diff --git a/openspec/changes/phase-1-infrastructure/tasks.md b/openspec/changes/phase-1-infrastructure/tasks.md
index 42840b1..236bd68 100644
--- a/openspec/changes/phase-1-infrastructure/tasks.md
+++ b/openspec/changes/phase-1-infrastructure/tasks.md
@@ -32,8 +32,8 @@
 ## 4. 代码结构重构
 
 - [x] 4.1 包名重构 (org.example → com.superbiz.agent)
-- [ ] 4.2 分层结构优化 (controller/service/repository/domain/tool/config/exception)
-- [ ] 4.3 创建 DTO 类 (DiagnosisRequest, DiagnosisResponse, DocumentUploadRequest, DocumentQueryResponse, Result)
+- [x] 4.2 分层结构优化 (controller/service/repository/domain/tool/config/exception)
+- [x] 4.3 创建 DTO 类 (DiagnosisRequest, DiagnosisResponse, DocumentUploadRequest, DocumentQueryResponse, Result)
 
 ## 5. 文档管理服务
 
diff --git a/src/main/java/com/superbiz/agent/dto/DiagnosisRequest.java b/src/main/java/com/superbiz/agent/dto/DiagnosisRequest.java
new file mode 100644
index 0000000..f20f4ad
--- /dev/null
+++ b/src/main/java/com/superbiz/agent/dto/DiagnosisRequest.java
@@ -0,0 +1,61 @@
+package com.superbiz.agent.dto;
+
+import lombok.AllArgsConstructor;
+import lombok.Builder;
+import lombok.Data;
+import lombok.NoArgsConstructor;
+
+/**
+ * 诊断请求 DTO
+ */
+@Data
+@Builder
+@NoArgsConstructor
+@AllArgsConstructor
+public class DiagnosisRequest {
+
+    /**
+     * 业务ID（订单号/请求ID等）
+     */
+    private String businessId;
+
+    /**
+     * 链路追踪ID
+     */
+    private String traceId;
+
+    /**
+     * 故障类别
+     */
+    private String faultCategory;
+
+    /**
+     * 故障源（省份/服务名/类名等）
+     */
+    private String faultSource;
+
+    /**
+     * 故障目标（接口URL/方法名/SQL等）
+     */
+    private String faultTarget;
+
+    /**
+     * 错误码
+     */
+    private String errorCode;
+
+    /**
+     * 错误消息
+     */
+    private String errorMessage;
+
+    /**
+     * 堆栈信息
+     */
+    private String stackTrace;
+
+    /**
+     * 用户描述
+     */
+    private String userDescription;
+}
diff --git a/src/main/java/com/superbiz/agent/dto/DiagnosisResponse.java b/src/main/java/com/superbiz/agent/dto/DiagnosisResponse.java
new file mode 100644
index 0000000..e1ae016
--- /dev/null
+++ b/src/main/java/com/superbiz/agent/dto/DiagnosisResponse.java
@@ -0,0 +1,92 @@
+package com.superbiz.agent.dto;
+
+import lombok.AllArgsConstructor;
+import lombok.Builder;
+import lombok.Data;
+import lombok.NoArgsConstructor;
+
+import java.time.LocalDateTime;
+import java.util.List;
+import java.util.Map;
+
+/**
+ * 诊断响应 DTO
+ */
+@Data
+@Builder
+@NoArgsConstructor
+@AllArgsConstructor
+public class DiagnosisResponse {
+
+    /**
+     * 诊断ID
+     */
+    private String diagnosisId;
+
+    /**
+     * 会话ID
+     */
+    private String sessionId;
+
+    /**
+     * 诊断状态（PENDING/RUNNING/SUCCESS/FAILED）
+     */
+    private String status;
+
+    /**
+     * 问题类型
+     */
+    private String problemType;
+
+    /**
+     * 根因分析
+     */
+    private String rootCause;
+
+    /**
+     * 修复方案
+     */
+    private String solution;
+
+    /**
+     * 完整诊断报告（Markdown格式）
+     */
+    private String reportMarkdown;
+
+    /**
+     * 诊断置信度（0-100）
+     */
+    private Integer confidence;
+
+    /**
+     * 诊断耗时（毫秒）
+     */
+    private Integer duration;
+
+    /**
+     * 工具调用记录
+     */
+    private List<Map<String, Object>> toolCalls;
+
+    /**
+     * 创建时间
+     */
+    private LocalDateTime createdAt;
+
+    /**
+     * 相似案例推荐
+     */
+    private List<RecommendedCase> recommendedCases;
+
+    @Data
+    @Builder
+    @NoArgsConstructor
+    @AllArgsConstructor
+    public static class RecommendedCase {
+        private String caseId;
+        private String title;
+        private String rootCause;
+        private String solution;
+        private Double similarity;
+    }
+}
diff --git a/src/main/java/com/superbiz/agent/dto/DocumentQueryResponse.java b/src/main/java/com/superbiz/agent/dto/DocumentQueryResponse.java
new file mode 100644
index 0000000..b29b1a9
--- /dev/null
+++ b/src/main/java/com/superbiz/agent/dto/DocumentQueryResponse.java
@@ -0,0 +1,89 @@
+package com.superbiz.agent.dto;
+
+import lombok.AllArgsConstructor;
+import lombok.Builder;
+import lombok.Data;
+import lombok.NoArgsConstructor;
+
+import java.time.LocalDateTime;
+import java.util.List;
+
+/**
+ * 文档查询响应 DTO
+ */
+@Data
+@Builder
+@NoArgsConstructor
+@AllArgsConstructor
+public class DocumentQueryResponse {
+
+    /**
+     * 文档ID
+     */
+    private String docId;
+
+    /**
+     * 文件名
+     */
+    private String fileName;
+
+    /**
+     * 故障类别
+     */
+    private String faultCategory;
+
+    /**
+     * 故障源
+     */
+    private String faultSource;
+
+    /**
+     * 接口名称
+     */
+    private String apiName;
+
+    /**
+     * 版本
+     */
+    private String version;
+
+    /**
+     * 文件大小（字节）
+     */
+    private Long fileSize;
+
+    /**
+     * 索引状态
+     */
+    private String status;
+
+    /**
+     * 分块数量
+     */
+    private Integer chunkCount;
+
+    /**
+     * 索引完成时间
+     */
+    private LocalDateTime indexedAt;
+
+    /**
+     * 创建时间
+     */
+    private LocalDateTime createdAt;
+
+    /**
+     * 检索到的相关内容（语义检索结果）
+     */
+    private List<SearchResult> searchResults;
+
+    @Data
+    @Builder
+    @NoArgsConstructor
+    @AllArgsConstructor
+    public static class SearchResult {
+        private String content;
+        private Double score;
+        private Integer chunkIndex;
+    }
+}
diff --git a/src/main/java/com/superbiz/agent/dto/DocumentUploadRequest.java b/src/main/java/com/superbiz/agent/dto/DocumentUploadRequest.java
new file mode 100644
index 0000000..535077c
--- /dev/null
+++ b/src/main/java/com/superbiz/agent/dto/DocumentUploadRequest.java
@@ -0,0 +1,52 @@
+package com.superbiz.agent.dto;
+
+import lombok.AllArgsConstructor;
+import lombok.Builder;
+import lombok.Data;
+import lombok.NoArgsConstructor;
+import org.springframework.web.multipart.MultipartFile;
+
+/**
+ * 文档上传请求 DTO
+ */
+@Data
+@Builder
+@NoArgsConstructor
+@AllArgsConstructor
+public class DocumentUploadRequest {
+
+    /**
+     * 上传的文件
+     */
+    private MultipartFile file;
+
+    /**
+     * 故障类别（默认 EXTERNAL_API）
+     */
+    private String faultCategory;
+
+    /**
+     * 故障源（省份/服务名）
+     */
+    private String faultSource;
+
+    /**
+     * 接口名称
+     */
+    private String apiName;
+
+    /**
+     * 文档版本
+     */
+    private String version;
+
+    /**
+     * 分块大小（默认 500）
+     */
+    private Integer chunkSize;
+
+    /**
+     * 重叠大小（默认 50）
+     */
+    private Integer chunkOverlap;
+}
diff --git a/src/main/java/com/superbiz/agent/dto/Result.java b/src/main/java/com/superbiz/agent/dto/Result.java
new file mode 100644
index 0000000..2fc3a3d
--- /dev/null
+++ b/src/main/java/com/superbiz/agent/dto/Result.java
@@ -0,0 +1,76 @@
+package com.superbiz.agent.dto;
+
+import lombok.AllArgsConstructor;
+import lombok.Builder;
+import lombok.Data;
+import lombok.NoArgsConstructor;
+
+/**
+ * 统一响应结果 DTO
+ *
+ * @param <T> 数据类型
+ */
+@Data
+@Builder
+@NoArgsConstructor
+@AllArgsConstructor
+public class Result<T> {
+
+    /**
+     * 响应码（200 成功，其他失败）
+     */
+    private Integer code;
+
+    /**
+     * 响应消息
+     */
+    private String message;
+
+    /**
+     * 响应数据
+     */
+    private T data;
+
+    /**
+     * 时间戳
+     */
+    private Long timestamp;
+
+    /**
+     * 成功响应
+     */
+    public static <T> Result<T> success(T data) {
+        return Result.<T>builder()
+            .code(200)
+            .message("success")
+            .data(data)
+            .timestamp(System.currentTimeMillis())
+            .build();
+    }
+
+    /**
+     * 成功响应（无数据）
+     */
+    public static <T> Result<T> success() {
+        return success(null);
+    }
+
+    /**
+     * 失败响应
+     */
+    public static <T> Result<T> error(Integer code, String message) {
+        return Result.<T>builder()
+            .code(code)
+            .message(message)
+            .data(null)
+            .timestamp(System.currentTimeMillis())
+            .build();
+    }
+
+    /**
+     * 失败响应（默认 500）
+     */
+    public static <T> Result<T> error(String message) {
+        return error(500, message);
+    }
+}
diff --git a/src/main/java/com/superbiz/agent/exception/DocumentProcessException.java b/src/main/java/com/superbiz/agent/exception/DocumentProcessException.java
new file mode 100644
index 0000000..b1ad4f3
--- /dev/null
+++ b/src/main/java/com/superbiz/agent/exception/DocumentProcessException.java
@@ -0,0 +1,30 @@
+package com.superbiz.agent.exception;
+
+/**
+ * 文档处理异常
+ */
+public class DocumentProcessException extends RuntimeException {
+
+    private final String docId;
+    private final String operation;
+
+    public DocumentProcessException(String docId, String operation, String message) {
+        super(String.format("Document process failed [docId=%s, operation=%s]: %s", docId, operation, message));
+        this.docId = docId;
+        this.operation = operation;
+    }
+
+    public DocumentProcessException(String docId, String operation, String message, Throwable cause) {
+        super(String.format("Document process failed [docId=%s, operation=%s]: %s", docId, operation, message), cause);
+        this.docId = docId;
+        this.operation = operation;
+    }
+
+    public String getDocId() {
+        return docId;
+    }
+
+    public String getOperation() {
+        return operation;
+    }
+}
diff --git a/src/main/java/com/superbiz/agent/exception/SessionNotFoundException.java b/src/main/java/com/superbiz/agent/exception/SessionNotFoundException.java
new file mode 100644
index 0000000..b15b24e
--- /dev/null
+++ b/src/main/java/com/superbiz/agent/exception/SessionNotFoundException.java
@@ -0,0 +1,23 @@
+package com.superbiz.agent.exception;
+
+/**
+ * 会话未找到异常
+ */
+public class SessionNotFoundException extends RuntimeException {
+
+    private final String sessionId;
+
+    public SessionNotFoundException(String sessionId) {
+        super("Session not found: " + sessionId);
+        this.sessionId = sessionId;
+    }
+
+    public SessionNotFoundException(String sessionId, String message) {
+        super(message);
+        this.sessionId = sessionId;
+    }
+
+    public String getSessionId() {
+        return sessionId;
+    }
+}