AIDEFEND SecureFlow / SecureFlow Case Index

Compaction Smuggling: Hidden Reasoning Survives a Change of Carrier

• AI Infrastructure
• Data Exfiltration

Xint tested OpenAI's conversation-compaction API, which compresses earlier work for later model calls. A client-steered compaction carried protected reasoning from gpt-5.6-sol into an encrypted item accepted by gpt-4.1 and gpt-4o, which echoed readable content. This was controlled API research using the researchers' own puzzles, not a demonstrated theft of another user's conversations. Xint reports an undisclosed fix on October 23, 2026.