# Task ID: 75

**Title:** Implement section-split Stage

**Status:** done

**Dependencies:** 71 ✓, 74 ✓

**Priority:** high

**Description:** Create the built-in section-split stage that splits content based on detected content type, using structural boundaries for JSON/YAML/XML and headers for prose.

**Details:**

Create `src/mcplocal/src/proxymodel/stages/section-split.ts`:

```typescript
import type { StageHandler, Section } from '../types';
import { detectContentType } from '../content-detection';

const handler: StageHandler = async (content, ctx) => {
  const minSize = (ctx.config.minSectionSize as number) ?? 2000;
  const maxSize = (ctx.config.maxSectionSize as number) ?? 15000;
  const contentType = detectContentType(content);
  
  let sections: Section[];
  
  switch (contentType) {
    case 'json':
      sections = splitJson(content, minSize, maxSize);
      break;
    case 'yaml':
      sections = splitYaml(content, minSize, maxSize);
      break;
    case 'xml':
      sections = splitXml(content, minSize, maxSize);
      break;
    case 'code':
      sections = splitCode(content, minSize);
      break;
    default:
      sections = splitProse(content, minSize);
  }
  
  if (sections.length === 0) {
    return { content, sections: [{ id: 'main', title: 'Content', content }] };
  }
  
  const toc = sections.map((s, i) => `[${s.id}] ${s.title}`).join('\n');
  return {
    content: `${sections.length} sections (${contentType}):\n${toc}`,
    sections,
  };
};

function splitJson(content: string, minSize: number, maxSize: number): Section[] {
  const parsed = JSON.parse(content);
  if (Array.isArray(parsed)) {
    return parsed.map((item, i) => ({
      id: item.id ?? item.name ?? `item-${i}`,
      title: item.label ?? item.title ?? item.name ?? `Item ${i}`,
      content: JSON.stringify(item, null, 2),
    }));
  }
  return Object.entries(parsed).map(([key, value]) => ({
    id: key,
    title: key,
    content: JSON.stringify(value, null, 2),
  }));
}

// Similar implementations for splitYaml, splitXml, splitCode, splitProse
```

**Test Strategy:**

Unit tests for each content type: JSON arrays split by element, JSON objects split by key, YAML split by top-level keys, XML split by elements, prose split by markdown headers. Test minSize/maxSize thresholds. Test fallback when content can't be parsed.