只是打开看看的文件，也被它格式化了
Reformatted files it only opened to read
智能体对与任务无关的文件做了格式化、换行或风格调整，真正的改动淹没在空白噪音里。
适用于: Claude Code · Cursor · Codex · Copilot agent
症状
改了几百行，几乎没有一行是功能性的。任务根本不需要的文件里，引号风格、尾逗号或 import 顺序都变了。
为什么会这样
智能体会“顺手跑格式化或整理一下”（agent-review AR004）。claudecodeguides.com 称之为“格式化冲动”：Claude 只是打开文件看个 import，也会顺手清理。
示例
摘自 agent-review 分类（AR004）。
diff- const x = 1; const y = 2; const z = 3
+ const x = 1
+ const y = 2
+ const z = 3
复制即用的修复
按你用的智能体挑选文件。规则片段用英文写，放进任何仓库都能用。
规则
Claude Code：加入 CLAUDE.md
CLAUDE.md## No drive-by formatting
- Do not reformat, re-indent, reorder imports or change quote style in code you are not functionally changing.
- Run the formatter only on the lines or files you changed (for example `npx prettier --write <changed files>`),
never on the whole repo, unless asked.
- If a file needs a format pass, propose it as a separate commit.
规则
Codex、Copilot 编码智能体等：加入 AGENTS.md
AGENTS.md## No drive-by formatting
- Do not reformat, re-indent, reorder imports or change quote style in code you are not functionally changing.
- Run the formatter only on the lines or files you changed (for example `npx prettier --write <changed files>`),
never on the whole repo, unless asked.
- If a file needs a format pass, propose it as a separate commit.
Cursor 规则
Cursor：项目规则
.cursor/rules/drive-by-reformat.mdc---
description: "AgentFails: Reformatted files it only opened to read"
alwaysApply: true
---
## No drive-by formatting
- Do not reformat, re-indent, reorder imports or change quote style in code you are not functionally changing.
- Run the formatter only on the lines or files you changed (for example `npx prettier --write <changed files>`),
never on the whole repo, unless asked.
- If a file needs a format pass, propose it as a separate commit.
钩子
只格式化改动过的文件（pre-commit）
lint-staged 只格式化暂存区的文件，提交钩子就不会把整个仓库重新格式化一遍。
package.json{
"lint-staged": {
"*.{ts,tsx,js,jsx,css,md}": "prettier --write"
}
}
CI / 脚本
Diff 预算检查（提交前或在 CI 中运行）
改编自 dev.to（yureki_lab）的 diff budget 文章。读取真实的 git diff，所以通过 shell 做的修改也逃不掉。用法：python3 scripts/diff_budget.py origin/main 6 150
scripts/diff_budget.py#!/usr/bin/env python3
"""Fail if the diff vs BASE touches files outside .agent-scope or exceeds the budget."""
import fnmatch, os, subprocess, sys
base = sys.argv[1] if len(sys.argv) > 1 else "HEAD"
max_files = int(sys.argv[2]) if len(sys.argv) > 2 else 6
max_lines = int(sys.argv[3]) if len(sys.argv) > 3 else 150
allowed = []
if os.path.exists(".agent-scope"):
allowed = [l.strip() for l in open(".agent-scope") if l.strip() and not l.startswith("#")]
out = subprocess.run(["git", "diff", "--numstat", base], capture_output=True, text=True, check=True).stdout
untracked = subprocess.run(["git", "ls-files", "--others", "--exclude-standard"],
capture_output=True, text=True, check=True).stdout.split()
files, lines, outside = 0, 0, []
rows = [r.split("\t") for r in out.strip().splitlines()] + [["0", "0", p] for p in untracked]
for added, deleted, path in rows:
files += 1
if added != "-":
lines += int(added) + int(deleted)
if allowed and not any(fnmatch.fnmatch(path, p) for p in allowed):
outside.append(path)
problems = []
if outside:
problems.append("out-of-scope files: " + ", ".join(outside))
if files > max_files:
problems.append(f"{files} files changed (budget {max_files})")
if lines > max_lines:
problems.append(f"{lines} lines changed (budget {max_lines})")
if problems:
print("OVER BUDGET: " + "; ".join(problems))
sys.exit(1)
print(f"within budget: {files} files, {lines} lines")