“Live in the Editor”: Low-Tech In-Situ Feedback for Plain-Text Live Programming

Programming often benefits from immediate, co-located behavioral feedback such as values, traces, and visual hints. Computational notebooks are a popular way to provide such feedback, but their reliance on cells, execution order, global state, and dedicated interfaces can introduce conceptual and practical overhead in some contexts. In this extended abstract, we explore a low-tech, complementary design point: providing in-situ runtime feedback directly within plain-text source files. Rather than competing with notebooks, the approach trades rich graphical interfaces for low implementation overhead, strong portability, and seamless integration with existing text-based workflows, while retaining much of the immediacy and expressiveness of live feedback. The core of the system is a runtime that incrementally re-evaluates semantically defined code cells and embeds their outputs adjacent to source code as specialized comments. We present a working prototype and outline its design rationale, implementation, and initial evaluation plan.