diff --git a/frontend/index.html b/frontend/index.html
index 19ad60c..6b06952 100644
--- a/frontend/index.html
+++ b/frontend/index.html
@@ -3127,8 +3127,8 @@ const PARSE_INS = {
 function parseBerLen(hex, i) {
 	const b = parseInt(hex.substr(i, 2), 16);
 	if (b < 128) return {len: b, consumed: 2};
-	const n = parseInt(hex.substr(i + 2, b * 2), 16);
-	return {len: n, consumed: 2 + b * 2};
+	const n = b & 0x7F;
+	return {len: parseInt(hex.substr(i + 2, n * 2), 16), consumed: 2 + n * 2};
 }
 
 function parseTlvList(hex) {
diff --git a/frontend/sw.js b/frontend/sw.js
index a490a1c..52a02ec 100644
--- a/frontend/sw.js
+++ b/frontend/sw.js
@@ -1,4 +1,4 @@
-const CACHE = 'otaman-v73';
+const CACHE = 'otaman-v74';
 const URLS = [
   'index.html',
   'help.html',
diff --git a/frontend/tests/apdu_parse.test.js b/frontend/tests/apdu_parse.test.js
index adcb44b..c4cc60b 100644
--- a/frontend/tests/apdu_parse.test.js
+++ b/frontend/tests/apdu_parse.test.js
@@ -165,6 +165,39 @@ test('parseTlvList handles BER-TLVs', () => {
 	assert.strictEqual(tlvs[1].tag, '82');
 });
 
+test('parseBerLen handles short and long form lengths (ISO 7816-4 5.2)', () => {
+	assert.deepStrictEqual(parseBerLen('1200', 0), { len: 18, consumed: 2 });
+	assert.deepStrictEqual(parseBerLen('8112', 0), { len: 18, consumed: 4 });
+	assert.deepStrictEqual(parseBerLen('820100', 0), { len: 256, consumed: 6 });
+	assert.deepStrictEqual(parseBerLen('820182' + '0102030405060708', 0), { len: 386, consumed: 6 });
+});
+
+test('parseTlvList parses long-form lengths (81/82)', () => {
+	const short = parseTlvList('6212' + '8202412183026F078A010580020009880110');
+	assert.strictEqual(short.length, 1);
+	assert.strictEqual(short[0].tag, '62');
+	assert.strictEqual(short[0].length, 18);
+
+	// same content with a long-form outer length
+	const long81 = parseTlvList('628112' + '8202412183026F078A010580020009880110');
+	assert.strictEqual(long81.length, 1);
+	assert.strictEqual(long81[0].length, 18);
+	assert.strictEqual(long81[0].value, short[0].value);
+
+	// 2-byte length form
+	const long82 = parseTlvList('62820004' + '80020009');
+	assert.strictEqual(long82.length, 1);
+	assert.strictEqual(long82[0].length, 4);
+	assert.strictEqual(long82[0].value, '80020009');
+
+	// inner TLV with a long-form length (A5 81 05 85 03 00 00 00)
+	const inner = parseTlvList('A581058503000000');
+	assert.strictEqual(inner.length, 1);
+	assert.strictEqual(inner[0].tag, 'A5');
+	assert.strictEqual(inner[0].length, 5);
+	assert.strictEqual(inner[0].value, '8503000000');
+});
+
 test('gsm7Decode unpacks "HI" from C824', () => {
 	const bytes = new Uint8Array([0xC8, 0x24]);
 	assert.strictEqual(gsm7Decode(bytes), 'HI');
diff --git a/frontend/tests/profiler.test.js b/frontend/tests/profiler.test.js
index 8239701..b053ff3 100644
--- a/frontend/tests/profiler.test.js
+++ b/frontend/tests/profiler.test.js
@@ -641,6 +641,35 @@ test('fcpDecode unwraps an FCI 6F template and rejects malformed input', () => {
 	assert.strictEqual(fcpDecode('6213' + FCP_TRANSPARENT.slice(4)).ok, false); // wrong outer length
 });
 
+test('fcpDecode accepts long-form BER lengths (81/82) — editor preview regression', () => {
+	// 62 12 <18B> vs 62 81 12 <same content>
+	const long81 = '628112' + FCP_TRANSPARENT.slice(4);
+	const d1 = fcpDecode(long81);
+	assert.strictEqual(d1.ok, true);
+	assert.strictEqual(d1.items.find(it => it.key === '80').decoded, '9 bytes');
+
+	// 2-byte length form
+	const d2 = fcpDecode('62820004' + '80020009');
+	assert.strictEqual(d2.ok, true);
+	assert.strictEqual(d2.items.find(it => it.key === '80').decoded, '9 bytes');
+
+	// nested A5 with a long-form length (A5 81 05 …)
+	const d3 = fcpDecode('62138202412183026F078A0105A581058503000000');
+	assert.strictEqual(d3.ok, true);
+	assert.strictEqual(d3.items.find(it => it.key === 'A5/85').decoded, '0 bytes');
+
+	// FCP content >= 128 bytes uses a long-form outer length
+	let big = '';
+	for (let i = 0; i < 13; i++) big += '8808' + '0102030405060708'; // 13 x 10B = 130B
+	const d4 = fcpDecode('628182' + big);
+	assert.strictEqual(d4.ok, true);
+	assert.strictEqual(d4.items.filter(it => it.key === '88').length, 13);
+
+	global.t = s => s;
+	assert.ok(profilerFciPreviewItems(long81).includes('File size: '));
+	delete global.t;
+});
+
 test('fcpDiffHtml highlights differing FCP parameters', () => {
 	global.t = s => s;
 	const same = fcpDiffHtml(FCP_TRANSPARENT, FCP_TRANSPARENT);