diff --git a/src/shared/auth.test.ts b/src/shared/auth.test.ts
index 41f9dc1a9..71877f341 100644
--- a/src/shared/auth.test.ts
+++ b/src/shared/auth.test.ts
@@ -1,5 +1,11 @@
 import { describe, it, expect } from '@jest/globals';
-import { SafeUrlSchema, OAuthMetadataSchema, OpenIdProviderMetadataSchema, OAuthClientMetadataSchema } from './auth.js';
+import {
+    SafeUrlSchema,
+    OAuthMetadataSchema,
+    OpenIdProviderMetadataSchema,
+    OAuthClientMetadataSchema,
+    OptionalSafeUrlSchema
+} from './auth.js';
 
 describe('SafeUrlSchema', () => {
     it('accepts valid HTTPS URLs', () => {
@@ -26,6 +32,12 @@ describe('SafeUrlSchema', () => {
     });
 });
 
+describe('OptionalSafeUrlSchema', () => {
+    it('accepts empty string and transforms it to undefined', () => {
+        expect(OptionalSafeUrlSchema.parse('')).toBe(undefined);
+    });
+});
+
 describe('OAuthMetadataSchema', () => {
     it('validates complete OAuth metadata', () => {
         const metadata = {
diff --git a/src/shared/auth.ts b/src/shared/auth.ts
index 0e079646b..c5ddbda16 100644
--- a/src/shared/auth.ts
+++ b/src/shared/auth.ts
@@ -151,6 +151,11 @@ export const OAuthErrorResponseSchema = z.object({
     error_uri: z.string().optional()
 });
 
+/**
+ * Optional version of SafeUrlSchema that allows empty string for retrocompatibility on tos_uri and logo_uri
+ */
+export const OptionalSafeUrlSchema = SafeUrlSchema.optional().or(z.literal('').transform(() => undefined));
+
 /**
  * RFC 7591 OAuth 2.0 Dynamic Client Registration metadata
  */
@@ -162,10 +167,10 @@ export const OAuthClientMetadataSchema = z
         response_types: z.array(z.string()).optional(),
         client_name: z.string().optional(),
         client_uri: SafeUrlSchema.optional(),
-        logo_uri: SafeUrlSchema.optional(),
+        logo_uri: OptionalSafeUrlSchema,
         scope: z.string().optional(),
         contacts: z.array(z.string()).optional(),
-        tos_uri: SafeUrlSchema.optional(),
+        tos_uri: OptionalSafeUrlSchema,
         policy_uri: z.string().optional(),
         jwks_uri: SafeUrlSchema.optional(),
         jwks: z.any().optional(),