diff --git a/docs/src/static/swagger.yaml b/docs/src/static/swagger.yaml
index 5d564f02..05aaa68b 100644
--- a/docs/src/static/swagger.yaml
+++ b/docs/src/static/swagger.yaml
@@ -1009,6 +1009,12 @@ paths:
             "*/*":
               schema:
                 "$ref": "#/components/schemas/EntityGraphFlatDtoOut"
+        '400':
+          description: Invalid graph query parameter value
+          content:
+            "*/*":
+              schema:
+                "$ref": "#/components/schemas/ErrorResponse"
         '404':
           description: Entity not found with the provided identifier
           content:
diff --git a/src/main/java/com/decathlon/idp_core/infrastructure/adapters/api/configuration/SwaggerDescription.java b/src/main/java/com/decathlon/idp_core/infrastructure/adapters/api/configuration/SwaggerDescription.java
index 213d51a6..fbb27c69 100644
--- a/src/main/java/com/decathlon/idp_core/infrastructure/adapters/api/configuration/SwaggerDescription.java
+++ b/src/main/java/com/decathlon/idp_core/infrastructure/adapters/api/configuration/SwaggerDescription.java
@@ -235,6 +235,7 @@ public class SwaggerDescription {
   public static final String ENDPOINT_GET_ENTITY_GRAPH_FLAT_SUMMARY = "Get entity relationship graph as flat nodes and edges";
   public static final String ENDPOINT_GET_ENTITY_GRAPH_FLAT_DESCRIPTION = "Retrieves the entity relationship graph as a flat nodes-and-edges structure, suitable for frontend visualization tools such as React Flow, Vis.js, and Cytoscape.";
   public static final String RESPONSE_ENTITY_GRAPH_FLAT_SUCCESS = "Flat entity graph successfully retrieved";
+  public static final String RESPONSE_INVALID_GRAPH_QUERY = "Invalid graph query parameter value";
   public static final String ENTITY_GRAPH_FLAT_NODES_DESCRIPTION = "All entity nodes in the graph";
   public static final String ENTITY_GRAPH_FLAT_EDGES_DESCRIPTION = "All directed relation edges in the graph";
   public static final String ENTITY_GRAPH_FLAT_NODE_ID_DESCRIPTION = "Unique node identifier composed of templateIdentifier:identifier";
diff --git a/src/main/java/com/decathlon/idp_core/infrastructure/adapters/api/controller/EntityGraphController.java b/src/main/java/com/decathlon/idp_core/infrastructure/adapters/api/controller/EntityGraphController.java
index 17e896fe..daf48385 100644
--- a/src/main/java/com/decathlon/idp_core/infrastructure/adapters/api/controller/EntityGraphController.java
+++ b/src/main/java/com/decathlon/idp_core/infrastructure/adapters/api/controller/EntityGraphController.java
@@ -1,5 +1,6 @@
 package com.decathlon.idp_core.infrastructure.adapters.api.controller;
 
+import static com.decathlon.idp_core.infrastructure.adapters.api.configuration.SwaggerDescription.BAD_REQUEST_CODE;
 import static com.decathlon.idp_core.infrastructure.adapters.api.configuration.SwaggerDescription.ENDPOINT_GET_ENTITY_GRAPH_FLAT_DESCRIPTION;
 import static com.decathlon.idp_core.infrastructure.adapters.api.configuration.SwaggerDescription.ENDPOINT_GET_ENTITY_GRAPH_FLAT_SUMMARY;
 import static com.decathlon.idp_core.infrastructure.adapters.api.configuration.SwaggerDescription.NOT_FOUND_CODE;
@@ -11,6 +12,7 @@
 import static com.decathlon.idp_core.infrastructure.adapters.api.configuration.SwaggerDescription.PARAM_TRAVERSAL_MODE_DESCRIPTION;
 import static com.decathlon.idp_core.infrastructure.adapters.api.configuration.SwaggerDescription.RESPONSE_ENTITY_GRAPH_FLAT_SUCCESS;
 import static com.decathlon.idp_core.infrastructure.adapters.api.configuration.SwaggerDescription.RESPONSE_ENTITY_NOT_FOUND_IDENTIFIER;
+import static com.decathlon.idp_core.infrastructure.adapters.api.configuration.SwaggerDescription.RESPONSE_INVALID_GRAPH_QUERY;
 import static org.springframework.http.HttpStatus.OK;
 
 import java.util.List;
@@ -77,6 +79,7 @@ public class EntityGraphController {
   @ResponseStatus(OK)
   @Operation(summary = ENDPOINT_GET_ENTITY_GRAPH_FLAT_SUMMARY, description = ENDPOINT_GET_ENTITY_GRAPH_FLAT_DESCRIPTION, responses = {
       @ApiResponse(responseCode = OK_CODE, description = RESPONSE_ENTITY_GRAPH_FLAT_SUCCESS, content = @Content(schema = @Schema(implementation = EntityGraphFlatDtoOut.class))),
+      @ApiResponse(responseCode = BAD_REQUEST_CODE, description = RESPONSE_INVALID_GRAPH_QUERY, content = @Content(schema = @Schema(implementation = ErrorResponse.class))),
       @ApiResponse(responseCode = NOT_FOUND_CODE, description = RESPONSE_ENTITY_NOT_FOUND_IDENTIFIER, content = @Content(schema = @Schema(implementation = ErrorResponse.class)))})
   public EntityGraphFlatDtoOut getEntityGraph(@PathVariable @NotBlank String templateIdentifier,
       @PathVariable @NotBlank String entityIdentifier,
diff --git a/src/main/java/com/decathlon/idp_core/infrastructure/adapters/api/handler/ApiExceptionHandler.java b/src/main/java/com/decathlon/idp_core/infrastructure/adapters/api/handler/ApiExceptionHandler.java
index 7627cd64..697d0dc5 100644
--- a/src/main/java/com/decathlon/idp_core/infrastructure/adapters/api/handler/ApiExceptionHandler.java
+++ b/src/main/java/com/decathlon/idp_core/infrastructure/adapters/api/handler/ApiExceptionHandler.java
@@ -2,6 +2,7 @@
 
 import static org.springframework.http.HttpStatus.NOT_FOUND;
 
+import java.util.Arrays;
 import java.util.List;
 import java.util.Map;
 import java.util.regex.Matcher;
@@ -20,6 +21,7 @@
 import org.springframework.web.bind.annotation.ControllerAdvice;
 import org.springframework.web.bind.annotation.ExceptionHandler;
 import org.springframework.web.method.annotation.HandlerMethodValidationException;
+import org.springframework.web.method.annotation.MethodArgumentTypeMismatchException;
 import org.springframework.web.servlet.NoHandlerFoundException;
 
 import com.decathlon.idp_core.domain.exception.entity.EntityAlreadyExistsException;
@@ -296,6 +298,22 @@ public ResponseEntity<ErrorResponse> handleMethodArgumentNotValidException(
     return createErrorResponse(HttpStatus.BAD_REQUEST, errorMessage);
   }
 
+  /// Handles invalid request parameter types, including unknown enum values.
+  @ExceptionHandler(MethodArgumentTypeMismatchException.class)
+  public ResponseEntity<ErrorResponse> handleMethodArgumentTypeMismatchException(
+      MethodArgumentTypeMismatchException ex) {
+    String errorMessage = "Invalid value '%s' for parameter '%s'.".formatted(ex.getValue(),
+        ex.getName());
+    Class<?> requiredType = ex.getRequiredType();
+    if (requiredType != null && requiredType.isEnum()) {
+      errorMessage += " Allowed values: " + Arrays.toString(requiredType.getEnumConstants()) + ".";
+    } else if (requiredType != null) {
+      errorMessage += " Expected type: " + requiredType.getSimpleName() + ".";
+    }
+    log.warn("Request parameter type mismatch: {}", errorMessage);
+    return createErrorResponse(HttpStatus.BAD_REQUEST, errorMessage);
+  }
+
   /// Handles JSON parsing and deserialization errors from request bodies.
   ///
   /// **User-friendly parsing:** Converts technical JSON parsing errors into
@@ -606,7 +624,6 @@ public ResponseEntity<ErrorResponse> handleEntityDynamicMappingNotFoundException
   }
 
   /// Handles creation of a dynamic mapping whose identifier already exists.
-  ///
   /// HTTP mapping: Maps EntityDynamicMappingAlreadyExistsException to HTTP 409
   /// Conflict, surfacing the uniqueness violation with business meaning.
   @ExceptionHandler(EntityDynamicMappingAlreadyExistsException.class)
diff --git a/src/test/java/com/decathlon/idp_core/infrastructure/adapters/api/handler/ApiExceptionHandlerTest.java b/src/test/java/com/decathlon/idp_core/infrastructure/adapters/api/handler/ApiExceptionHandlerTest.java
index f29c7213..5d0b0ee2 100644
--- a/src/test/java/com/decathlon/idp_core/infrastructure/adapters/api/handler/ApiExceptionHandlerTest.java
+++ b/src/test/java/com/decathlon/idp_core/infrastructure/adapters/api/handler/ApiExceptionHandlerTest.java
@@ -2,6 +2,8 @@
 
 import static org.junit.jupiter.api.Assertions.*;
 import static org.mockito.Mockito.mock;
+import static org.mockito.Mockito.verify;
+import static org.mockito.Mockito.verifyNoInteractions;
 import static org.mockito.Mockito.when;
 
 import java.lang.reflect.Constructor;
@@ -17,14 +19,18 @@
 import org.junit.jupiter.api.Test;
 import org.junit.jupiter.params.ParameterizedTest;
 import org.junit.jupiter.params.provider.Arguments;
+import org.junit.jupiter.params.provider.CsvSource;
+import org.junit.jupiter.params.provider.EnumSource;
 import org.junit.jupiter.params.provider.MethodSource;
 import org.springframework.core.MethodParameter;
 import org.springframework.http.HttpStatus;
 import org.springframework.http.ResponseEntity;
 import org.springframework.http.converter.HttpMessageNotReadableException;
+import org.springframework.test.web.servlet.client.RestTestClient;
 import org.springframework.validation.BeanPropertyBindingResult;
 import org.springframework.validation.FieldError;
 import org.springframework.web.bind.MethodArgumentNotValidException;
+import org.springframework.web.method.annotation.MethodArgumentTypeMismatchException;
 
 import com.decathlon.idp_core.domain.exception.entity.EntityAlreadyExistsException;
 import com.decathlon.idp_core.domain.exception.entity.EntityValidationException;
@@ -35,6 +41,10 @@
 import com.decathlon.idp_core.domain.exception.entity_template.PropertyNameNotFoundEntityTemplatePropertiesException;
 import com.decathlon.idp_core.domain.exception.entity_template.RelationNameNotFoundEntityTemplateRelationsException;
 import com.decathlon.idp_core.domain.exception.webhook.WebhookSecurityConfigurationException;
+import com.decathlon.idp_core.domain.model.entity_graph.EntityGraphQueryOptions;
+import com.decathlon.idp_core.domain.model.entity_graph.EntityGraphTraversalMode;
+import com.decathlon.idp_core.domain.service.entity_graph.EntityGraphService;
+import com.decathlon.idp_core.infrastructure.adapters.api.controller.EntityGraphController;
 import com.decathlon.idp_core.infrastructure.adapters.common.model.ErrorResponse;
 
 /// Comprehensive unit tests for [ApiExceptionHandler].
@@ -55,6 +65,87 @@ void setUp() throws Exception {
     exceptionHandler = constructor.newInstance();
   }
 
+  @Nested
+  @DisplayName("Request parameter conversion")
+  class RequestParameterConversionTests {
+
+    private EntityGraphService graphService;
+    private RestTestClient client;
+
+    @BeforeEach
+    void setUpClient() {
+      graphService = mock(EntityGraphService.class);
+      client = RestTestClient.bindToController(new EntityGraphController(graphService))
+          .configureServer(builder -> builder.setControllerAdvice(exceptionHandler)).build();
+    }
+
+    @ParameterizedTest
+    @CsvSource({"traversal_mode, OUTBOUND_ONL", "traversal_mode, UNKNOWN",
+        "traversal_mode, outbound_only", "depth, abc", "include_data, invalid"})
+    @DisplayName("Should return 400 with a description for invalid graph parameters")
+    void shouldRejectInvalidGraphParameters(String parameter, String value) {
+      client.get().uri("/api/v1/entities/product/test/graph?{parameter}={value}", parameter, value)
+          .exchange().expectStatus().isBadRequest().expectBody(ErrorResponse.class).value(body -> {
+            assertEquals("BAD_REQUEST", body.getError());
+            assertTrue(body.getErrorDescription().contains(parameter));
+            assertTrue(body.getErrorDescription().contains(value));
+            if ("traversal_mode".equals(parameter)) {
+              assertTrue(body.getErrorDescription()
+                  .contains("Allowed values: [DIRECT_LINEAGE, BIDIRECTIONAL, OUTBOUND_ONLY]."));
+            }
+          });
+      verifyNoInteractions(graphService);
+    }
+
+    @ParameterizedTest
+    @EnumSource(EntityGraphTraversalMode.class)
+    @DisplayName("Should continue accepting all supported traversal modes")
+    void shouldAcceptSupportedTraversalModes(EntityGraphTraversalMode mode) {
+      client.get().uri("/api/v1/entities/product/test/graph?traversal_mode={mode}", mode).exchange()
+          .expectStatus().isOk();
+
+      verify(graphService).getEntityGraph("product", "test",
+          new EntityGraphQueryOptions(1, false, false, Set.of(), Set.of(), mode));
+    }
+
+    @Test
+    @DisplayName("Should preserve the default traversal mode")
+    void shouldPreserveDefaultTraversalMode() {
+      client.get().uri("/api/v1/entities/product/test/graph").exchange().expectStatus().isOk();
+
+      verify(graphService).getEntityGraph("product", "test", new EntityGraphQueryOptions(1, false,
+          false, Set.of(), Set.of(), EntityGraphTraversalMode.DIRECT_LINEAGE));
+    }
+
+    @Test
+    @DisplayName("Should describe the expected type for non-enum parameters")
+    void shouldDescribeExpectedType() {
+      var exception = new MethodArgumentTypeMismatchException("abc", int.class, "depth",
+          mock(MethodParameter.class), new IllegalArgumentException());
+
+      var response = exceptionHandler.handleMethodArgumentTypeMismatchException(exception);
+
+      assertEquals(HttpStatus.BAD_REQUEST, response.getStatusCode());
+      assertNotNull(response.getBody());
+      assertEquals("Invalid value 'abc' for parameter 'depth'. Expected type: int.",
+          response.getBody().getErrorDescription());
+    }
+
+    @Test
+    @DisplayName("Should handle parameter type mismatches without a required type")
+    void shouldHandleUnknownRequiredType() {
+      var exception = new MethodArgumentTypeMismatchException("invalid", null, "parameter",
+          mock(MethodParameter.class), new IllegalArgumentException());
+
+      var response = exceptionHandler.handleMethodArgumentTypeMismatchException(exception);
+
+      assertEquals(HttpStatus.BAD_REQUEST, response.getStatusCode());
+      assertNotNull(response.getBody());
+      assertEquals("Invalid value 'invalid' for parameter 'parameter'.",
+          response.getBody().getErrorDescription());
+    }
+  }
+
   @Nested
   @DisplayName("Domain Exception Handling")
   class DomainExceptionTests {