BREAKING CHANGE(vercel-ai-sdk): migrate to Vercel AI SDK v6 and introduce provider registry (getModel) returning LanguageModelV3

ts/smartai.middleware.anthropic.ts

@@ -0,0 +1,38 @@
+import type { LanguageModelV3Middleware, LanguageModelV3Prompt } from '@ai-sdk/provider';
+
+/**
+ * Creates middleware that adds Anthropic prompt caching directives.
+ * Marks the last system message and last user message with ephemeral cache control,
+ * reducing input token cost and latency on repeated calls.
+ */
+export function createAnthropicCachingMiddleware(): LanguageModelV3Middleware {
+  return {
+    specificationVersion: 'v3',
+    transformParams: async ({ params }) => {
+      const messages = [...params.prompt] as Array<Record<string, unknown>>;
+
+      // Find the last system message and last user message
+      let lastSystemIdx = -1;
+      let lastUserIdx = -1;
+      for (let i = 0; i < messages.length; i++) {
+        if (messages[i].role === 'system') lastSystemIdx = i;
+        if (messages[i].role === 'user') lastUserIdx = i;
+      }
+
+      const targets = [lastSystemIdx, lastUserIdx].filter(i => i >= 0);
+      for (const idx of targets) {
+        const msg = { ...messages[idx] };
+        msg.providerOptions = {
+          ...(msg.providerOptions as Record<string, unknown> || {}),
+          anthropic: {
+            ...((msg.providerOptions as Record<string, unknown>)?.anthropic as Record<string, unknown> || {}),
+            cacheControl: { type: 'ephemeral' },
+          },
+        };
+        messages[idx] = msg;
+      }
+
+      return { ...params, prompt: messages as unknown as LanguageModelV3Prompt };
+    },
+  };
+}