initial commit: slides + practica_resueltos + README

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

slides/pages/agents/18.md

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+---
+layout: default
+---
+
+# Middleware: wrapModelCall
+
+<div class="mt-4 text-xs">
+
+<v-click>
+
+Permite interceptar y modificar la llamada al modelo:
+
+```typescript
+import { ChatMistralAI } from "@langchain/mistralai";
+import { createAgent, createMiddleware } from "langchain";
+
+const basicModel = new ChatMistralAI({ model: "mistral-small-latest" });
+const advancedModel = new ChatMistralAI({ model: "mistral-large-latest" });
+
+const dynamicModelSelection = createMiddleware({
+  name: "DynamicModelSelection",
+  wrapModelCall: (request, handler) => {
+    // Elegir modelo según complejidad de la conversación
+    const messageCount = request.messages.length;
+    const model = messageCount > 10 ? advancedModel : basicModel;
+
+    return handler({ ...request, model });
+  },
+});
+
+const agent = createAgent({
+  model: basicModel,
+  tools: [searchTool],
+  middleware: [dynamicModelSelection],
+});
+```
+
+</v-click>
+
+</div>