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Skill0 starsChanged 2 months agoMITView on GitHub

The 600-line file limit and how to split a file that hits it. Use when a write is denied by the metal hook, when a file needs splitting into a module directory, or when the user says "metal" or "split this file".

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    1. wolffe/three.js-skills★ 4same name

    How matches are found. Word for word: the exact same text. Edited: shares passages with this file (“99% same” means 99% of its five-word phrases also appear here; 10% or more counts). Their own version: similar meaning, or, weakest, the same name. We can’t tell which project had it first. Projects are counted among the 200 most-starred candidates, and mentions are links to the repository we found, up to 50 per site, so both counts are a floor.

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SKILL.md

metal

One rule, enforced by a hook rather than by asking nicely.

No large files

Hard limit: 600 lines of code per source file. A PreToolUse hook denies any Write over it, and a PostToolUse hook warns on any Edit that pushes a file past it. Do not work around it: no 400-character lines, no heredoc through Bash, no "just for now".

It counts code, not prose. Comments, blank lines and string bodies are stripped before counting, so a file is judged on what you have to read to understand it. Measured across 555 files in seven repos: median comment share 33%, so 600 code lines is roughly 900 raw.

Advisory at 440. Act on it then. At 601 you cut wherever you happen to be standing, which is how one coherent file becomes two incoherent ones.

Test files: 1000, advisory at 800. A suite is a list of cases, not logic that decomposes. Detected by path (test/, tests/, spec/, __tests__/, a test_ prefix, a .test./.spec. in the name), so latest.cpp and contest.c are not tests.

Only code you wrote. Skipped by path segment: node_modules, target, vendor, dist, build, .git, .venv, venv, site-packages, __pycache__, .cache, .next, third_party, plus /tmp and scratchpad/. Nobody maintains a vendored dependency, so "split it into a directory" is a method with no one left to apply it.

The one legal exception. A genuinely cohesive unit may grant itself room, in the file, with a reason:

// metal: allow 700 - one lexer state machine, the transition table does not split

At most 1000, the reason must be a real sentence, and going past your own number is denied like any other file. If you cannot write the sentence, the file splits.

How to split

  • Directory named after the file, one concern per file, one entry point re-exporting them. Rust: parser.rs → parser/lex.rs + parser/expr.rs + parser/emit.rs, with parser.rs keeping only the mod/pub use lines. C: render.c → render/lex.c + render/emit.c behind render.h. Python: parser.py → parser/ with __init__.py re-exporting.
  • Cut along seams that already exist: parse / emit / state / io / errors. Never at an arbitrary line.
  • One file, one job. If naming that job takes more than three words, it is two files.
  • Eight 80-line files beat one 640-line file. Every file fits on a screen and is findable by its name alone.

metal has no opinion about which language you write in, and no opinion about your build flags.

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