diff --git a/packages/frontend/src/components/MkAutocomplete.vue b/packages/frontend/src/components/MkAutocomplete.vue
index 412325bfee..07747d3e5c 100644
--- a/packages/frontend/src/components/MkAutocomplete.vue
+++ b/packages/frontend/src/components/MkAutocomplete.vue
@@ -15,12 +15,12 @@ SPDX-License-Identifier: AGPL-3.0-only
 		</li>
 		<li tabindex="-1" :class="$style.item" @click="chooseUser()" @keydown="onKeydown">{{ i18n.ts.selectUser }}</li>
 	</ol>
-	<ol v-else-if="hashtags.length > 0" ref="suggests" :class="$style.list">
+	<ol v-else-if="type === 'hashtag' && hashtags.length > 0" ref="suggests" :class="$style.list">
 		<li v-for="hashtag in hashtags" tabindex="-1" :class="$style.item" @click="complete(type, hashtag)" @keydown="onKeydown">
 			<span class="name">{{ hashtag }}</span>
 		</li>
 	</ol>
-	<ol v-else-if="emojis.length > 0" ref="suggests" :class="$style.list">
+	<ol v-else-if="type === 'emoji' && emojis.length > 0" ref="suggests" :class="$style.list">
 		<li v-for="emoji in emojis" :key="emoji.emoji" :class="$style.item" tabindex="-1" @click="complete(type, emoji.emoji)" @keydown="onKeydown">
 			<MkCustomEmoji v-if="'isCustomEmoji' in emoji && emoji.isCustomEmoji" :name="emoji.emoji" :class="$style.emoji"/>
 			<MkEmoji v-else :emoji="emoji.emoji" :class="$style.emoji"/>
@@ -30,12 +30,12 @@ SPDX-License-Identifier: AGPL-3.0-only
 			<span v-if="emoji.aliasOf" :class="$style.emojiAlias">({{ emoji.aliasOf }})</span>
 		</li>
 	</ol>
-	<ol v-else-if="mfmTags.length > 0" ref="suggests" :class="$style.list">
+	<ol v-else-if="type === 'mfmTag' && mfmTags.length > 0" ref="suggests" :class="$style.list">
 		<li v-for="tag in mfmTags" tabindex="-1" :class="$style.item" @click="complete(type, tag)" @keydown="onKeydown">
 			<span>{{ tag }}</span>
 		</li>
 	</ol>
-	<ol v-else-if="mfmParams.length > 0" ref="suggests" :class="$style.list">
+	<ol v-else-if="type === 'mfmParam' && mfmParams.length > 0" ref="suggests" :class="$style.list">
 		<li v-for="param in mfmParams" tabindex="-1" :class="$style.item" @click="complete(type, q.params.toSpliced(-1, 1, param).join(','))" @keydown="onKeydown">
 			<span>{{ param }}</span>
 		</li>
@@ -58,6 +58,32 @@ import { miLocalStorage } from '@/local-storage.js';
 import { customEmojis } from '@/custom-emojis.js';
 import { MFM_TAGS, MFM_PARAMS } from '@/const.js';
 
+export type CompleteInfo = {
+	user: {
+		payload: any;
+		query: string | null;
+	},
+	hashtag: {
+		payload: string;
+		query: string;
+	},
+	emoji: {
+		payload: string;
+		query: string;
+	},
+	mfmTag: {
+		payload: string;
+		query: string;
+	},
+	mfmParam: {
+		payload: string;
+		query: {
+			tag: string;
+			params: string[];
+		};
+	},
+}
+
 type EmojiDef = {
 	emoji: string;
 	name: string;
@@ -132,18 +158,23 @@ export default {
 };
 </script>
 
-<script lang="ts" setup>
-const props = defineProps<{
-	type: string;
-	q: any;
-	textarea: HTMLTextAreaElement;
+<script lang="ts" setup generic="T extends keyof CompleteInfo">
+type PropsType<T extends keyof CompleteInfo> = {
+	type: T;
+	q: CompleteInfo[T]['query'];
+	// なぜかわからないけど HTMLTextAreaElement | HTMLInputElement だと addEventListener/removeEventListenerがエラー
+	textarea: (HTMLTextAreaElement | HTMLInputElement) & HTMLElement;
 	close: () => void;
 	x: number;
 	y: number;
-}>();
+}
+//const props = defineProps<PropsType<keyof CompleteInfo>>();
+// ↑と同じだけど↓にしないとdiscriminated unionにならない。
+// https://www.typescriptlang.org/docs/handbook/typescript-in-5-minutes-func.html#discriminated-unions
+const props = defineProps<PropsType<'user'> | PropsType<'hashtag'> | PropsType<'emoji'> | PropsType<'mfmTag'> | PropsType<'mfmParam'>>();
 
 const emit = defineEmits<{
-	(event: 'done', value: { type: string; value: any }): void;
+	<T extends keyof CompleteInfo>(event: 'done', value: { type: T; value: CompleteInfo[T]['payload'] }): void;
 	(event: 'closed'): void;
 }>();
 
@@ -160,7 +191,7 @@ const mfmParams = ref<string[]>([]);
 const select = ref(-1);
 const zIndex = os.claimZIndex('high');
 
-function complete(type: string, value: any) {
+function complete<T extends keyof CompleteInfo>(type: T, value: CompleteInfo[T]['payload']) {
 	emit('done', { type, value });
 	emit('closed');
 	if (type === 'emoji') {
diff --git a/packages/frontend/src/scripts/autocomplete.ts b/packages/frontend/src/scripts/autocomplete.ts
index fe515d81a1..3a4160a3d7 100644
--- a/packages/frontend/src/scripts/autocomplete.ts
+++ b/packages/frontend/src/scripts/autocomplete.ts
@@ -6,6 +6,7 @@
 import { nextTick, Ref, ref, defineAsyncComponent } from 'vue';
 import getCaretCoordinates from 'textarea-caret';
 import { toASCII } from 'punycode/';
+import type { CompleteInfo } from '@/components/MkAutocomplete.vue';
 import { popup } from '@/os.js';
 
 export type SuggestionType = 'user' | 'hashtag' | 'emoji' | 'mfmTag' | 'mfmParam';
@@ -18,7 +19,7 @@ export class Autocomplete {
 		close: () => void;
 	} | null;
 	private textarea: HTMLInputElement | HTMLTextAreaElement;
-	private currentType: string;
+	private currentType: keyof CompleteInfo | undefined;
 	private textRef: Ref<string | number | null>;
 	private opening: boolean;
 	private onlyType: SuggestionType[];
@@ -73,7 +74,7 @@ export class Autocomplete {
 	 * テキスト入力時
 	 */
 	private onInput() {
-		const caretPos = this.textarea.selectionStart;
+		const caretPos = Number(this.textarea.selectionStart);
 		const text = this.text.substring(0, caretPos).split('\n').pop()!;
 
 		const mentionIndex = text.lastIndexOf('@');
@@ -155,7 +156,7 @@ export class Autocomplete {
 	/**
 	 * サジェストを提示します。
 	 */
-	private async open(type: string, q: any) {
+	private async open<T extends keyof CompleteInfo>(type: T, q: CompleteInfo[T]['query']) {
 		if (type !== this.currentType) {
 			this.close();
 		}
@@ -222,10 +223,10 @@ export class Autocomplete {
 	/**
 	 * オートコンプリートする
 	 */
-	private complete({ type, value }) {
+	private complete<T extends keyof CompleteInfo>({ type, value }: { type: T; value: CompleteInfo[T]['payload'] }) {
 		this.close();
 
-		const caret = this.textarea.selectionStart;
+		const caret = Number(this.textarea.selectionStart);
 
 		if (type === 'user') {
 			const source = this.text;