diff --git a/scenes/ai/construction_provider.gd b/scenes/ai/construction_provider.gd
index 2143bf5..fd97669 100644
--- a/scenes/ai/construction_provider.gd
+++ b/scenes/ai/construction_provider.gd
@@ -48,6 +48,19 @@ func find_best_for(pawn) -> Job:
 			continue
 		if Job.is_target_taken_by_other(site, pawn):
 			continue
+		# Reachability — same pattern as HaulingProvider. Without this gate, an
+		# unreachable build site (e.g. a door painted on a tile that already has
+		# a pre-built wall) is offered every tick, Decision picks it over lower-
+		# priority work like chop, and JobRunner cancels the doomed walk each
+		# tick — a busy-spin that starves all elective work. For pathing-blocking
+		# sites (walls) we check from an adjacent tile; for others, from the tile.
+		var probe_tile: Vector2i = site.tile
+		if site.has_method("blocks_pathing_when_complete") and site.blocks_pathing_when_complete():
+			probe_tile = _find_adjacent_walkable(site.tile, pawn.tile)
+			if probe_tile == site.tile:
+				continue  # no walkable neighbour at all → boxed-in site, skip silently
+		if pawn.tile != probe_tile and World.pathfinder.find_path(pawn.tile, probe_tile).is_empty():
+			continue
 		var d: int = abs(site.tile.x - pawn.tile.x) + abs(site.tile.y - pawn.tile.y)
 		if d < best_dist:
 			best_dist = d