def chunk(text, size=700, overlap=100):
    """Split on sentence ends so an idea is never cut in half."""
    import re
    sentences = re.split(r'(?<=[.!?])\s+', text.strip())
    chunks, current = [], ''

    for s in sentences:
        if len(current) + len(s) > size and current:
            chunks.append(current.strip())
            # carry the tail forward so context survives the boundary
            current = current[-overlap:] + ' '
        current += s + ' '

    if current.strip():
        chunks.append(current.strip())
    return chunks