fix: pick copilot provider depend on model (#6540)

packages/backend/server/src/plugins/copilot/controller.ts

@@ -89,8 +89,10 @@ export class CopilotController {
     @Query('messageId') messageId: string | undefined,
     @Query() params: Record<string, string | string[]>
   ): Promise<string> {
+    const model = await this.chatSession.get(sessionId).then(s => s?.model);
     const provider = this.provider.getProviderByCapability(
-      CopilotCapability.TextToText
+      CopilotCapability.TextToText,
+      model
     );
     if (!provider) {
       throw new InternalServerErrorException('No provider available');
@@ -139,8 +141,10 @@ export class CopilotController {
     @Query('messageId') messageId: string | undefined,
     @Query() params: Record<string, string>
   ): Promise<Observable<ChatEvent>> {
+    const model = await this.chatSession.get(sessionId).then(s => s?.model);
     const provider = this.provider.getProviderByCapability(
-      CopilotCapability.TextToText
+      CopilotCapability.TextToText,
+      model
     );
     if (!provider) {
       throw new InternalServerErrorException('No provider available');
@@ -194,10 +198,13 @@ export class CopilotController {
     @Query('messageId') messageId: string | undefined,
     @Query() params: Record<string, string>
   ): Promise<Observable<ChatEvent>> {
+    const hasAttachment = await this.hasAttachment(sessionId, messageId);
+    const model = await this.chatSession.get(sessionId).then(s => s?.model);
     const provider = this.provider.getProviderByCapability(
-      (await this.hasAttachment(sessionId, messageId))
+      hasAttachment
         ? CopilotCapability.ImageToImage
-        : CopilotCapability.TextToImage
+        : CopilotCapability.TextToImage,
+      model
     );
     if (!provider) {
       throw new InternalServerErrorException('No provider available');

packages/backend/server/src/plugins/copilot/providers/fal.ts

@@ -4,6 +4,7 @@ import {
   CopilotCapability,
   CopilotImageToImageProvider,
   CopilotProviderType,
+  CopilotTextToImageProvider,
   PromptMessage,
 } from '../types';
 
@@ -12,17 +13,24 @@ export type FalConfig = {
 };
 
 export type FalResponse = {
+  detail: Array<{ msg: string }>;
   images: Array<{ url: string }>;
 };
 
-export class FalProvider implements CopilotImageToImageProvider {
+export class FalProvider
+  implements CopilotTextToImageProvider, CopilotImageToImageProvider
+{
   static readonly type = CopilotProviderType.FAL;
-  static readonly capabilities = [CopilotCapability.ImageToImage];
+  static readonly capabilities = [
+    CopilotCapability.TextToImage,
+    CopilotCapability.ImageToImage,
+  ];
 
   readonly availableModels = [
+    // text to image
+    'fast-turbo-diffusion',
     // image to image
-    // https://blog.fal.ai/building-applications-with-real-time-stable-diffusion-apis/
-    '110602490-lcm-sd15-i2i',
+    'lcm-sd15-i2i',
   ];
 
   constructor(private readonly config: FalConfig) {
@@ -37,6 +45,10 @@ export class FalProvider implements CopilotImageToImageProvider {
     return FalProvider.capabilities;
   }
 
+  isModelAvailable(model: string): boolean {
+    return this.availableModels.includes(model);
+  }
+
   // ====== image to image ======
   async generateImages(
     messages: PromptMessage[],
@@ -50,21 +62,20 @@ export class FalProvider implements CopilotImageToImageProvider {
     if (!this.availableModels.includes(model)) {
       throw new Error(`Invalid model: ${model}`);
     }
-    if (!content) {
-      throw new Error('Prompt is required');
-    }
-    if (!Array.isArray(attachments) || !attachments.length) {
-      throw new Error('Attachments is required');
+
+    // prompt attachments require at least one
+    if (!content && (!Array.isArray(attachments) || !attachments.length)) {
+      throw new Error('Prompt or Attachments is empty');
     }
 
-    const data = (await fetch(`https://${model}.gateway.alpha.fal.ai/`, {
+    const data = (await fetch(`https://fal.run/fal-ai/${model}`, {
       method: 'POST',
       headers: {
         Authorization: `key ${this.config.apiKey}`,
         'Content-Type': 'application/json',
       },
       body: JSON.stringify({
-        image_url: attachments[0],
+        image_url: attachments?.[0],
         prompt: content,
         sync_mode: true,
         seed: 42,
@@ -73,7 +84,13 @@ export class FalProvider implements CopilotImageToImageProvider {
       signal: options.signal,
     }).then(res => res.json())) as FalResponse;
 
-    return data.images.map(image => image.url);
+    if (!data.images?.length) {
+      const error = data.detail?.[0]?.msg;
+      throw new Error(
+        error ? `Invalid message: ${error}` : 'No images generated'
+      );
+    }
+    return data.images?.map(image => image.url) || [];
   }
 
   async *generateImagesStream(

packages/backend/server/src/plugins/copilot/providers/index.ts

@@ -118,17 +118,36 @@ export class CopilotProviderService {
 
   getProviderByCapability<C extends CopilotCapability>(
     capability: C,
+    model?: string,
     prefer?: CopilotProviderType
   ): CapabilityToCopilotProvider[C] | null {
     const providers = PROVIDER_CAPABILITY_MAP.get(capability);
     if (Array.isArray(providers) && providers.length) {
-      const selectedCapability =
-        prefer && providers.includes(prefer) ? prefer : providers[0];
+      let selectedProvider: CopilotProviderType | undefined = prefer;
+      let currentIndex = -1;
 
-      const provider = this.getProvider(selectedCapability);
-      assert(provider.getCapabilities().includes(capability));
+      if (!selectedProvider) {
+        currentIndex = 0;
+        selectedProvider = providers[currentIndex];
+      }
 
-      return provider as CapabilityToCopilotProvider[C];
+      while (selectedProvider) {
+        // find first provider that supports the capability and model
+        if (providers.includes(selectedProvider)) {
+          const provider = this.getProvider(selectedProvider);
+          if (provider.getCapabilities().includes(capability)) {
+            if (model) {
+              if (provider.isModelAvailable(model)) {
+                return provider as CapabilityToCopilotProvider[C];
+              }
+            } else {
+              return provider as CapabilityToCopilotProvider[C];
+            }
+          }
+        }
+        currentIndex += 1;
+        selectedProvider = providers[currentIndex];
+      }
     }
     return null;
   }

packages/backend/server/src/plugins/copilot/providers/openai.ts

@@ -63,6 +63,10 @@ export class OpenAIProvider
     return OpenAIProvider.capabilities;
   }
 
+  isModelAvailable(model: string): boolean {
+    return this.availableModels.includes(model);
+  }
+
   private chatToGPTMessage(
     messages: PromptMessage[]
   ): OpenAI.Chat.Completions.ChatCompletionMessageParam[] {

packages/backend/server/src/plugins/copilot/types.ts

@@ -141,6 +141,7 @@ export enum CopilotCapability {
 
 export interface CopilotProvider {
   getCapabilities(): CopilotCapability[];
+  isModelAvailable(model: string): boolean;
 }
 
 export interface CopilotTextToTextProvider extends CopilotProvider {