How to Signal the LLM to stop generating content in nodejs?

Effective Strategies for Halting Content Generation from Language Models Using Node.js

When integrating large language models (LLMs) into your Node.js applications, managing ongoing content generation is crucial—especially when you want to terminate the process based on client actions, such as closing a connection. This article explores how to effectively signal an LLM to stop generating content, focusing on server-side implementation details and best practices.

Context Overview

Suppose you’re creating an API endpoint that streams responses from an LLM to clients via Server-Sent Events (SSE). The typical flow involves initiating a content generation stream, forwarding chunks to the client, and monitoring for connection closures to halt processing appropriately.

Here’s a simplified version of such an implementation:

“`js
router.get(“/prompt/stream”, async (req, res) => {
try {
const { prompt, model } = req.query;
if (!prompt) {
return res.status(400).json({ error: “Prompt is required” });
}

res.setHeader("Content-Type", "text/event-stream");
res.setHeader("Cache-Control", "no-cache");
res.setHeader("Connection", "keep-alive");
res.flushHeaders();

const stream = await ai.models.generateContentStream({
  model: (model as string) || "gemini-2.5-flash",
  contents: [{ role: "user", parts: [{ text: prompt as string }] }],
  config,
});

let clientDisconnected = false;

req.on("close", () => {
  clientDisconnected = true;
  console.log("Client disconnected");
  res.end();
});

for await (const chunk of stream) {
  if (clientDisconnected) break;

  if (chunk.text) {
    res.write(`data: ${JSON.stringify({ response: chunk.text })}\n\n`);
  }
}

res.write("event: complete\ndata: {}\n\n");
res.end();

} catch (error) {
console.error(“Streaming error:”, error);
res.end();
}
});
“`

The core challenge here: When a client disconnects, how can you gracefully signal the LLM to halt generation? This is crucial to conserve resources and prevent unnecessary processing.

The Problem with Stream Termination and the stream.throw() Approach

Initially, you might attempt to throw an exception within the streaming loop to stop the content generation, such as:

“`js