> ## Documentation Index
> Fetch the complete documentation index at: https://docs.trulayer.ai/llms.txt
> Use this file to discover all available pages before exploring further.

# Vercel AI SDK

> Trace every streamText, generateText, and generateObject call.

## Install

```bash theme={null}
npm install @trulayer/sdk ai
```

## Instrument

`instrumentVercelAI` takes the `ai` module's functions and returns instrumented replacements. Import it once at the top of any module that uses the Vercel AI SDK.

```typescript theme={null}
import { generateText, streamText, generateObject } from "ai";
import { TruLayer, instrumentVercelAI } from "@trulayer/sdk";

const tl = new TruLayer({
  apiKey: process.env.TRULAYER_API_KEY!,
  projectName: "my-app",
});

const ai = instrumentVercelAI(tl, { generateText, streamText, generateObject });

// Use ai.generateText / ai.streamText / ai.generateObject from here on.
```

## Minimal example — `streamText` in a Next.js Route Handler

```typescript app/api/chat/route.ts theme={null}
import { openai } from "@ai-sdk/openai";
import { TruLayer, instrumentVercelAI } from "@trulayer/sdk";
import { streamText } from "ai";

export const runtime = "nodejs"; // required — edge runtime is not supported

const tl = new TruLayer({ apiKey: process.env.TRULAYER_API_KEY!, projectName: "chat" });
const ai = instrumentVercelAI(tl, { streamText });

export async function POST(req: Request) {
  const { messages } = await req.json();
  const result = await ai.streamText({
    model: openai("gpt-4o-mini"),
    messages,
  });
  return result.toDataStreamResponse();
}
```

## `generateObject` with a Zod schema

```typescript theme={null}
import { anthropic } from "@ai-sdk/anthropic";
import { z } from "zod";

const { object } = await ai.generateObject({
  model: anthropic("claude-sonnet-4-6"),
  schema: z.object({
    sentiment: z.enum(["positive", "neutral", "negative"]),
    reasoning: z.string(),
  }),
  prompt: "Classify: 'The onboarding was great but docs were sparse.'",
});
```

The span captures the structured `object` as output and any validation error as `span.status = error`.

## What gets captured

* `llm` spans around every wrapped call with:
  * `input` — the last message (or prompt string)
  * `output` — completed text, or the structured object for `generateObject`
  * `model` — the model id (for example `gpt-4o-mini`)
  * `prompt_tokens` / `completion_tokens`
  * `latency_ms`
* Stream results hold the span open until the final token arrives; `usage` is recorded from the resolved `result.usage` promise.

## Known gotchas

* **Next.js Edge runtime is unsupported.** Add `export const runtime = "nodejs"` to any Route Handler or Server Action that calls an instrumented function. The SDK relies on `node:async_hooks` for trace context propagation, which is not available on Edge.
* **Only wrapped functions are traced.** If you import `generateText` directly from `ai` elsewhere in your code, those calls bypass TruLayer. Pick one convention per module.
* **Tool calls are recorded on the parent `llm` span.** For a dedicated `tool` span per tool execution, wrap the tool body with `tl.span("tool:name", { spanType: "tool" })`.