fix gemini image api usage

Author: bbohlender

packages/prai/src/history.ts

@@ -118,6 +118,8 @@ export type HistoryState = {
   usedSchemas: Set<Schema>
 }
 
+export const base64UrlPrefix = 'data:image/jpeg;base64,'
+
 export class History {
   public readonly id = crypto.randomUUID()
   private readonly subscriptionMap = new Map<string, Set<(data: any) => void>>()
@@ -326,7 +328,7 @@ export class History {
           content.push({ type: 'input_audio', input_audio: { data: toBase64(value), format: fileType } })
           break
         case 'image':
-          content.push({ type: 'image_url', image_url: { url: `data:image/jpeg;base64,${toBase64(value)}` } })
+          content.push({ type: 'image_url', image_url: { url: `${base64UrlPrefix}${toBase64(value)}` } })
           break
         case 'data':
           content.push({ type: 'text', text: JSON.stringify(value) })

packages/prai/src/provider/gemini.ts

@@ -3,6 +3,7 @@ import { Provider } from '../model.js'
 import { buildJsonSchema } from '../schema/json.js'
 import { Schema, ZodString } from 'zod'
 import { Message } from '../step.js'
+import { base64UrlPrefix } from '../history.js'
 
 function buildAdditionalConfig(schema: Schema): GenerateContentConfig {
   if (schema instanceof ZodString) {
@@ -79,7 +80,12 @@ export function gemini(
 function messageContentToPartUnion(content: Message['content'][number]): Part {
   switch (content.type) {
     case 'image_url':
-      return { fileData: { fileUri: content.image_url.url, mimeType: 'image/jpeg' } }
+      return {
+        inlineData: {
+          data: content.image_url.url.slice(base64UrlPrefix.length),
+          mimeType: `image/jpeg`,
+        },
+      }
     case 'input_audio':
       return {
         inlineData: {