Recent scholarship has emphasized variation in militarized interstate dispute (MIDs) propensity across authoritarian regime type. There is little agreement, however, on what structural features make some autocracies more or less pacific. To address this puzzle, this article examines the dyadic interaction between different autocratic types. Using recently updated data, I find that conflict between party-dominant regimes occurs as frequently as democratic dyads. Furthermore, whereas previous work situations decreased MID propensity in the context of audience costs, I find evidence for deeper institutionalized structural causes. As with autocracies more broadly, coup risk plagues the stability and future of party-dominant regimes. Unlike other autocracies, these regimes mitigate such risks by relying on cooptation, legitimization, and power-sharing agreements. I argue that these same mechanisms that make commitments between the dictator and regime insiders credible do so also for agreements between party-dominant regimes. I support this hypothesis quantitatively by in-country regime-type variation. This evidence challenges prior claims about the irrelevance of institutional features in autocracies and shows how domestic institutional constraints enable states to make effective, credible commitments.