When LLMs Forget What They Believe: Characterizing State Integrity Collapse in Long-Horizon Dialogues
A rule you put in the system prompt survives in the model long after it stops governing the output: ask it to list its active instructions and it recites the constraint it just violated. Across seven pinned model snapshots, 125 scripted conversations each and probes from 3 to 12 turns, strict retention of a single persistent constraint ranged from 62.4% to 100%, and a forked audit — from one identical history, one branch asked for the next answer while the other asked the model to restate the rule — found 70 of 79 failures (88.6%) were recalled-then-violated rather than forgotten. That rules out the reflex fix: more context cannot restore something already in there. What worked was restating the rule as checkable predicates in a short block prepended to every turn and verifying the answer against them, which took the weakest model from 54.0% to 78.4% at twelve turns for 1.18-1.47x the tokens — with the obvious trap that the same block kept enforcing a rule the user had since revoked in 74.3% of cases until the block itself was updated.