llm-coding-agent 0.1a0

Simon Willison's AI Notes published: Release: llm-coding-agent 0.1a0 Another Fable 5 experiment. Now that my LLM library has evolved into more of an agent framework it's time to see what a simple coding agent would look like built on it. I started a new Python library using my python-lib-template-repository GitHub template repository, then ran these two prompts (here's the Claude Code for web transcript ): Write a spec.md for this project - it will depend on the latest “llm” alpha from PyPI and implement a Claude code style coding agent complete with tools for reading and editing files and executing commands Then: Commit the spec, then build it using red/green TDD in a series of sensible commits (each with passing tests and updated docs) - occasionally manually test it using the OpenAI API key in your environment Here's the spec , the resulting README file , and the sequence of commits . I've shipped a slop-alpha to PyPI, so you can run the new agent like this: uvx --prerelease=allow --with llm-coding-agent llm code It's pretty good for a first attempt! Here's the (Fable-authored) README , which lists recipes like llm code --yolo and llm code --allow "pytest*" --allow "git diff*" . It also presents a Python API based around a CodingAgent(model="gpt-5.5", root="/path", approve=True).run("Fix the failing test in tests/test_parser.py") class which I didn't ask for but I'm delighted to see implemented. Here's the suite of tools it implemented , listed using uvx ... llm tools : CodingTools_edit_file(path: str, old_string: str, new_string: str, replace_all: bool = False) -> str Replace an exact string in a file. old_string must match the file contents exactly (including whitespace) and must identify a unique location unless replace_all is true. Returns a diff of the change so it can be verified. CodingTools_execute_command(command: str, timeout: int = 120) -> str Run a shell command in the session root directory. Returns combined stdout and stderr followed by an Exit code line. timeout is in seconds (maximum 600); on timeout the whole process tree is killed. CodingTools_list_files(pattern: str = '**/*', path: str = '.') -> str List files matching a glob pattern, newest first. Skips hidden directories, node_modules, __pycache__ and (in a git repository) anything covered by .gitignore. Returns at most 200 paths relative to the searched directory. CodingTools_read_file(path: str, offset: int = 0, limit: int = 2000) -> str Read a text file, returning numbered lines like cat -n. Paths are relative to the session root. Use offset (0-based first line) and limit (max lines) to page through files too large to read in one call. CodingTools_search_files(pattern: str, path: str = '.', glob: str = None, max_results: int = 100) -> str Search file contents for a regular expression. Returns matches as path:line_number:line, capped at max_results. Use glob (e.g. "*.py") to restrict which files are searched. CodingTools_write_file(path: str, content: str) -> str Create or overwrite a file with the given content. Parent directories are created as needed. Prefer edit_file for modifying existing files. I tried it out by running llm code --yolo and then prompting: mkdir /tmp/demo and then in that folder create a simple swiftui CLI app for telling the time in ascii art Here's the transcript , in which GPT-5.5 reasoning notes that "SwiftUI isn't suitable for a true CLI" and then builds an app that outputs this on swift run AsciiTime : █ █████ ████ █ █ ███ ██ █ █ █ ██ █ ██ █ █ █ ████ ███ █ █ █ █ █ █ █ █ █ █ █ ███ ████ ████ ███ ███ █████ Tags: projects , ai , generative-ai , llm , llm-tool-use , coding-agents , claude-code , claude-mythos-fable