accreting millisecond X-ray pulsar (AMXP) SAX J1808.4–3658 (hereafter [SAX J1808]{}), was first discovered through the detection of a thermonuclear (Type I) X-ray burst with the *BeppoSAX* satellite in September 1996 [@Zand1998]. With X-ray outbursts recurring every $2-4$ years, this source has been extensively monitored ever since, leading to the first detection of accretion-powered millisecond pulsations [@Wijnands1998a], and the confirmation that X-ray burst oscillations correspond with the stellar spin frequency [@Chakrabarty2003].

In each of the eight outbursts from [SAX J1808]{}that occurred between 1996 and 2015, at least one X-ray burst has been detected [@Zand2001a; @Bult2015b; @Patruno2017b; @Sanna2017c]. The majority of these bursts showed burst oscillations [@Bilous2019] and were observed near peak luminosity of their respective outbursts, when the accretion rate was $\approx(3-5){\ensuremath{\times 10^{-10}} }$[$M_{\odot}$]{}[yr$^{-1}$]{} [@Bult2015b]. Detailed modelling of a well sampled burst train observed with the *Rossi X-ray Timing Explorer* ([*RXTE*]{}) in October 2002 [@Galloway2006] demonstrated that these events are examples of X-ray bursts in the “delayed helium" regime [@Narayan2003; @Galloway2017]. In brief, these bursts are due to a thermonuclear flash in a nearly pure helium layer of the neutron star envelope. This layer of helium builds up on a timescale of one to a few days, through a stable $\beta$-limited 