In this dissertation, I make hidden, protected, and deleted interaction context measurable and actionable by extracting it from real software stacks. In DVa, I uncover victim apps and attribute victim-specific a11y abuse vectors by combining victim modeling with abuse-vector-guided symbolic analysis on real malware. In SOMBRA, I identify where app-side a11y protections fail to transfer to mobile websites by modeling and comparing the a11y information exposed by native apps and by browser-rendered counterparts across four different browsers. In ORISA, I recover and rehost deleted conversation context from local LLM apps by extracting and realigning batch tokens and KV cache state so investigators can interrogate a live session with recovered context.