Conflicts are common in text-based communication, particularly in intimate relationships, where misunderstandings can easily escalate into verbal aggression. To address this, we present SpeakSoftly, a system that applies Nonviolent Communication (NVC) principles to scaffold couples' conflict communication through LLM-powered just-in-time interventions. Informed by formative interviews with couples and NVC principles, we designed two core features: NVC-Prompt, which detects verbal aggression and suggests revisions to prevent escalation, and NVC-Guide, which analyzes dialogues to uncover users' feelings and needs, fostering self-awareness and perspective-taking. These features were implemented across three progressive intervention modes, each varying in intervention depth and tone: Basic Reminder, Neutral Guide, and Empathetic Guide. We conducted a mixed-methods user study with 18 couples across simulated and real-life conflict settings to evaluate the effectiveness of each mode. Results showed that Empathetic Guide significantly facilitated both behavioral and cognitive changes, while Neutral Guide was effective only for behavioral changes in simulated conflicts. In real-life conflicts, Neutral Guide showed distinct advantages due to lower cognitive load demands. We discuss the mechanisms behind these findings and propose design implications for in-situ interventions in high-stakes communication contexts.

翻译：冲突在基于文本的交流中普遍存在，尤其在亲密关系中，误解容易升级为言语攻击。为解决此问题，我们提出SpeakSoftly系统，该系统应用非暴力沟通原则，通过大语言模型驱动的即时干预来支撑伴侣间的冲突沟通。基于与伴侣的前瞻性访谈及非暴力沟通原则，我们设计了两项核心功能：非暴力沟通提示，用于检测言语攻击并建议修改以防止冲突升级；非暴力沟通引导，则通过分析对话揭示用户的感受与需求，促进自我意识与换位思考。这些功能以三种渐进式干预模式实现，分别在不同干预深度与语调上有所差异：基础提醒、中立引导与共情引导。我们开展了一项混合方法用户研究，涉及18对伴侣在模拟与现实冲突场景下的测试，以评估各模式的有效性。结果表明，共情引导显著促进了行为与认知的双重变化，而中立引导仅在模拟冲突中对行为变化有效。在现实冲突中，中立引导因认知负荷需求较低而展现出明显优势。我们探讨了这些发现背后的机制，并提出了在高风险沟通场景中进行现场干预的设计启示。