Summarization Patterns

1. Single-pass summarization

The cheapest and fastest pattern. Send the full document in one request and ask for a bounded summary. Works for anything under the model's effective context budget — typically articles, short reports, and meeting transcripts under 30k tokens. Route toazure/model-routerand let Meridian choose between fast and reasoning models based on length.

Best for: news articles, single meetings, support tickets, short PDFs.

2. Map-reduce over chunks

For documents that exceed the context window, split into overlapping chunks, summarize each in parallel, then summarize the summaries. The map stage runs on a cheap fast model; the reduce stage on a reasoning model. Overlap of 10–15% keeps cross-chunk context from being lost at boundaries.

Best for: long PDFs, books, multi-hour transcripts, large codebases.

3. Refine (rolling summary)

Process chunks sequentially. Each call receives the previous running summary plus the next chunk and produces an updated summary. Slower than map-reduce because it cannot parallelize, but preserves narrative order — ideal when the document tells a story or accumulates state.

Best for: legal contracts, novels, incident timelines, long email threads.

Example: map-reduce with Meridian

import OpenAI from 'openai';

const client = new OpenAI({
  apiKey: process.env.MERIDIAN_KEY,
  baseURL: 'https://llm.getnimbus.net/v1',
});

async function summarize(chunks: string[]) {
  const partials = await Promise.all(
    chunks.map((c) =>
      client.chat.completions.create({
        model: 'azure/model-router',
        messages: [
          { role: 'system', content: 'Summarize in 3 bullets.' },
          { role: 'user', content: c },
        ],
      }).then((r) => r.choices[0].message.content)
    )
  );

  const merged = partials.join('\n---\n');
  const final = await client.chat.completions.create({
    model: 'azure/model-router',
    messages: [
      { role: 'system', content: 'Combine into a unified summary.' },
      { role: 'user', content: merged },
    ],
  });
  return final.choices[0].message.content;
}