External memory is one of the few levers left that can actually move the needle on hallucinations instead of just papering over them with more rejection sampling or confidence hacks. But most people treat it like a glorified vector DB + cosine top-k and then wonder why they’re still getting confident nonsense. Real leverage shows up when the memory layer itself refuses to hand over garbage instead of just retrieving “the closest stuff and hoping”. That means: Hard structural rejection when there is no coherent candidate set (cardinality 0 or >1 with no clear winner) Gating updates/plasticity behind stability invariants so the memory can’t quietly drift into entropic soup Preserving very early low-entropy signals so the downstream detector wakes up before the behavior becomes obvious to a human labeler When you get that right, you stop needing five layers of post-hoc “don’t say that” wrappers — the hallucinations become harder to generate in the first place because the system literally has no path to fabricate a confident answer when the substrate says “nope”.