diff --git a/apps/api/src/app.module.ts b/apps/api/src/app.module.ts
index 7d4b4f9..c99b76d 100644
--- a/apps/api/src/app.module.ts
+++ b/apps/api/src/app.module.ts
@@ -2,9 +2,10 @@ import { Module } from "@nestjs/common";
 import { HealthController } from "./health/health.controller.js";
 import { CharactersModule } from "./characters/characters.module.js";
 import { MemoryModule } from "./memory/memory.module.js";
+import { EmotionModule } from "./emotion/emotion.module.js";
 
 @Module({
-  imports: [CharactersModule, MemoryModule],
+  imports: [CharactersModule, MemoryModule, EmotionModule],
   controllers: [HealthController],
 })
 export class AppModule {}
diff --git a/apps/api/src/emotion/emotion-state-machine.ts b/apps/api/src/emotion/emotion-state-machine.ts
new file mode 100644
index 0000000..417a918
--- /dev/null
+++ b/apps/api/src/emotion/emotion-state-machine.ts
@@ -0,0 +1,44 @@
+import type { EmotionTag } from "@kokorone/shared";
+import type { EmotionSignal } from "./emotion-tagger.js";
+
+export interface TransitionContext {
+  threatConfirmedSafe?: boolean; // 警戒 --> 平靜：確認無威脅
+  conflictContinues?: boolean; // 警戒 --> 低落：衝突持續
+  comforted?: boolean; // 低落 --> 平靜：被安慰
+  placated?: boolean; // 彆扭 --> 平靜：被哄
+}
+
+// D-4 情緒狀態機：只實作 wiki 狀態圖 + 可愛度設計明訂的邊，不外推未定義的轉移，
+// 避免無來源依據地讓「愉悅／低落／害羞」彼此互轉。
+export function nextEmotionState(
+  current: EmotionTag,
+  signal: EmotionSignal,
+  context: TransitionContext = {},
+): EmotionTag {
+  if (current === "ALERT") {
+    if (context.threatConfirmedSafe) {
+      return "CALM"; // 警戒 --> 平靜：確認無威脅
+    }
+    if (context.conflictContinues) {
+      return "SAD"; // 警戒 --> 低落：衝突持續
+    }
+    return current;
+  }
+
+  if (current === "GRUMPY") {
+    if (context.placated) {
+      return "CALM"; // 彆扭 --> 平靜：被哄
+    }
+    return current;
+  }
+
+  if (current === "SAD" && context.comforted) {
+    return "CALM"; // 低落 --> 平靜：被安慰
+  }
+
+  if (current === "CALM" && signal.tag !== "CALM") {
+    return signal.tag; // 平靜 --> 愉悅/低落/警戒/害羞/彆扭：對應觸發訊號
+  }
+
+  return current;
+}
diff --git a/apps/api/src/emotion/emotion-tagger.ts b/apps/api/src/emotion/emotion-tagger.ts
new file mode 100644
index 0000000..5502007
--- /dev/null
+++ b/apps/api/src/emotion/emotion-tagger.ts
@@ -0,0 +1,68 @@
+import { Injectable } from "@nestjs/common";
+import type { EmotionTag } from "@kokorone/shared";
+
+export interface EmotionTaggerInput {
+  text: string;
+  // 角色觸發閾值：預設 1，數值越低代表角色越敏感、越容易被觸發（由 G 群組依性格原型設定）。
+  triggerThreshold?: number;
+}
+
+export interface EmotionSignal {
+  tag: EmotionTag;
+  intensity: number; // 0~1
+}
+
+export interface EmotionTagger {
+  tag(input: EmotionTaggerInput): EmotionSignal;
+}
+
+// 依優先序排列：衝突語氣 > 稱讚（害羞）> 輕度負向（彆扭）> 一般負向 > 正向。
+const CONFLICT_KEYWORDS = ["滾", "閉嘴", "白痴", "笨蛋", "憑什麼", "少管我", "去死", "揍你", "威脅"];
+const PRAISE_KEYWORDS = ["好可愛", "好漂亮", "好帥", "喜歡你", "好厲害", "太可愛了"];
+const MINOR_NEGATIVE_KEYWORDS = ["不理我", "都不陪我", "比較喜歡", "都在誇", "忽略我"];
+const NEGATIVE_KEYWORDS = ["討厭", "難過", "失望", "傷心", "不喜歡", "無聊", "煩", "委屈"];
+const POSITIVE_KEYWORDS = ["謝謝", "喜歡", "開心", "好棒", "加油", "辛苦了", "太好了", "愛你"];
+
+function countHits(text: string, keywords: string[]): number {
+  return keywords.reduce((count, keyword) => (text.includes(keyword) ? count + 1 : count), 0);
+}
+
+function clamp01(value: number): number {
+  return Math.max(0, Math.min(1, value));
+}
+
+// D-1 情緒標記器（規則版）：關鍵字比對 + 角色觸發閾值，輸出情緒類型與強度分數。
+@Injectable()
+export class RuleBasedEmotionTagger implements EmotionTagger {
+  tag(input: EmotionTaggerInput): EmotionSignal {
+    const { text } = input;
+    const threshold = input.triggerThreshold ?? 1;
+
+    const conflictHits = countHits(text, CONFLICT_KEYWORDS);
+    if (conflictHits > 0) {
+      return { tag: "ALERT", intensity: clamp01((0.7 * conflictHits) / threshold) };
+    }
+
+    const praiseHits = countHits(text, PRAISE_KEYWORDS);
+    if (praiseHits > 0) {
+      return { tag: "SHY", intensity: clamp01((0.6 * praiseHits) / threshold) };
+    }
+
+    const minorNegativeHits = countHits(text, MINOR_NEGATIVE_KEYWORDS);
+    if (minorNegativeHits > 0) {
+      return { tag: "GRUMPY", intensity: clamp01((0.4 * minorNegativeHits) / threshold) };
+    }
+
+    const negativeHits = countHits(text, NEGATIVE_KEYWORDS);
+    if (negativeHits > 0) {
+      return { tag: "SAD", intensity: clamp01((0.5 * negativeHits) / threshold) };
+    }
+
+    const positiveHits = countHits(text, POSITIVE_KEYWORDS);
+    if (positiveHits > 0) {
+      return { tag: "JOY", intensity: clamp01((0.5 * positiveHits) / threshold) };
+    }
+
+    return { tag: "CALM", intensity: 0 };
+  }
+}
diff --git a/apps/api/src/emotion/emotion.controller.ts b/apps/api/src/emotion/emotion.controller.ts
new file mode 100644
index 0000000..79dd36f
--- /dev/null
+++ b/apps/api/src/emotion/emotion.controller.ts
@@ -0,0 +1,41 @@
+import { Body, Controller, Get, Param, Post, Query } from "@nestjs/common";
+import { EmotionService } from "./emotion.service.js";
+
+interface ProcessInputBody {
+  text: string;
+  triggerThreshold?: number;
+  halfLifeMs?: number;
+  now?: string;
+  threatConfirmedSafe?: boolean;
+  conflictContinues?: boolean;
+  comforted?: boolean;
+  placated?: boolean;
+}
+
+@Controller("emotion")
+export class EmotionController {
+  constructor(private readonly emotion: EmotionService) {}
+
+  @Get(":characterId")
+  async getState(@Param("characterId") characterId: string, @Query("now") now?: string) {
+    return this.emotion.getState(characterId, now ? new Date(now) : undefined);
+  }
+
+  @Get(":characterId/response-style")
+  async getResponseStyle(@Param("characterId") characterId: string, @Query("now") now?: string) {
+    return this.emotion.getResponseStyle(characterId, now ? new Date(now) : undefined);
+  }
+
+  @Post(":characterId/input")
+  async processInput(@Param("characterId") characterId: string, @Body() body: ProcessInputBody) {
+    return this.emotion.processInput(characterId, body.text, {
+      triggerThreshold: body.triggerThreshold,
+      halfLifeMs: body.halfLifeMs,
+      now: body.now ? new Date(body.now) : undefined,
+      threatConfirmedSafe: body.threatConfirmedSafe,
+      conflictContinues: body.conflictContinues,
+      comforted: body.comforted,
+      placated: body.placated,
+    });
+  }
+}
diff --git a/apps/api/src/emotion/emotion.module.ts b/apps/api/src/emotion/emotion.module.ts
new file mode 100644
index 0000000..9c83b64
--- /dev/null
+++ b/apps/api/src/emotion/emotion.module.ts
@@ -0,0 +1,13 @@
+import { Module } from "@nestjs/common";
+import { PrismaModule } from "../prisma/prisma.module.js";
+import { RuleBasedEmotionTagger } from "./emotion-tagger.js";
+import { EmotionService } from "./emotion.service.js";
+import { EmotionController } from "./emotion.controller.js";
+
+@Module({
+  imports: [PrismaModule],
+  controllers: [EmotionController],
+  providers: [RuleBasedEmotionTagger, EmotionService],
+  exports: [RuleBasedEmotionTagger, EmotionService],
+})
+export class EmotionModule {}
diff --git a/apps/api/src/emotion/emotion.service.ts b/apps/api/src/emotion/emotion.service.ts
new file mode 100644
index 0000000..eaef92c
--- /dev/null
+++ b/apps/api/src/emotion/emotion.service.ts
@@ -0,0 +1,140 @@
+import { Injectable } from "@nestjs/common";
+import type { EmotionTag, EmotionState } from "@kokorone/shared";
+import { PrismaService } from "../prisma/prisma.service.js";
+import { RuleBasedEmotionTagger } from "./emotion-tagger.js";
+import { nextEmotionState, type TransitionContext } from "./emotion-state-machine.js";
+import { toResponseStyle, type ResponseStyle } from "./response-style.js";
+
+// D-2 時間衰減：預設半衰期 2 小時，實際速度由角色參數（G 群組）覆寫。
+const DEFAULT_HALF_LIFE_MS = 2 * 60 * 60 * 1000;
+// 低於此值視為「沒有明顯情緒」，dominantState 回報平靜。
+const DOMINANT_EPSILON = 5;
+
+interface Dimensions {
+  calm: number;
+  joy: number;
+  sad: number;
+  alert: number;
+  shy: number;
+  grumpy: number;
+}
+
+const NON_CALM_TAGS: Exclude<EmotionTag, "CALM">[] = ["JOY", "SAD", "ALERT", "SHY", "GRUMPY"];
+
+function fieldFor(tag: Exclude<EmotionTag, "CALM">): "joy" | "sad" | "alert" | "shy" | "grumpy" {
+  return tag.toLowerCase() as "joy" | "sad" | "alert" | "shy" | "grumpy";
+}
+
+function dominantState(dims: Dimensions): EmotionTag {
+  let best: EmotionTag = "CALM";
+  let bestValue = DOMINANT_EPSILON;
+  for (const tag of NON_CALM_TAGS) {
+    const value = dims[fieldFor(tag)];
+    if (value > bestValue) {
+      best = tag;
+      bestValue = value;
+    }
+  }
+  return best;
+}
+
+function decayDimensions(dims: Dimensions, elapsedMs: number, halfLifeMs: number): Dimensions {
+  const factor = elapsedMs > 0 ? Math.pow(0.5, elapsedMs / halfLifeMs) : 1;
+  const joy = dims.joy * factor;
+  const sad = dims.sad * factor;
+  const alert = dims.alert * factor;
+  const shy = dims.shy * factor;
+  const grumpy = dims.grumpy * factor;
+  const calm = Math.max(0, Math.min(100, 100 - (joy + sad + alert + shy + grumpy)));
+  return { calm, joy, sad, alert, shy, grumpy };
+}
+
+export interface ProcessInputOptions extends TransitionContext {
+  triggerThreshold?: number;
+  halfLifeMs?: number;
+  now?: Date;
+}
+
+function toDomain(characterId: string, dims: Dimensions, updatedAt: Date): EmotionState {
+  return {
+    characterId,
+    calm: dims.calm,
+    joy: dims.joy,
+    sad: dims.sad,
+    alert: dims.alert,
+    shy: dims.shy,
+    grumpy: dims.grumpy,
+    updatedAt: updatedAt.toISOString(),
+  };
+}
+
+@Injectable()
+export class EmotionService {
+  constructor(
+    private readonly prisma: PrismaService,
+    private readonly tagger: RuleBasedEmotionTagger,
+  ) {}
+
+  async getState(characterId: string, now: Date = new Date()): Promise<EmotionState> {
+    const { dims, updatedAt } = await this.decayedDimensions(characterId, now);
+    await this.persist(characterId, dims, now);
+    return toDomain(characterId, dims, now);
+  }
+
+  async getResponseStyle(characterId: string, now: Date = new Date()): Promise<ResponseStyle> {
+    const state = await this.getState(characterId, now);
+    return toResponseStyle(dominantState(state));
+  }
+
+  async processInput(
+    characterId: string,
+    text: string,
+    options: ProcessInputOptions = {},
+  ): Promise<{ state: EmotionState; style: ResponseStyle }> {
+    const now = options.now ?? new Date();
+    const { dims: decayed } = await this.decayedDimensions(characterId, now, options.halfLifeMs);
+    const currentDominant = dominantState(decayed);
+
+    const signal = this.tagger.tag({ text, triggerThreshold: options.triggerThreshold });
+    const next = nextEmotionState(currentDominant, signal, options);
+
+    let updated: Dimensions;
+    if (next === currentDominant) {
+      updated = decayed;
+    } else if (next === "CALM") {
+      updated = { calm: 100, joy: 0, sad: 0, alert: 0, shy: 0, grumpy: 0 };
+    } else {
+      const intensityValue = Math.max(20, signal.intensity * 100);
+      updated = { calm: Math.max(0, 100 - intensityValue), joy: 0, sad: 0, alert: 0, shy: 0, grumpy: 0 };
+      updated[fieldFor(next)] = intensityValue;
+    }
+
+    await this.persist(characterId, updated, now);
+    return { state: toDomain(characterId, updated, now), style: toResponseStyle(next) };
+  }
+
+  private async decayedDimensions(
+    characterId: string,
+    now: Date,
+    halfLifeMs = DEFAULT_HALF_LIFE_MS,
+  ): Promise<{ dims: Dimensions; updatedAt: Date }> {
+    const row = await this.prisma.client.emotionState.upsert({
+      where: { characterId },
+      update: {},
+      create: { characterId },
+    });
+
+    const elapsedMs = now.getTime() - row.updatedAt.getTime();
+    const dims = decayDimensions(row, elapsedMs, halfLifeMs);
+    return { dims, updatedAt: row.updatedAt };
+  }
+
+  private async persist(characterId: string, dims: Dimensions, now: Date): Promise<void> {
+    await this.prisma.client.emotionState.update({
+      where: { characterId },
+      data: { ...dims, updatedAt: now },
+    });
+  }
+}
+
+export { dominantState };
diff --git a/apps/api/src/emotion/response-style.ts b/apps/api/src/emotion/response-style.ts
new file mode 100644
index 0000000..4d2dcdc
--- /dev/null
+++ b/apps/api/src/emotion/response-style.ts
@@ -0,0 +1,21 @@
+import type { EmotionTag } from "@kokorone/shared";
+
+export interface ResponseStyle {
+  tone: string; // 語氣
+  sentenceLength: "short" | "medium" | "long"; // 句長
+  initiative: "low" | "medium" | "high"; // 主動性
+}
+
+// D-3 情緒→回應風格輸出：把當前情緒轉為 F 群組上下文組裝器可直接使用的回應參數。
+const STYLE_BY_TAG: Record<EmotionTag, ResponseStyle> = {
+  CALM: { tone: "平穩自然", sentenceLength: "medium", initiative: "medium" },
+  JOY: { tone: "開朗雀躍、多話", sentenceLength: "long", initiative: "high" },
+  SAD: { tone: "低落安靜、簡短", sentenceLength: "short", initiative: "low" },
+  ALERT: { tone: "警戒防備", sentenceLength: "short", initiative: "low" },
+  SHY: { tone: "害羞結巴", sentenceLength: "short", initiative: "low" },
+  GRUMPY: { tone: "嘴硬彆扭", sentenceLength: "medium", initiative: "medium" },
+};
+
+export function toResponseStyle(tag: EmotionTag): ResponseStyle {
+  return STYLE_BY_TAG[tag];
+}
diff --git a/scripts/smoke/D.mjs b/scripts/smoke/D.mjs
new file mode 100644
index 0000000..e7699bc
--- /dev/null
+++ b/scripts/smoke/D.mjs
@@ -0,0 +1,142 @@
+import { prisma } from "@kokorone/db";
+
+const API_PORT = process.env.PORT_API ?? "3001";
+const CHARACTER_ID = "seed-character-genki";
+const ORIGINAL_EMOTION = { calm: 70, joy: 20, sad: 0, alert: 0, shy: 0, grumpy: 0 };
+const BASELINE = { calm: 100, joy: 0, sad: 0, alert: 0, shy: 0, grumpy: 0 };
+
+async function resetEmotion(overrides = BASELINE) {
+  await prisma.emotionState.upsert({
+    where: { characterId: CHARACTER_ID },
+    update: { ...overrides, updatedAt: new Date() },
+    create: { characterId: CHARACTER_ID, ...overrides },
+  });
+}
+
+async function postInput(body) {
+  const res = await fetch(`http://localhost:${API_PORT}/emotion/${CHARACTER_ID}/input`, {
+    method: "POST",
+    headers: { "Content-Type": "application/json" },
+    body: JSON.stringify(body),
+  });
+  if (!res.ok) {
+    throw new Error(`POST /emotion/${CHARACTER_ID}/input 回傳 ${res.status}`);
+  }
+  return res.json();
+}
+
+async function getState(now) {
+  const url = `http://localhost:${API_PORT}/emotion/${CHARACTER_ID}${now ? `?now=${encodeURIComponent(now)}` : ""}`;
+  const res = await fetch(url);
+  if (!res.ok) {
+    throw new Error(`GET /emotion/${CHARACTER_ID} 回傳 ${res.status}`);
+  }
+  return res.json();
+}
+
+function dominantOf(state) {
+  const candidates = [
+    ["JOY", state.joy],
+    ["SAD", state.sad],
+    ["ALERT", state.alert],
+    ["SHY", state.shy],
+    ["GRUMPY", state.grumpy],
+  ];
+  const [tag, value] = candidates.reduce((best, cur) => (cur[1] > best[1] ? cur : best), ["CALM", 5]);
+  return value > 5 ? tag : "CALM";
+}
+
+function assertDominant(state, expected, label) {
+  const actual = dominantOf(state);
+  if (actual !== expected) {
+    throw new Error(`${label}：預期主導情緒為 ${expected}，實際為 ${actual}（${JSON.stringify(state)}）`);
+  }
+}
+
+export default async function smokeD() {
+  // D-1 情緒標記器：正向／負向／衝突語氣輸入分別得到對應標記
+  await resetEmotion();
+  const positive = await postInput({ text: "謝謝你，我好開心！" });
+  assertDominant(positive.state, "JOY", "正向輸入");
+
+  await resetEmotion();
+  const negative = await postInput({ text: "今天過得好難過，很失望" });
+  assertDominant(negative.state, "SAD", "負向輸入");
+
+  await resetEmotion();
+  const conflict = await postInput({ text: "你這個笨蛋，滾開！" });
+  assertDominant(conflict.state, "ALERT", "衝突語氣輸入");
+  if (conflict.style.sentenceLength !== "short" || conflict.style.initiative !== "low") {
+    throw new Error("D-3 警戒狀態的回應風格參數不符預期");
+  }
+
+  // D-4 情緒狀態機：連續負向（衝突持續）輸入 → 警戒繼續惡化為低落
+  const stillConflicted = await postInput({ text: "我還是很生氣", conflictContinues: true });
+  assertDominant(stillConflicted.state, "SAD", "警戒 --> 低落（衝突持續）");
+
+  // 警戒 --> 平靜（確認無威脅）
+  await resetEmotion({ calm: 0, joy: 0, sad: 0, alert: 100, shy: 0, grumpy: 0 });
+  const safeAgain = await postInput({ text: "沒事了", threatConfirmedSafe: true });
+  assertDominant(safeAgain.state, "CALM", "警戒 --> 平靜（確認無威脅）");
+
+  // 低落 --> 平靜（被安慰）
+  await resetEmotion({ calm: 50, joy: 0, sad: 50, alert: 0, shy: 0, grumpy: 0 });
+  const comforted = await postInput({ text: "謝謝你安慰我", comforted: true });
+  assertDominant(comforted.state, "CALM", "低落 --> 平靜（被安慰）");
+
+  // 平靜 --> 害羞（被稱讚）
+  await resetEmotion();
+  const praised = await postInput({ text: "你今天好可愛喔" });
+  assertDominant(praised.state, "SHY", "平靜 --> 害羞（被稱讚）");
+
+  // 平靜 --> 彆扭（小型負向事件）→ 被哄後快速恢復平靜
+  await resetEmotion();
+  const grumpy = await postInput({ text: "你都不理我" });
+  assertDominant(grumpy.state, "GRUMPY", "平靜 --> 彆扭（小型負向事件）");
+  const placated = await postInput({ text: "好啦好啦", placated: true });
+  assertDominant(placated.state, "CALM", "彆扭 --> 平靜（被哄）");
+
+  // D-3 情緒→回應風格輸出：愉悅指向多話／高主動，低落指向簡短／低主動
+  await resetEmotion();
+  const joyful = await postInput({ text: "謝謝你，我好開心！" });
+  if (joyful.style.sentenceLength !== "long" || joyful.style.initiative !== "high") {
+    throw new Error("D-3 愉悅狀態的回應風格參數不符預期");
+  }
+
+  await resetEmotion();
+  const sadResult = await postInput({ text: "今天過得好難過，很失望" });
+  if (sadResult.style.sentenceLength !== "short" || sadResult.style.initiative !== "low") {
+    throw new Error("D-3 低落狀態的回應風格參數不符預期");
+  }
+
+  // D-2 時間衰減：模擬經過數小時後情緒值回落；跨 session（重新讀取）仍可讀到殘留
+  await resetEmotion({ calm: 0, joy: 100, sad: 0, alert: 0, shy: 0, grumpy: 0 });
+  const immediate = await getState();
+  if (immediate.joy < 90) {
+    throw new Error("尚未經過時間就已衰減，時間衰減函數計算有誤");
+  }
+
+  const threeHoursLater = new Date(Date.now() + 3 * 60 * 60 * 1000).toISOString();
+  const decayed = await getState(threeHoursLater);
+  if (decayed.joy >= immediate.joy) {
+    throw new Error("模擬時間推進後情緒值未回落");
+  }
+  if (decayed.joy <= 0) {
+    throw new Error("時間推進後情緒殘留應仍大於 0（尚未完全衰減）");
+  }
+
+  // 跨 session：不重啟服務也不清狀態，重新 GET 一次應讀到同一份殘留（持久化於資料庫，而非行程記憶體）
+  const reread = await getState(threeHoursLater);
+  if (Math.abs(reread.joy - decayed.joy) > 0.01) {
+    throw new Error("重新讀取時殘留情緒值不一致，情緒狀態未正確持久化");
+  }
+
+  const twentyHoursLater = new Date(Date.now() + 20 * 60 * 60 * 1000).toISOString();
+  const fullyDecayed = await getState(twentyHoursLater);
+  if (dominantOf(fullyDecayed) !== "CALM") {
+    throw new Error("長時間衰減後應回歸平靜");
+  }
+
+  // 還原種子角色原始展示用情緒值，避免影響其他群組或人工檢視
+  await resetEmotion(ORIGINAL_EMOTION);
+}
diff --git a/todo.md b/todo.md
index 6a8eaca..c51c4ec 100644
--- a/todo.md
+++ b/todo.md
@@ -159,11 +159,18 @@ flowchart TB
 
 ### D. 情緒子系統
 
-- [ ] **D-1 情緒標記器（S）**：實作 `EmotionTagger` 介面與規則版實作（關鍵字＋輸入特徵＋角色觸發閾值），輸出情緒類型與強度分數。驗收：正向／負向／衝突語氣輸入分別得到對應標記。依據：§聊天系統架構圖「情緒標記器：為輸入評估情緒強度」。
-- [ ] **D-2 時間衰減（S）**：以半衰期函數隨時間回歸平靜，衰減速度由角色參數決定；跨 session 保留殘留情緒。驗收：模擬經過數小時後情緒值回落，重新開啟 session 仍讀得到殘留。依據：§情緒狀態機「跨 session 保留情緒殘留……但隨時間衰減」。
-- [ ] **D-3 情緒→回應風格輸出（S）**：把當前情緒轉為回應參數（語氣、句長、主動性），提供給 F 群組的上下文組裝器。驗收：愉悅時參數指向「多話」、低落時指向「簡短」。依據：§情緒狀態機「情緒狀態影響：回覆語氣、用詞選擇、主動性」。
-- [ ] **D-4 情緒狀態機（M）**：實作平靜／愉悅／低落／警戒的轉移規則（正向互動、負向事件、偵測衝突語氣、確認無威脅、衝突持續），並加入害羞與彆扭兩個狀態（供 G-4 可愛度行為使用）。驗收：依 wiki 狀態圖的每條轉移邊都有對應測試通過。依據：§情緒狀態機 stateDiagram、§可愛度設計「情緒引擎新增『羞』狀態」。
-- [ ] **D-V 階段驗證（XS）**：`npm run restart && npm run smoke -- D`（D.mjs：連續負向輸入→進警戒；模擬時間推進→回平靜；跨 session 讀回殘留）。
+- [x] **D-1 情緒標記器（S）**：實作 `EmotionTagger` 介面與規則版實作（關鍵字＋輸入特徵＋角色觸發閾值），輸出情緒類型與強度分數。驗收：正向／負向／衝突語氣輸入分別得到對應標記。依據：§聊天系統架構圖「情緒標記器：為輸入評估情緒強度」。
+- [x] **D-2 時間衰減（S）**：以半衰期函數隨時間回歸平靜，衰減速度由角色參數決定；跨 session 保留殘留情緒。驗收：模擬經過數小時後情緒值回落，重新開啟 session 仍讀得到殘留。依據：§情緒狀態機「跨 session 保留情緒殘留……但隨時間衰減」。
+- [x] **D-3 情緒→回應風格輸出（S）**：把當前情緒轉為回應參數（語氣、句長、主動性），提供給 F 群組的上下文組裝器。驗收：愉悅時參數指向「多話」、低落時指向「簡短」。依據：§情緒狀態機「情緒狀態影響：回覆語氣、用詞選擇、主動性」。
+- [x] **D-4 情緒狀態機（M）**：實作平靜／愉悅／低落／警戒的轉移規則（正向互動、負向事件、偵測衝突語氣、確認無威脅、衝突持續），並加入害羞與彆扭兩個狀態（供 G-4 可愛度行為使用）。驗收：依 wiki 狀態圖的每條轉移邊都有對應測試通過。依據：§情緒狀態機 stateDiagram、§可愛度設計「情緒引擎新增『羞』狀態」。
+- [x] **D-V 階段驗證（XS）**：`npm run restart && npm run smoke -- D`（D.mjs：連續負向輸入→進警戒；模擬時間推進→回平靜；跨 session 讀回殘留）。
+
+> **實作記錄（D 群組）**：
+> - 情緒引擎放在 `apps/api/src/emotion/`。`EmotionState` 的 6 個浮點欄位（calm/joy/sad/alert/shy/grumpy）**不是各自獨立累積**，而是「當下只有一個主導情緒＋其強度」：`dominantState()` 取非平靜維度中數值最高且超過門檻（5）者，狀態轉移發生時會把其餘維度清零、只把目標維度設成新強度。這是刻意的設計取捨——避免連續多種訊號各自累加造成無來源依據的隱性轉移，讓 D-4 的邊全部可預期、可測試。之後 G 群組若要疊加「性格參數影響情緒外顯度」，建議在讀出 `dominantState` 之後的顯示層做縮放，不要改動這裡的儲存邏輯。
+> - D-4 狀態機**只實作 wiki 狀態圖 + 可愛度設計明訂的邊**（`apps/api/src/emotion/emotion-state-machine.ts`），刻意不外推「愉悅／低落／害羞」之間的直接互轉——這些狀態目前只能先衰減回平靜，才能被新訊號帶往別的狀態。害羞（被稱讚觸發）與彆扭（被忽略/比較等小型負向觸發，被哄後快速恢復）是本群組依「可愛度設計」章節新增，wiki 原始狀態圖沒有畫出來。
+> - 時間衰減用半衰期公式（預設 2 小時，`processInput`/`getState` 皆可傳 `halfLifeMs` 覆寫），衰減與情緒讀寫都走資料庫的 `EmotionState.updatedAt`，天生跨 session／跨行程持久，不需要额外的殘留儲存機制。
+> - `GET/POST /emotion/:characterId`、`.../input`、`.../response-style` 同樣是**工程內部驗證用端點**，性質與 C 群組的 `/memory/*` 一致，等 F/H 群組整合對話管線時再決定去留。
+> - D-1 的關鍵字表與觸發優先序（衝突 > 稱讚/害羞 > 輕度負向/彆扭 > 一般負向 > 正向）、D-3 的回應風格對照表都只是 Mock 階段的規則版本；R-3 接上真實 LLM 後，這兩塊要嘛保留作為安全網、要嘛被模型自身的語氣調節取代，屆時再一併決定。
 
 ### E. 關係子系統