🖼️ feat: File Size and MIME Type Filtering at Agent level (#10446)

* refactor: add image file size validation as part of payload build

* feat: implement file size and MIME type filtering in endpoint configuration

* chore: import order

api/server/services/Files/images/encode.js

@@ -1,12 +1,14 @@
 const axios = require('axios');
-const { logAxiosError } = require('@librechat/api');
 const { logger } = require('@librechat/data-schemas');
+const { logAxiosError, validateImage } = require('@librechat/api');
 const {
   FileSources,
   VisionModes,
   ImageDetail,
   ContentTypes,
   EModelEndpoint,
+  mergeFileConfig,
+  getEndpointFileConfig,
 } = require('librechat-data-provider');
 const { getStrategyFunctions } = require('~/server/services/Files/strategies');
 
@@ -152,6 +154,17 @@ async function encodeAndFormat(req, files, params, mode) {
   const formattedImages = await Promise.all(promises);
   promises.length = 0;
 
+  /** Extract configured file size limit from fileConfig for this endpoint */
+  let configuredFileSizeLimit;
+  if (req.config?.fileConfig) {
+    const fileConfig = mergeFileConfig(req.config.fileConfig);
+    const endpointConfig = getEndpointFileConfig({
+      fileConfig,
+      endpoint: effectiveEndpoint,
+    });
+    configuredFileSizeLimit = endpointConfig?.fileSizeLimit;
+  }
+
   for (const [file, imageContent] of formattedImages) {
     const fileMetadata = {
       type: file.type,
@@ -172,6 +185,26 @@ async function encodeAndFormat(req, files, params, mode) {
       continue;
     }
 
+    /** Validate image buffer against size limits */
+    if (file.height && file.width) {
+      const imageBuffer = imageContent.startsWith('http')
+        ? null
+        : Buffer.from(imageContent, 'base64');
+
+      if (imageBuffer) {
+        const validation = await validateImage(
+          imageBuffer,
+          imageBuffer.length,
+          effectiveEndpoint,
+          configuredFileSizeLimit,
+        );
+
+        if (!validation.isValid) {
+          throw new Error(`Image validation failed for ${file.filename}: ${validation.error}`);
+        }
+      }
+    }
+
     const imagePart = {
       type: ContentTypes.IMAGE_URL,
       image_url: {

packages/api/src/files/filter.spec.ts

@@ -689,4 +689,625 @@ describe('filterFilesByEndpointConfig', () => {
       expect(result).toEqual([]);
     });
   });
+
+  describe('file size filtering', () => {
+    it('should filter out files exceeding fileSizeLimit', () => {
+      const req = {
+        config: {
+          fileConfig: {
+            endpoints: {
+              [Providers.OPENAI]: {
+                disabled: false,
+                fileSizeLimit: 5 /** 5 MB in config (gets converted to bytes) */,
+              },
+            },
+          },
+        },
+      } as unknown as ServerRequest;
+
+      const smallFile = {
+        ...createMockFile('small.pdf'),
+        bytes: 1024 * 1024 * 3 /** 3 MB */,
+      } as IMongoFile;
+
+      const largeFile = {
+        ...createMockFile('large.pdf'),
+        bytes: 1024 * 1024 * 10 /** 10 MB */,
+      } as IMongoFile;
+
+      const files = [smallFile, largeFile];
+
+      const result = filterFilesByEndpointConfig(req, {
+        files,
+        endpoint: Providers.OPENAI,
+      });
+
+      /** Only small file should pass */
+      expect(result).toEqual([smallFile]);
+    });
+
+    it('should keep all files when no fileSizeLimit is set', () => {
+      const req = {
+        config: {
+          fileConfig: {
+            endpoints: {
+              [Providers.OPENAI]: {
+                disabled: false,
+              },
+            },
+          },
+        },
+      } as unknown as ServerRequest;
+
+      const files = [
+        { ...createMockFile('file1.pdf'), bytes: 1024 * 1024 * 100 } as IMongoFile,
+        { ...createMockFile('file2.pdf'), bytes: 1024 * 1024 * 200 } as IMongoFile,
+      ];
+
+      const result = filterFilesByEndpointConfig(req, {
+        files,
+        endpoint: Providers.OPENAI,
+      });
+
+      expect(result).toEqual(files);
+    });
+
+    it('should filter all files if all exceed fileSizeLimit', () => {
+      const req = {
+        config: {
+          fileConfig: {
+            endpoints: {
+              [Providers.OPENAI]: {
+                disabled: false,
+                fileSizeLimit: 1 /** 1 MB */,
+              },
+            },
+          },
+        },
+      } as unknown as ServerRequest;
+
+      const files = [
+        { ...createMockFile('file1.pdf'), bytes: 1024 * 1024 * 5 } as IMongoFile,
+        { ...createMockFile('file2.pdf'), bytes: 1024 * 1024 * 10 } as IMongoFile,
+      ];
+
+      const result = filterFilesByEndpointConfig(req, {
+        files,
+        endpoint: Providers.OPENAI,
+      });
+
+      expect(result).toEqual([]);
+    });
+
+    it('should handle fileSizeLimit of 0 as unlimited', () => {
+      const req = {
+        config: {
+          fileConfig: {
+            endpoints: {
+              [Providers.OPENAI]: {
+                disabled: false,
+                fileSizeLimit: 0,
+                totalSizeLimit: 0 /** Also set total limit to 0 for unlimited */,
+              },
+            },
+          },
+        },
+      } as unknown as ServerRequest;
+
+      const files = [{ ...createMockFile('huge.pdf'), bytes: 1024 * 1024 * 1000 } as IMongoFile];
+
+      const result = filterFilesByEndpointConfig(req, {
+        files,
+        endpoint: Providers.OPENAI,
+      });
+
+      /** 0 means no limit, so file should pass */
+      expect(result).toEqual(files);
+    });
+  });
+
+  describe('MIME type filtering', () => {
+    it('should filter out files with unsupported MIME types', () => {
+      const req = {
+        config: {
+          fileConfig: {
+            endpoints: {
+              [Providers.OPENAI]: {
+                disabled: false,
+                supportedMimeTypes: ['^application/pdf$', '^image/png$'],
+              },
+            },
+          },
+        },
+      } as unknown as ServerRequest;
+
+      const pdfFile = {
+        ...createMockFile('doc.pdf'),
+        type: 'application/pdf',
+      } as IMongoFile;
+
+      const pngFile = {
+        ...createMockFile('image.png'),
+        type: 'image/png',
+      } as IMongoFile;
+
+      const videoFile = {
+        ...createMockFile('video.mp4'),
+        type: 'video/mp4',
+      } as IMongoFile;
+
+      const files = [pdfFile, pngFile, videoFile];
+
+      const result = filterFilesByEndpointConfig(req, {
+        files,
+        endpoint: Providers.OPENAI,
+      });
+
+      /** Only PDF and PNG should pass */
+      expect(result).toEqual([pdfFile, pngFile]);
+    });
+
+    it('should keep all files when supportedMimeTypes is not set', () => {
+      const req = {
+        config: {
+          fileConfig: {
+            endpoints: {
+              [Providers.OPENAI]: {
+                disabled: false,
+              },
+            },
+          },
+        },
+      } as unknown as ServerRequest;
+
+      const files = [
+        { ...createMockFile('doc.pdf'), type: 'application/pdf' } as IMongoFile,
+        { ...createMockFile('video.mp4'), type: 'video/mp4' } as IMongoFile,
+        { ...createMockFile('audio.mp3'), type: 'audio/mp3' } as IMongoFile,
+      ];
+
+      const result = filterFilesByEndpointConfig(req, {
+        files,
+        endpoint: Providers.OPENAI,
+      });
+
+      expect(result).toEqual(files);
+    });
+
+    it('should handle regex patterns for MIME type matching', () => {
+      const req = {
+        config: {
+          fileConfig: {
+            endpoints: {
+              [Providers.OPENAI]: {
+                disabled: false,
+                supportedMimeTypes: ['^image/.*$'] /** All image types */,
+              },
+            },
+          },
+        },
+      } as unknown as ServerRequest;
+
+      const jpegFile = {
+        ...createMockFile('photo.jpg'),
+        type: 'image/jpeg',
+      } as IMongoFile;
+
+      const pngFile = {
+        ...createMockFile('graphic.png'),
+        type: 'image/png',
+      } as IMongoFile;
+
+      const gifFile = {
+        ...createMockFile('animation.gif'),
+        type: 'image/gif',
+      } as IMongoFile;
+
+      const pdfFile = {
+        ...createMockFile('doc.pdf'),
+        type: 'application/pdf',
+      } as IMongoFile;
+
+      const files = [jpegFile, pngFile, gifFile, pdfFile];
+
+      const result = filterFilesByEndpointConfig(req, {
+        files,
+        endpoint: Providers.OPENAI,
+      });
+
+      /** Only image files should pass */
+      expect(result).toEqual([jpegFile, pngFile, gifFile]);
+    });
+
+    it('should filter all files if none match supported MIME types', () => {
+      const req = {
+        config: {
+          fileConfig: {
+            endpoints: {
+              [Providers.OPENAI]: {
+                disabled: false,
+                supportedMimeTypes: ['^application/pdf$'],
+              },
+            },
+          },
+        },
+      } as unknown as ServerRequest;
+
+      const files = [
+        { ...createMockFile('video.mp4'), type: 'video/mp4' } as IMongoFile,
+        { ...createMockFile('audio.mp3'), type: 'audio/mp3' } as IMongoFile,
+      ];
+
+      const result = filterFilesByEndpointConfig(req, {
+        files,
+        endpoint: Providers.OPENAI,
+      });
+
+      expect(result).toEqual([]);
+    });
+
+    it('should handle empty supportedMimeTypes array', () => {
+      const req = {
+        config: {
+          fileConfig: {
+            endpoints: {
+              [Providers.OPENAI]: {
+                disabled: false,
+                supportedMimeTypes: [],
+              },
+            },
+          },
+        },
+      } as unknown as ServerRequest;
+
+      const files = [{ ...createMockFile('doc.pdf'), type: 'application/pdf' } as IMongoFile];
+
+      const result = filterFilesByEndpointConfig(req, {
+        files,
+        endpoint: Providers.OPENAI,
+      });
+
+      /** Empty array means allow all */
+      expect(result).toEqual(files);
+    });
+  });
+
+  describe('total size limit filtering', () => {
+    it('should filter files when total size exceeds totalSizeLimit', () => {
+      const req = {
+        config: {
+          fileConfig: {
+            endpoints: {
+              [Providers.OPENAI]: {
+                disabled: false,
+                totalSizeLimit: 10 /** 10 MB total */,
+              },
+            },
+          },
+        },
+      } as unknown as ServerRequest;
+
+      const file1 = {
+        ...createMockFile('file1.pdf'),
+        bytes: 1024 * 1024 * 4 /** 4 MB */,
+      } as IMongoFile;
+
+      const file2 = {
+        ...createMockFile('file2.pdf'),
+        bytes: 1024 * 1024 * 4 /** 4 MB */,
+      } as IMongoFile;
+
+      const file3 = {
+        ...createMockFile('file3.pdf'),
+        bytes: 1024 * 1024 * 4 /** 4 MB */,
+      } as IMongoFile;
+
+      const files = [file1, file2, file3];
+
+      const result = filterFilesByEndpointConfig(req, {
+        files,
+        endpoint: Providers.OPENAI,
+      });
+
+      /** Only first two files should pass (8 MB total) */
+      expect(result).toEqual([file1, file2]);
+    });
+
+    it('should keep all files when totalSizeLimit is not exceeded', () => {
+      const req = {
+        config: {
+          fileConfig: {
+            endpoints: {
+              [Providers.OPENAI]: {
+                disabled: false,
+                totalSizeLimit: 20 /** 20 MB total */,
+              },
+            },
+          },
+        },
+      } as unknown as ServerRequest;
+
+      const files = [
+        { ...createMockFile('file1.pdf'), bytes: 1024 * 1024 * 5 } as IMongoFile,
+        { ...createMockFile('file2.pdf'), bytes: 1024 * 1024 * 5 } as IMongoFile,
+      ];
+
+      const result = filterFilesByEndpointConfig(req, {
+        files,
+        endpoint: Providers.OPENAI,
+      });
+
+      expect(result).toEqual(files);
+    });
+
+    it('should handle totalSizeLimit of 0 as unlimited', () => {
+      const req = {
+        config: {
+          fileConfig: {
+            endpoints: {
+              [Providers.OPENAI]: {
+                disabled: false,
+                totalSizeLimit: 0,
+              },
+            },
+          },
+        },
+      } as unknown as ServerRequest;
+
+      const files = [
+        { ...createMockFile('file1.pdf'), bytes: 1024 * 1024 * 100 } as IMongoFile,
+        { ...createMockFile('file2.pdf'), bytes: 1024 * 1024 * 100 } as IMongoFile,
+      ];
+
+      const result = filterFilesByEndpointConfig(req, {
+        files,
+        endpoint: Providers.OPENAI,
+      });
+
+      /** 0 means no limit */
+      expect(result).toEqual(files);
+    });
+
+    it('should skip files that exceed totalSizeLimit and continue with remaining files', () => {
+      const req = {
+        config: {
+          fileConfig: {
+            endpoints: {
+              [Providers.OPENAI]: {
+                disabled: false,
+                totalSizeLimit: 5 /** 5 MB total */,
+              },
+            },
+          },
+        },
+      } as unknown as ServerRequest;
+
+      const files = [
+        { ...createMockFile('large.pdf'), bytes: 1024 * 1024 * 10 } as IMongoFile,
+        { ...createMockFile('small.pdf'), bytes: 1024 * 1024 * 1 } as IMongoFile,
+      ];
+
+      const result = filterFilesByEndpointConfig(req, {
+        files,
+        endpoint: Providers.OPENAI,
+      });
+
+      /** First file exceeds total limit, so it's skipped. Small file fits and is included. */
+      expect(result).toEqual([files[1]]);
+    });
+
+    it('should keep files in order until total size limit is reached', () => {
+      const req = {
+        config: {
+          fileConfig: {
+            endpoints: {
+              [Providers.OPENAI]: {
+                disabled: false,
+                totalSizeLimit: 7 /** 7 MB total */,
+              },
+            },
+          },
+        },
+      } as unknown as ServerRequest;
+
+      const file1 = {
+        ...createMockFile('file1.pdf'),
+        bytes: 1024 * 1024 * 2 /** 2 MB */,
+      } as IMongoFile;
+
+      const file2 = {
+        ...createMockFile('file2.pdf'),
+        bytes: 1024 * 1024 * 3 /** 3 MB */,
+      } as IMongoFile;
+
+      const file3 = {
+        ...createMockFile('file3.pdf'),
+        bytes: 1024 * 1024 * 2 /** 2 MB */,
+      } as IMongoFile;
+
+      const file4 = {
+        ...createMockFile('file4.pdf'),
+        bytes: 1024 * 1024 * 1 /** 1 MB */,
+      } as IMongoFile;
+
+      const files = [file1, file2, file3, file4];
+
+      const result = filterFilesByEndpointConfig(req, {
+        files,
+        endpoint: Providers.OPENAI,
+      });
+
+      /** file1 (2MB) + file2 (3MB) = 5MB ✓, + file3 (2MB) = 7MB ✓, + file4 would exceed */
+      expect(result).toEqual([file1, file2, file3]);
+    });
+  });
+
+  describe('combined filtering scenarios', () => {
+    it('should apply size and MIME type filters together', () => {
+      const req = {
+        config: {
+          fileConfig: {
+            endpoints: {
+              [Providers.OPENAI]: {
+                disabled: false,
+                fileSizeLimit: 5 /** 5 MB per file */,
+                supportedMimeTypes: ['^application/pdf$', '^image/.*$'],
+              },
+            },
+          },
+        },
+      } as unknown as ServerRequest;
+
+      const validPdf = {
+        ...createMockFile('valid.pdf'),
+        type: 'application/pdf',
+        bytes: 1024 * 1024 * 3 /** 3 MB */,
+      } as IMongoFile;
+
+      const validImage = {
+        ...createMockFile('valid.png'),
+        type: 'image/png',
+        bytes: 1024 * 1024 * 2 /** 2 MB */,
+      } as IMongoFile;
+
+      const tooLargePdf = {
+        ...createMockFile('large.pdf'),
+        type: 'application/pdf',
+        bytes: 1024 * 1024 * 10 /** 10 MB - exceeds size limit */,
+      } as IMongoFile;
+
+      const wrongTypeVideo = {
+        ...createMockFile('video.mp4'),
+        type: 'video/mp4',
+        bytes: 1024 * 1024 * 2 /** 2 MB - wrong MIME type */,
+      } as IMongoFile;
+
+      const files = [validPdf, validImage, tooLargePdf, wrongTypeVideo];
+
+      const result = filterFilesByEndpointConfig(req, {
+        files,
+        endpoint: Providers.OPENAI,
+      });
+
+      /** Only validPdf and validImage should pass both filters */
+      expect(result).toEqual([validPdf, validImage]);
+    });
+
+    it('should apply all three filters together', () => {
+      const req = {
+        config: {
+          fileConfig: {
+            endpoints: {
+              [Providers.OPENAI]: {
+                disabled: false,
+                fileSizeLimit: 5 /** 5 MB per file */,
+                totalSizeLimit: 8 /** 8 MB total */,
+                supportedMimeTypes: ['^application/pdf$'],
+              },
+            },
+          },
+        },
+      } as unknown as ServerRequest;
+
+      const pdf1 = {
+        ...createMockFile('pdf1.pdf'),
+        type: 'application/pdf',
+        bytes: 1024 * 1024 * 3 /** 3 MB */,
+      } as IMongoFile;
+
+      const pdf2 = {
+        ...createMockFile('pdf2.pdf'),
+        type: 'application/pdf',
+        bytes: 1024 * 1024 * 4 /** 4 MB */,
+      } as IMongoFile;
+
+      const pdf3 = {
+        ...createMockFile('pdf3.pdf'),
+        type: 'application/pdf',
+        bytes: 1024 * 1024 * 2 /** 2 MB */,
+      } as IMongoFile;
+
+      const largePdf = {
+        ...createMockFile('large.pdf'),
+        type: 'application/pdf',
+        bytes: 1024 * 1024 * 10 /** 10 MB - exceeds individual size limit */,
+      } as IMongoFile;
+
+      const wrongType = {
+        ...createMockFile('image.png'),
+        type: 'image/png',
+        bytes: 1024 * 1024 * 1 /** Wrong type */,
+      } as IMongoFile;
+
+      const files = [pdf1, pdf2, pdf3, largePdf, wrongType];
+
+      const result = filterFilesByEndpointConfig(req, {
+        files,
+        endpoint: Providers.OPENAI,
+      });
+
+      /**
+       * largePdf filtered by size (10MB > 5MB limit)
+       * wrongType filtered by MIME type
+       * Remaining: pdf1 (3MB) + pdf2 (4MB) = 7MB ✓
+       * pdf3 (2MB) would make total 9MB > 8MB limit, so filtered by total
+       */
+      expect(result).toEqual([pdf1, pdf2]);
+    });
+
+    it('should handle mixed validation with some files passing all checks', () => {
+      const req = {
+        config: {
+          fileConfig: {
+            endpoints: {
+              [Providers.ANTHROPIC]: {
+                disabled: false,
+                fileSizeLimit: 10,
+                totalSizeLimit: 20,
+                supportedMimeTypes: ['^application/.*$', '^text/.*$'],
+              },
+            },
+          },
+        },
+      } as unknown as ServerRequest;
+
+      const file1 = {
+        ...createMockFile('doc.pdf'),
+        type: 'application/pdf',
+        bytes: 1024 * 1024 * 5,
+      } as IMongoFile;
+
+      const file2 = {
+        ...createMockFile('text.txt'),
+        type: 'text/plain',
+        bytes: 1024 * 1024 * 8,
+      } as IMongoFile;
+
+      const file3 = {
+        ...createMockFile('data.json'),
+        type: 'application/json',
+        bytes: 1024 * 1024 * 6,
+      } as IMongoFile;
+
+      const file4 = {
+        ...createMockFile('video.mp4'),
+        type: 'video/mp4',
+        bytes: 1024 * 1024 * 3 /** Wrong MIME type */,
+      } as IMongoFile;
+
+      const files = [file1, file2, file3, file4];
+
+      const result = filterFilesByEndpointConfig(req, {
+        files,
+        endpoint: Providers.ANTHROPIC,
+      });
+
+      /**
+       * file4 filtered by MIME type
+       * file1 (5MB) + file2 (8MB) = 13MB ✓
+       * file3 (6MB) would make 19MB < 20MB ✓
+       */
+      expect(result).toEqual([file1, file2, file3]);
+    });
+  });
 });

packages/api/src/files/filter.ts

@@ -1,15 +1,32 @@
-import { getEndpointFileConfig, mergeFileConfig } from 'librechat-data-provider';
+import { getEndpointFileConfig, mergeFileConfig, fileConfig } from 'librechat-data-provider';
 import type { IMongoFile } from '@librechat/data-schemas';
 import type { ServerRequest } from '~/types';
 
 /**
- * Filters out files if the endpoint/provider has file uploads disabled
+ * Checks if a MIME type is supported by the endpoint configuration
+ * @param mimeType - The MIME type to check
+ * @param supportedMimeTypes - Array of RegExp patterns to match against
+ * @returns True if the MIME type matches any pattern
+ */
+function isMimeTypeSupported(mimeType: string, supportedMimeTypes?: RegExp[]): boolean {
+  if (!supportedMimeTypes || supportedMimeTypes.length === 0) {
+    return true;
+  }
+  return fileConfig.checkType(mimeType, supportedMimeTypes);
+}
+
+/**
+ * Filters out files based on endpoint configuration including:
+ * - Disabled status
+ * - File size limits
+ * - MIME type restrictions
+ * - Total size limits
  * @param req - The server request object containing config
  * @param params - Object containing files, endpoint, and endpointType
  * @param params.files - Array of processed file documents from MongoDB
  * @param params.endpoint - The endpoint name to check configuration for
  * @param params.endpointType - The endpoint type to check configuration for
- * @returns Filtered array of files (empty if disabled)
+ * @returns Filtered array of files
  */
 export function filterFilesByEndpointConfig(
   req: ServerRequest,
@@ -25,9 +42,9 @@ export function filterFilesByEndpointConfig(
     return [];
   }
 
-  const fileConfig = mergeFileConfig(req.config?.fileConfig);
+  const mergedFileConfig = mergeFileConfig(req.config?.fileConfig);
   const endpointFileConfig = getEndpointFileConfig({
-    fileConfig,
+    fileConfig: mergedFileConfig,
     endpoint,
     endpointType,
   });
@@ -40,5 +57,40 @@ export function filterFilesByEndpointConfig(
     return [];
   }
 
-  return files;
+  const { fileSizeLimit, supportedMimeTypes, totalSizeLimit } = endpointFileConfig;
+
+  /** Filter files based on individual file size and MIME type */
+  let filteredFiles = files;
+
+  /** Filter by individual file size limit */
+  if (fileSizeLimit !== undefined && fileSizeLimit > 0) {
+    filteredFiles = filteredFiles.filter((file) => {
+      return file.bytes <= fileSizeLimit;
+    });
+  }
+
+  /** Filter by MIME type */
+  if (supportedMimeTypes && supportedMimeTypes.length > 0) {
+    filteredFiles = filteredFiles.filter((file) => {
+      return isMimeTypeSupported(file.type, supportedMimeTypes);
+    });
+  }
+
+  /** Filter by total size limit - keep files until total exceeds limit */
+  if (totalSizeLimit !== undefined && totalSizeLimit > 0) {
+    let totalSize = 0;
+    const withinTotalLimit: IMongoFile[] = [];
+
+    for (let i = 0; i < filteredFiles.length; i++) {
+      const file = filteredFiles[i];
+      if (totalSize + file.bytes <= totalSizeLimit) {
+        withinTotalLimit.push(file);
+        totalSize += file.bytes;
+      }
+    }
+
+    filteredFiles = withinTotalLimit;
+  }
+
+  return filteredFiles;
 }

packages/api/src/files/validation.ts

@@ -16,6 +16,11 @@ export interface AudioValidationResult {
   error?: string;
 }
 
+export interface ImageValidationResult {
+  isValid: boolean;
+  error?: string;
+}
+
 export async function validatePdf(
   pdfBuffer: Buffer,
   fileSize: number,
@@ -229,3 +234,53 @@ export async function validateAudio(
 
   return { isValid: true };
 }
+
+/**
+ * Validates image files for different providers
+ * @param imageBuffer - The image file as a buffer
+ * @param fileSize - The file size in bytes
+ * @param provider - The provider to validate for
+ * @param configuredFileSizeLimit - Optional configured file size limit from fileConfig (in bytes)
+ * @returns Promise that resolves to validation result
+ */
+export async function validateImage(
+  imageBuffer: Buffer,
+  fileSize: number,
+  provider: Providers | string,
+  configuredFileSizeLimit?: number,
+): Promise<ImageValidationResult> {
+  if (provider === Providers.GOOGLE || provider === Providers.VERTEXAI) {
+    const providerLimit = mbToBytes(20);
+    const effectiveLimit = configuredFileSizeLimit ?? providerLimit;
+
+    if (fileSize > effectiveLimit) {
+      const limitMB = Math.round(effectiveLimit / (1024 * 1024));
+      return {
+        isValid: false,
+        error: `Image file size (${Math.round(fileSize / (1024 * 1024))}MB) exceeds the ${limitMB}MB limit`,
+      };
+    }
+  }
+
+  if (provider === Providers.ANTHROPIC) {
+    const providerLimit = mbToBytes(5);
+    const effectiveLimit = configuredFileSizeLimit ?? providerLimit;
+
+    if (fileSize > effectiveLimit) {
+      const limitMB = Math.round(effectiveLimit / (1024 * 1024));
+      return {
+        isValid: false,
+        error: `Image file size (${Math.round(fileSize / (1024 * 1024))}MB) exceeds the ${limitMB}MB limit`,
+      };
+    }
+  }
+
+  if (!imageBuffer || imageBuffer.length < 10) {
+    return {
+      isValid: false,
+      error: 'Invalid image file: too small or corrupted',
+    };
+  }
+
+  return { isValid: true };
+}