diff --git a/code/display.cpp b/code/display.cpp
index cc1fc98c5..46380c00a 100644
--- a/code/display.cpp
+++ b/code/display.cpp
@@ -2986,41 +2986,44 @@ void DisplayClass::Encroach_Fog(void)
 /// <param name="cell">The cell that the fog is to be regrown upon.</param>
 void DisplayClass::Fog_Cell(Cell const & cell)
 {
-	if (!In_Radar(cell)) return;
+	// An explicit queue avoids running the stack out on a cascade that spans most of the map.
+	std::vector<Cell> pending;
+	pending.push_back(cell);
 
-	CellClass * cellptr = &(*this)[cell];
-	bool fog = false;
+	while (!pending.empty()) {
+		Cell current = pending.back();
+		pending.pop_back();
 
-	if (cellptr->IsFogMapped || cellptr->IsFogVisible) {
-		fog = true;
-	}
+		if (!In_Radar(current)) continue;
 
-	cellptr->IsFogMapped = false;
-	cellptr->IsFogVisible = false;
-	cellptr->FogFrame = -2;
+		CellClass * cellptr = &(*this)[current];
+		bool fog = cellptr->IsFogMapped || cellptr->IsFogVisible;
 
-	if (cellptr->IsMapped) {
-		TacticalMap->Flag_Cell(*cellptr);
-	}
+		cellptr->IsFogMapped = false;
+		cellptr->IsFogVisible = false;
+		cellptr->FogFrame = -2;
 
-	for (FacingType dir = FACING_FIRST; dir < FACING_COUNT; dir++) {
-		Cell c = Adjacent_Cell(cell, dir);
-		CellClass * cptr = &(*this)[c];
-		int fog = TacticalMap->Cell_Shadow(cptr->Fetch_CellID(), true);
+		if (cellptr->IsMapped) {
+			TacticalMap->Flag_Cell(*cellptr);
+		}
 
-		if (fog == -2 && cptr->FogFrame != -2) {
-			Fog_Cell(c);
-		} else {
-			if ((cptr->IsFogVisible || fog != cptr->FogFrame) && fog >= 0 && cptr->FogFrame >= -1) {
-				cptr->FogFrame = fog;
+		for (FacingType dir = FACING_FIRST; dir < FACING_COUNT; dir++) {
+			Cell c = Adjacent_Cell(current, dir);
+			CellClass * cptr = &(*this)[c];
+			int fogshape = TacticalMap->Cell_Shadow(cptr->Fetch_CellID(), true);
+
+			if (fogshape == -2 && cptr->FogFrame != -2) {
+				pending.push_back(c);
+			} else if ((cptr->IsFogVisible || fogshape != cptr->FogFrame) && fogshape >= 0 && cptr->FogFrame >= -1) {
+				cptr->FogFrame = fogshape;
 				cptr->IsFogMapped = true;
 				cptr->IsFogVisible = false;
 				TacticalMap->Flag_Cell(*cptr);
 			}
 		}
-	}
-	if (fog) {
-		cellptr->Fog_Cell();
+		if (fog) {
+			cellptr->Fog_Cell();
+		}
 	}
 }
 
diff --git a/code/mainloop.cpp b/code/mainloop.cpp
index 16f292b44..28d086dec 100644
--- a/code/mainloop.cpp
+++ b/code/mainloop.cpp
@@ -40,6 +40,7 @@
 #include "ipxmgr.h"
 #include "language/language.h"
 #include "logic.h"
+#include "map.h"
 #include "misc.h"
 #include "mpscore.h"
 #include "msgbox.h"
@@ -540,7 +541,14 @@ void Keyboard_Process(KeyNumType & input)
 		if ((Debug_Flag || Debug_Playtest) && plain == KN_F4) {
 			if (Session.Type == GAME_NORMAL) {
 				Debug_Unshroud = (Debug_Unshroud == false);
-				Map.Flag_To_Redraw(GS_REDRAW_ALL);
+
+				// The same pair the reveal and blackout crates use, so turning this off
+				// leaves normal vision to re-explore the map rather than leaving it dark.
+				if (Debug_Unshroud) {
+					Map.Reveal_The_Map(true);
+				} else {
+					Map.Shroud_The_Map();
+				}
 			}
 		}
 
diff --git a/code/map.cpp b/code/map.cpp
index 9429804c6..4f8aa9ce7 100644
--- a/code/map.cpp
+++ b/code/map.cpp
@@ -11640,29 +11640,32 @@ bool MapClass::Is_Something_Nearby(Cell const & cell, int radius)
 /// <summary>
 /// Determines if a coordinate is still under the shroud.
 /// Which cell a coordinate appears over depends on how high it is, so the height is folded
-/// into the lookup before the shroud is consulted.
+/// into the lookup before the shroud is consulted. The map debugger's unshroud toggle sees
+/// through it, and nothing is reported as hidden while that is active.
 /// </summary>
 /// <returns>bool; Is the coordinate still shrouded?</returns>
 bool MapClass::Is_Shrouded(Coord const & coord)
 {
-	int level_height = coord.Z / LEVEL_LEPTON_H;
-	if ((level_height & 1) != 0) {
-		int offset = level_height / 2 + 1;
-		Cell cell = coord.As_Cell();
-		CellClass * cptr = &Map[Cell(cell.X - offset, cell.Y - offset)];
-		if (cptr->IsMapped) {
-			return(false);
-		}
-		cptr = &cptr->Adjacent_Cell(FACING_SE);
-		if (!cptr->IsMapped) {
-			return(true);
-		}
-	} else {
-		int offset = level_height / 2;
-		Cell cell = coord.As_Cell();
-		CellClass * cptr = &Map[Cell(cell.X - offset, cell.Y - offset)];
-		if (!cptr->IsMapped) {
-			return(true);
+	if (!Debug_Unshroud) {
+		int level_height = coord.Z / LEVEL_LEPTON_H;
+		if ((level_height & 1) != 0) {
+			int offset = level_height / 2 + 1;
+			Cell cell = coord.As_Cell();
+			CellClass * cptr = &Map[Cell(cell.X - offset, cell.Y - offset)];
+			if (cptr->IsMapped) {
+				return(false);
+			}
+			cptr = &cptr->Adjacent_Cell(FACING_SE);
+			if (!cptr->IsMapped) {
+				return(true);
+			}
+		} else {
+			int offset = level_height / 2;
+			Cell cell = coord.As_Cell();
+			CellClass * cptr = &Map[Cell(cell.X - offset, cell.Y - offset)];
+			if (!cptr->IsMapped) {
+				return(true);
+			}
 		}
 	}
 	return(false);
diff --git a/manual/changes/f4-debug-unshroud-toggle.md b/manual/changes/f4-debug-unshroud-toggle.md
new file mode 100644
index 000000000..b4e25d634
--- /dev/null
+++ b/manual/changes/f4-debug-unshroud-toggle.md
@@ -0,0 +1,17 @@
+---
+title: Fix the F4 playtest shroud toggle doing nothing
+category: fix
+release: 0.2.0
+targets:
+- type: command
+  id: fixed:debug-unshroud
+  effect: changed
+credit:
+- torradmin
+---
+
+Pressing F4 flagged the whole tactical view for redraw but never touched the shroud data
+itself, so the map stayed exactly as shrouded as before. F4 now reveals the map when
+turning the toggle on and reshrouds it when turning the toggle off, the same pair the
+reveal-the-map and blackout crates use, and coordinate shroud checks now see through an
+active toggle instead of only the redraw seeing it.
diff --git a/manual/changes/stack-overflow-on-mass-shroud-unshroud.md b/manual/changes/stack-overflow-on-mass-shroud-unshroud.md
new file mode 100644
index 000000000..abc78dcd1
--- /dev/null
+++ b/manual/changes/stack-overflow-on-mass-shroud-unshroud.md
@@ -0,0 +1,17 @@
+---
+title: Fix crash when large fog changes unwound recursively
+category: fix
+release: 0.2.0
+targets:
+- type: system
+  id: map-visibility
+  effect: changed
+credit:
+- torradmin
+---
+
+Regrowing fog over a cell recursed into every neighbor that also needed to regrow, so
+shrouding or unshrouding a large connected area — a big map, a reveal-the-map crate, or the
+[map shroud toggle](/commands/fixed-debug-unshroud/) — could recurse deeply enough to
+overflow the stack and crash. Fog regrowth now walks an explicit queue instead, so the
+depth of a shroud change no longer bounds how much fog can change at once.