diff --git a/README.md b/README.md
index bdbf8b3..d173b6d 100644
--- a/README.md
+++ b/README.md
@@ -12,6 +12,9 @@ pnpm dev
 
 启动时自动加载项目根目录的 `.env`。
 
+其中设置 `DEEPSEEK_API_KEY`；
+也可用 `LLM_TO_AGENT_HOME` 修改数据根目录，用 `DEEPSEEK_MODEL` 修改模型。
+
 文档：
 
 - [架构总览](docs/architecture.md)
diff --git a/src/extensions/shared/agent/index.ts b/src/extensions/shared/agent/index.ts
new file mode 100644
index 0000000..ed244b4
--- /dev/null
+++ b/src/extensions/shared/agent/index.ts
@@ -0,0 +1,95 @@
+import { randomUUID } from "node:crypto";
+
+import type {
+  Extension,
+  ExtensionRuntimeContext,
+} from "../../../kernel";
+import { Event, ExtensionId, Hook } from "../../catalog";
+import {
+  type ChatMessage,
+  type WorkspaceService,
+} from "../workspace";
+
+export interface ModelProvider {
+  id: string;
+  chat(messages: ChatMessage[], signal?: AbortSignal): AsyncIterable<string>;
+}
+
+export interface AgentService {
+  chat(input: string, signal?: AbortSignal): AsyncIterable<string>;
+}
+
+export function createAgentExtension(): Extension {
+  let runtime: ExtensionRuntimeContext | undefined;
+  let workspace: WorkspaceService | undefined;
+  let model: ModelProvider | undefined;
+
+  const agent: AgentService = {
+    async *chat(input, signal) {
+      if (!runtime || !workspace || !model) {
+        throw new Error("Agent is not running.");
+      }
+
+      const activeRuntime = runtime;
+      const activeWorkspace = workspace;
+      const activeModel = model;
+      const runId = randomUUID();
+
+      const userMessage = await activeWorkspace.append("user", input);
+      await activeRuntime.emit(Event.MessageAdded, {
+        workspaceId: activeWorkspace.workspaceId,
+        conversationId: activeWorkspace.conversationId,
+        message: userMessage,
+      });
+      await activeRuntime.emit(Event.RunStarted, { runId, input });
+
+      let answer = "";
+
+      try {
+        const messages = await activeWorkspace.messages();
+
+        for await (const chunk of activeModel.chat(messages, signal)) {
+          answer += chunk;
+          yield chunk;
+        }
+
+        const assistantMessage = await activeWorkspace.append("assistant", answer);
+        await activeRuntime.emit(Event.MessageAdded, {
+          workspaceId: activeWorkspace.workspaceId,
+          conversationId: activeWorkspace.conversationId,
+          message: assistantMessage,
+        });
+        await activeRuntime.emit(Event.RunCompleted, { runId });
+      } catch (error) {
+        await activeRuntime.emit(Event.RunFailed, { runId, error: String(error) });
+        throw error;
+      }
+    },
+  };
+
+  return {
+    id: ExtensionId.Agent,
+
+    setup(context) {
+      context.add(Hook.Agent, agent);
+    },
+
+    start(context) {
+      const providers = context.all<ModelProvider>(Hook.ModelProviders);
+
+      if (providers.length === 0) {
+        throw new Error("Agent needs at least one model provider.");
+      }
+
+      runtime = context;
+      workspace = context.get<WorkspaceService>(Hook.Workspace);
+      model = providers[0];
+    },
+
+    stop() {
+      runtime = undefined;
+      workspace = undefined;
+      model = undefined;
+    },
+  };
+}
diff --git a/src/extensions/shared/deepseek/index.ts b/src/extensions/shared/deepseek/index.ts
new file mode 100644
index 0000000..4447489
--- /dev/null
+++ b/src/extensions/shared/deepseek/index.ts
@@ -0,0 +1,96 @@
+import type { Extension } from "../../../kernel";
+import { ExtensionId, Hook } from "../../catalog";
+import type { ModelProvider } from "../agent";
+
+export interface DeepSeekOptions {
+  apiKey?: string;
+  baseUrl?: string;
+  model?: string;
+  request?: (url: string, init: RequestInit) => Promise<Response>;
+}
+
+export function createDeepSeekExtension(options: DeepSeekOptions = {}): Extension {
+  const apiKey = options.apiKey ?? process.env.DEEPSEEK_API_KEY;
+  const baseUrl = (
+    options.baseUrl ??
+    process.env.DEEPSEEK_BASE_URL ??
+    "https://api.deepseek.com"
+  ).replace(/\/+$/, "");
+  const model = options.model ?? process.env.DEEPSEEK_MODEL ?? "deepseek-v4-flash";
+  const request = options.request ?? fetch;
+
+  const provider: ModelProvider = {
+    id: "deepseek",
+
+    async *chat(messages, signal) {
+      const response = await request(`${baseUrl}/chat/completions`, {
+        method: "POST",
+        headers: {
+          authorization: `Bearer ${apiKey}`,
+          "content-type": "application/json",
+        },
+        body: JSON.stringify({
+          model,
+          messages: messages.map(({ role, content }) => ({ role, content })),
+          thinking: { type: "disabled" },
+          stream: true,
+        }),
+        signal,
+      });
+
+      if (!response.ok) {
+        throw new Error(
+          `DeepSeek request failed (${response.status}): ${await response.text()}`,
+        );
+      }
+
+      if (!response.body) {
+        throw new Error("DeepSeek returned an empty response body.");
+      }
+
+      const reader = response.body.getReader();
+      const decoder = new TextDecoder();
+      let buffer = "";
+
+      try {
+        while (true) {
+          const { done, value } = await reader.read();
+          buffer += decoder.decode(value, { stream: !done });
+
+          const events = buffer.split(/\r?\n\r?\n/);
+          buffer = events.pop() ?? "";
+
+          for (const entry of events) {
+            for (const line of entry.split(/\r?\n/)) {
+              if (!line.startsWith("data:")) continue;
+
+              const data = line.slice(5).trim();
+              if (data === "[DONE]") return;
+              if (!data) continue;
+
+              const chunk = JSON.parse(data);
+              const content = chunk.choices?.[0]?.delta?.content;
+              if (content) yield content;
+            }
+          }
+
+          if (done) break;
+        }
+      } finally {
+        reader.releaseLock();
+      }
+    },
+  };
+
+  return {
+    id: ExtensionId.DeepSeek,
+
+    setup(context) {
+      if (!apiKey) {
+        throw new Error("DEEPSEEK_API_KEY is required.");
+      }
+
+      context.add(Hook.ModelProviders, provider);
+    },
+  };
+}