Suppress subtitle annotations for grammar fragments

- Hide annotation metadata for auxiliary inflection and ja-nai endings
- Preserve lexical `くれる` forms and add regression coverage

backlog/tasks/task-311 - Suppress-auxiliary-inflection-fragments-from-subtitle-annotations.md

@@ -0,0 +1,43 @@
+---
+id: TASK-311
+title: Suppress auxiliary inflection fragments from subtitle annotations
+status: Done
+assignee: []
+created_date: '2026-05-02 09:07'
+updated_date: '2026-05-02 09:10'
+labels:
+  - tokenizer
+  - annotations
+  - bug
+dependencies: []
+priority: medium
+---
+
+## Description
+
+<!-- SECTION:DESCRIPTION:BEGIN -->
+Suppress standalone Japanese auxiliary/inflection subtitle fragments such as `れる` and `れた` from frequency/JLPT/N+1/known annotation styling while keeping lexical verbs such as `くれ` / `くれる` annotatable. Tokens must remain hoverable; only annotation metadata should be stripped.
+<!-- SECTION:DESCRIPTION:END -->
+
+## Acceptance Criteria
+<!-- AC:BEGIN -->
+- [x] #1 `れる` and `れた`-style standalone helper fragments render as plain hoverable subtitle tokens.
+- [x] #2 Lexical verbs like `くれ` / `くれる` remain eligible for annotation.
+- [x] #3 Regression tests cover unit filter behavior and tokenizer integration.
+<!-- AC:END -->
+
+## Implementation Notes
+
+<!-- SECTION:NOTES:BEGIN -->
+Implemented with TDD. Added failing coverage first for standalone `れる`/`れた` auxiliary fragments and a lexical `くれ`/`くれる` guard. Updated the shared subtitle annotation filter to strip annotation metadata for kana-only auxiliary inflection fragments identified by MeCab POS (`助動詞` only, or `動詞/接尾` with optional trailing `助動詞`) while preserving lexical `くれ` as `くれる` when tagged `動詞/自立`. Added tokenizer integration coverage for `れた` and neighboring lexical N+1 behavior.
+<!-- SECTION:NOTES:END -->
+
+## Final Summary
+
+<!-- SECTION:FINAL_SUMMARY:BEGIN -->
+Suppressed annotation metadata for standalone auxiliary inflection fragments such as `れる` and `れた` in subtitle tokens, leaving them hoverable but plain. Preserved lexical `くれ` -> `くれる` verb metadata when MeCab tags it as `動詞/自立`.
+
+Added unit and tokenizer regression coverage, plus a release fragment in `changes/311-auxiliary-inflection-annotation-filter.md`.
+
+Validation: targeted annotation/tokenizer tests passed; `bun run typecheck` passed; `bun run changelog:lint` passed. `bun run test:fast` was attempted twice and failed in unrelated `src/core/services/subsync.test.ts` cross-file state (`window.electronAPI` undefined), while `bun test src/core/services/subsync.test.ts` passes by itself.
+<!-- SECTION:FINAL_SUMMARY:END -->

backlog/tasks/task-312 - Suppress-ja-nai-explanatory-ending-subtitle-annotations.md

@@ -0,0 +1,42 @@
+---
+id: TASK-312
+title: Suppress ja-nai explanatory ending subtitle annotations
+status: Done
+assignee: []
+created_date: '2026-05-02 09:55'
+updated_date: '2026-05-02 10:03'
+labels:
+  - tokenizer
+  - annotations
+  - bug
+dependencies: []
+priority: medium
+---
+
+## Description
+
+<!-- SECTION:DESCRIPTION:BEGIN -->
+Suppress subtitle annotation styling for grammar-only explanatory endings like `じゃない` and `じゃないですか` while preserving nearby lexical content annotations.
+<!-- SECTION:DESCRIPTION:END -->
+
+## Acceptance Criteria
+<!-- AC:BEGIN -->
+- [x] #1 `じゃない` and `じゃないですか`-style endings render as plain hoverable subtitle tokens.
+- [x] #2 The reported phrase `みたいなのあるじゃないですか` does not annotate `じゃない`/`じゃないですか` as lexical/frequency content.
+- [x] #3 Regression tests cover unit filter behavior and tokenizer integration without suppressing lexical content tokens.
+- [x] #4 Standalone polite copula endings such as `です` / `ですよ` render as plain hoverable subtitle tokens even if POS metadata is missing or too lexical.
+<!-- AC:END -->
+
+## Implementation Notes
+
+<!-- SECTION:NOTES:BEGIN -->
+Added failing coverage first for `じゃない` / `じゃないですか` and `ですよ` leaking annotation metadata when POS metadata is missing or too lexical. Implemented term-family exclusions in the shared subtitle annotation filter for the `じゃない` explanatory family and polite copula suffix endings (`ですか`, `ですね`, `ですよ`, `ですな`). Kept bare `です` term-only behavior unchanged to preserve existing no-POS frequency tests; POS-tagged `です` is already stripped by the grammar POS exclusion path.
+<!-- SECTION:NOTES:END -->
+
+## Final Summary
+
+<!-- SECTION:FINAL_SUMMARY:BEGIN -->
+Suppressed subtitle annotation metadata for grammar-only endings like `じゃないですか` and `ですよ`, while preserving nearby lexical content annotations. Added unit and tokenizer regression coverage for the reported `みたいなのあるじゃないですか` and `感じですよ` shapes, plus changelog fragment `changes/312-grammar-ending-annotation-filter.md`.
+
+Validation: `bun test src/core/services/tokenizer/annotation-stage.test.ts`; `bun test src/core/services/tokenizer.test.ts`; `bun run typecheck`; `bun run changelog:lint`; `git diff --check`.
+<!-- SECTION:FINAL_SUMMARY:END -->

changes/311-auxiliary-inflection-annotation-filter.md

@@ -0,0 +1,4 @@
+type: fixed
+area: overlay
+
+- Suppressed subtitle annotation styling for standalone auxiliary inflection fragments such as `れる` and `れた` while keeping lexical `くれる` forms eligible for lookup metadata.

changes/312-grammar-ending-annotation-filter.md

@@ -0,0 +1,4 @@
+type: fixed
+area: overlay
+
+- Suppressed subtitle annotation styling for grammar-only endings such as `じゃないですか` and standalone polite copula tails like `です` / `ですよ`.

src/core/services/tokenizer.test.ts

@@ -4227,6 +4227,211 @@ test('tokenizeSubtitle clears all annotations for explanatory contrast endings',
   );
 });
 
+test('tokenizeSubtitle clears annotations for ja-nai explanatory endings while preserving lexical content', async () => {
+  const result = await tokenizeSubtitle(
+    'みたいなのあるじゃないですか',
+    makeDepsFromYomitanTokens(
+      [
+        { surface: 'みたいな', reading: 'みたいな', headword: 'みたい' },
+        { surface: 'の', reading: 'の', headword: 'の' },
+        { surface: 'ある', reading: 'ある', headword: 'ある' },
+        { surface: 'じゃないですか', reading: 'じゃないですか', headword: 'じゃない' },
+      ],
+      {
+        getFrequencyDictionaryEnabled: () => true,
+        getFrequencyRank: (text) =>
+          text === 'みたい' ? 320 : text === 'ある' ? 240 : text === 'じゃない' ? 80 : null,
+        getJlptLevel: (text) =>
+          text === 'みたい' ? 'N4' : text === 'ある' ? 'N5' : text === 'じゃない' ? 'N5' : null,
+        isKnownWord: (text) => text === 'みたい' || text === 'の',
+        getMinSentenceWordsForNPlusOne: () => 1,
+        tokenizeWithMecab: async () => [
+          {
+            headword: 'みたい',
+            surface: 'みたい',
+            reading: 'ミタイ',
+            startPos: 0,
+            endPos: 3,
+            partOfSpeech: PartOfSpeech.noun,
+            pos1: '名詞',
+            pos2: '非自立',
+            pos3: '形容動詞語幹',
+            isMerged: false,
+            isKnown: false,
+            isNPlusOneTarget: false,
+          },
+          {
+            headword: 'だ',
+            surface: 'な',
+            reading: 'ナ',
+            startPos: 3,
+            endPos: 4,
+            partOfSpeech: PartOfSpeech.bound_auxiliary,
+            pos1: '助動詞',
+            pos2: '*',
+            isMerged: false,
+            isKnown: false,
+            isNPlusOneTarget: false,
+          },
+          {
+            headword: 'の',
+            surface: 'の',
+            reading: 'ノ',
+            startPos: 4,
+            endPos: 5,
+            partOfSpeech: PartOfSpeech.noun,
+            pos1: '名詞',
+            pos2: '非自立',
+            isMerged: false,
+            isKnown: false,
+            isNPlusOneTarget: false,
+          },
+          {
+            headword: 'ある',
+            surface: 'ある',
+            reading: 'アル',
+            startPos: 5,
+            endPos: 7,
+            partOfSpeech: PartOfSpeech.verb,
+            pos1: '動詞',
+            pos2: '自立',
+            isMerged: false,
+            isKnown: false,
+            isNPlusOneTarget: false,
+          },
+          {
+            headword: 'じゃない',
+            surface: 'じゃない',
+            reading: 'ジャナイ',
+            startPos: 7,
+            endPos: 11,
+            partOfSpeech: PartOfSpeech.i_adjective,
+            pos1: '接続詞|形容詞',
+            pos2: '*|自立',
+            isMerged: false,
+            isKnown: false,
+            isNPlusOneTarget: false,
+          },
+          {
+            headword: 'です',
+            surface: 'です',
+            reading: 'デス',
+            startPos: 11,
+            endPos: 13,
+            partOfSpeech: PartOfSpeech.bound_auxiliary,
+            pos1: '助動詞',
+            pos2: '*',
+            isMerged: false,
+            isKnown: false,
+            isNPlusOneTarget: false,
+          },
+          {
+            headword: 'か',
+            surface: 'か',
+            reading: 'カ',
+            startPos: 13,
+            endPos: 14,
+            partOfSpeech: PartOfSpeech.particle,
+            pos1: '助詞',
+            pos2: '副助詞／並立助詞／終助詞',
+            isMerged: false,
+            isKnown: false,
+            isNPlusOneTarget: false,
+          },
+        ],
+      },
+    ),
+  );
+
+  const tokenSummary = result.tokens?.map((token) => ({
+    surface: token.surface,
+    headword: token.headword,
+    isKnown: token.isKnown,
+    isNPlusOneTarget: token.isNPlusOneTarget,
+    frequencyRank: token.frequencyRank,
+    jlptLevel: token.jlptLevel,
+  }));
+
+  assert.deepEqual(
+    tokenSummary?.find((token) => token.surface === 'じゃないですか'),
+    {
+      surface: 'じゃないですか',
+      headword: 'じゃない',
+      isKnown: false,
+      isNPlusOneTarget: false,
+      frequencyRank: undefined,
+      jlptLevel: undefined,
+    },
+  );
+  assert.deepEqual(
+    tokenSummary?.find((token) => token.surface === 'ある'),
+    {
+      surface: 'ある',
+      headword: 'ある',
+      isKnown: false,
+      isNPlusOneTarget: false,
+      frequencyRank: 240,
+      jlptLevel: 'N5',
+    },
+  );
+});
+
+test('tokenizeSubtitle clears annotations for standalone polite copula endings without POS metadata', async () => {
+  const result = await tokenizeSubtitle(
+    '現実は感じですよ',
+    makeDepsFromYomitanTokens(
+      [
+        { surface: '現実', reading: 'げんじつ', headword: '現実' },
+        { surface: 'は', reading: 'は', headword: 'は' },
+        { surface: '感じ', reading: 'かんじ', headword: '感じ' },
+        { surface: 'ですよ', reading: 'ですよ', headword: 'です' },
+      ],
+      {
+        getFrequencyDictionaryEnabled: () => true,
+        getFrequencyRank: (text) =>
+          text === '現実' ? 600 : text === '感じ' ? 240 : text === 'です' ? 50 : null,
+        getJlptLevel: (text) =>
+          text === '現実' ? 'N3' : text === '感じ' ? 'N4' : text === 'です' ? 'N5' : null,
+        isKnownWord: (text) => text === '現実' || text === 'は' || text === 'です',
+        getMinSentenceWordsForNPlusOne: () => 1,
+        tokenizeWithMecab: async () => null,
+      },
+    ),
+  );
+
+  const tokenSummary = result.tokens?.map((token) => ({
+    surface: token.surface,
+    headword: token.headword,
+    isKnown: token.isKnown,
+    isNPlusOneTarget: token.isNPlusOneTarget,
+    frequencyRank: token.frequencyRank,
+    jlptLevel: token.jlptLevel,
+  }));
+
+  assert.deepEqual(
+    tokenSummary?.find((token) => token.surface === 'ですよ'),
+    {
+      surface: 'ですよ',
+      headword: 'です',
+      isKnown: false,
+      isNPlusOneTarget: false,
+      frequencyRank: undefined,
+      jlptLevel: undefined,
+    },
+  );
+  assert.deepEqual(
+    tokenSummary?.find((token) => token.surface === '感じ'),
+    {
+      surface: '感じ',
+      headword: '感じ',
+      isKnown: false,
+      isNPlusOneTarget: true,
+      frequencyRank: 240,
+      jlptLevel: 'N4',
+    },
+  );
+});
+
 test('tokenizeSubtitle clears annotations for ことに while preserving lexical N+1 target', async () => {
   const result = await tokenizeSubtitle(
     'さっきの俺と違うことに気付かないのかい？',
@@ -4446,6 +4651,114 @@ test('tokenizeSubtitle clears annotations for ことに while preserving lexical
   );
 });
 
+test('tokenizeSubtitle clears annotations for auxiliary inflection fragments while preserving lexical N+1 target', async () => {
+  const result = await tokenizeSubtitle(
+    '私れた猫',
+    makeDepsFromYomitanTokens(
+      [
+        { surface: '私', reading: 'わたし', headword: '私' },
+        { surface: 'れた', reading: 'れた', headword: 'れる' },
+        { surface: '猫', reading: 'ねこ', headword: '猫' },
+      ],
+      {
+        getFrequencyDictionaryEnabled: () => true,
+        getFrequencyRank: (text) =>
+          text === '私' ? 50 : text === 'れる' ? 18 : text === '猫' ? 900 : null,
+        getJlptLevel: (text) =>
+          text === '私' ? 'N5' : text === 'れる' ? 'N4' : text === '猫' ? 'N5' : null,
+        isKnownWord: (text) => text === '私' || text === 'れる',
+        getMinSentenceWordsForNPlusOne: () => 1,
+        tokenizeWithMecab: async () => [
+          {
+            headword: '私',
+            surface: '私',
+            reading: 'ワタシ',
+            startPos: 0,
+            endPos: 1,
+            partOfSpeech: PartOfSpeech.noun,
+            pos1: '名詞',
+            pos2: '代名詞',
+            isMerged: false,
+            isKnown: false,
+            isNPlusOneTarget: false,
+          },
+          {
+            headword: 'れる',
+            surface: 'れ',
+            reading: 'レ',
+            startPos: 1,
+            endPos: 2,
+            partOfSpeech: PartOfSpeech.verb,
+            pos1: '動詞',
+            pos2: '接尾',
+            isMerged: false,
+            isKnown: false,
+            isNPlusOneTarget: false,
+          },
+          {
+            headword: 'た',
+            surface: 'た',
+            reading: 'タ',
+            startPos: 2,
+            endPos: 3,
+            partOfSpeech: PartOfSpeech.bound_auxiliary,
+            pos1: '助動詞',
+            pos2: '*',
+            isMerged: false,
+            isKnown: false,
+            isNPlusOneTarget: false,
+          },
+          {
+            headword: '猫',
+            surface: '猫',
+            reading: 'ネコ',
+            startPos: 3,
+            endPos: 4,
+            partOfSpeech: PartOfSpeech.noun,
+            pos1: '名詞',
+            pos2: '一般',
+            isMerged: false,
+            isKnown: false,
+            isNPlusOneTarget: false,
+          },
+        ],
+      },
+    ),
+  );
+
+  const tokenSummary = result.tokens?.map((token) => ({
+    surface: token.surface,
+    headword: token.headword,
+    isKnown: token.isKnown,
+    isNPlusOneTarget: token.isNPlusOneTarget,
+    frequencyRank: token.frequencyRank,
+    jlptLevel: token.jlptLevel,
+  }));
+
+  assert.deepEqual(
+    tokenSummary?.find((token) => token.surface === 'れた'),
+    {
+      surface: 'れた',
+      headword: 'れる',
+      isKnown: false,
+      isNPlusOneTarget: false,
+      frequencyRank: undefined,
+      jlptLevel: undefined,
+    },
+  );
+  assert.deepEqual(
+    tokenSummary?.find((token) => token.surface === '猫'),
+    {
+      surface: '猫',
+      headword: '猫',
+      isKnown: false,
+      isNPlusOneTarget: true,
+      frequencyRank: 900,
+      jlptLevel: 'N5',
+    },
+  );
+});
+
 test('tokenizeSubtitle excludes default non-independent pos2 from N+1 when JLPT/frequency are disabled', async () => {
   let mecabCalls = 0;
   const result = await tokenizeSubtitle(

src/core/services/tokenizer/annotation-stage.test.ts

@@ -258,6 +258,48 @@ test('shouldExcludeTokenFromSubtitleAnnotations excludes explanatory contrast en
   assert.equal(shouldExcludeTokenFromSubtitleAnnotations(token), true);
 });
 
+test('shouldExcludeTokenFromSubtitleAnnotations excludes ja-nai explanatory endings', () => {
+  const tokens = [
+    makeToken({
+      surface: 'じゃない',
+      headword: 'じゃない',
+      reading: 'ジャナイ',
+      partOfSpeech: PartOfSpeech.i_adjective,
+      pos1: '接続詞|形容詞',
+      pos2: '*|自立',
+    }),
+    makeToken({
+      surface: 'じゃないですか',
+      headword: 'じゃない',
+      reading: 'ジャナイデスカ',
+      partOfSpeech: PartOfSpeech.i_adjective,
+      pos1: '接続詞|形容詞|助動詞|助詞',
+      pos2: '*|自立|*|副助詞／並立助詞／終助詞',
+    }),
+  ];
+
+  for (const token of tokens) {
+    assert.equal(shouldExcludeTokenFromSubtitleAnnotations(token), true, token.surface);
+  }
+});
+
+test('shouldExcludeTokenFromSubtitleAnnotations excludes standalone polite copula suffix endings without POS tags', () => {
+  const tokens = [
+    makeToken({
+      surface: 'ですよ',
+      headword: 'です',
+      reading: 'デスヨ',
+      partOfSpeech: PartOfSpeech.other,
+      pos1: '',
+      pos2: '',
+    }),
+  ];
+
+  for (const token of tokens) {
+    assert.equal(shouldExcludeTokenFromSubtitleAnnotations(token), true, token.surface);
+  }
+});
+
 test('shouldExcludeTokenFromSubtitleAnnotations excludes auxiliary-stem そうだ grammar tails', () => {
   const token = makeToken({
     surface: 'そうだ',
@@ -1204,6 +1246,78 @@ test('annotateTokens clears all annotations for kana-only non-independent noun h
   assert.equal(result[0]?.jlptLevel, undefined);
 });
 
+test('annotateTokens clears all annotations for standalone auxiliary inflection fragments', () => {
+  const tokens = [
+    makeToken({
+      surface: 'れる',
+      headword: 'れる',
+      reading: 'レル',
+      partOfSpeech: PartOfSpeech.verb,
+      pos1: '動詞',
+      pos2: '接尾',
+      startPos: 0,
+      endPos: 2,
+      frequencyRank: 18,
+    }),
+    makeToken({
+      surface: 'れた',
+      headword: 'れる',
+      reading: 'レタ',
+      partOfSpeech: PartOfSpeech.verb,
+      pos1: '動詞|助動詞',
+      pos2: '接尾|*',
+      startPos: 2,
+      endPos: 4,
+      frequencyRank: 19,
+    }),
+  ];
+
+  const result = annotateTokens(
+    tokens,
+    makeDeps({
+      isKnownWord: (text) => text === 'れる',
+      getJlptLevel: (text) => (text === 'れる' ? 'N4' : null),
+    }),
+    { minSentenceWordsForNPlusOne: 1 },
+  );
+
+  for (const token of result) {
+    assert.equal(token.isKnown, false, token.surface);
+    assert.equal(token.isNPlusOneTarget, false, token.surface);
+    assert.equal(token.frequencyRank, undefined, token.surface);
+    assert.equal(token.jlptLevel, undefined, token.surface);
+  }
+});
+
+test('annotateTokens keeps lexical くれる forms eligible for annotation', () => {
+  const tokens = [
+    makeToken({
+      surface: 'くれ',
+      headword: 'くれる',
+      reading: 'クレ',
+      partOfSpeech: PartOfSpeech.verb,
+      pos1: '動詞',
+      pos2: '自立',
+      startPos: 0,
+      endPos: 2,
+      frequencyRank: 20,
+    }),
+  ];
+
+  const result = annotateTokens(
+    tokens,
+    makeDeps({
+      getJlptLevel: (text) => (text === 'くれる' ? 'N4' : null),
+    }),
+    { minSentenceWordsForNPlusOne: 1 },
+  );
+
+  assert.equal(result[0]?.isKnown, false);
+  assert.equal(result[0]?.isNPlusOneTarget, false);
+  assert.equal(result[0]?.frequencyRank, 20);
+  assert.equal(result[0]?.jlptLevel, 'N4');
+});
+
 test('annotateTokens clears all annotations for standalone して helper fragments', () => {
   const tokens = [
     makeToken({

src/core/services/tokenizer/subtitle-annotation-filter.ts

@@ -63,6 +63,24 @@ const SUBTITLE_ANNOTATION_EXCLUDED_EXPLANATORY_ENDING_THOUGHT_SUFFIXES = [
   'かな',
   'かね',
 ] as const;
+const SUBTITLE_ANNOTATION_EXCLUDED_POLITE_COPULA_SUFFIXES = [
+  'か',
+  'ね',
+  'よ',
+  'な',
+] as const;
+const SUBTITLE_ANNOTATION_EXCLUDED_JA_NAI_SUFFIXES = [
+  '',
+  'か',
+  'ね',
+  'よ',
+  'な',
+  'です',
+  'ですか',
+  'ですよ',
+  'ですね',
+  'ですな',
+] as const;
 const SUBTITLE_ANNOTATION_EXCLUDED_EXPLANATORY_ENDINGS = new Set(
   SUBTITLE_ANNOTATION_EXCLUDED_EXPLANATORY_ENDING_PREFIXES.flatMap((prefix) =>
     SUBTITLE_ANNOTATION_EXCLUDED_EXPLANATORY_ENDING_CORES.flatMap((core) =>
@@ -72,6 +90,12 @@ const SUBTITLE_ANNOTATION_EXCLUDED_EXPLANATORY_ENDINGS = new Set(
     ),
   ),
 );
+const SUBTITLE_ANNOTATION_EXCLUDED_POLITE_COPULA_ENDINGS = new Set(
+  SUBTITLE_ANNOTATION_EXCLUDED_POLITE_COPULA_SUFFIXES.map((suffix) => `です${suffix}`),
+);
+const SUBTITLE_ANNOTATION_EXCLUDED_JA_NAI_ENDINGS = new Set(
+  SUBTITLE_ANNOTATION_EXCLUDED_JA_NAI_SUFFIXES.map((suffix) => `じゃない${suffix}`),
+);
 const SUBTITLE_ANNOTATION_EXCLUDED_TRAILING_PARTICLE_SUFFIXES = new Set([
   'って',
   'ってよ',
@@ -83,6 +107,7 @@ const SUBTITLE_ANNOTATION_EXCLUDED_TRAILING_PARTICLE_SUFFIXES = new Set([
 ]);
 const AUXILIARY_STEM_GRAMMAR_TAIL_POS1 = new Set(['名詞', '助動詞', '助詞']);
 const NON_INDEPENDENT_NOUN_HELPER_TAIL_POS1 = new Set(['助詞', '助動詞']);
+const AUXILIARY_INFLECTION_TRAILING_POS1 = new Set(['助動詞']);
 const STANDALONE_GRAMMAR_PARTICLE_SURFACES = new Set([
   'か',
   'が',
@@ -312,6 +337,44 @@ function isKanaOnlyText(text: string): boolean {
   return normalized.length > 0 && [...normalized].every(isKanaChar);
 }
 
+function isLexicalKureruVerb(token: MergedToken): boolean {
+  const normalizedSurface = normalizeKana(token.surface);
+  const normalizedHeadword = normalizeKana(token.headword);
+  const pos1Parts = splitNormalizedTagParts(normalizePosTag(token.pos1));
+  const pos2Parts = splitNormalizedTagParts(normalizePosTag(token.pos2));
+  return (
+    normalizedSurface === 'くれ' &&
+    normalizedHeadword === 'くれる' &&
+    pos1Parts.length === 1 &&
+    pos1Parts[0] === '動詞' &&
+    pos2Parts.length === 1 &&
+    pos2Parts[0] === '自立'
+  );
+}
+
+function isStandaloneAuxiliaryInflectionFragment(token: MergedToken): boolean {
+  const normalizedSurface = normalizeKana(token.surface);
+  if (!isKanaOnlyText(normalizedSurface)) {
+    return false;
+  }
+
+  const pos1Parts = splitNormalizedTagParts(normalizePosTag(token.pos1));
+  if (pos1Parts.length === 0) {
+    return false;
+  }
+
+  if (pos1Parts.every((part) => part === '助動詞')) {
+    return true;
+  }
+
+  const pos2Parts = splitNormalizedTagParts(normalizePosTag(token.pos2));
+  return (
+    pos1Parts[0] === '動詞' &&
+    pos2Parts[0] === '接尾' &&
+    pos1Parts.slice(1).every((part) => AUXILIARY_INFLECTION_TRAILING_POS1.has(part))
+  );
+}
+
 function isStandaloneSuruTeGrammarHelper(token: MergedToken): boolean {
   const normalizedSurface = normalizeKana(token.surface);
   const normalizedHeadword = normalizeKana(token.headword);
@@ -370,6 +433,10 @@ function isExcludedByTerm(token: MergedToken): boolean {
       SUBTITLE_ANNOTATION_EXCLUDED_TERMS.has(normalized) ||
       SUBTITLE_ANNOTATION_EXCLUDED_EXPLANATORY_ENDINGS.has(trimmed) ||
       SUBTITLE_ANNOTATION_EXCLUDED_EXPLANATORY_ENDINGS.has(normalized) ||
+      SUBTITLE_ANNOTATION_EXCLUDED_POLITE_COPULA_ENDINGS.has(trimmed) ||
+      SUBTITLE_ANNOTATION_EXCLUDED_POLITE_COPULA_ENDINGS.has(normalized) ||
+      SUBTITLE_ANNOTATION_EXCLUDED_JA_NAI_ENDINGS.has(trimmed) ||
+      SUBTITLE_ANNOTATION_EXCLUDED_JA_NAI_ENDINGS.has(normalized) ||
       shouldIgnoreJlptByTerm(trimmed) ||
       shouldIgnoreJlptByTerm(normalized)
     ) {
@@ -426,6 +493,10 @@ export function shouldExcludeTokenFromSubtitleAnnotations(
     return true;
   }
 
+  if (isStandaloneAuxiliaryInflectionFragment(token)) {
+    return true;
+  }
+
   if (isStandaloneSuruTeGrammarHelper(token)) {
     return true;
   }
@@ -442,6 +513,10 @@ export function shouldExcludeTokenFromSubtitleAnnotations(
     return true;
   }
 
+  if (isLexicalKureruVerb(token)) {
+    return false;
+  }
+
   return isExcludedByTerm(token);
 }