The present study addresses the question of whether the grammatical configuration of prosodic units (i.e., their alignment with the clause unit) may contribute to systematic prosodic patterns. Specifically, we focus on the pitch variation on prosodic boundaries in conversational Mandarin. Results demonstrate that the grammatical configuration of the prosodic phrasing correlates with systematic pitch variation, on which implications for incremental production are drawn. The cross-boundary pitch variation signals not only whether speakers are going to finish their proposition by the end of the prosodic phrasing, but also how much information they have planned to package in the prosodic unit. A clause-based conceptual planning in conversational speech is empirically supported by our observation of the pitch variation on prosodic boundaries. Prosodic phrasing is found to emerge from the stream of conversational speech with a high degree of satisfying consistency reflecting our clause-based conceptualization in interaction.