diff --git a/mvp/architecture/confidence-feedback.md b/mvp/architecture/confidence-feedback.md
new file mode 100644
index 0000000..24d3016
--- /dev/null
+++ b/mvp/architecture/confidence-feedback.md
@@ -0,0 +1,157 @@
+# 证据评分与用户反馈架构
+
+## 一、整体架构
+
+```
+用户对话
+  ↓
+ChatService.executeChat / executeChatComplex
+  ↓ SUCCESS 后写入 answer，异步触发
+EvaluationService.evaluate(sessionId, answer)
+  └─ 读取 tool_invocation 事实 → 规则引擎 → 写 selfEvaluation
+
+用户提交反馈
+  ↓
+POST /api/feedback { sessionId, feedback: "useful" | "not_useful" }
+  ↓
+FeedbackService.submitFeedback
+  ├─ 写 DiagnosisSession.feedback
+  ├─ useful   → CaseLibraryService.createFromSession → 写 case_library
+  └─ not_useful → 仅写 feedback，status 不变
+```
+
+---
+
+## 二、评分规则（evidence_score）
+
+### 定位
+
+`evidence_score` 衡量的是**证据收集充分度**，不是答案准确性。
+
+- 能证明的：Agent 是否有尝试收集证据、检索是否命中
+- 不能证明的：答案是否有幻觉、推理是否正确
+
+### 数据来源
+
+规则引擎只消费 `tool_invocation` 表的事实记录，不依赖 LLM 判断。
+
+### 规则定义
+
+| 规则名 | 条件 | delta |
+|---|---|---|
+| `no_tool_call` | 无任何工具调用 | 直接 0 分，不参与加权 |
+| `execution_failed` | status = FAILED | 直接 0 分，不参与加权 |
+| `has_successful_tool_call` | 至少 1 次成功调用 | +30 |
+| `l0_exact_match` | 任意调用有 L0 精确匹配命中 | +35 |
+| `l1_semantic_match` | 无 L0 命中但有 L1 语义匹配 | +20 |
+| `retrieval_no_hit` | 有检索调用但无任何命中 | -10 |
+| `all_tool_calls_failed` | 全部调用失败 | -20 |
+
+> L0 和 L1 互斥取高优先级（L0 命中时跳过 L1 分支）。
+
+### selfEvaluation 字段格式
+
+```json
+{
+  "evidence_score": 65,
+  "source": "rule",
+  "factors": [
+    {"name": "has_successful_tool_call", "delta": 30, "description": "有成功的工具调用(20次)"},
+    {"name": "l0_exact_match",           "delta": 35, "description": "L0 精确匹配命中"}
+  ]
+}
+```
+
+| 字段 | 说明 |
+|---|---|
+| `evidence_score` | 0-100 整数 |
+| `source` | 当前固定为 `"rule"`；预留 `"llm"` 供后续扩展 |
+| `factors` | 命中的规则列表，含 name / delta / description |
+| `llm_opinion` | 预留字段（未实现），LLM 观点叠加时在此扩展 |
+
+### 已知边界
+
+- 非检索工具（DateTimeTools、QueryMetricsTools 等）不写 `tool_invocation`，这类 session 的 evidence_score = 0，属于设计边界
+- 评分为异步写入（`@Async`），失败时 `selfEvaluation` 保持 null，前端需处理 null
+
+---
+
+## 三、反馈机制
+
+### API
+
+```
+POST /api/feedback
+Content-Type: application/json
+
+{
+  "sessionId": "xxx",
+  "feedback": "useful" | "not_useful"
+}
+```
+
+**响应**
+
+```json
+{
+  "success": true,
+  "message": "反馈已记录",
+  "caseId": "uuid 或 null"
+}
+```
+
+### 后端行为
+
+| feedback 值 | 操作 |
+|---|---|
+| `useful` | 写 `DiagnosisSession.feedback = "useful"`，生成 `CaseLibrary` 记录，返回 caseId |
+| `not_useful` | 写 `DiagnosisSession.feedback = "not_useful"`，status 不变 |
+| 其他值 | 返回 HTTP 400 |
+
+### 重要设计决策
+
+**BAD_CASE 不改 status 字段**
+
+`status` 表示执行状态（RUNNING/SUCCESS/FAILED），是独立维度，不能被质量标签覆盖。
+查询 BadCase 使用：`WHERE feedback = 'not_useful'`
+
+**useful 触发案例沉淀规则**
+
+| CaseLibrary 字段 | 来源 |
+|---|---|
+| caseId | UUID |
+| diagnosisId | DiagnosisSession.sessionId |
+| sourceType | AUTO |
+| faultCategory | GENERAL（暂时，后续人工补充） |
+| title | query 前 100 字符 |
+| rootCause / solution | DiagnosisSession.answer（完整答案） |
+| createdBy | "system" |
+
+**幂等性**：同一 sessionId 重复提交 useful，返回已有 caseId，不重复插入 case_library。
+
+---
+
+## 四、数据库变更
+
+### V008（新增）
+
+```sql
+ALTER TABLE diagnosis_session ADD COLUMN answer LONGTEXT COMMENT 'Agent 返回给用户的完整答案';
+```
+
+### diagnosis_session 关键字段
+
+| 字段 | 类型 | 说明 |
+|---|---|---|
+| `answer` | LONGTEXT | Agent 完整回答，useful 案例沉淀的内容来源 |
+| `self_evaluation` | JSON | 证据评分结果，格式见上 |
+| `feedback` | VARCHAR(16) | useful / not_useful / null |
+| `status` | VARCHAR(16) | 执行状态，不受 feedback 影响 |
+
+---
+
+## 五、扩展方向（Phase 2）
+
+- **LLM 观点层**：在 `selfEvaluation` 的 `llm_opinion` 字段叠加 LLM 结构化观点（has_root_cause、has_solution 等），作为独立 factors，不改变现有规则逻辑
+- **案例结构化字段**：useful 触发时自动提取 faultCategory / errorCode，替代暂时的 GENERAL
+- **重复召回问题**：Executor Prompt 约束或工具层 session 维度去重（见 [ISS-001](../issues/ISS-001-duplicate-retrieval.md)）
diff --git a/src/main/java/com/superbiz/agent/config/AsyncConfig.java b/src/main/java/com/superbiz/agent/config/AsyncConfig.java
new file mode 100644
index 0000000..1646faa
--- /dev/null
+++ b/src/main/java/com/superbiz/agent/config/AsyncConfig.java
@@ -0,0 +1,9 @@
+package com.superbiz.agent.config;
+
+import org.springframework.context.annotation.Configuration;
+import org.springframework.scheduling.annotation.EnableAsync;
+
+@Configuration
+@EnableAsync
+public class AsyncConfig {
+}
diff --git a/src/main/java/com/superbiz/agent/controller/FeedbackController.java b/src/main/java/com/superbiz/agent/controller/FeedbackController.java
new file mode 100644
index 0000000..556443d
--- /dev/null
+++ b/src/main/java/com/superbiz/agent/controller/FeedbackController.java
@@ -0,0 +1,25 @@
+package com.superbiz.agent.controller;
+
+import com.superbiz.agent.dto.FeedbackRequest;
+import com.superbiz.agent.dto.FeedbackResponse;
+import com.superbiz.agent.service.FeedbackService;
+import org.springframework.beans.factory.annotation.Autowired;
+import org.springframework.http.ResponseEntity;
+import org.springframework.web.bind.annotation.*;
+
+@RestController
+@RequestMapping("/api")
+public class FeedbackController {
+
+    @Autowired
+    private FeedbackService feedbackService;
+
+    @PostMapping("/feedback")
+    public ResponseEntity<FeedbackResponse> submitFeedback(@RequestBody FeedbackRequest request) {
+        FeedbackResponse response = feedbackService.submitFeedback(request.getSessionId(), request.getFeedback());
+        if (!response.isSuccess()) {
+            return ResponseEntity.badRequest().body(response);
+        }
+        return ResponseEntity.ok(response);
+    }
+}
diff --git a/src/main/java/com/superbiz/agent/dto/FeedbackRequest.java b/src/main/java/com/superbiz/agent/dto/FeedbackRequest.java
new file mode 100644
index 0000000..8bf8649
--- /dev/null
+++ b/src/main/java/com/superbiz/agent/dto/FeedbackRequest.java
@@ -0,0 +1,11 @@
+package com.superbiz.agent.dto;
+
+import lombok.Getter;
+import lombok.Setter;
+
+@Getter
+@Setter
+public class FeedbackRequest {
+    private String sessionId;
+    private String feedback;
+}
diff --git a/src/main/java/com/superbiz/agent/dto/FeedbackResponse.java b/src/main/java/com/superbiz/agent/dto/FeedbackResponse.java
new file mode 100644
index 0000000..226095b
--- /dev/null
+++ b/src/main/java/com/superbiz/agent/dto/FeedbackResponse.java
@@ -0,0 +1,12 @@
+package com.superbiz.agent.dto;
+
+import lombok.Builder;
+import lombok.Getter;
+
+@Getter
+@Builder
+public class FeedbackResponse {
+    private boolean success;
+    private String message;
+    private String caseId;
+}
diff --git a/src/main/java/com/superbiz/agent/service/CaseLibraryService.java b/src/main/java/com/superbiz/agent/service/CaseLibraryService.java
new file mode 100644
index 0000000..09cad07
--- /dev/null
+++ b/src/main/java/com/superbiz/agent/service/CaseLibraryService.java
@@ -0,0 +1,53 @@
+package com.superbiz.agent.service;
+
+import com.superbiz.agent.domain.entity.CaseLibrary;
+import com.superbiz.agent.domain.entity.DiagnosisSession;
+import com.superbiz.agent.domain.enums.FaultCategory;
+import com.superbiz.agent.domain.enums.SourceType;
+import com.superbiz.agent.repository.CaseLibraryRepository;
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
+import org.springframework.beans.factory.annotation.Autowired;
+import org.springframework.stereotype.Service;
+
+import java.util.UUID;
+
+@Service
+public class CaseLibraryService {
+
+    private static final Logger logger = LoggerFactory.getLogger(CaseLibraryService.class);
+
+    @Autowired
+    private CaseLibraryRepository caseLibraryRepository;
+
+    public CaseLibrary createFromSession(DiagnosisSession session) {
+        return caseLibraryRepository.findByDiagnosisId(session.getSessionId())
+                .orElseGet(() -> {
+                    String content = session.getAnswer();
+                    if (content == null || content.isBlank()) {
+                        content = session.getQuery() + "\n（自动提取失败，请人工补充）";
+                    }
+
+                    String title = session.getQuery();
+                    if (title.length() > 100) {
+                        title = title.substring(0, 100);
+                    }
+
+                    CaseLibrary caseLibrary = CaseLibrary.builder()
+                            .caseId(UUID.randomUUID().toString())
+                            .diagnosisId(session.getSessionId())
+                            .sourceType(SourceType.AUTO)
+                            .faultCategory(FaultCategory.GENERAL)
+                            .title(title)
+                            .rootCause(content)
+                            .solution(content)
+                            .createdBy("system")
+                            .referenceCount(0)
+                            .build();
+
+                    CaseLibrary saved = caseLibraryRepository.save(caseLibrary);
+                    logger.info("案例已沉淀: caseId={}, sessionId={}", saved.getCaseId(), session.getSessionId());
+                    return saved;
+                });
+    }
+}
diff --git a/src/main/java/com/superbiz/agent/service/EvaluationService.java b/src/main/java/com/superbiz/agent/service/EvaluationService.java
new file mode 100644
index 0000000..157f181
--- /dev/null
+++ b/src/main/java/com/superbiz/agent/service/EvaluationService.java
@@ -0,0 +1,141 @@
+package com.superbiz.agent.service;
+
+import com.fasterxml.jackson.databind.ObjectMapper;
+import com.superbiz.agent.domain.entity.DiagnosisSession;
+import com.superbiz.agent.domain.entity.ToolInvocation;
+import com.superbiz.agent.repository.DiagnosisSessionRepository;
+import com.superbiz.agent.repository.ToolInvocationRepository;
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
+import org.springframework.beans.factory.annotation.Autowired;
+import org.springframework.scheduling.annotation.Async;
+import org.springframework.stereotype.Service;
+
+import java.util.ArrayList;
+import java.util.List;
+import java.util.Map;
+
+/**
+ * 证据评分服务
+ *
+ * 当前实现：基于 tool_invocation 事实的规则引擎，输出 evidence_score（0-100）。
+ * 扩展预留：LLM 观点辅助评估（evaluateWithLlm），未来可叠加到 factors 中作为独立维度。
+ */
+@Service
+public class EvaluationService {
+
+    private static final Logger logger = LoggerFactory.getLogger(EvaluationService.class);
+
+    @Autowired
+    private DiagnosisSessionRepository diagnosisSessionRepository;
+
+    @Autowired
+    private ToolInvocationRepository toolInvocationRepository;
+
+    private final ObjectMapper objectMapper = new ObjectMapper();
+
+    @Async
+    public void evaluate(String sessionId, String answer) {
+        diagnosisSessionRepository.findBySessionId(sessionId).ifPresent(session -> {
+            try {
+                List<ToolInvocation> toolInvocations = toolInvocationRepository.findBySessionId(sessionId);
+                String selfEvaluation = evaluateWithRules(session, toolInvocations);
+                session.setSelfEvaluation(selfEvaluation);
+                diagnosisSessionRepository.save(session);
+                logger.info("证据评分已写入: sessionId={}, result={}", sessionId, selfEvaluation);
+            } catch (Exception e) {
+                logger.error("评分失败: sessionId={}", sessionId, e);
+            }
+        });
+    }
+
+    // -------------------------------------------------------------------------
+    // 规则引擎（事实层）
+    // -------------------------------------------------------------------------
+
+    private String evaluateWithRules(DiagnosisSession session, List<ToolInvocation> invocations) {
+        List<Map<String, Object>> factors = new ArrayList<>();
+
+        if ("FAILED".equals(session.getStatus())) {
+            factors.add(factor("execution_failed", -100, "执行失败"));
+            return buildResult(0, factors);
+        }
+
+        int total = invocations.size();
+        long successCount = invocations.stream().filter(t -> Boolean.TRUE.equals(t.getSuccess())).count();
+        boolean hasRetrieval = invocations.stream().anyMatch(t -> t.getRetrievalLayer() != null);
+        boolean hasL0Hit = invocations.stream()
+                .anyMatch(t -> t.getL0MatchCount() != null && t.getL0MatchCount() > 0);
+        boolean hasL1Hit = invocations.stream()
+                .anyMatch(t -> t.getL1MatchCount() != null && t.getL1MatchCount() > 0);
+
+        if (total == 0) {
+            factors.add(factor("no_tool_call", 0, "无工具调用，无法评估证据充分度"));
+            return buildResult(0, factors);
+        }
+
+        int score = 0;
+
+        // 工具成功调用
+        if (successCount > 0) {
+            int delta = 30;
+            factors.add(factor("has_successful_tool_call", delta, "有成功的工具调用(" + successCount + "次)"));
+            score += delta;
+        }
+
+        // 检索命中（L0 精确匹配，证据最强）
+        if (hasL0Hit) {
+            int delta = 35;
+            factors.add(factor("l0_exact_match", delta, "L0 精确匹配命中"));
+            score += delta;
+        }
+        // 检索命中（L1 语义匹配）
+        else if (hasL1Hit) {
+            int delta = 20;
+            factors.add(factor("l1_semantic_match", delta, "L1 语义匹配命中"));
+            score += delta;
+        }
+        // 有检索但无命中
+        else if (hasRetrieval) {
+            int delta = -10;
+            factors.add(factor("retrieval_no_hit", delta, "检索工具调用但无匹配结果"));
+            score += delta;
+        }
+
+        // 全部工具调用失败
+        if (successCount == 0) {
+            int delta = -20;
+            factors.add(factor("all_tool_calls_failed", delta, "所有工具调用均失败"));
+            score += delta;
+        }
+
+        score = Math.max(0, Math.min(100, score));
+        return buildResult(score, factors);
+    }
+
+    private Map<String, Object> factor(String name, int delta, String description) {
+        return Map.of("name", name, "delta", delta, "description", description);
+    }
+
+    private String buildResult(int score, List<Map<String, Object>> factors) {
+        try {
+            Map<String, Object> result = Map.of(
+                    "evidence_score", score,
+                    "source", "rule",
+                    "factors", factors
+                    // llm_opinion: null  ← 预留字段，LLM 观点叠加时在此处扩展
+            );
+            return objectMapper.writeValueAsString(result);
+        } catch (Exception e) {
+            logger.error("序列化评分结果失败", e);
+            return "{\"evidence_score\":0,\"source\":\"rule\",\"factors\":[]}";
+        }
+    }
+
+    // -------------------------------------------------------------------------
+    // 预留：LLM 观点辅助（Phase 2）
+    // 实现时在此处添加 evaluateWithLlm(session, answer) 方法，
+    // 返回结构化观点（如 has_root_cause、has_solution 等），
+    // 作为独立 factors 叠加到 buildResult 中，不改变现有规则逻辑。
+    // -------------------------------------------------------------------------
+}
diff --git a/src/main/java/com/superbiz/agent/service/FeedbackService.java b/src/main/java/com/superbiz/agent/service/FeedbackService.java
new file mode 100644
index 0000000..a78657e
--- /dev/null
+++ b/src/main/java/com/superbiz/agent/service/FeedbackService.java
@@ -0,0 +1,57 @@
+package com.superbiz.agent.service;
+
+import com.superbiz.agent.domain.entity.DiagnosisSession;
+import com.superbiz.agent.dto.FeedbackResponse;
+import com.superbiz.agent.repository.DiagnosisSessionRepository;
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
+import org.springframework.beans.factory.annotation.Autowired;
+import org.springframework.stereotype.Service;
+
+@Service
+public class FeedbackService {
+
+    private static final Logger logger = LoggerFactory.getLogger(FeedbackService.class);
+
+    private static final String FEEDBACK_USEFUL = "useful";
+    private static final String FEEDBACK_NOT_USEFUL = "not_useful";
+
+    @Autowired
+    private DiagnosisSessionRepository diagnosisSessionRepository;
+
+    @Autowired
+    private CaseLibraryService caseLibraryService;
+
+    public FeedbackResponse submitFeedback(String sessionId, String feedback) {
+        if (sessionId == null || sessionId.isBlank()) {
+            return FeedbackResponse.builder().success(false).message("sessionId 不能为空").build();
+        }
+        if (!FEEDBACK_USEFUL.equals(feedback) && !FEEDBACK_NOT_USEFUL.equals(feedback)) {
+            return FeedbackResponse.builder().success(false)
+                    .message("feedback 只能是 useful 或 not_useful").build();
+        }
+
+        DiagnosisSession session = diagnosisSessionRepository.findBySessionId(sessionId)
+                .orElse(null);
+        if (session == null) {
+            return FeedbackResponse.builder().success(false).message("会话不存在").build();
+        }
+
+        session.setFeedback(feedback);
+
+        String caseId = null;
+        if (FEEDBACK_USEFUL.equals(feedback)) {
+            var caseLibrary = caseLibraryService.createFromSession(session);
+            caseId = caseLibrary.getCaseId();
+        }
+
+        diagnosisSessionRepository.save(session);
+        logger.info("反馈已记录: sessionId={}, feedback={}, caseId={}", sessionId, feedback, caseId);
+
+        return FeedbackResponse.builder()
+                .success(true)
+                .message("反馈已记录")
+                .caseId(caseId)
+                .build();
+    }
+}
diff --git a/src/main/resources/db/migration/V008__add_answer_to_diagnosis_session.sql b/src/main/resources/db/migration/V008__add_answer_to_diagnosis_session.sql
new file mode 100644
index 0000000..45005d8
--- /dev/null
+++ b/src/main/resources/db/migration/V008__add_answer_to_diagnosis_session.sql
@@ -0,0 +1 @@
+ALTER TABLE diagnosis_session ADD COLUMN answer LONGTEXT COMMENT 'Agent 返回给用户的完整答案';