diff --git a/packages/agent-core-v2/src/app/llmProtocol/errors.ts b/packages/agent-core-v2/src/app/llmProtocol/errors.ts
index 9657d6626..a5d8c812c 100644
--- a/packages/agent-core-v2/src/app/llmProtocol/errors.ts
+++ b/packages/agent-core-v2/src/app/llmProtocol/errors.ts
@@ -136,6 +136,18 @@ export class APIEmptyResponseError extends ChatProviderError {
   }
 }
 
+const DETERMINISTIC_PROVIDER_VALIDATION_MESSAGE_PATTERNS = [
+  /unsupported media type for base64 image/,
+  /invalid data url for image/,
+] as const;
+
+function isDeterministicProviderValidationError(error: ChatProviderError): boolean {
+  const lowerMessage = error.message.toLowerCase();
+  return DETERMINISTIC_PROVIDER_VALIDATION_MESSAGE_PATTERNS.some((pattern) =>
+    pattern.test(lowerMessage),
+  );
+}
+
 export function isRetryableGenerateError(error: unknown): boolean {
   if (error instanceof APIConnectionError || error instanceof APITimeoutError) {
     return true;
@@ -149,7 +161,9 @@ export function isRetryableGenerateError(error: unknown): boolean {
   if (error instanceof APIStatusError) {
     return [408, 409, 429, 500, 502, 503, 504, 529].includes(error.statusCode);
   }
-  return error instanceof ChatProviderError;
+  return (
+    error instanceof ChatProviderError && !isDeterministicProviderValidationError(error)
+  );
 }
 
 const NETWORK_RE = /network|connection|connect|disconnect|terminated/i;
diff --git a/packages/agent-core-v2/test/app/llmProtocol/errors.test.ts b/packages/agent-core-v2/test/app/llmProtocol/errors.test.ts
index 634880700..5ffab3d6e 100644
--- a/packages/agent-core-v2/test/app/llmProtocol/errors.test.ts
+++ b/packages/agent-core-v2/test/app/llmProtocol/errors.test.ts
@@ -193,6 +193,15 @@ describe('isRetryableGenerateError', () => {
   it('retries an unclassified provider error as a transient fallback', () => {
     expect(isRetryableGenerateError(new ChatProviderError('upstream failure'))).toBe(true);
   });
+
+  it.each([
+    ['Invalid data URL for image: data:image/png;base64'],
+    [
+      'Unsupported media type for base64 image: image/avif, url: data:image/avif;base64,AAAA',
+    ],
+  ])('does not retry deterministic provider validation error: %s', (message) => {
+    expect(isRetryableGenerateError(new ChatProviderError(message))).toBe(false);
+  });
 });
 
 describe('error hierarchy instanceof checks', () => {