Index: edit.js
===================================================================
--- edit.js	(revision 65892)
+++ edit.js	(working copy)
@@ -229,3 +229,36 @@
 	editForm
 } );
 
+//make sure edit summary does not exceed byte limit
+addOnloadHook(function () {
+	var summary = document.getElementById('wpSummary');
+	summary.maxLength = 250; //L must be capitalized in length.
+
+	checkSummary = function (e) {
+		if (!e) e = window.event; //IE
+		
+		//first check to see if this is actually a character key
+		// being pressed.
+		//Based on key-event info from http://unixpapa.com/js/key.html
+		//note === sign, if undefined, still could be a real key
+
+		if (e.which === 0 || e.charCode === 0 || e.ctrlKey || e.altKey || e.metaKey) {
+			return true; //a special key (backspace, etc) so don't interefere.
+		}
+
+		//This basically figures out how many bytes a utf-16 string (which is what js sees) will take in utf-8
+		//by replacing a 2 byte character with 2 *'s, etc, and counting that.
+		//Note, surogate (\uD800-\uDFFF) characters are counted as 2 bytes, since theres two of them
+		//and the actual character takes 4 bytes in utf-8 (2*2=4). might not work perfectly in edge cases such as
+		//such as illegal sequences, but that should never happen.
+
+		len = summary.value.replace(/[\u0080-\u07FF\uD800-\uDFFF]/g, '**').replace(/[\u0800-\uD7FF\uE000-\uFFFF]/g, '***').length;
+		if (len > 250) {
+			if (e.preventDefault) e.preventDefault();
+			e.returnValue = false; //IE
+		}
+	}
+
+	addHandler(summary, 'keypress', checkSummary);
+});
+
Index: ../../includes/EditPage.php
===================================================================
--- ../../includes/EditPage.php	(revision 65892)
+++ ../../includes/EditPage.php	(working copy)
@@ -1486,6 +1486,7 @@
 	 */
 	function getSummaryInput($summary = "", $labelText = null, $inputAttrs = null, $spanLabelAttrs = null) {
 		global $wgUser;
+		//Note: the maxlength is overriden in JS to 250 and to make it use UTF-8 bytes, not characters.
 		$inputAttrs = ( is_array($inputAttrs) ? $inputAttrs : array() ) + array(
 			'id' => 'wpSummary',
 			'maxlength' => '200',