import re
from typing import List

def split_text_into_chunks(text: str, max_chars: int = 256) -> List[str]:
    """
    Split raw text into chunks no longer than max_chars.
    Preference is given to sentence boundaries; otherwise falls back to word-based splitting.
    """
    sentences = re.split(r"(?<=[\.\!\?\…])\s+", text.strip())
    chunks: List[str] = []
    buffer = ""

    def flush_buffer():
        nonlocal buffer
        if buffer:
            chunks.append(buffer.strip())
            buffer = ""

    for sentence in sentences:
        sentence = sentence.strip()
        if not sentence:
            continue

        if len(sentence) <= max_chars:
            candidate = f"{buffer} {sentence}".strip() if buffer else sentence
            if len(candidate) <= max_chars:
                buffer = candidate
            else:
                flush_buffer()
                buffer = sentence
            continue

        flush_buffer()
        words = sentence.split()
        current = ""
        for word in words:
            candidate = f"{current} {word}".strip() if current else word
            if len(candidate) > max_chars and current:
                chunks.append(current.strip())
                current = word
            else:
                current = candidate
        if current:
            chunks.append(current.strip())

    flush_buffer()
    return [chunk for chunk in chunks if chunk]