refactor: share platform file and route helpers

src/server/proxy-core/capabilities/conversationFileCapabilities.ts

@@ -1,4 +1,5 @@
 import { inferInputFileMimeType, normalizeInputFileBlock } from '../../transformers/shared/inputFile.js';
+import { classifyConversationFileMimeType } from '../../../shared/conversationFileTypes.js';
 
 export type ConversationFileTransport = 'unsupported' | 'inline_only' | 'native';
 export type ConversationFileEndpoint = 'chat' | 'messages' | 'responses';
@@ -25,13 +26,6 @@ function asTrimmedString(value: unknown): string {
   return typeof value === 'string' ? value.trim() : '';
 }
 
-function classifyMimeFamily(mimeType: string | null): 'image' | 'audio' | 'document' {
-  const normalized = asTrimmedString(mimeType).toLowerCase();
-  if (normalized.startsWith('image/')) return 'image';
-  if (normalized.startsWith('audio/')) return 'audio';
-  return 'document';
-}
-
 function appendConversationFileSummary(
   summary: ConversationFileInputSummary,
   item: Record<string, unknown>,
@@ -39,7 +33,7 @@ function appendConversationFileSummary(
   const normalizedFile = normalizeInputFileBlock(item);
   if (normalizedFile) {
     const mimeType = inferInputFileMimeType(normalizedFile);
-    const family = classifyMimeFamily(mimeType);
+    const family = classifyConversationFileMimeType(mimeType);
     if (family === 'image') {
       summary.hasImage = true;
       return;

src/server/proxy-core/surfaces/filesSurface.ts

@@ -8,6 +8,7 @@ import {
   softDeleteProxyFileByPublicIdForOwner,
 } from '../../services/proxyFileStore.js';
 import { ensureMultipartBufferParser, parseMultipartFormData } from '../../routes/proxy/multipart.js';
+import { isSupportedConversationFileMimeType } from '../../../shared/conversationFileTypes.js';
 
 function invalidRequest(reply: FastifyReply, message: string) {
   return reply.code(400).send({ error: { message, type: 'invalid_request_error' } });
@@ -58,15 +59,6 @@ function inferMimeTypeFromFilename(filename: string): string {
   return 'application/octet-stream';
 }
 
-function isSupportedProxyFileMimeType(mimeType: string): boolean {
-  return mimeType === 'application/pdf'
-    || mimeType === 'text/plain'
-    || mimeType === 'text/markdown'
-    || mimeType === 'application/json'
-    || mimeType.startsWith('image/')
-    || mimeType.startsWith('audio/');
-}
-
 export async function filesProxyRoute(app: FastifyInstance) {
   ensureMultipartBufferParser(app);
 
@@ -88,7 +80,7 @@ export async function filesProxyRoute(app: FastifyInstance) {
 
     const filename = fileEntry.name || 'upload.bin';
     const mimeType = (fileEntry.type || inferMimeTypeFromFilename(filename)).trim().toLowerCase();
-    if (!isSupportedProxyFileMimeType(mimeType)) {
+    if (!isSupportedConversationFileMimeType(mimeType)) {
       return invalidRequest(reply, `unsupported file mime type: ${mimeType || 'application/octet-stream'}`);
     }