feat: 添加 DeepSeek 模型支持，集成 @langchain/deepseek，添加 DeepSeek 提供商支持，修复多轮对话中 reasoning_content 的处理逻辑。

Author: bealqiu

packages/app/package.json

@@ -13,6 +13,7 @@
     "@huggingface/transformers": "^3.8.1",
     "@langchain/anthropic": "^1.3.21",
     "@langchain/core": "^1.1.29",
+    "@langchain/deepseek": "^1.0.15",
     "@langchain/google-genai": "^2.1.21",
     "@langchain/langgraph": "^1.2.0",
     "@langchain/openai": "^1.2.11",

packages/app/src/components/chat/PartRenderer.tsx

@@ -107,16 +107,14 @@ function TextPartView({ part }: { part: TextPart }) {
 }
 
 function ReasoningPartView({ part }: { part: ReasoningPart }) {
-  // Auto-expand when streaming (running), auto-collapse when completed
-  const [isOpen, setIsOpen] = useState(part.status === "running");
+  // Start expanded when streaming; keep expanded after completion
+  const [isOpen, setIsOpen] = useState(part.status === "running" || part.status === "completed");
   const throttledText = useThrottledText(part.text);
 
-  // Sync isOpen with part status: expand on running, collapse on completed
+  // Expand when streaming starts
   useEffect(() => {
     if (part.status === "running") {
       setIsOpen(true);
-    } else if (part.status === "completed") {
-      setIsOpen(false);
     }
   }, [part.status]);
 
@@ -158,9 +156,6 @@ function ReasoningPartView({ part }: { part: ReasoningPart }) {
               <p className="whitespace-pre-wrap text-sm leading-relaxed text-violet-900">
                 {throttledText}
               </p>
-              {part.status === "running" && (
-                <span className="inline-block h-4 w-1 animate-pulse bg-violet-500" />
-              )}
             </div>
           </CollapsibleContent>
         </div>

packages/app/src/components/settings/AISettings.tsx

@@ -27,6 +27,7 @@ const PROVIDER_DEFAULTS: Record<AIProviderType, { baseUrl: string; placeholder:
   openai: { baseUrl: "https://api.openai.com/v1", placeholder: "https://api.openai.com/v1", keyPlaceholder: "sk-..." },
   anthropic: { baseUrl: "", placeholder: "https://api.anthropic.com", keyPlaceholder: "sk-ant-..." },
   google: { baseUrl: "", placeholder: "https://generativelanguage.googleapis.com", keyPlaceholder: "AIza..." },
+  deepseek: { baseUrl: "https://api.deepseek.com", placeholder: "https://api.deepseek.com", keyPlaceholder: "sk-..." },
 };
 
 function EndpointCard({
@@ -128,6 +129,7 @@ function EndpointCard({
             <SelectItem value="openai">{t("settings.ai_provider_openai")}</SelectItem>
             <SelectItem value="anthropic">{t("settings.ai_provider_anthropic")}</SelectItem>
             <SelectItem value="google">{t("settings.ai_provider_google")}</SelectItem>
+            <SelectItem value="deepseek">{t("settings.ai_provider_deepseek")}</SelectItem>
           </SelectContent>
         </Select>
       </div>

packages/app/src/i18n/locales/en.json

@@ -230,6 +230,7 @@
     "ai_provider_openai": "OpenAI Compatible",
     "ai_provider_anthropic": "Anthropic Claude",
     "ai_provider_google": "Google Gemini",
+    "ai_provider_deepseek": "DeepSeek",
     "ai_endpointName": "Name",
     "ai_endpointNamePlaceholder": "e.g. OpenAI, Ollama, Claude...",
     "ai_apiKey": "API Key",

packages/app/src/i18n/locales/zh.json

@@ -230,6 +230,7 @@
     "ai_provider_openai": "OpenAI 兼容",
     "ai_provider_anthropic": "Anthropic Claude",
     "ai_provider_google": "Google Gemini",
+    "ai_provider_deepseek": "DeepSeek",
     "ai_endpointName": "名称",
     "ai_endpointNamePlaceholder": "如 OpenAI、Ollama、Claude...",
     "ai_apiKey": "API 密钥",

packages/app/src/lib/ai/agents/reading-agent.ts

@@ -88,7 +88,7 @@ async function executeTool(tool: ToolDefinition, args: Record<string, unknown>):
 export async function* streamReadingAgent(
   options: ReadingAgentOptions,
   userInput: string,
-  history: Array<{ role: "user" | "assistant"; content: string }> = [],
+  history: Array<{ role: "user" | "assistant"; content: string; reasoning?: string }> = [],
 ): AsyncGenerator<AgentStreamEvent> {
   const { aiConfig, book, semanticContext, enabledSkills, isVectorized, deepThinking } = options;
 
@@ -119,10 +119,26 @@ export async function* streamReadingAgent(
     });
 
     // Build input messages (history + user input, without system — handled by agent prompt)
+    // For DeepSeek reasoner, we must include reasoning_content in assistant messages
+    // to avoid 400 errors during multi-turn tool-calling conversations.
+    const isDeepSeek = aiConfig.endpoints.find(
+      (e) => e.id === aiConfig.activeEndpointId,
+    )?.provider === "deepseek";
+
     const inputMessages: BaseMessage[] = [
-      ...history.map((h) =>
-        h.role === "user" ? new HumanMessage(h.content) : new AIMessage(h.content),
-      ),
+      ...history.map((h) => {
+        if (h.role === "user") {
+          return new HumanMessage(h.content);
+        }
+        // For DeepSeek, include reasoning_content in additional_kwargs
+        if (isDeepSeek && h.reasoning) {
+          return new AIMessage({
+            content: h.content,
+            additional_kwargs: { reasoning_content: h.reasoning },
+          });
+        }
+        return new AIMessage(h.content);
+      }),
       new HumanMessage(userInput),
     ];
 
@@ -202,6 +218,13 @@ export async function* streamReadingAgent(
           }
         }
 
+        // Handle DeepSeek reasoning_content from @langchain/deepseek
+        // ChatDeepSeek puts reasoning_content in additional_kwargs.reasoning_content
+        const reasoningContent = chunk.additional_kwargs?.reasoning_content;
+        if (typeof reasoningContent === "string" && reasoningContent) {
+          yield { type: "reasoning", content: reasoningContent, stepType: "thinking" };
+        }
+
         // Detect tool_call_chunks in streaming and emit tool_call as soon as we have the name.
         // This eliminates the delay between the last text token and on_chat_model_end.
         const toolCallChunks = chunk.tool_call_chunks;

packages/app/src/lib/ai/llm-provider.ts

@@ -95,6 +95,75 @@ export async function createChatModelFromEndpoint(
         streaming,
       });
     }
+
+    case "deepseek": {
+      const { ChatDeepSeek } = await import("@langchain/deepseek");
+
+      // Create a subclass that fixes the missing reasoning_content issue.
+      // Bug: @langchain/deepseek stores reasoning_content in additional_kwargs
+      // when receiving, but doesn't inject it back when sending requests.
+      // DeepSeek API requires reasoning_content on every assistant message
+      // during tool-calling loops, or it returns a 400 error.
+      class ChatDeepSeekFixed extends ChatDeepSeek {
+        private _reasoningMap = new Map<number, string>();
+
+        // biome-ignore lint: override needs any
+        async _generate(messages: any[], options: any, runManager?: any) {
+          this._buildReasoningMap(messages);
+          return super._generate(messages, options, runManager);
+        }
+
+        // biome-ignore lint: override needs any
+        async *_streamResponseChunks(messages: any[], options: any, runManager?: any) {
+          this._buildReasoningMap(messages);
+          yield* super._streamResponseChunks(messages, options, runManager);
+        }
+
+        // biome-ignore lint: override needs any
+        // @ts-expect-error -- overloaded signature; runtime type is correct
+        async completionWithRetry(request: any, requestOptions?: any) {
+          // Inject reasoning_content into assistant messages in the API request
+          if (request.messages && this._reasoningMap.size > 0) {
+            let assistantIdx = 0;
+            for (const msg of request.messages) {
+              if (msg.role === "assistant") {
+                const reasoning = this._reasoningMap.get(assistantIdx);
+                if (reasoning !== undefined) {
+                  msg.reasoning_content = reasoning;
+                }
+                assistantIdx++;
+              }
+            }
+          }
+          return super.completionWithRetry(request, requestOptions);
+        }
+
+        // biome-ignore lint: messages is BaseMessage[]
+        private _buildReasoningMap(messages: any[]) {
+          this._reasoningMap.clear();
+          let assistantIdx = 0;
+          for (const msg of messages) {
+            if (msg._getType?.() === "ai" || msg.constructor?.name === "AIMessage" || msg.constructor?.name === "AIMessageChunk") {
+              const reasoning = msg.additional_kwargs?.reasoning_content;
+              if (typeof reasoning === "string") {
+                this._reasoningMap.set(assistantIdx, reasoning);
+              }
+              assistantIdx++;
+            }
+          }
+        }
+      }
+
+      return new ChatDeepSeekFixed({
+        model,
+        apiKey: endpoint.apiKey,
+        configuration: endpoint.baseUrl ? { baseURL: endpoint.baseUrl } : undefined,
+        temperature,
+        maxTokens,
+        streaming,
+      } as ConstructorParameters<typeof ChatDeepSeek>[0]);
+    }
+
     default: {
       const { ChatOpenAI } = await import("@langchain/openai");
 

packages/app/src/lib/ai/message-pipeline.ts

@@ -20,9 +20,16 @@ interface PipelineContext {
   userLanguage: string;
 }
 
+export interface ProcessedMessage {
+  role: "user" | "assistant";
+  content: string;
+  /** DeepSeek reasoning_content — needed for multi-turn tool-calling with reasoner models */
+  reasoning?: string;
+}
+
 interface ProcessedMessages {
   systemPrompt: string;
-  messages: Array<{ role: "user" | "assistant"; content: string }>;
+  messages: ProcessedMessage[];
 }
 
 const DEFAULT_CONFIG: PipelineConfig = {
@@ -40,13 +47,20 @@ export function processMessages(
   // Apply sliding window — keep last N messages
   const windowedMessages = applySlidingWindow(thread.messages, config.slidingWindowSize);
 
-  // Process citations in messages
-  const processed = windowedMessages
+  // Process citations in messages, preserving reasoning for DeepSeek multi-turn
+  const processed: ProcessedMessage[] = windowedMessages
     .filter((m) => m.role !== "system")
-    .map((m) => ({
-      role: m.role as "user" | "assistant",
-      content: injectCitations(m),
-    }));
+    .map((m) => {
+      const msg: ProcessedMessage = {
+        role: m.role as "user" | "assistant",
+        content: injectCitations(m),
+      };
+      // Preserve reasoning content for assistant messages (needed by DeepSeek reasoner)
+      if (m.role === "assistant" && m.reasoning && m.reasoning.length > 0) {
+        msg.reasoning = m.reasoning.map((r) => r.content).join("\n");
+      }
+      return msg;
+    });
 
   return { systemPrompt, messages: processed };
 }

packages/app/src/lib/ai/streaming.ts

@@ -48,6 +48,7 @@ export class StreamingChat {
     const history = messages.slice(0, -1).map((m) => ({
       role: m.role as "user" | "assistant",
       content: m.content,
+      reasoning: m.reasoning,
     }));
 
     try {

packages/app/src/stores/settings-store.ts

@@ -80,6 +80,8 @@ async function fetchModelsFromEndpoint(endpoint: AIEndpoint): Promise<string[]>
       return fetchAnthropicModels(endpoint);
     case "google":
       return fetchGoogleModels(endpoint);
+    case "deepseek":
+      return fetchDeepSeekModels(endpoint);
     case "openai":
     default:
       return fetchOpenAIModels(endpoint);
@@ -160,6 +162,27 @@ async function fetchGoogleModels(endpoint: AIEndpoint): Promise<string[]> {
     .sort((a: string, b: string) => a.localeCompare(b));
 }
 
+/** DeepSeek — uses OpenAI-compatible /models endpoint with fallback */
+async function fetchDeepSeekModels(endpoint: AIEndpoint): Promise<string[]> {
+  const baseUrl = (endpoint.baseUrl || "https://api.deepseek.com").replace(/\/+$/, "");
+  try {
+    const response = await fetch(`${baseUrl}/models`, {
+      headers: { Authorization: `Bearer ${endpoint.apiKey}` },
+    });
+    if (response.ok) {
+      const data = await response.json();
+      const models = (data.data || [])
+        .map((m: { id: string }) => m.id)
+        .sort((a: string, b: string) => a.localeCompare(b));
+      if (models.length > 0) return models;
+    }
+  } catch {
+    // Fall through to fallback
+  }
+  // Fallback: well-known DeepSeek models
+  return ["deepseek-chat", "deepseek-reasoner"];
+}
+
 export const useSettingsStore = create<SettingsState>()(
   withPersist("settings", (set, get, _api) => ({
   readSettings: defaultReadSettings,