No-code platforms and source-level debugging are fundamentally at odds over the role of code in software development. This tension arises because no-code platforms abstract away from code to prioritize simplicity and ease of use, while source-level debugging depends on visibility into the code that actually executes. Even when no-code platforms do generate code explicitly, they often conceal it from developers, treating it as a blackbox. This creates a debugging barrier: users can observe behavior in the visual interface, but cannot trace that behavior to the code that produced it.

To overcome this barrier, this paper introduces a glassbox approach to no-code debugging. In this approach, the generated code behind visual components is exposed as a read-only, synchronized debugging view. The visual program remains the source-of-truth, while the generated code becomes an explanatory interface for inspecting behavior and synchronizing control. The approach further supports cross-language and cross-session debugging, making generated artifacts, runtime behavior, breakpoints, logs, and execution snapshots comparable across target languages and debugging sessions.

y adding source-level inspection and synchronized control without requiring users to edit generated code, glassbox debugging may extend no-code platforms toward fuller development environments, while preserving their accessibility for citizen developers and transitional users. We instantiate this approach in Glancer, a prototype glassbox debugger for Blockly. Because Blockly can generate multiple target languages from the same visual program, Glancer provides a concrete setting for exposing behavioral divergences that single-target blackbox debuggers may hide.