diff --git a/packages/ai/src/providers/google-shared.ts b/packages/ai/src/providers/google-shared.ts
index 9c2381a7..93fe596c 100644
--- a/packages/ai/src/providers/google-shared.ts
+++ b/packages/ai/src/providers/google-shared.ts
@@ -58,6 +58,13 @@ function resolveThoughtSignature(isSameProviderAndModel: boolean, signature: str
 	return isSameProviderAndModel && isValidThoughtSignature(signature) ? signature : undefined;
 }
 
+/**
+ * Claude models via Google APIs require explicit tool call IDs in function calls/responses.
+ */
+export function requiresToolCallId(modelId: string): boolean {
+	return modelId.startsWith("claude-");
+}
+
 /**
  * Convert internal messages to Gemini Content[] format.
  */
@@ -128,6 +135,7 @@ export function convertMessages<T extends GoogleApiType>(model: Model<T>, contex
 						functionCall: {
 							name: block.name,
 							args: block.arguments,
+							...(requiresToolCallId(model.id) ? { id: block.id } : {}),
 						},
 					};
 					const thoughtSignature = resolveThoughtSignature(isSameProviderAndModel, block.thoughtSignature);
@@ -169,12 +177,14 @@ export function convertMessages<T extends GoogleApiType>(model: Model<T>, contex
 				},
 			}));
 
+			const includeId = requiresToolCallId(model.id);
 			const functionResponsePart: Part = {
 				functionResponse: {
 					name: msg.toolName,
 					response: msg.isError ? { error: responseValue } : { output: responseValue },
 					// Nest images inside functionResponse.parts for Gemini 3
 					...(hasImages && supportsMultimodalFunctionResponse && { parts: imageParts }),
+					...(includeId ? { id: msg.toolCallId } : {}),
 				},
 			};