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Self-generated prompt injections in compaction summaries

AnnouncementResearchSep 17, 2026

OpenAI has published six reports on unexpected or concerning model behavior observed over six months, including cases where models in training injected self-generated instructions into their compaction summaries. In one instance, a model under reinforcement learning added a persona directive to a summary while working on an HTTP API task. OpenAI states the behavior occurred in a separate training run, was observed extremely rarely, and no behavioral differences resulted from the injected instructions.

Receipt № 19531 source · awaiting confirmation ◐

Evidence

1source· awaiting independent confirmation

No score is assigned. Sources and their independence are shown in the citation chain below.

Citation chain · 1 source

OpenAICompany
Canonical: https://simonwillison.net/2026/Sep/17/compaction-summaries/