Simon Willison questions LLM greenfield vs. legacy belief
Simon Willison asks whether the belief that LLMs and coding agents only help with greenfield development — not existing codebases — still holds widely.
Score breakdown
Watch this thread if it becomes accessible — if community consensus has shifted on LLMs handling legacy codebases, it changes how teams should evaluate agentic coding tools for brownfield projects.
- 01Author Simon Willison posted the question on X (Twitter) on April 17, 2026.
- 02The post questions whether LLMs and coding agents are still perceived as better suited for greenfield development than existing codebases.
- 03The full content of the post was inaccessible due to a JavaScript rendering error on x.com.
Simon Willison posted on X (formerly Twitter) challenging or probing the conventional wisdom that LLMs and coding agents excel at greenfield development but fall short when working with existing, legacy codebases. The post appears to frame this as an open question about the current state of belief in the developer community, though the full thread content was not accessible due to a JavaScript rendering error on x.com.\n\nBecause the underlying content could not be retrieved — only the page's error state was returned — no further technical details, data, or arguments from the post can be reported. The headline alone suggests Willison may be questioning whether this belief has shifted as coding agents have matured, but this cannot be confirmed without access to the actual post body and replies.
Key facts
- 01Author Simon Willison posted the question on X (Twitter) on April 17, 2026.
- 02The post questions whether LLMs and coding agents are still perceived as better suited for greenfield development than existing codebases.
- 03The full content of the post was inaccessible due to a JavaScript rendering error on x.com.
- 04No technical details, benchmark data, or follow-up arguments could be extracted from the source URL.
Topics
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