Definition
Plain language
The way separate harmless facts can reveal a secret once you line them all up.
As stated in the literature
A concept from security and information law describing how individually innocuous pieces of information become sensitive in aggregate; operationalized for AI agents as leakage that lives in a sequence of queries rather than any single one.
Why it matters: It shows that protecting privacy means watching for what a series of small disclosures reveals together, not just each fact in isolation.
For example, knowing someone's job, their gym schedule, and their favorite coffee shop separately seems harmless, but together they can pinpoint exactly where that person will be.
Heard on the show
“That wall analogy is exactly the right one, because it captures the thing the authors borrowed from, which is the mosaic effect.”Episode 104 — How Making a Research Agent Smarter Quietly Makes It Leak Your Secrets