From a Lua author’s point of view the debugger is a thin layer around a single Lua feature — a line hook — plus a UI that knows how to inspect the Lua stack while that hook is stopped at a line:

           Your Lua script
                 |
                 v
         +---------------+     on every line:
         |    Lua VM     | --- is this line a breakpoint
         +-------+-------+     or the next step target?
                 |                   |
                 | run               | pause
                 v                   v
         (next Lua line)   +---------------------+
                           |   Debugger dialog   |
                           |  Stack / Variables  |
                           |   Watch / Evaluate  |
                           +----------+----------+
                                      |
                                      | Continue / Step
                                      v
                                (back to Lua VM)

While the debugger is Enabled, a line hook (the same mechanism debug.sethook exposes to Lua) runs before every line of Lua code and checks the current source and line against the breakpoint list and any pending step target. Until a hit, scripts run at full speed; the hook has no effect on dissector output.

When the hook decides to pause, your Lua code is frozen mid-line. The rest of Wireshark cannot dissect packets, run taps, or call any other Lua code until you resume — that is why the main window grays out and why live capture is not compatible with pausing (see Section 14.2.1, “Live-capture suppression”).

Everything shown in the Variables tree, Watch tree, and Stack Trace is read directly from the paused Lua state through the standard Lua reflection surface — debug.getlocal, debug.getupvalue, and the Globals environment as described in Section 14.5, “Variables”. Reload Lua Plugins in the toolbar re-runs the full plugin load sequence in a fresh VM (see Section 14.4, “Toolbar”); debugger state — breakpoints, watches, open editor tabs, and the current theme — survives the reload, anything the script stashed in globals does not.