CodeEraser: the write that would bloat your repo is refused before it lands

LLM-assisted codebases drift the same way every time. The same function gets written twice. The same paragraph is pasted into three files. Files only grow. Nobody wrote a bad commit; the repository just got worse one reasonable-looking write at a time. CodeEraser is a sanitizer for agent-written code. It sits in the loop where the agent writes, and it refuses the write that would do one of those things, before the file reaches disk. A write that copies code already in the tree is refused, and the refusal names the region it duplicates and what would pass instead. A write that leaves a file over its line budget (750 by default) is refused the same way, with the budget it crossed. Everything else is a report or a gate: the Stop audit refuses the end of the turn while duplicate blocks remain, ce precommit refuses the commit, and CI refuses the merge. The refusal tells the agent what to change. When an agent asks to create invoicer/discount.py and that content already exists, the answer is one line: the file and lines it duplicates, the token count, and the ordering that would be accepted. The agent reuses the existing implementation and moves on. As a Claude Code plugin it is four hooks and one skill. The same engine runs as a command-line tool and as a desktop GUI, and judges thirteen languages: Python, TypeScript and TSX, Rust, Go, Haskell, C, C++, Java, Lua, R, Markdown and HTML. The repository carries the evidence. One seven-step task was run twice on the same seed, once with CodeEraser in the loop and once without. Without it: four duplicate clone blocks left behind, one duplicated doc segment, one removal still owed. With it: two writes refused before they reached disk, zero of each. Both transcripts and the JSON behind the table are replayed byte for byte in CI. Who it is for: anyone who lets an agent write into a repository they have to keep maintaining. Install from crates.io, Homebrew or winget, or add the plugin to Claude Code; the README at https://github.com/skymanbp/CodeEraser has the one-line setup for each.