We investigate the nuclear γ-ray line emission from rare isotopes produced in the astrophysical intermediate neutron-capture process (i process) and assess the prospects of observing these emissions with γ-ray telescopes. The astrophysical sites of the i process remain uncertain, but two candidates with predicted rapid mass ejections at metallicities of stars in the solar neighborhood are postasymptotic giant branch (post-AGB) stars, such as Sakurai’s object (V4334 Sagittarii), and rapidlyaccreting white dwarfs (RAWDs). Detailed 1D and 3D simulations of these scenarios indicate that the convective-reactive astrophysical fluid dynamics responsible for i-process nucleosynthesis can lead to violent, non-radial outbursts that ultimately result in mass ejections of i-process products. We calculate the ejected yields of rare isotopes whose radioactive decays may produce detectable γ-ray lines, particularly in the 0.5–2 MeV energy range. Our analysis focuses on isotopes such as 22Na, 89Sr, and 95Zr, which are expected to generate long-lasting emissions potentially observable by the COSI γ-ray telescope. We estimate the formation rates of these sources and the likelihood of detecting their γ-ray emissions within 1000 parsecs of the Sun. We find that the probability of observing i-process emission lines during COSI’s operational period is up to ≈ 1%, but could rise to 11% for [89]Sr if the event is observed within a few days. Due to the long lifetime and large production of [22]Na from proton-capture reactions its detection is more likely, with a probability of ≈ 5%. Future space missions could significantly enhance detection capabilities, potentially increasing the observation probability to several tens of percent. Detection of long-lived neutron-rich isotopes such as [137]Cs would provide the first direct γ-ray signature of intermediate neutron-density nucleosynthesis, distinguishing the i process from classical s- and r-process pathways. These findings outline a multi-messenger approach to studying dynamic stellar neutron-capture nucleosynthesis through γ-ray observations.