[cesarb]

You might be thinking of KeyKOS, and of the anecdote which can be found at https://lists.inf.ethz.ch/pipermail/oberon/2010/005734.html (it should also be at the EROS homepage, but it's down for me at the moment).

See also: "Crash-only software" https://lwn.net/Articles/191059/

[klibertp]

Yes, exactly this! Thank you.