diff --git a/CLAUDE.md b/CLAUDE.md
index cc2c128..a2b0545 100644
--- a/CLAUDE.md
+++ b/CLAUDE.md
@@ -101,6 +101,7 @@ domain/{도메인}/
 | AI 오늘 사용량 | `AiToneUsageResult getTodayUsage(Long userId)` (`AiToneUsageQueryService`) | ai → user |
 | 가입 시 회원 생성 | `Long signUp(UserSignUpCommand)` | user → auth |
 | 회원 행 잠금 | `void lockUser(Long userId)` (`UserCommandService`, 호출자 트랜잭션 필수) | user → template |
+| 회원 존재 확인 | `void validateActive(Long userId)` (`UserQueryService`, 없거나 탈퇴면 `USER404_1`) | user → ai |
 
 - **다른 도메인 서비스를 조합하는 조회는 별도 서비스로 분리한다.** 예: 사용량 API는 `UserUsageQueryService`
   - 순환 참조를 막기 위해서다. 사용량 조합(template·ai 서비스 호출)을 `UserQueryService`에 넣으면, template·ai가 `UserQueryService`를 부르게 될 때 생성자 주입 순환으로 앱이 뜨지 않는다
diff --git a/src/main/java/com/sniptext/domain/ai/annotation/ToneStyleConstraintValidator.java b/src/main/java/com/sniptext/domain/ai/annotation/ToneStyleConstraintValidator.java
new file mode 100644
index 0000000..603f8f5
--- /dev/null
+++ b/src/main/java/com/sniptext/domain/ai/annotation/ToneStyleConstraintValidator.java
@@ -0,0 +1,18 @@
+package com.sniptext.domain.ai.annotation;
+
+import java.util.Arrays;
+
+import com.sniptext.domain.ai.entity.ToneStyle;
+
+import jakarta.validation.ConstraintValidator;
+import jakarta.validation.ConstraintValidatorContext;
+
+/** ToneStyle 상수 이름 중 하나와 대소문자까지 같을 때만 통과한다. */
+public class ToneStyleConstraintValidator implements ConstraintValidator<ValidToneStyle, String> {
+
+	@Override
+	public boolean isValid(String style, ConstraintValidatorContext context) {
+		return style != null && Arrays.stream(ToneStyle.values()).anyMatch(each -> each.name().equals(style));
+	}
+
+}
diff --git a/src/main/java/com/sniptext/domain/ai/annotation/ToneTextConstraintValidator.java b/src/main/java/com/sniptext/domain/ai/annotation/ToneTextConstraintValidator.java
new file mode 100644
index 0000000..f9baefb
--- /dev/null
+++ b/src/main/java/com/sniptext/domain/ai/annotation/ToneTextConstraintValidator.java
@@ -0,0 +1,32 @@
+package com.sniptext.domain.ai.annotation;
+
+import com.sniptext.domain.ai.exception.AiErrorCode;
+import com.sniptext.global.text.TextWhitespace;
+
+import jakarta.validation.ConstraintValidator;
+import jakarta.validation.ConstraintValidatorContext;
+
+/** 비었으면 AI400_2, 길면 AI400_3을 메시지로 남긴다. */
+public class ToneTextConstraintValidator implements ConstraintValidator<ValidToneText, String> {
+
+	/** 교정할 원문 최대 길이 (명세 22번, 템플릿 본문 한도와 같다) */
+	static final int MAX_LENGTH = 3000;
+
+	@Override
+	public boolean isValid(String text, ConstraintValidatorContext context) {
+		if (text == null || TextWhitespace.isBlank(text)) {
+			return reject(context, AiErrorCode.TEXT_EMPTY);
+		}
+		if (text.length() > MAX_LENGTH) {
+			return reject(context, AiErrorCode.TEXT_TOO_LONG);
+		}
+		return true;
+	}
+
+	private static boolean reject(ConstraintValidatorContext context, AiErrorCode errorCode) {
+		context.disableDefaultConstraintViolation();
+		context.buildConstraintViolationWithTemplate(errorCode.getCode()).addConstraintViolation();
+		return false;
+	}
+
+}
diff --git a/src/main/java/com/sniptext/domain/ai/annotation/ValidToneStyle.java b/src/main/java/com/sniptext/domain/ai/annotation/ValidToneStyle.java
new file mode 100644
index 0000000..0c60de1
--- /dev/null
+++ b/src/main/java/com/sniptext/domain/ai/annotation/ValidToneStyle.java
@@ -0,0 +1,28 @@
+package com.sniptext.domain.ai.annotation;
+
+import java.lang.annotation.Documented;
+import java.lang.annotation.ElementType;
+import java.lang.annotation.Retention;
+import java.lang.annotation.RetentionPolicy;
+import java.lang.annotation.Target;
+
+import jakarta.validation.Constraint;
+import jakarta.validation.Payload;
+
+/**
+ * 요청 객체의 문체 검증. null·빈 값·ToneStyle 상수 이름과 정확히 같지 않은 값(소문자 포함)이면 AI400_1.
+ * 요청 필드를 ToneStyle로 받으면 없는 값이 JSON 변환 실패(COMMON400_1)가 되므로, 문자열로 받아 이것으로 검사한다.
+ */
+@Documented
+@Target({ElementType.FIELD, ElementType.PARAMETER})
+@Retention(RetentionPolicy.RUNTIME)
+@Constraint(validatedBy = ToneStyleConstraintValidator.class)
+public @interface ValidToneStyle {
+
+	String message() default "AI400_1";
+
+	Class<?>[] groups() default {};
+
+	Class<? extends Payload>[] payload() default {};
+
+}
diff --git a/src/main/java/com/sniptext/domain/ai/annotation/ValidToneText.java b/src/main/java/com/sniptext/domain/ai/annotation/ValidToneText.java
new file mode 100644
index 0000000..22f4e3c
--- /dev/null
+++ b/src/main/java/com/sniptext/domain/ai/annotation/ValidToneText.java
@@ -0,0 +1,29 @@
+package com.sniptext.domain.ai.annotation;
+
+import java.lang.annotation.Documented;
+import java.lang.annotation.ElementType;
+import java.lang.annotation.Retention;
+import java.lang.annotation.RetentionPolicy;
+import java.lang.annotation.Target;
+
+import jakarta.validation.Constraint;
+import jakarta.validation.Payload;
+
+/**
+ * 요청 객체의 교정할 원문 검증. null·빈 값·공백만(TextWhitespace 기준, NBSP·BOM 포함)이면 AI400_2,
+ * String.length()가 3000을 넘으면 AI400_3. 정규화하지 않고 받은 그대로 센다 (NFC 규칙은 템플릿 이름·본문 대상).
+ * @NotBlank·@Size를 같이 붙이지 않는다 (공백 기준이 화면과 달라진다).
+ */
+@Documented
+@Target({ElementType.FIELD, ElementType.PARAMETER})
+@Retention(RetentionPolicy.RUNTIME)
+@Constraint(validatedBy = ToneTextConstraintValidator.class)
+public @interface ValidToneText {
+
+	String message() default "AI400_2";
+
+	Class<?>[] groups() default {};
+
+	Class<? extends Payload>[] payload() default {};
+
+}
diff --git a/src/main/java/com/sniptext/domain/ai/exception/AiErrorCode.java b/src/main/java/com/sniptext/domain/ai/exception/AiErrorCode.java
index 1e56e58..60623a2 100644
--- a/src/main/java/com/sniptext/domain/ai/exception/AiErrorCode.java
+++ b/src/main/java/com/sniptext/domain/ai/exception/AiErrorCode.java
@@ -11,8 +11,20 @@
 @RequiredArgsConstructor
 public enum AiErrorCode implements ResultCode {
 
+	/** style 누락 또는 없는 값 */
+	STYLE_INVALID(HttpStatus.BAD_REQUEST, "AI400_1", "문체를 선택해주세요."),
+	/** text가 비었거나 공백만 입력 */
+	TEXT_EMPTY(HttpStatus.BAD_REQUEST, "AI400_2", "교정할 문장을 입력해주세요."),
+	/** text 3000자 초과 */
+	TEXT_TOO_LONG(HttpStatus.BAD_REQUEST, "AI400_3", "문장은 3,000자까지 입력할 수 있어요."),
+	/** 혐오·차별 표현 또는 욕설·비속어 감지. 횟수 미차감 */
+	INAPPROPRIATE_TEXT(HttpStatus.UNPROCESSABLE_CONTENT, "AI422_1", "부적절한 표현이 있어 교정할 수 없어요. 수정 후 다시 시도해 주세요."),
 	/** 하루 한도 소진. 자정(KST)에 리셋 */
-	DAILY_LIMIT_EXCEEDED(HttpStatus.TOO_MANY_REQUESTS, "AI429_1", "오늘 톤 교정 횟수를 모두 사용했어요.");
+	DAILY_LIMIT_EXCEEDED(HttpStatus.TOO_MANY_REQUESTS, "AI429_1", "오늘 톤 교정 횟수를 모두 사용했어요."),
+	/** 외부 AI 오류. 횟수 미차감 */
+	LANGUAGE_MODEL_FAILED(HttpStatus.BAD_GATEWAY, "AI502_1", "일시적인 오류로 요청을 처리하지 못했어요. 다시 한 번 물어봐 주시겠어요?"),
+	/** 외부 AI 20초 타임아웃. 횟수 미차감 */
+	LANGUAGE_MODEL_TIMEOUT(HttpStatus.GATEWAY_TIMEOUT, "AI504_1", "일시적인 오류로 요청을 처리하지 못했어요. 다시 한 번 물어봐 주시겠어요?");
 
 	private final HttpStatus httpStatus;
 	private final String code;
diff --git a/src/main/java/com/sniptext/domain/user/service/UserQueryService.java b/src/main/java/com/sniptext/domain/user/service/UserQueryService.java
index 4c8855b..9c9b07f 100644
--- a/src/main/java/com/sniptext/domain/user/service/UserQueryService.java
+++ b/src/main/java/com/sniptext/domain/user/service/UserQueryService.java
@@ -3,7 +3,9 @@
 import org.springframework.stereotype.Service;
 import org.springframework.transaction.annotation.Transactional;
 
+import com.sniptext.domain.user.exception.UserErrorCode;
 import com.sniptext.domain.user.repository.UserRepository;
+import com.sniptext.global.exception.BusinessException;
 
 import lombok.RequiredArgsConstructor;
 
@@ -15,4 +17,14 @@ public class UserQueryService {
 
 	private final UserRepository userRepository;
 
+	/**
+	 * 탈퇴하지 않은 회원인지 확인한다. 없거나 탈퇴했으면 USER404_1.
+	 * 회원 행을 외래 키로 쓰는 저장(예: AI 사용량 선점) 전에 불러, 없는 회원이 외래 키 위반(500)으로 끝나지 않게 한다.
+	 */
+	public void validateActive(Long userId) {
+		if (userRepository.findByIdAndDeletedAtIsNull(userId).isEmpty()) {
+			throw new BusinessException(UserErrorCode.USER_NOT_FOUND);
+		}
+	}
+
 }
diff --git a/src/main/java/com/sniptext/global/client/llm/AnthropicLanguageModelClient.java b/src/main/java/com/sniptext/global/client/llm/AnthropicLanguageModelClient.java
index bed9ba6..402aee6 100644
--- a/src/main/java/com/sniptext/global/client/llm/AnthropicLanguageModelClient.java
+++ b/src/main/java/com/sniptext/global/client/llm/AnthropicLanguageModelClient.java
@@ -88,8 +88,9 @@ private static LanguageModelResult toResult(MessagesResponse response) {
 			throw new LanguageModelException("언어 모델 응답 없음");
 		}
 		String stopReason = response.stopReason();
+		int outputTokens = outputTokens(response);
 		if (REFUSAL.equals(stopReason)) {
-			return new LanguageModelResult(joinText(response), true);
+			return new LanguageModelResult(joinText(response), true, outputTokens);
 		}
 		if (MAX_TOKENS.equals(stopReason)) {
 			// 잘린 결과는 내보내지 않는다
@@ -105,7 +106,14 @@ private static LanguageModelResult toResult(MessagesResponse response) {
 		if (TextWhitespace.isBlank(text)) {
 			throw new LanguageModelException("언어 모델 응답이 빈 텍스트");
 		}
-		return new LanguageModelResult(text, false);
+		return new LanguageModelResult(text, false, outputTokens);
+	}
+
+	private static int outputTokens(MessagesResponse response) {
+		if (response.usage() == null || response.usage().outputTokens() == null) {
+			return 0;
+		}
+		return response.usage().outputTokens();
 	}
 
 	private static List<ContentBlock> textBlocks(MessagesResponse response) {
@@ -130,7 +138,12 @@ record Message(String role, String content) {
 	}
 
 	@JsonIgnoreProperties(ignoreUnknown = true)
-	record MessagesResponse(List<ContentBlock> content, @JsonProperty("stop_reason") String stopReason) {
+	record MessagesResponse(List<ContentBlock> content, @JsonProperty("stop_reason") String stopReason, Usage usage) {
+	}
+
+	// 잭슨 3은 원시 타입에 값이 없으면 실패할 수 있어, 없을 수 있는 값은 Integer로 받는다
+	@JsonIgnoreProperties(ignoreUnknown = true)
+	record Usage(@JsonProperty("output_tokens") Integer outputTokens) {
 	}
 
 	@JsonIgnoreProperties(ignoreUnknown = true)
diff --git a/src/main/java/com/sniptext/global/client/llm/FakeLanguageModelClient.java b/src/main/java/com/sniptext/global/client/llm/FakeLanguageModelClient.java
index 29d0ff9..1eed7ce 100644
--- a/src/main/java/com/sniptext/global/client/llm/FakeLanguageModelClient.java
+++ b/src/main/java/com/sniptext/global/client/llm/FakeLanguageModelClient.java
@@ -4,7 +4,7 @@
 
 /**
  * 로컬·테스트용 가짜 언어 모델. 외부를 부르지 않고 사용자 메시지의 원문에 표시만 붙여 돌려준다.
- * 사용자 메시지가 &lt;text&gt;...&lt;/text&gt;로 감싸져 있으면 태그와 그 안쪽 앞뒤 줄바꿈을 벗긴 원문을 쓴다.
+ * 사용자 메시지가 &lt;text&gt;...&lt;/text&gt;로 감싸져 있으면 태그와 그 안쪽 앞뒤 줄바꿈을 벗긴 원문을 쓴다. 출력 토큰 수는 0이다.
  * 원문을 로그에 남기지 않는다.
  */
 public class FakeLanguageModelClient implements LanguageModelClient {
@@ -17,7 +17,7 @@ public class FakeLanguageModelClient implements LanguageModelClient {
 
 	@Override
 	public LanguageModelResult complete(LanguageModelRequest request) {
-		return new LanguageModelResult(PREFIX + unwrap(request.userText()), false);
+		return new LanguageModelResult(PREFIX + unwrap(request.userText()), false, 0);
 	}
 
 	private static String unwrap(String userText) {
diff --git a/src/main/java/com/sniptext/global/client/llm/LanguageModelResult.java b/src/main/java/com/sniptext/global/client/llm/LanguageModelResult.java
index 6f5cb72..b43f38a 100644
--- a/src/main/java/com/sniptext/global/client/llm/LanguageModelResult.java
+++ b/src/main/java/com/sniptext/global/client/llm/LanguageModelResult.java
@@ -3,8 +3,9 @@
 /**
  * 언어 모델 응답. 결과 문장이 들어 있으므로 로그에 남기지 않는다.
  *
- * @param text    모델이 만든 텍스트
- * @param refused 모델이 답변을 거절했는지 (stop_reason이 refusal)
+ * @param text         모델이 만든 텍스트
+ * @param refused      모델이 답변을 거절했는지 (stop_reason이 refusal)
+ * @param outputTokens 출력 토큰 수 (생각 토큰 포함). 응답에 없으면 0
  */
-public record LanguageModelResult(String text, boolean refused) {
+public record LanguageModelResult(String text, boolean refused, int outputTokens) {
 }
diff --git a/src/test/java/com/sniptext/domain/ai/annotation/ValidToneStyleTest.java b/src/test/java/com/sniptext/domain/ai/annotation/ValidToneStyleTest.java
new file mode 100644
index 0000000..d9970df
--- /dev/null
+++ b/src/test/java/com/sniptext/domain/ai/annotation/ValidToneStyleTest.java
@@ -0,0 +1,62 @@
+package com.sniptext.domain.ai.annotation;
+
+import static org.assertj.core.api.Assertions.assertThat;
+
+import java.util.List;
+
+import org.junit.jupiter.api.AfterAll;
+import org.junit.jupiter.api.BeforeAll;
+import org.junit.jupiter.api.DisplayName;
+import org.junit.jupiter.params.ParameterizedTest;
+import org.junit.jupiter.params.provider.EnumSource;
+import org.junit.jupiter.params.provider.NullAndEmptySource;
+import org.junit.jupiter.params.provider.ValueSource;
+
+import com.sniptext.domain.ai.entity.ToneStyle;
+
+import jakarta.validation.ConstraintViolation;
+import jakarta.validation.Validation;
+import jakarta.validation.Validator;
+import jakarta.validation.ValidatorFactory;
+
+class ValidToneStyleTest {
+
+	private static ValidatorFactory validatorFactory;
+	private static Validator validator;
+
+	record Request(@ValidToneStyle String style) {
+	}
+
+	@BeforeAll
+	static void setUp() {
+		validatorFactory = Validation.buildDefaultValidatorFactory();
+		validator = validatorFactory.getValidator();
+	}
+
+	@AfterAll
+	static void tearDown() {
+		validatorFactory.close();
+	}
+
+	@ParameterizedTest
+	@EnumSource(ToneStyle.class)
+	@DisplayName("문체 상수 이름이면 통과한다")
+	void valid(ToneStyle style) {
+		assertThat(messagesOf(style.name())).isEmpty();
+	}
+
+	@ParameterizedTest
+	@NullAndEmptySource
+	@ValueSource(strings = {" ", "ESSAY", "boss_external", "Casual", " CASUAL", "CASUAL ", "UNKNOWN"})
+	@DisplayName("없거나, 비었거나, 없는 값(삭제한 ESSAY 포함)이거나, 대소문자·공백이 다르면 AI400_1")
+	void invalid(String style) {
+		assertThat(messagesOf(style)).containsExactly("AI400_1");
+	}
+
+	private static List<String> messagesOf(String style) {
+		return validator.validate(new Request(style)).stream()
+			.map(ConstraintViolation::getMessage)
+			.toList();
+	}
+
+}
diff --git a/src/test/java/com/sniptext/domain/ai/annotation/ValidToneTextTest.java b/src/test/java/com/sniptext/domain/ai/annotation/ValidToneTextTest.java
new file mode 100644
index 0000000..21b4b3a
--- /dev/null
+++ b/src/test/java/com/sniptext/domain/ai/annotation/ValidToneTextTest.java
@@ -0,0 +1,74 @@
+package com.sniptext.domain.ai.annotation;
+
+import static org.assertj.core.api.Assertions.assertThat;
+
+import java.text.Normalizer;
+import java.util.List;
+
+import org.junit.jupiter.api.AfterAll;
+import org.junit.jupiter.api.BeforeAll;
+import org.junit.jupiter.api.DisplayName;
+import org.junit.jupiter.api.Test;
+import org.junit.jupiter.params.ParameterizedTest;
+import org.junit.jupiter.params.provider.NullAndEmptySource;
+import org.junit.jupiter.params.provider.ValueSource;
+
+import jakarta.validation.ConstraintViolation;
+import jakarta.validation.Validation;
+import jakarta.validation.Validator;
+import jakarta.validation.ValidatorFactory;
+
+class ValidToneTextTest {
+
+	private static ValidatorFactory validatorFactory;
+	private static Validator validator;
+
+	record Request(@ValidToneText String text) {
+	}
+
+	@BeforeAll
+	static void setUp() {
+		validatorFactory = Validation.buildDefaultValidatorFactory();
+		validator = validatorFactory.getValidator();
+	}
+
+	@AfterAll
+	static void tearDown() {
+		validatorFactory.close();
+	}
+
+	@ParameterizedTest
+	@NullAndEmptySource
+	@ValueSource(strings = {"   ", "\r\n\t", " ", "", "　", "  　\n"})
+	@DisplayName("없거나 비었거나 공백만(NBSP·BOM·전각 공백 포함) 있으면 AI400_2")
+	void empty(String text) {
+		assertThat(messagesOf(text)).containsExactly("AI400_2");
+	}
+
+	@Test
+	@DisplayName("3000자는 통과하고 3001자는 AI400_3")
+	void lengthBoundary() {
+		assertThat(messagesOf("가".repeat(3000))).isEmpty();
+		assertThat(messagesOf("가".repeat(3001))).containsExactly("AI400_3");
+	}
+
+	@Test
+	@DisplayName("정규화하지 않고 받은 그대로 센다 (자모 분리형 1500음절은 3000자라 통과, 1501음절은 AI400_3)")
+	void countsAsReceived() {
+		assertThat(messagesOf(Normalizer.normalize("가".repeat(1500), Normalizer.Form.NFD))).isEmpty();
+		assertThat(messagesOf(Normalizer.normalize("가".repeat(1501), Normalizer.Form.NFD))).containsExactly("AI400_3");
+	}
+
+	@Test
+	@DisplayName("앞뒤 공백이 있어도 내용이 있으면 통과한다")
+	void valid() {
+		assertThat(messagesOf("  이번 달은 외주 못 받는다고 해줘  ")).isEmpty();
+	}
+
+	private static List<String> messagesOf(String text) {
+		return validator.validate(new Request(text)).stream()
+			.map(ConstraintViolation::getMessage)
+			.toList();
+	}
+
+}
diff --git a/src/test/java/com/sniptext/domain/ai/exception/AiErrorCodeTest.java b/src/test/java/com/sniptext/domain/ai/exception/AiErrorCodeTest.java
index 3e4ec37..bbd945e 100644
--- a/src/test/java/com/sniptext/domain/ai/exception/AiErrorCodeTest.java
+++ b/src/test/java/com/sniptext/domain/ai/exception/AiErrorCodeTest.java
@@ -2,20 +2,42 @@
 
 import static org.assertj.core.api.Assertions.assertThat;
 
+import java.util.stream.Stream;
+
 import org.junit.jupiter.api.DisplayName;
 import org.junit.jupiter.api.Test;
-import org.springframework.http.HttpStatus;
+import org.junit.jupiter.params.ParameterizedTest;
+import org.junit.jupiter.params.provider.Arguments;
+import org.junit.jupiter.params.provider.MethodSource;
 
 class AiErrorCodeTest {
 
-	@Test
-	@DisplayName("하루 한도 소진은 명세의 429 결과 코드와 문구다")
-	void dailyLimitExceeded() {
-		AiErrorCode errorCode = AiErrorCode.DAILY_LIMIT_EXCEEDED;
+	private static final String TEMPORARY_FAILURE = "일시적인 오류로 요청을 처리하지 못했어요. 다시 한 번 물어봐 주시겠어요?";
+
+	static Stream<Arguments> specCodes() {
+		return Stream.of(
+			Arguments.of(AiErrorCode.STYLE_INVALID, 400, "AI400_1", "문체를 선택해주세요."),
+			Arguments.of(AiErrorCode.TEXT_EMPTY, 400, "AI400_2", "교정할 문장을 입력해주세요."),
+			Arguments.of(AiErrorCode.TEXT_TOO_LONG, 400, "AI400_3", "문장은 3,000자까지 입력할 수 있어요."),
+			Arguments.of(AiErrorCode.INAPPROPRIATE_TEXT, 422, "AI422_1", "부적절한 표현이 있어 교정할 수 없어요. 수정 후 다시 시도해 주세요."),
+			Arguments.of(AiErrorCode.DAILY_LIMIT_EXCEEDED, 429, "AI429_1", "오늘 톤 교정 횟수를 모두 사용했어요."),
+			Arguments.of(AiErrorCode.LANGUAGE_MODEL_FAILED, 502, "AI502_1", TEMPORARY_FAILURE),
+			Arguments.of(AiErrorCode.LANGUAGE_MODEL_TIMEOUT, 504, "AI504_1", TEMPORARY_FAILURE));
+	}
 
-		assertThat(errorCode.getHttpStatus()).isEqualTo(HttpStatus.TOO_MANY_REQUESTS);
-		assertThat(errorCode.getCode()).isEqualTo("AI429_1");
-		assertThat(errorCode.getMessage()).isEqualTo("오늘 톤 교정 횟수를 모두 사용했어요.");
+	@ParameterizedTest
+	@MethodSource("specCodes")
+	@DisplayName("명세 22번의 HTTP 상태·결과 코드·문구와 같다")
+	void matchesSpec(AiErrorCode errorCode, int status, String code, String message) {
+		assertThat(errorCode.getHttpStatus().value()).isEqualTo(status);
+		assertThat(errorCode.getCode()).isEqualTo(code);
+		assertThat(errorCode.getMessage()).isEqualTo(message);
+	}
+
+	@Test
+	@DisplayName("명세에 없는 에러 코드를 두지 않는다")
+	void noExtraCodes() {
+		assertThat(AiErrorCode.values()).hasSize((int)specCodes().count());
 	}
 
 }
diff --git a/src/test/java/com/sniptext/domain/user/service/UserQueryServiceTest.java b/src/test/java/com/sniptext/domain/user/service/UserQueryServiceTest.java
new file mode 100644
index 0000000..aee3c5a
--- /dev/null
+++ b/src/test/java/com/sniptext/domain/user/service/UserQueryServiceTest.java
@@ -0,0 +1,57 @@
+package com.sniptext.domain.user.service;
+
+import static org.assertj.core.api.Assertions.assertThatCode;
+import static org.assertj.core.api.Assertions.assertThatThrownBy;
+
+import java.time.LocalDateTime;
+
+import org.junit.jupiter.api.DisplayName;
+import org.junit.jupiter.api.Test;
+import org.springframework.beans.factory.annotation.Autowired;
+import org.springframework.transaction.annotation.Transactional;
+
+import com.sniptext.domain.user.exception.UserErrorCode;
+import com.sniptext.domain.user.repository.UserRepository;
+import com.sniptext.fixture.UserFixture;
+import com.sniptext.global.exception.BusinessException;
+import com.sniptext.support.IntegrationTestSupport;
+
+@Transactional
+class UserQueryServiceTest extends IntegrationTestSupport {
+
+	@Autowired
+	private UserQueryService userQueryService;
+
+	@Autowired
+	private UserRepository userRepository;
+
+	@Test
+	@DisplayName("탈퇴하지 않은 회원이면 통과한다")
+	void activeUser() {
+		Long userId = userRepository.save(UserFixture.user("active@sniptext.com")).getId();
+
+		assertThatCode(() -> userQueryService.validateActive(userId)).doesNotThrowAnyException();
+	}
+
+	@Test
+	@DisplayName("없는 회원이면 USER404_1")
+	void missingUser() {
+		assertThatThrownBy(() -> userQueryService.validateActive(-1L))
+			.isInstanceOf(BusinessException.class)
+			.extracting("resultCode")
+			.isEqualTo(UserErrorCode.USER_NOT_FOUND);
+	}
+
+	@Test
+	@DisplayName("탈퇴 회원이면 USER404_1")
+	void deletedUser() {
+		Long userId = userRepository.save(
+			UserFixture.deletedUser("deleted@sniptext.com", LocalDateTime.of(2026, 10, 1, 0, 0))).getId();
+
+		assertThatThrownBy(() -> userQueryService.validateActive(userId))
+			.isInstanceOf(BusinessException.class)
+			.extracting("resultCode")
+			.isEqualTo(UserErrorCode.USER_NOT_FOUND);
+	}
+
+}
diff --git a/src/test/java/com/sniptext/global/client/llm/AnthropicLanguageModelClientTest.java b/src/test/java/com/sniptext/global/client/llm/AnthropicLanguageModelClientTest.java
index 906319d..3aecea0 100644
--- a/src/test/java/com/sniptext/global/client/llm/AnthropicLanguageModelClientTest.java
+++ b/src/test/java/com/sniptext/global/client/llm/AnthropicLanguageModelClientTest.java
@@ -95,6 +95,33 @@ void endTurnJoinsTextBlocks() {
 		assertThat(result.refused()).isFalse();
 	}
 
+	@Test
+	@DisplayName("응답의 usage.output_tokens를 출력 토큰 수로 돌려준다 (거절 응답도 같다)")
+	void outputTokens() {
+		respond(response("end_turn", 4361, "{\"type\":\"text\",\"text\":\"교정\"}"));
+		assertThat(client.complete(REQUEST).outputTokens()).isEqualTo(4361);
+
+		server.reset();
+		respond(response("refusal", 21));
+		assertThat(client.complete(REQUEST).outputTokens()).isEqualTo(21);
+	}
+
+	@ParameterizedTest
+	@ValueSource(strings = {
+		"{\"content\":[{\"type\":\"text\",\"text\":\"교정\"}],\"stop_reason\":\"end_turn\"}",
+		"{\"content\":[{\"type\":\"text\",\"text\":\"교정\"}],\"stop_reason\":\"end_turn\",\"usage\":{\"input_tokens\":1}}",
+		"{\"content\":[{\"type\":\"text\",\"text\":\"교정\"}],\"stop_reason\":\"end_turn\",\"usage\":null}"
+	})
+	@DisplayName("usage나 output_tokens가 없으면 출력 토큰 수는 0이고 결과는 정상이다")
+	void outputTokensMissing(String body) {
+		respond(body);
+
+		LanguageModelResult result = client.complete(REQUEST);
+
+		assertThat(result.text()).isEqualTo("교정");
+		assertThat(result.outputTokens()).isZero();
+	}
+
 	@Test
 	@DisplayName("stop_sequence도 정상 응답이다")
 	void stopSequence() {
@@ -194,8 +221,12 @@ private void respond(String body) {
 	}
 
 	private static String response(String stopReason, String... blocks) {
-		return "{\"id\":\"msg_1\",\"type\":\"message\",\"role\":\"assistant\",\"content\":[%s],\"stop_reason\":\"%s\",\"usage\":{\"input_tokens\":1,\"output_tokens\":1}}"
-			.formatted(String.join(",", blocks), stopReason);
+		return response(stopReason, 1, blocks);
+	}
+
+	private static String response(String stopReason, int outputTokens, String... blocks) {
+		return "{\"id\":\"msg_1\",\"type\":\"message\",\"role\":\"assistant\",\"content\":[%s],\"stop_reason\":\"%s\",\"usage\":{\"input_tokens\":1,\"output_tokens\":%d}}"
+			.formatted(String.join(",", blocks), stopReason, outputTokens);
 	}
 
 	private static AnthropicLanguageModelClient realClient(String baseUrl, Duration timeout) {
diff --git a/src/test/java/com/sniptext/global/client/llm/FakeLanguageModelClientTest.java b/src/test/java/com/sniptext/global/client/llm/FakeLanguageModelClientTest.java
index 5485a9b..102e7a7 100644
--- a/src/test/java/com/sniptext/global/client/llm/FakeLanguageModelClientTest.java
+++ b/src/test/java/com/sniptext/global/client/llm/FakeLanguageModelClientTest.java
@@ -17,6 +17,7 @@ void unwrapsTextTag() {
 		assertThat(result.text()).isEqualTo("[가짜 교정] 안녕하세요\n두 번째 줄")
 			.doesNotContain("<text>", "</text>");
 		assertThat(result.refused()).isFalse();
+		assertThat(result.outputTokens()).isZero();
 	}
 
 	@Test