diff --git a/src/core/services/subtitle-cue-parser.test.ts b/src/core/services/subtitle-cue-parser.test.ts
new file mode 100644
index 0000000..7702312
--- /dev/null
+++ b/src/core/services/subtitle-cue-parser.test.ts
@@ -0,0 +1,246 @@
+import assert from 'node:assert/strict';
+import test from 'node:test';
+import { parseSrtCues, parseAssCues, parseSubtitleCues } from './subtitle-cue-parser';
+import type { SubtitleCue } from './subtitle-cue-parser';
+
+test('parseSrtCues parses basic SRT content', () => {
+  const content = [
+    '1',
+    '00:00:01,000 --> 00:00:04,000',
+    'こんにちは',
+    '',
+    '2',
+    '00:00:05,000 --> 00:00:08,500',
+    '元気ですか',
+    '',
+  ].join('\n');
+
+  const cues = parseSrtCues(content);
+
+  assert.equal(cues.length, 2);
+  assert.equal(cues[0]!.startTime, 1.0);
+  assert.equal(cues[0]!.endTime, 4.0);
+  assert.equal(cues[0]!.text, 'こんにちは');
+  assert.equal(cues[1]!.startTime, 5.0);
+  assert.equal(cues[1]!.endTime, 8.5);
+  assert.equal(cues[1]!.text, '元気ですか');
+});
+
+test('parseSrtCues handles multi-line subtitle text', () => {
+  const content = [
+    '1',
+    '00:01:00,000 --> 00:01:05,000',
+    'これは',
+    'テストです',
+    '',
+  ].join('\n');
+
+  const cues = parseSrtCues(content);
+
+  assert.equal(cues.length, 1);
+  assert.equal(cues[0]!.text, 'これは\nテストです');
+});
+
+test('parseSrtCues handles hours in timestamps', () => {
+  const content = [
+    '1',
+    '01:30:00,000 --> 01:30:05,000',
+    'テスト',
+    '',
+  ].join('\n');
+
+  const cues = parseSrtCues(content);
+
+  assert.equal(cues[0]!.startTime, 5400.0);
+  assert.equal(cues[0]!.endTime, 5405.0);
+});
+
+test('parseSrtCues handles VTT-style dot separator', () => {
+  const content = [
+    '1',
+    '00:00:01.000 --> 00:00:04.000',
+    'VTTスタイル',
+    '',
+  ].join('\n');
+
+  const cues = parseSrtCues(content);
+
+  assert.equal(cues.length, 1);
+  assert.equal(cues[0]!.startTime, 1.0);
+});
+
+test('parseSrtCues returns empty array for empty content', () => {
+  assert.deepEqual(parseSrtCues(''), []);
+  assert.deepEqual(parseSrtCues('  \n\n  '), []);
+});
+
+test('parseSrtCues skips malformed timing lines gracefully', () => {
+  const content = [
+    '1',
+    'NOT A TIMING LINE',
+    'テスト',
+    '',
+    '2',
+    '00:00:01,000 --> 00:00:02,000',
+    '有効',
+    '',
+  ].join('\n');
+
+  const cues = parseSrtCues(content);
+
+  assert.equal(cues.length, 1);
+  assert.equal(cues[0]!.text, '有効');
+});
+
+test('parseAssCues parses basic ASS dialogue lines', () => {
+  const content = [
+    '[Script Info]',
+    'Title: Test',
+    '',
+    '[Events]',
+    'Format: Layer, Start, End, Style, Name, MarginL, MarginR, MarginV, Effect, Text',
+    'Dialogue: 0,0:00:01.00,0:00:04.00,Default,,0,0,0,,こんにちは',
+    'Dialogue: 0,0:00:05.00,0:00:08.50,Default,,0,0,0,,元気ですか',
+  ].join('\n');
+
+  const cues = parseAssCues(content);
+
+  assert.equal(cues.length, 2);
+  assert.equal(cues[0]!.startTime, 1.0);
+  assert.equal(cues[0]!.endTime, 4.0);
+  assert.equal(cues[0]!.text, 'こんにちは');
+  assert.equal(cues[1]!.startTime, 5.0);
+  assert.equal(cues[1]!.endTime, 8.5);
+  assert.equal(cues[1]!.text, '元気ですか');
+});
+
+test('parseAssCues strips override tags from text', () => {
+  const content = [
+    '[Events]',
+    'Format: Layer, Start, End, Style, Name, MarginL, MarginR, MarginV, Effect, Text',
+    'Dialogue: 0,0:00:01.00,0:00:04.00,Default,,0,0,0,,{\\b1}太字{\\b0}テスト',
+  ].join('\n');
+
+  const cues = parseAssCues(content);
+
+  assert.equal(cues[0]!.text, '太字テスト');
+});
+
+test('parseAssCues handles text containing commas', () => {
+  const content = [
+    '[Events]',
+    'Format: Layer, Start, End, Style, Name, MarginL, MarginR, MarginV, Effect, Text',
+    'Dialogue: 0,0:00:01.00,0:00:04.00,Default,,0,0,0,,はい、そうです、ね',
+  ].join('\n');
+
+  const cues = parseAssCues(content);
+
+  assert.equal(cues[0]!.text, 'はい、そうです、ね');
+});
+
+test('parseAssCues handles \\N line breaks', () => {
+  const content = [
+    '[Events]',
+    'Format: Layer, Start, End, Style, Name, MarginL, MarginR, MarginV, Effect, Text',
+    'Dialogue: 0,0:00:01.00,0:00:04.00,Default,,0,0,0,,一行目\\N二行目',
+  ].join('\n');
+
+  const cues = parseAssCues(content);
+
+  assert.equal(cues[0]!.text, '一行目\\N二行目');
+});
+
+test('parseAssCues returns empty for content without Events section', () => {
+  const content = [
+    '[Script Info]',
+    'Title: Test',
+  ].join('\n');
+
+  assert.deepEqual(parseAssCues(content), []);
+});
+
+test('parseAssCues skips Comment lines', () => {
+  const content = [
+    '[Events]',
+    'Format: Layer, Start, End, Style, Name, MarginL, MarginR, MarginV, Effect, Text',
+    'Comment: 0,0:00:01.00,0:00:04.00,Default,,0,0,0,,これはコメント',
+    'Dialogue: 0,0:00:05.00,0:00:08.00,Default,,0,0,0,,これは字幕',
+  ].join('\n');
+
+  const cues = parseAssCues(content);
+
+  assert.equal(cues.length, 1);
+  assert.equal(cues[0]!.text, 'これは字幕');
+});
+
+test('parseAssCues handles hour timestamps', () => {
+  const content = [
+    '[Events]',
+    'Format: Layer, Start, End, Style, Name, MarginL, MarginR, MarginV, Effect, Text',
+    'Dialogue: 0,1:30:00.00,1:30:05.00,Default,,0,0,0,,テスト',
+  ].join('\n');
+
+  const cues = parseAssCues(content);
+
+  assert.equal(cues[0]!.startTime, 5400.0);
+  assert.equal(cues[0]!.endTime, 5405.0);
+});
+
+test('parseSubtitleCues auto-detects SRT format', () => {
+  const content = [
+    '1',
+    '00:00:01,000 --> 00:00:04,000',
+    'SRTテスト',
+    '',
+  ].join('\n');
+
+  const cues = parseSubtitleCues(content, 'test.srt');
+  assert.equal(cues.length, 1);
+  assert.equal(cues[0]!.text, 'SRTテスト');
+});
+
+test('parseSubtitleCues auto-detects ASS format', () => {
+  const content = [
+    '[Events]',
+    'Format: Layer, Start, End, Style, Name, MarginL, MarginR, MarginV, Effect, Text',
+    'Dialogue: 0,0:00:01.00,0:00:04.00,Default,,0,0,0,,ASSテスト',
+  ].join('\n');
+
+  const cues = parseSubtitleCues(content, 'test.ass');
+  assert.equal(cues.length, 1);
+  assert.equal(cues[0]!.text, 'ASSテスト');
+});
+
+test('parseSubtitleCues auto-detects VTT format', () => {
+  const content = [
+    '1',
+    '00:00:01.000 --> 00:00:04.000',
+    'VTTテスト',
+    '',
+  ].join('\n');
+
+  const cues = parseSubtitleCues(content, 'test.vtt');
+  assert.equal(cues.length, 1);
+  assert.equal(cues[0]!.text, 'VTTテスト');
+});
+
+test('parseSubtitleCues returns empty for unknown format', () => {
+  assert.deepEqual(parseSubtitleCues('random content', 'test.xyz'), []);
+});
+
+test('parseSubtitleCues returns cues sorted by start time', () => {
+  const content = [
+    '1',
+    '00:00:10,000 --> 00:00:14,000',
+    '二番目',
+    '',
+    '2',
+    '00:00:01,000 --> 00:00:04,000',
+    '一番目',
+    '',
+  ].join('\n');
+
+  const cues = parseSubtitleCues(content, 'test.srt');
+  assert.equal(cues[0]!.text, '一番目');
+  assert.equal(cues[1]!.text, '二番目');
+});
diff --git a/src/core/services/subtitle-cue-parser.ts b/src/core/services/subtitle-cue-parser.ts
new file mode 100644
index 0000000..d118cfd
--- /dev/null
+++ b/src/core/services/subtitle-cue-parser.ts
@@ -0,0 +1,63 @@
+export interface SubtitleCue {
+  startTime: number;
+  endTime: number;
+  text: string;
+}
+
+const SRT_TIMING_PATTERN =
+  /^\s*(?:(\d{1,2}):)?(\d{2}):(\d{2})[,.](\d{1,3})\s*-->\s*(?:(\d{1,2}):)?(\d{2}):(\d{2})[,.](\d{1,3})/;
+
+function parseTimestamp(
+  hours: string | undefined,
+  minutes: string,
+  seconds: string,
+  millis: string,
+): number {
+  return (
+    Number(hours || 0) * 3600 +
+    Number(minutes) * 60 +
+    Number(seconds) +
+    Number(millis.padEnd(3, '0')) / 1000
+  );
+}
+
+export function parseSrtCues(content: string): SubtitleCue[] {
+  const cues: SubtitleCue[] = [];
+  const lines = content.split(/\r?\n/);
+  let i = 0;
+
+  while (i < lines.length) {
+    const line = lines[i]!;
+    const timingMatch = SRT_TIMING_PATTERN.exec(line);
+    if (!timingMatch) {
+      i += 1;
+      continue;
+    }
+
+    const startTime = parseTimestamp(timingMatch[1], timingMatch[2]!, timingMatch[3]!, timingMatch[4]!);
+    const endTime = parseTimestamp(timingMatch[5], timingMatch[6]!, timingMatch[7]!, timingMatch[8]!);
+
+    i += 1;
+    const textLines: string[] = [];
+    while (i < lines.length && lines[i]!.trim() !== '') {
+      textLines.push(lines[i]!);
+      i += 1;
+    }
+
+    const text = textLines.join('\n').trim();
+    if (text) {
+      cues.push({ startTime, endTime, text });
+    }
+  }
+
+  return cues;
+}
+
+// Stub exports — will be implemented in subsequent tasks
+export function parseAssCues(_content: string): SubtitleCue[] {
+  throw new Error('parseAssCues not yet implemented');
+}
+
+export function parseSubtitleCues(_content: string, _filename: string): SubtitleCue[] {
+  throw new Error('parseSubtitleCues not yet implemented');
+}