Only remove lines from shell scripts if we're sure it's safe to remove

src/shell-integration/helpers.js

@@ -28,11 +28,35 @@ export function removeLinesMatchingPattern(filePath, pattern) {
   }
 
   const fileContent = fs.readFileSync(filePath, "utf-8");
-  const lines = fileContent.split(os.EOL);
-  const updatedLines = lines.filter((line) => !pattern.test(line));
+  const lines = fileContent.split(/[\r\n]+/);
+  const updatedLines = lines.filter((line) => !shouldRemoveLine(line, pattern));
   fs.writeFileSync(filePath, updatedLines.join(os.EOL), "utf-8");
 }
 
+const maxLineLength = 100;
+function shouldRemoveLine(line, pattern) {
+  const isPatternMatch = pattern.test(line);
+
+  if (!isPatternMatch) {
+    return false;
+  }
+
+  if (line.length > maxLineLength) {
+    // safe-chain only adds lines shorter than maxLineLength
+    // so if the line is longer, it must be from a different 
+    // source and could be dangerous to remove
+    return false;
+  }
+
+  if (line.includes("\n") || line.includes("\r") || line.includes("\u2028") || line.includes("\u2029")) {
+    // If the line contains newlines, something has gone wrong in splitting
+    // \u2028 and \u2029 are Unicode line separator characters (line and paragraph separators)
+    return false;
+  }
+
+  return true;
+}
+
 export function addLineToFile(filePath, line) {
   if (!fs.existsSync(filePath)) {
     fs.writeFileSync(filePath, "", "utf-8");