News · October 17, 2026
One debugger for both ends: following a step from the device to the server
Debugging a client/server app usually means two debuggers: the browser's for the device side, and whatever the server offers, often just its logs. A fault that crosses the line between them is reconstructed by hand, from timestamps and guesses. Exotool has one debugger, and it follows the step across the line.
Why it is hard
In a hand-built app the device side and the server side are two programs that happen to talk. They are written in different languages, run in different places, and know nothing of each other's source. A request leaves one and arrives in the other as bytes; the mapping from a line of code on one side to the line it caused on the other exists only in the developer's head. No single tool can set a breakpoint in the browser and have it continue, as the same step, on the server.
What the engine knows
In Exotool both sides come from one source: the activities in the diagram, written in the Exotool language. The engine decides which statement runs where and generates both programs and the APIs between them. Because it generated them, it knows which generated line on either side came from which statement of which activity, and it leaves markers in the generated code that say so. The visual debugger reads those markers.
What that gives you
Set a breakpoint on a statement in an activity. Run the app. When execution reaches that statement it stops, whether the engine placed it on the device or on the server, and the debugger shows the activity, the line, and the variables in scope on that side. Step, and the next statement is followed even if it runs on the other side. One session, one view, both ends.
Who it is for
For a newcomer it means the app explains itself: stop it, look at the values, see what happened. For a professional developer it means the hardest class of fault in a client/server app, the one that lives in the hand-off, is an ordinary one. And when Claude has built or changed the app through the Exotool connector, the debugger is how you watch what it made actually run.
How to use it, step by step, is in Using the editor in the Help Center.