feat(core): add o4-mini model (#12175)

Close [AI-85](https://linear.app/affine-design/issue/AI-85)

<!-- This is an auto-generated comment: release notes by coderabbit.ai -->
## Summary by CodeRabbit

- **New Features**
	- Enhanced AI chat experience with improved web search integration, including a new "AUTO" mode that allows the AI to search the web only when needed.
	- Updated AI model for chat to "o4-mini" for improved performance.
- **Improvements**
	- Refined instructions to reduce hallucinations and ensure the AI admits uncertainty when unsure.
	- Enhanced streaming responses to display web search queries and results more clearly.
	- Updated web search tool modes for more accurate and flexible search behavior.
	- Centralized AI provider options and improved tool selection logic for better response quality.
- **Bug Fixes**
	- Improved handling of tool calls and reasoning steps in AI chat responses.
<!-- end of auto-generated comment: release notes by coderabbit.ai -->

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

@@ -177,6 +177,12 @@ export class AnthropicProvider
             yield message.textDelta;
             break;
           }
+          case 'tool-call': {
+            if (message.toolName === 'web_search') {
+              yield '\n' + `Searching the web "${message.args.query}"` + '\n';
+            }
+            break;
+          }
           case 'tool-result': {
             if (message.toolName === 'web_search') {
               this.toolResults.push(this.getWebSearchLinks(message.result));
@@ -219,18 +225,15 @@ export class AnthropicProvider
     return undefined;
   }
 
-  private getAnthropicOptions(
-    options: CopilotChatOptions
-  ): AnthropicProviderOptions {
+  private getAnthropicOptions(options: CopilotChatOptions) {
+    const result: AnthropicProviderOptions = {};
     if (options?.reasoning) {
-      return {
-        thinking: {
-          type: 'enabled',
-          budgetTokens: 12000,
-        },
+      result.thinking = {
+        type: 'enabled',
+        budgetTokens: 12000,
       };
     }
-    return {};
+    return result;
   }
 
   private getWebSearchLinks(

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

@@ -2,6 +2,7 @@ import {
   createOpenAI,
   openai,
   type OpenAIProvider as VercelOpenAIProvider,
+  OpenAIResponsesProviderOptions,
 } from '@ai-sdk/openai';
 import {
   AISDKError,
@@ -10,7 +11,6 @@ import {
   generateObject,
   generateText,
   streamText,
-  ToolSet,
 } from 'ai';
 
 import {
@@ -19,6 +19,7 @@ import {
   metrics,
   UserFriendlyError,
 } from '../../../base';
+import { createExaTool } from '../tools';
 import { CopilotProvider } from './provider';
 import {
   ChatMessageRole,
@@ -42,6 +43,11 @@ export type OpenAIConfig = {
   baseUrl?: string;
 };
 
+type OpenAITools = {
+  web_search_preview: ReturnType<typeof openai.tools.webSearchPreview>;
+  web_search: ReturnType<typeof createExaTool>;
+};
+
 export class OpenAIProvider
   extends CopilotProvider<OpenAIConfig>
   implements
@@ -68,7 +74,7 @@ export class OpenAIProvider
     'gpt-4.1-2025-04-14',
     'gpt-4.1-mini',
     'o1',
-    'o3-mini',
+    'o4-mini',
     // embeddings
     'text-embedding-3-large',
     'text-embedding-3-small',
@@ -81,6 +87,8 @@ export class OpenAIProvider
     'gpt-image-1',
   ];
 
+  private readonly MAX_STEPS = 20;
+
   #instance!: VercelOpenAIProvider;
 
   override configured(): boolean {
@@ -179,21 +187,28 @@ export class OpenAIProvider
     }
   }
 
-  private getTools(options: CopilotChatOptions): ToolSet | undefined {
+  private getTools(
+    options: CopilotChatOptions,
+    model: string
+  ): Partial<OpenAITools> {
+    const tools: Partial<OpenAITools> = {};
     if (options?.tools?.length) {
-      const tools: ToolSet = {};
       for (const tool of options.tools) {
         switch (tool) {
           case 'webSearch': {
-            tools.web_search_preview = openai.tools.webSearchPreview();
+            // o series reasoning models
+            if (model.startsWith('o')) {
+              tools.web_search = createExaTool(this.AFFiNEConfig);
+            } else {
+              tools.web_search_preview = openai.tools.webSearchPreview();
+            }
             break;
           }
         }
       }
       return tools;
     }
-
-    return undefined;
+    return tools;
   }
 
   // ====== text to text ======
@@ -231,10 +246,10 @@ export class OpenAIProvider
         : await generateText({
             ...commonParams,
             providerOptions: {
-              openai: options.user ? { user: options.user } : {},
+              openai: this.getOpenAIOptions(options),
             },
-            toolChoice: options.webSearch ? 'required' : 'auto',
-            tools: this.getTools(options),
+            tools: this.getTools(options, model),
+            maxSteps: this.MAX_STEPS,
           });
 
       return text.trim();
@@ -258,14 +273,16 @@ export class OpenAIProvider
 
       const modelInstance = this.#instance.responses(model);
 
+      const tools = this.getTools(options, model);
       const { fullStream } = streamText({
         model: modelInstance,
         system,
         messages: msgs,
-        tools: this.getTools(options),
         providerOptions: {
-          openai: options.user ? { user: options.user } : {},
+          openai: this.getOpenAIOptions(options),
         },
+        tools: tools as OpenAITools,
+        maxSteps: this.MAX_STEPS,
         frequencyPenalty: options.frequencyPenalty || 0,
         presencePenalty: options.presencePenalty || 0,
         temperature: options.temperature || 0,
@@ -274,25 +291,53 @@ export class OpenAIProvider
       });
 
       const parser = new CitationParser();
+      let lastType;
       for await (const chunk of fullStream) {
         if (chunk) {
           switch (chunk.type) {
             case 'text-delta': {
+              if (lastType !== chunk.type) {
+                yield `\n`;
+              }
               const result = parser.parse(chunk.textDelta);
               yield result;
               break;
             }
+            case 'reasoning': {
+              if (lastType !== chunk.type) {
+                yield `\n`;
+              }
+              yield chunk.textDelta;
+              break;
+            }
+            case 'tool-call': {
+              if (chunk.toolName === 'web_search') {
+                yield '\n' + `Searching the web "${chunk.args.query}"` + '\n';
+              }
+              break;
+            }
+            case 'tool-result': {
+              if (chunk.toolName === 'web_search') {
+                yield '\n' + this.getWebSearchLinks(chunk.result) + '\n';
+              }
+              break;
+            }
             case 'step-finish': {
               const result = parser.end();
               yield result;
               break;
             }
+            case 'error': {
+              const error = chunk.error as { type: string; message: string };
+              throw new Error(error.message);
+            }
           }
 
           if (options.signal?.aborted) {
             await fullStream.cancel();
             break;
           }
+          lastType = chunk.type;
         }
       }
     } catch (e: any) {
@@ -380,4 +425,28 @@ export class OpenAIProvider
       throw e;
     }
   }
+
+  private getOpenAIOptions(options: CopilotChatOptions) {
+    const result: OpenAIResponsesProviderOptions = {};
+    if (options?.reasoning) {
+      result.reasoningEffort = 'medium';
+      result.reasoningSummary = 'auto';
+    }
+    if (options?.user) {
+      result.user = options.user;
+    }
+    return result;
+  }
+
+  private getWebSearchLinks(
+    list: {
+      title: string | null;
+      url: string;
+    }[]
+  ): string {
+    const links = list.reduce((acc, result) => {
+      return acc + `\n[${result.title ?? result.url}](${result.url})\n`;
+    }, '\n');
+    return links + '\n';
+  }
 }