index.js

const {
  BedrockRuntimeClient,
  InvokeModelWithResponseStreamCommand,
} = require("@aws-sdk/client-bedrock-runtime");

const client = new BedrockRuntimeClient();
const MODEL_ID = process.env.MODEL_ID;

exports.handler = awslambda.streamifyResponse(
  async (event, responseStream, _context) => {
    const body = JSON.parse(event.body || "{}");
    const prompt = body.prompt || "Hello";

    const httpMetadata = {
      statusCode: 200,
      headers: {
        "Content-Type": "text/event-stream",
        "Cache-Control": "no-cache",
        Connection: "keep-alive",
      },
    };

    responseStream = awslambda.HttpResponseStream.from(
      responseStream,
      httpMetadata
    );

    try {
      const command = new InvokeModelWithResponseStreamCommand({
        modelId: MODEL_ID,
        contentType: "application/json",
        accept: "application/json",
        body: JSON.stringify({
          anthropic_version: "bedrock-2023-05-31",
          max_tokens: 2048,
          messages: [{ role: "user", content: prompt }],
        }),
      });

      const response = await client.send(command);

      for await (const event of response.body) {
        if (event.chunk) {
          const parsed = JSON.parse(
            new TextDecoder().decode(event.chunk.bytes)
          );
          if (
            parsed.type === "content_block_delta" &&
            parsed.delta?.text
          ) {
            responseStream.write(`data: ${JSON.stringify({ text: parsed.delta.text })}\n\n`);
          }
        }
      }

      responseStream.write("data: [DONE]\n\n");
    } catch (err) {
      responseStream.write(
        `data: ${JSON.stringify({ error: err.message })}\n\n`
      );
    }

    responseStream.end();
  }
);