the source page on Sep 25, 2026.

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I can churn out code a hundred times faster. I don’t have the cognitive capacity to stay on top of 100 times the amount of code. So you still need a team of engineers, so you can load balance that cognitive capacity across the team.Aug 19, 2026· Post
I can do way more work as a single engineer than I could without agents.Aug 19, 2026· Post
It used to be that the discipline was enforced on you by the amount of time it took.Aug 19, 2026· Post
That’s exactly the problem with coding agents and software: it’s very easy to keep adding new rooms, because the cost of adding those rooms is so much cheaper.Aug 19, 2026· Post
A prompt injection attack against a browsing agent that can exfiltrate or modify that data is a terrifying prospect.Dec 31, 2025· Post
But if you define agents as LLM systems that can perform useful work via tool calls over multiple steps then agents are here and they are proving to be extraordinarily useful.Dec 31, 2025· Post
Claude Code and friends have conclusively demonstrated that developers will embrace LLMs on the command line, given powerful enough models and the right harness.Dec 31, 2025· Post
I think that’s a waste of a great term, especially since it’s becoming clear likely that most programming will involve some level of AI-assistance in the near future.Dec 31, 2025· Post
The most impactful event of 2025 happened in February, with the quiet release of Claude Code.Dec 31, 2025· Post
The reason I think MCP may be a one-year wonder is the stratospheric growth of coding agents.Dec 31, 2025· Post

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Truly effective defense will mean truly trusting agents to act autonomously, but most companies won’t do that until they are forced to by regular and unremitting hacks by fully autonomous attackers.Ben ThompsonSep 21, 2026· Post
About this quote
Said by
Simon Willison, Independent developer and writer
Where
2025: The year in LLMs
Topics
Coding, Agents
Source
simonwillison.net/2025/Dec/31/the-year-in-llms/

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