That can happen if the history got compacted away in a long session. But usually AI agents also have a way to re-read the entire log from the disk. Eg Claude Code stores all user messages, LLM messages and thinking traces, tool calls etc in json files that the agent can query. In my experience it can do it very well. But the AI might not reach for those logs unless asked directly. I can see that it could be more proactive but this is certainly not some fundamental AI limitation.