fix: type error

Author: techstrom

src/api/providers/gemini.ts

@@ -195,7 +195,29 @@ export class GeminiHandler extends BaseProvider implements SingleCompletionHandl
 				// Create a new text part for the system instruction
 				const systemPart = { text: systemInstruction }
 				// Prepend it to the existing parts
-				firstMessage.parts = [systemPart, ...firstMessage.parts]
+				firstMessage.parts = [systemPart, ...(firstMessage.parts || [])]
+			} else {
+				// If no messages or first message is not user (e.g. starts with model),
+				// prepend a new user message with the system instruction.
+				contents.unshift({
+					role: "user",
+					parts: [{ text: systemInstruction }],
+				})
+			}
+		}
+
+		// Check if the model is a Gemma 3 model
+		const isGemma3 = model.includes("gemma-3")
+
+		// Prepend system instruction to the first user message if it's a Gemma 3 model,
+		// as they don't support the system instruction parameter.
+		if (isGemma3 && systemInstruction) {
+			if (contents.length > 0 && contents[0].role === "user") {
+				const firstMessage = contents[0]
+				// Create a new text part for the system instruction
+				const systemPart = { text: systemInstruction }
+				// Prepend it to the existing parts
+				firstMessage.parts = [systemPart, ...(firstMessage.parts || [])]
 			} else {
 				// If no messages or first message is not user (e.g. starts with model),
 				// prepend a new user message with the system instruction.