diff --git a/DOCUMENTATION.md b/DOCUMENTATION.md
index bf43abd..c4ed46a 100644
--- a/DOCUMENTATION.md
+++ b/DOCUMENTATION.md
@@ -160,7 +160,7 @@ Handles the loading of plan data.
     *   **maxItems**: Optional limit on the number of plans to load.
     *   **logger**: Optional callback to receive real-time progress updates (e.g., dependency installation logs, download progress).
     *   **constraints**: Optional `PlanGenerationConstraints` to filter or orient plans.
-        *   **BoundingPolygon**: If set, only plans whose bounds are completely contained within this polygon are returned.
+        *   **BoundingPolygon**: If set, only plans whose geometry is completely contained within this polygon are returned. The check first validates the plan's Axis-Aligned Bounding Box (AABB) for performance, and if that fails, performs a precise geometry-by-geometry containment check to support rotated plans.
         *   **FrontDoorFacing**: If set, plans are rotated so their front door (vector from center to door) aligns with this vector.
         *   **GarageFacing**: Currently unsupported; will log a warning if set.
     *   **Returns**: A list of `Plan` objects.
diff --git a/ResPlan.Library/AssemblyInfo.cs b/ResPlan.Library/AssemblyInfo.cs
new file mode 100644
index 0000000..a4991f7
--- /dev/null
+++ b/ResPlan.Library/AssemblyInfo.cs
@@ -0,0 +1,3 @@
+using System.Runtime.CompilerServices;
+
+[assembly: InternalsVisibleTo("ResPlan.Tests")]
diff --git a/ResPlan.Library/PlanLoader.cs b/ResPlan.Library/PlanLoader.cs
index 6b281c0..6036012 100644
--- a/ResPlan.Library/PlanLoader.cs
+++ b/ResPlan.Library/PlanLoader.cs
@@ -175,17 +175,9 @@ private static List<Plan> ApplyConstraints(List<Plan> plans, PlanGenerationConst
                 }
 
                 // Apply Bounding Constraint
-                if (constraints.BoundingPolygon != null)
+                if (!IsPlanCompatible(plan, constraints.BoundingPolygon))
                 {
-                    // Check if plan bounds are within polygon
-                    // Since plan.Bounds is an Envelope, we convert to geometry
-                    var geometryFactory = new GeometryFactory();
-                    var planGeom = geometryFactory.ToGeometry(plan.Bounds);
-
-                    if (!constraints.BoundingPolygon.Contains(planGeom))
-                    {
-                        continue; // Filter out
-                    }
+                    continue;
                 }
 
                 result.Add(plan);
@@ -193,6 +185,41 @@ private static List<Plan> ApplyConstraints(List<Plan> plans, PlanGenerationConst
             return result;
         }
 
+        internal static bool IsPlanCompatible(Plan plan, Polygon boundingPolygon)
+        {
+            if (boundingPolygon == null) return true;
+
+            // Check if plan bounds are within polygon
+            // Since plan.Bounds is an Envelope, we convert to geometry
+            var geometryFactory = new GeometryFactory();
+            var planGeom = geometryFactory.ToGeometry(plan.Bounds);
+
+            // Fast check: if AABB is contained, we are good.
+            if (boundingPolygon.Contains(planGeom))
+            {
+                return true;
+            }
+
+            // Fallback: Precise check using actual geometries
+            // If the AABB doesn't fit (e.g. rotated plan), check if all individual geometries fit
+            bool allInside = true;
+            foreach (var kvp in plan.Geometries)
+            {
+                foreach (var geom in kvp.Value)
+                {
+                    // Use Covers instead of Contains to allow boundary contact
+                    if (!boundingPolygon.Covers(geom))
+                    {
+                        allInside = false;
+                        break;
+                    }
+                }
+                if (!allInside) break;
+            }
+
+            return allInside;
+        }
+
         private static Plan ConvertDataToPlan(ResPlanData data)
         {
             var plan = new Plan
diff --git a/ResPlan.Tests/ConstraintTests.cs b/ResPlan.Tests/ConstraintTests.cs
new file mode 100644
index 0000000..72abd53
--- /dev/null
+++ b/ResPlan.Tests/ConstraintTests.cs
@@ -0,0 +1,64 @@
+using System.Collections.Generic;
+using NetTopologySuite.Geometries;
+using ResPlan.Library;
+using Xunit;
+
+namespace ResPlan.Tests
+{
+    public class ConstraintTests
+    {
+        [Fact]
+        public void IsPlanCompatible_RotatedPlanInRotatedLot_ReturnsTrue()
+        {
+            // Arrange
+            var geometryFactory = new GeometryFactory();
+
+            // Create a Plan with a 10x10 square at (0,0)
+            // Centered at 5,5
+            var coords = new Coordinate[]
+            {
+                new Coordinate(0, 0),
+                new Coordinate(10, 0),
+                new Coordinate(10, 10),
+                new Coordinate(0, 10),
+                new Coordinate(0, 0)
+            };
+            var shell = geometryFactory.CreateLinearRing(coords);
+            var poly = geometryFactory.CreatePolygon(shell);
+
+            var plan = new Plan
+            {
+                Id = 1,
+                Geometries = new Dictionary<string, List<Geometry>>
+                {
+                    { "room", new List<Geometry> { poly } }
+                }
+            };
+            // Initial bounds (0,0) to (10,10)
+            plan.Bounds = new Envelope(0, 10, 0, 10);
+
+            // Rotate the plan by 45 degrees around its center (5,5)
+            plan.Rotate(System.Math.PI / 4.0, new Coordinate(5, 5));
+
+            // Now create a bounding polygon that matches the rotated plan geometry exactly
+            // We can cheat by using the plan's geometry itself (the rotated poly)
+            // But to be rigorous, let's use the rotated poly from the plan
+            var rotatedGeom = plan.Geometries["room"][0];
+            Assert.True(rotatedGeom is Polygon);
+            var boundingPolygon = (Polygon)rotatedGeom.Copy();
+
+            // The bounding polygon now matches the plan's geometry.
+            // However, plan.Bounds (AABB) will be larger than the rotated geometry.
+            // AABB of a 45-degree rotated 10x10 square is roughly 14.14x14.14.
+            // This AABB will NOT be contained in the 10x10 rotated square (which is the boundingPolygon).
+
+            // Act
+            bool isCompatible = PlanLoader.IsPlanCompatible(plan, boundingPolygon);
+
+            // Assert
+            // This should be true if we are checking geometry containment correctly.
+            // It will be false if we are only checking AABB containment.
+            Assert.True(isCompatible, "Plan should be compatible with a bounding polygon that exactly matches its geometry.");
+        }
+    }
+}