diff --git a/api/src/attachment/controllers/attachment.controller.spec.ts b/api/src/attachment/controllers/attachment.controller.spec.ts
index a0cf19e8..55103b72 100644
--- a/api/src/attachment/controllers/attachment.controller.spec.ts
+++ b/api/src/attachment/controllers/attachment.controller.spec.ts
@@ -27,7 +27,7 @@ import {
 
 import { attachment, attachmentFile } from '../mocks/attachment.mock';
 import { AttachmentRepository } from '../repositories/attachment.repository';
-import { AttachmentModel, Attachment } from '../schemas/attachment.schema';
+import { Attachment, AttachmentModel } from '../schemas/attachment.schema';
 import { AttachmentService } from '../services/attachment.service';
 
 import { AttachmentController } from './attachment.controller';
@@ -35,7 +35,7 @@ import { AttachmentController } from './attachment.controller';
 describe('AttachmentController', () => {
   let attachmentController: AttachmentController;
   let attachmentService: AttachmentService;
-  let attachmentToDelete: Attachment;
+  let attachmentToDelete: Attachment | null;
 
   beforeAll(async () => {
     const module: TestingModule = await Test.createTestingModule({
@@ -79,7 +79,7 @@ describe('AttachmentController', () => {
   describe('Upload', () => {
     it('should throw BadRequestException if no file is selected to be uploaded', async () => {
       const promiseResult = attachmentController.uploadFile({
-        file: undefined,
+        file: [],
       });
       await expect(promiseResult).rejects.toThrow(
         new BadRequestException('No file was selected'),
@@ -121,17 +121,17 @@ describe('AttachmentController', () => {
         name: 'store1.jpg',
       });
       const result = await attachmentController.download({
-        id: storedAttachment.id,
+        id: storedAttachment!.id,
       });
 
       expect(attachmentService.findOne).toHaveBeenCalledWith(
-        storedAttachment.id,
+        storedAttachment!.id,
       );
-      expect(result.options).toEqual({
-        type: storedAttachment.type,
-        length: storedAttachment.size,
+      expect(result?.options).toEqual({
+        type: storedAttachment!.type,
+        length: storedAttachment!.size,
         disposition: `attachment; filename="${encodeURIComponent(
-          storedAttachment.name,
+          storedAttachment!.name,
         )}"`,
       });
     });
@@ -141,11 +141,11 @@ describe('AttachmentController', () => {
     it('should delete an attachment by id', async () => {
       jest.spyOn(attachmentService, 'deleteOne');
       const result = await attachmentController.deleteOne(
-        attachmentToDelete.id,
+        attachmentToDelete!.id,
       );
 
       expect(attachmentService.deleteOne).toHaveBeenCalledWith(
-        attachmentToDelete.id,
+        attachmentToDelete!.id,
       );
       expect(result).toEqual({
         acknowledged: true,
@@ -155,10 +155,10 @@ describe('AttachmentController', () => {
 
     it('should throw a NotFoundException when attempting to delete an attachment by id', async () => {
       await expect(
-        attachmentController.deleteOne(attachmentToDelete.id),
+        attachmentController.deleteOne(attachmentToDelete!.id),
       ).rejects.toThrow(
         new NotFoundException(
-          `Attachment with ID ${attachmentToDelete.id} not found`,
+          `Attachment with ID ${attachmentToDelete!.id} not found`,
         ),
       );
     });
diff --git a/api/src/attachment/controllers/attachment.controller.ts b/api/src/attachment/controllers/attachment.controller.ts
index 3607903f..90964dea 100644
--- a/api/src/attachment/controllers/attachment.controller.ts
+++ b/api/src/attachment/controllers/attachment.controller.ts
@@ -146,7 +146,7 @@ export class AttachmentController extends BaseController<Attachment> {
   @Get('download/:id/:filename?')
   async download(
     @Param() params: AttachmentDownloadDto,
-  ): Promise<StreamableFile> {
+  ): Promise<StreamableFile | undefined> {
     const attachment = await this.attachmentService.findOne(params.id);
 
     if (!attachment) {
diff --git a/api/src/extensions/helpers/llm-nlu/index.helper.ts b/api/src/extensions/helpers/llm-nlu/index.helper.ts
index 814f24cf..8591d954 100644
--- a/api/src/extensions/helpers/llm-nlu/index.helper.ts
+++ b/api/src/extensions/helpers/llm-nlu/index.helper.ts
@@ -100,32 +100,31 @@ export default class LlmNluHelper
    *
    * @returns An array of objects representing the found entities, with their `value`, `start`, and `end` positions.
    */
-  private findKeywordEntities(
-    text: string,
-    entity: NlpEntityFull,
-  ): NLU.ParseEntity[] {
-    return entity.values
-      .flatMap(({ value, expressions }) => {
-        const allValues = [value, ...expressions];
+  private findKeywordEntities(text: string, entity: NlpEntityFull) {
+    return (
+      entity.values
+        .flatMap(({ value, expressions }) => {
+          const allValues = [value, ...expressions];
 
-        // Filter the terms that are found in the text
-        return allValues
-          .flatMap((term) => {
-            const regex = new RegExp(`\\b${term}\\b`, 'g');
-            const matches = [...text.matchAll(regex)];
+          // Filter the terms that are found in the text
+          return allValues
+            .flatMap((term) => {
+              const regex = new RegExp(`\\b${term}\\b`, 'g');
+              const matches = [...text.matchAll(regex)];
 
-            // Map matches to FoundEntity format
-            return matches.map((match) => ({
-              entity: entity.name,
-              value: term,
-              start: match.index!,
-              end: match.index! + term.length,
-              confidence: 1,
-            }));
-          })
-          .shift();
-      })
-      .filter((v) => !!v);
+              // Map matches to FoundEntity format
+              return matches.map((match) => ({
+                entity: entity.name,
+                value: term,
+                start: match.index!,
+                end: match.index! + term.length,
+                confidence: 1,
+              }));
+            })
+            .shift();
+        })
+        .filter((v) => !!v) || []
+    );
   }
 
   async predict(text: string): Promise<NLU.ParseEntities> {
@@ -133,7 +132,7 @@ export default class LlmNluHelper
     const helper = await this.helperService.getDefaultLlmHelper();
     const defaultLanguage = await this.languageService.getDefaultLanguage();
     // Detect language
-    const language = await helper.generateStructuredResponse<string>(
+    const language = await helper.generateStructuredResponse<string>?.(
       `input text: ${text}`,
       settings.model,
       this.languageClassifierPrompt,
@@ -147,13 +146,13 @@ export default class LlmNluHelper
       {
         entity: 'language',
         value: language || defaultLanguage.code,
-        confidence: undefined,
+        confidence: 0.0,
       },
     ];
     for await (const { name, doc, prompt, values } of this
       .traitClassifierPrompts) {
       const allowedValues = values.map(({ value }) => value);
-      const result = await helper.generateStructuredResponse<string>(
+      const result = await helper.generateStructuredResponse<string>?.(
         `input text: ${text}`,
         settings.model,
         prompt,
@@ -163,12 +162,13 @@ export default class LlmNluHelper
           enum: allowedValues.concat('unknown'),
         },
       );
-      const safeValue = result.toLowerCase().trim();
-      const value = allowedValues.includes(safeValue) ? safeValue : '';
+      const safeValue = result?.toLowerCase().trim();
+      const value =
+        safeValue && allowedValues.includes(safeValue) ? safeValue : '';
       traits.push({
         entity: name,
         value,
-        confidence: undefined,
+        confidence: 0.0,
       });
     }
 
@@ -179,7 +179,7 @@ export default class LlmNluHelper
     });
     const entities = keywordEntities.flatMap((keywordEntity) =>
       this.findKeywordEntities(text, keywordEntity),
-    );
+    ) as NLU.ParseEntity[];
 
     return { entities: traits.concat(entities) };
   }
diff --git a/api/src/migration/migration.service.spec.ts b/api/src/migration/migration.service.spec.ts
index 87a64ba3..1ef257fd 100644
--- a/api/src/migration/migration.service.spec.ts
+++ b/api/src/migration/migration.service.spec.ts
@@ -186,7 +186,7 @@ describe('MigrationService', () => {
 
       await service.run({
         action: MigrationAction.UP,
-        version: null,
+        version: undefined,
         isAutoMigrate: false,
       });
 
diff --git a/api/src/migration/migration.service.ts b/api/src/migration/migration.service.ts
index e74a9b0e..df16f53c 100644
--- a/api/src/migration/migration.service.ts
+++ b/api/src/migration/migration.service.ts
@@ -28,6 +28,7 @@ import { Migration, MigrationDocument } from './migration.schema';
 import {
   MigrationAction,
   MigrationName,
+  MigrationRunOneParams,
   MigrationRunParams,
   MigrationSuccessCallback,
   MigrationVersion,
@@ -237,7 +238,7 @@ module.exports = {
    *
    * @returns Resolves when the migration action is successfully executed or stops if the migration already exists.
    */
-  private async runOne({ version, action }: MigrationRunParams) {
+  private async runOne({ version, action }: MigrationRunOneParams) {
     // Verify DB status
     const { exist, migrationDocument } = await this.verifyStatus({
       version,
@@ -255,7 +256,7 @@ module.exports = {
         http: this.httpService,
       });
 
-      if (result) {
+      if (result && migrationDocument) {
         await this.successCallback({
           version,
           action,
diff --git a/api/src/migration/types.ts b/api/src/migration/types.ts
index 2bf93cdd..92134800 100644
--- a/api/src/migration/types.ts
+++ b/api/src/migration/types.ts
@@ -27,6 +27,10 @@ export interface MigrationRunParams {
   isAutoMigrate?: boolean;
 }
 
+export interface MigrationRunOneParams extends MigrationRunParams {
+  version: MigrationVersion;
+}
+
 export interface MigrationSuccessCallback extends MigrationRunParams {
   migrationDocument: MigrationDocument;
 }
diff --git a/api/src/nlp/controllers/nlp-entity.controller.spec.ts b/api/src/nlp/controllers/nlp-entity.controller.spec.ts
index c33f8955..d678dcac 100644
--- a/api/src/nlp/controllers/nlp-entity.controller.spec.ts
+++ b/api/src/nlp/controllers/nlp-entity.controller.spec.ts
@@ -109,7 +109,7 @@ describe('NlpEntityController', () => {
           acc.push({
             ...curr,
             values: nlpValueFixtures.filter(
-              ({ entity }) => parseInt(entity) === index,
+              ({ entity }) => parseInt(entity!) === index,
             ) as NlpEntityFull['values'],
             lookups: curr.lookups!,
             builtin: curr.builtin!,
diff --git a/api/src/nlp/controllers/nlp-value.controller.spec.ts b/api/src/nlp/controllers/nlp-value.controller.spec.ts
index 58be7aa8..97b7c437 100644
--- a/api/src/nlp/controllers/nlp-value.controller.spec.ts
+++ b/api/src/nlp/controllers/nlp-value.controller.spec.ts
@@ -98,7 +98,7 @@ describe('NlpValueController', () => {
           acc.push({
             ...curr,
             entity: nlpEntityFixtures[
-              parseInt(curr.entity)
+              parseInt(curr.entity!)
             ] as NlpValueFull['entity'],
             builtin: curr.builtin!,
             expressions: curr.expressions!,
@@ -125,7 +125,7 @@ describe('NlpValueController', () => {
         (acc, curr) => {
           const ValueWithEntities = {
             ...curr,
-            entity: nlpEntities[parseInt(curr.entity)].id,
+            entity: nlpEntities[parseInt(curr.entity!)].id,
             expressions: curr.expressions!,
             metadata: curr.metadata!,
             builtin: curr.builtin!,
diff --git a/api/src/nlp/controllers/nlp-value.controller.ts b/api/src/nlp/controllers/nlp-value.controller.ts
index 1d241ce0..3bae3093 100644
--- a/api/src/nlp/controllers/nlp-value.controller.ts
+++ b/api/src/nlp/controllers/nlp-value.controller.ts
@@ -75,8 +75,9 @@ export class NlpValueController extends BaseController<
     this.validate({
       dto: createNlpValueDto,
       allowedIds: {
-        entity: (await this.nlpEntityService.findOne(createNlpValueDto.entity))
-          ?.id,
+        entity: createNlpValueDto.entity
+          ? (await this.nlpEntityService.findOne(createNlpValueDto.entity))?.id
+          : null,
       },
     });
     return await this.nlpValueService.create(createNlpValueDto);
@@ -167,7 +168,10 @@ export class NlpValueController extends BaseController<
     @Param('id') id: string,
     @Body() updateNlpValueDto: NlpValueUpdateDto,
   ): Promise<NlpValue> {
-    const result = await this.nlpValueService.updateOne(id, updateNlpValueDto);
+    const result = await this.nlpValueService.updateOne(id, {
+      ...updateNlpValueDto,
+      entity: updateNlpValueDto.entity || undefined,
+    });
     if (!result) {
       this.logger.warn(`Unable to update NLP Value by id ${id}`);
       throw new NotFoundException(`NLP Value with ID ${id} not found`);
diff --git a/api/src/nlp/dto/nlp-value.dto.ts b/api/src/nlp/dto/nlp-value.dto.ts
index 3848718c..a60ffa60 100644
--- a/api/src/nlp/dto/nlp-value.dto.ts
+++ b/api/src/nlp/dto/nlp-value.dto.ts
@@ -49,7 +49,7 @@ export class NlpValueCreateDto {
   @IsString()
   @IsNotEmpty()
   @IsObjectId({ message: 'Entity must be a valid ObjectId' })
-  entity: string;
+  entity: string | null;
 }
 
 export class NlpValueUpdateDto extends PartialType(NlpValueCreateDto) {}
diff --git a/api/src/nlp/repositories/nlp-value.repository.spec.ts b/api/src/nlp/repositories/nlp-value.repository.spec.ts
index 3186cc26..0b3a7ce7 100644
--- a/api/src/nlp/repositories/nlp-value.repository.spec.ts
+++ b/api/src/nlp/repositories/nlp-value.repository.spec.ts
@@ -87,7 +87,7 @@ describe('NlpValueRepository', () => {
           const ValueWithEntities = {
             ...curr,
             entity: nlpEntityFixtures[
-              parseInt(curr.entity)
+              parseInt(curr.entity!)
             ] as NlpValueFull['entity'],
             builtin: curr.builtin!,
             expressions: curr.expressions!,
diff --git a/api/src/nlp/seeds/nlp-value.seed.ts b/api/src/nlp/seeds/nlp-value.seed.ts
index d8fd5f7a..d78bf29e 100644
--- a/api/src/nlp/seeds/nlp-value.seed.ts
+++ b/api/src/nlp/seeds/nlp-value.seed.ts
@@ -38,7 +38,7 @@ export class NlpValueSeeder extends BaseSeeder<
       const entities = await this.nlpEntityRepository.findAll();
       const modelDtos = models.map((v) => ({
         ...v,
-        entity: entities.find(({ name }) => name === v.entity)?.id,
+        entity: entities.find(({ name }) => name === v.entity)?.id || null,
       }));
       await this.repository.createMany(modelDtos);
       return true;
diff --git a/api/src/nlp/services/nlp-value.service.spec.ts b/api/src/nlp/services/nlp-value.service.spec.ts
index 35202015..f62ed7cb 100644
--- a/api/src/nlp/services/nlp-value.service.spec.ts
+++ b/api/src/nlp/services/nlp-value.service.spec.ts
@@ -69,9 +69,7 @@ describe('NlpValueService', () => {
     nlpValues = await nlpValueRepository.findAll();
   });
 
-  afterAll(async () => {
-    await closeInMongodConnection();
-  });
+  afterAll(closeInMongodConnection);
 
   afterEach(jest.clearAllMocks);
 
@@ -94,9 +92,7 @@ describe('NlpValueService', () => {
         (acc, curr) => {
           const ValueWithEntities = {
             ...curr,
-            entity: nlpEntityFixtures[
-              parseInt(curr.entity)
-            ] as NlpValueFull['entity'],
+            entity: nlpEntityFixtures[parseInt(curr.entity!)] as NlpEntity,
             expressions: curr.expressions!,
             metadata: curr.metadata!,
             builtin: curr.builtin!,
diff --git a/api/src/nlp/services/nlp-value.service.ts b/api/src/nlp/services/nlp-value.service.ts
index 2d20bde5..d721efd3 100644
--- a/api/src/nlp/services/nlp-value.service.ts
+++ b/api/src/nlp/services/nlp-value.service.ts
@@ -11,11 +11,7 @@ import { forwardRef, Inject, Injectable } from '@nestjs/common';
 import { DeleteResult } from '@/utils/generics/base-repository';
 import { BaseService } from '@/utils/generics/base-service';
 
-import {
-  NlpValueCreateDto,
-  NlpValueDto,
-  NlpValueUpdateDto,
-} from '../dto/nlp-value.dto';
+import { NlpValueCreateDto, NlpValueDto } from '../dto/nlp-value.dto';
 import { NlpValueRepository } from '../repositories/nlp-value.repository';
 import { NlpEntity } from '../schemas/nlp-entity.schema';
 import {
@@ -139,7 +135,7 @@ export class NlpValueService extends BaseService<
           expressions: vMap[e.value].expressions?.concat([
             sampleText.slice(e.start, e.end),
           ]),
-        } as NlpValueUpdateDto);
+        });
       });
 
     await Promise.all(synonymsToAdd);
diff --git a/api/src/utils/helpers/fs.ts b/api/src/utils/helpers/fs.ts
index d9c3ae39..653aaa7b 100644
--- a/api/src/utils/helpers/fs.ts
+++ b/api/src/utils/helpers/fs.ts
@@ -48,7 +48,7 @@ export async function moveFiles(
   const files = await fs.promises.readdir(sourceFolder);
 
   // Filter only files (skip directories)
-  const filePaths = [];
+  const filePaths: string[] = [];
   for (const file of files) {
     const filePath = join(sourceFolder, file);
     const stat = await fs.promises.stat(filePath);
diff --git a/api/src/utils/pipes/object-id.pipe.ts b/api/src/utils/pipes/object-id.pipe.ts
index 9c504c4f..fd2d1527 100644
--- a/api/src/utils/pipes/object-id.pipe.ts
+++ b/api/src/utils/pipes/object-id.pipe.ts
@@ -7,10 +7,10 @@
  */
 
 import {
-  Injectable,
-  PipeTransform,
   ArgumentMetadata,
   BadRequestException,
+  Injectable,
+  PipeTransform,
 } from '@nestjs/common';
 import { plainToClass } from 'class-transformer';
 import { validate } from 'class-validator';
@@ -33,7 +33,7 @@ export class ObjectIdPipe implements PipeTransform<string, Promise<string>> {
   async transform(value: string, { type, data }: ArgumentMetadata) {
     if (typeof value === 'string' && data === 'id' && type === 'param') {
       const errors = await this.getErrors(value);
-      if (errors)
+      if (errors.constraints)
         throw new BadRequestException(Object.values(errors.constraints)[0]);
     } else if (
       typeof value === 'object' &&
@@ -45,7 +45,7 @@ export class ObjectIdPipe implements PipeTransform<string, Promise<string>> {
           if (param.startsWith('id')) {
             const errors = await this.getErrors(String(paramValue));
 
-            if (errors)
+            if (errors.constraints)
               throw new BadRequestException(
                 Object.values(errors.constraints)[0],
               );
diff --git a/api/src/utils/test/fixtures/conversation.ts b/api/src/utils/test/fixtures/conversation.ts
index fca24ce1..c438f301 100644
--- a/api/src/utils/test/fixtures/conversation.ts
+++ b/api/src/utils/test/fixtures/conversation.ts
@@ -136,8 +136,10 @@ export const installConversationTypeFixtures = async () => {
     conversationFixtures.map((conversationFixture) => ({
       ...conversationFixture,
       sender: subscribers[parseInt(conversationFixture.sender)].id,
-      current: blocks[parseInt(conversationFixture.current)].id,
-      next: conversationFixture.next.map((n) => blocks[parseInt(n)].id),
+      current: conversationFixture?.current
+        ? blocks[parseInt(conversationFixture.current)].id
+        : null,
+      next: conversationFixture.next?.map((n) => blocks[parseInt(n)].id),
     })),
   );
 };
diff --git a/api/src/utils/test/fixtures/nlpvalue.ts b/api/src/utils/test/fixtures/nlpvalue.ts
index 94b4c28c..fa882014 100644
--- a/api/src/utils/test/fixtures/nlpvalue.ts
+++ b/api/src/utils/test/fixtures/nlpvalue.ts
@@ -51,12 +51,10 @@ export const installNlpValueFixtures = async () => {
 
   const NlpValue = mongoose.model(NlpValueModel.name, NlpValueModel.schema);
   const nlpValues = await NlpValue.insertMany(
-    nlpValueFixtures.map((v) => {
-      return {
-        ...v,
-        entity: nlpEntities[parseInt(v.entity)].id,
-      };
-    }),
+    nlpValueFixtures.map((v) => ({
+      ...v,
+      entity: v?.entity ? nlpEntities[parseInt(v.entity)].id : null,
+    })),
   );
   return { nlpEntities, nlpValues };
 };
diff --git a/api/tsconfig.json b/api/tsconfig.json
index 4cf9e50c..0201e55c 100644
--- a/api/tsconfig.json
+++ b/api/tsconfig.json
@@ -13,7 +13,7 @@
     "baseUrl": "./",
     "incremental": true,
     "skipLibCheck": true,
-    "strictNullChecks": false,
+    "strictNullChecks": true,
     "strictPropertyInitialization": false,
     "noImplicitAny": false,
     "strictBindCallApply": false,