  About one percent of giants\upcite{Brown1989} are detected to have
anomalously high lithium (Li) abundances in their atmospheres, conflicting
directly with the prediction of the standard stellar evolution
models\upcite{Iben1967}, and making the production and evolution of Li more
intriguing, not only in the sense of the Big Bang
nucleosynthesis\upcite{Cyburt2016,Spite1982} or the Galactic
medium\upcite{Tajitsu2015}, but also the evolution of stars. Decades of efforts
have been put into explaining why such outliers exist\upcite{Sackmann1999,
Denissenkov2004, Charbonnel2010}, yet the origins of Li-rich giants are still
being debated. Here we report the discovery of the most Li-rich giant known to
date, with a super-high Li abundance of 4.51. This rare phenomenon was
snapshotted together with another short-term event that the star is
experiencing its luminosity bump on the red giant branch. Such high Li
abundance indicates that the star might be at the very beginning of its Li-rich
phase, which provides a great opportunity to investigate the origin and
evolution of Li in the Galaxy. A detailed nuclear simulation is presented with
up-to-date reaction rates to recreate the Li enriching process in this star.
Our results provide tight constraints on both observational and theoretical
points of view, suggesting that low-mass giants can produce Li inside
themselves to a super high level via $^{7}$Be transportation during the red
giant phase.
