Add support for base64 images in chat messages

Handle base64 image data for Llama 4 in chat messages.

Author: celestial-rose

packages/workers-ai-provider/src/convert-to-workersai-chat-messages.ts

@@ -42,6 +42,15 @@ export function convertToWorkersAIChatMessages(prompt: LanguageModelV2Prompt): {
 											providerOptions: part.providerOptions,
 										});
 									}
+									// For Llama 4, images are expected to be in the input messages array in base64
+									if (typeof part.data === "string") {
+	                  return {
+	                    image_url: {url : `data:${part.mimeType};base64,${part.data}`},
+	                    type: "image_url",
+	                    mimeType: part.mediaType,
+	                    providerOptions: part.providerOptions
+	                  }
+	                }
 									return ""; // No text for the image part
 								}
 							}