What is compaction in AI chat?
Compaction is when an AI system summarizes earlier parts of a conversation and replaces them with that summary, freeing space in the context window so the thread can continue.
Rather than letting a conversation die at the context limit, compaction condenses the older turns into a summary and continues from there. Anthropic's API documentation describes the mechanism plainly: the system detects when input tokens reach a threshold, generates a summary, and drops every content block prior to it. Claude Code exposes the same idea as a command you can run yourself.
Consumer apps handle this inconsistently, which is the main source of confusion. Claude applies automatic context management on paid plans, but only when code execution is enabled. Gemini's app applies sliding-window compression server-side without telling you. ChatGPT offers branching instead, letting you fork from an earlier message into a thread with a fresh budget. Several assistants do none of it and simply stop.
Compaction is inherently lossy. What survives depends entirely on the quality of the summary, and summaries are generated at the moment the model has the least room to think. This is why a manually written handoff note often preserves more of what matters than an automatic one.
how this works in folk
Folk compacts automatically using a structured handoff summary that protects the newest turns and tracks what is still unresolved, so a long thread keeps going without you noticing the seam.
frequently asked
Does ChatGPT automatically compact conversations?
Not in the way Claude Code does. ChatGPT stops the thread at its ceiling and offers branching from an earlier message instead, which starts a new conversation carrying the history up to that point.
Is compaction lossy?
Yes. Detail is discarded by design, and the summary is produced when the model has the least available context. Copying important numbers and decisions verbatim before a compaction protects them.
Can I trigger compaction myself?
In developer tools like Claude Code, yes, with a compact command. In most consumer chat apps there is no manual trigger, so the workaround is asking for a handoff summary and pasting it into a new chat.