Wait, why would you feed it the context JSON from the last conversation?
The harness comes in several kinds — AGENTS.md, rules, skills, hooks — and they can all carry the load. Summarizing the key points from the previous conversation into a temporary doc works well too.
Raw session history holds too many tool calls, outputs, and flags that are useless; even auto compact strips those out.
I’d suggest doing a fresh checkup on your harness first.