Simon Willison
8/10 signal
llm-coding-agent 0.1a0
agentictool-use
What happened
Simon Willison released `llm-coding-agent 0.1a0`, a lightweight Claude Code-style coding agent built on his `llm` library. The agent was bootstrapped using Claude Code and TDD. It implements specific tools for exact string replacement in files (`CodingTools_edit_file`) and shell command execution with timeouts.
Why it matters
It provides a simple, transparent, and highly functional blueprint for building custom file-editing and execution tools for LLMs.
The take
This is a great, lightweight reference implementation of a coding agent. Willison's choice of an exact-string-replacement tool (`old_string` to `new_string` with diff verification) is a highly reliable alternative to full-file rewrites or complex AST parsers. It's a clean, educational codebase for anyone wanting to build custom coding tools.
Do this
Examine the codebase of `llm-coding-agent` on GitHub, specifically looking at how the `CodingTools_edit_file` tool is designed to safely modify files without breaking context.
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