This is why I keep advocating that JSON should die, or at least no longer be used with LLMs. LLMs (and human brains) are simply not wired up for counting nested curly brackets across long spans of quoted text joined by colons and commas, and it is far too easy for humans to make mistakes when chunking JSON.

IMO, (Strict)YAML is a very good alternative, it has even been suggested to me by multiple LLMs when I asked them what they thought the best format for presenting conversations to an LLM would be. It is very easy to chunk simple YAML and present it to an LLM directly off the wire: you only need to remember to repeat the indentation and names of all higher level keys (properties) pertaining to the current chunk at the top of the chunk, then start a text block containing the remaining text in the chunk, and the LLM will happily take it from there:

    topic:
      subtopic:
        text: |
          Subtopic text for this chunk.

If you want to make sure that the LLM understands that it is dealing with chunks of a larger body of text, you can start and end the text blocks of the chunks with an ellipsis ('...').