diff --git a/model/sketch.py b/model/sketch.py
index c0b5a81a..1180f8ad 100644
--- a/model/sketch.py
+++ b/model/sketch.py
@@ -100,8 +100,8 @@ def is_visible(self, context):
     def get_solver_state(self):
         return bpyEnum(global_data.solver_state_items, identifier=self.solver_state)
 
-    def solve(self, context):
-        return solve_system(context, sketch=self)
+    def solve(self, context, report=True, update_entities=True):
+        return solve_system(context, sketch=self, report=report, update_entities=update_entities)
 
     @classmethod
     def is_sketch(cls):
diff --git a/operators/add_line_2d.py b/operators/add_line_2d.py
index eca58bee..5590e4d0 100644
--- a/operators/add_line_2d.py
+++ b/operators/add_line_2d.py
@@ -12,7 +12,7 @@
 from ..solver import solve_system
 from .base_2d import Operator2d
 from .constants import types_point_2d
-from .utilities import ignore_hover
+from .utilities import ignore_hover, safe_constraints
 
 logger = logging.getLogger(__name__)
 
@@ -54,16 +54,16 @@ def main(self, context: Context):
             self.target.construction = True
 
         # auto vertical/horizontal constraint
-        constraints = context.scene.sketcher.constraints
         vec_dir = self.target.direction_vec()
         if vec_dir.length:
             angle = vec_dir.angle(Vector((1, 0)))
-
             threshold = 0.1
-            if angle < threshold or angle > HALF_TURN - threshold:
-                constraints.add_horizontal(self.target, sketch=self.sketch)
-            elif (QUARTER_TURN - threshold) < angle < (QUARTER_TURN + threshold):
-                constraints.add_vertical(self.target, sketch=self.sketch)
+
+            with safe_constraints(context, sketch=self.sketch) as constraints:
+                if angle < threshold or angle > HALF_TURN - threshold:
+                    constraints.add_horizontal(self.target, sketch=self.sketch)
+                elif (QUARTER_TURN - threshold) < angle < (QUARTER_TURN + threshold):
+                    constraints.add_vertical(self.target, sketch=self.sketch)
 
         ignore_hover(self.target)
         return True
diff --git a/operators/utilities.py b/operators/utilities.py
index 495a219c..a3a4aa62 100644
--- a/operators/utilities.py
+++ b/operators/utilities.py
@@ -1,4 +1,5 @@
 import logging
+from contextlib import contextmanager
 
 import bpy
 from bpy.types import Context, Operator
@@ -7,6 +8,9 @@
 from .. import global_data
 from ..declarations import GizmoGroups, WorkSpaceTools
 from ..converters import update_convertor_geometry
+from ..model.base_constraint import GenericConstraint
+from ..model.group_constraints import SlvsConstraints
+from ..model.sketch import SlvsSketch
 from ..utilities.preferences import use_experimental, get_prefs
 from ..utilities.data_handling import entities_3d
 
@@ -201,3 +205,33 @@ def select_target_ob(context, sketch):
     if target_ob.name in context.view_layer.objects:
         target_ob.select_set(True)
         context.view_layer.objects.active = target_ob
+
+
+@contextmanager
+def safe_constraints(
+    context: Context,
+    sketch: SlvsSketch = None,
+    constraints: SlvsConstraints = None,
+    remove_only_failed=False,
+):
+    sketch = sketch or context.scene.sketcher.active_sketch
+    constraints = constraints or context.scene.sketcher.constraints
+
+    solvable = sketch.solver_state == "OKAY"
+    old: set[GenericConstraint] = set(constraints.all)
+
+    try:
+        yield constraints
+
+    finally:
+        if not solvable:
+            return
+
+        if not sketch.solve(context, update_entities=False):
+            new: set[GenericConstraint] = set(constraints.all) - old
+
+            for constraint in new:
+                if constraint.failed or not remove_only_failed:
+                    constraints.remove(constraint)
+
+            sketch.solve(context, update_entities=False)
diff --git a/solver.py b/solver.py
index f95645c6..09ee6580 100644
--- a/solver.py
+++ b/solver.py
@@ -192,7 +192,7 @@ def needs_update(self, e):
         # TODO: skip entities that aren't in active group
         return True
 
-    def solve(self, report=True):
+    def solve(self, report=True, update_entities=True):
         self.report = report
         self._init_slvs_data()
 
@@ -249,11 +249,12 @@ def _get_msg_failed():
                     logger.debug(_get_msg_failed())
 
         # Update entities from solver
-        for e in self.entities:
-            if not self.needs_update(e):
-                continue
+        if update_entities:
+            for e in self.entities:
+                if not self.needs_update(e):
+                    continue
 
-            e.update_from_slvs(self.solvesys)
+                e.update_from_slvs(self.solvesys)
 
         def _get_msg_update():
             msg = "Update entities from solver:"
@@ -269,6 +270,6 @@ def _get_msg_update():
         return self.ok
 
 
-def solve_system(context, sketch=None):
+def solve_system(context, sketch=None, report=True, update_entities=True):
     solver = Solver(context, sketch)
-    return solver.solve()
+    return solver.solve(report=report, update_entities=update_entities)