diff --git a/CHANGELOG.md b/CHANGELOG.md
index b6cfda5301..e9e7cd2363 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -36,6 +36,7 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 - `tidy3d.plugins.design.DesignSpace.run(..., fn_post=...)` now accepts a `priority` keyword to propagate vGPU queue priority to all automatically batched simulations.
 - Introduced `BroadbandPulse` for exciting simulations across a wide frequency spectrum.
 - Added `interp_spec` in `ModeSpec` to allow downsampling and interpolation of waveguide modes in frequency.
+- Added warning if port mesh refinement is incompatible with the `GridSpec` in the `TerminalComponentModeler`.
 
 ### Breaking Changes
 - Edge singularity correction at PEC and lossy metal edges defaults to `True`.
diff --git a/tests/test_plugins/smatrix/terminal_component_modeler_def.py b/tests/test_plugins/smatrix/terminal_component_modeler_def.py
index 8e500875be..806e667e5a 100644
--- a/tests/test_plugins/smatrix/terminal_component_modeler_def.py
+++ b/tests/test_plugins/smatrix/terminal_component_modeler_def.py
@@ -267,8 +267,10 @@ def make_coaxial_component_modeler(
     def make_port(center, direction, type, name) -> Union[CoaxialLumpedPort, WavePort]:
         if type is CoaxialLumpedPort:
             port_cells = None
+            enable_snapping_points = False
             if port_refinement:
                 port_cells = 21
+                enable_snapping_points = True
             port = CoaxialLumpedPort(
                 center=center,
                 outer_diameter=2 * Router,
@@ -278,6 +280,7 @@ def make_port(center, direction, type, name) -> Union[CoaxialLumpedPort, WavePor
                 name="coax" + name,
                 num_grid_cells=port_cells,
                 impedance=reference_impedance,
+                enable_snapping_points=enable_snapping_points,
             )
         else:
             mean_radius = (Router + Rinner) / 2
diff --git a/tests/test_plugins/smatrix/test_component_modeler_autograd.py b/tests/test_plugins/smatrix/test_component_modeler_autograd.py
index faeb0acda1..f7b476c891 100644
--- a/tests/test_plugins/smatrix/test_component_modeler_autograd.py
+++ b/tests/test_plugins/smatrix/test_component_modeler_autograd.py
@@ -197,6 +197,8 @@ def build_terminal_modeler(scale: float) -> TerminalComponentModeler:
         voltage_axis=1,
         name="lp1",
         impedance=50.0,
+        num_grid_cells=None,
+        enable_snapping_points=False,
     )
     p2 = RectLumpedPort(
         center=(0.0, 0.0, 1.5),
@@ -204,6 +206,8 @@ def build_terminal_modeler(scale: float) -> TerminalComponentModeler:
         voltage_axis=1,
         name="lp2",
         impedance=50.0,
+        num_grid_cells=None,
+        enable_snapping_points=False,
     )
 
     freqs = [2.0e14]
diff --git a/tests/test_plugins/smatrix/test_terminal_component_modeler.py b/tests/test_plugins/smatrix/test_terminal_component_modeler.py
index 898dcdd9fc..4bb4649cee 100644
--- a/tests/test_plugins/smatrix/test_terminal_component_modeler.py
+++ b/tests/test_plugins/smatrix/test_terminal_component_modeler.py
@@ -29,7 +29,7 @@
 from tidy3d.plugins.smatrix.ports.base_lumped import AbstractLumpedPort
 from tidy3d.plugins.smatrix.utils import s_to_z, validate_square_matrix
 
-from ...utils import run_emulated
+from ...utils import AssertLogLevel, run_emulated
 from .terminal_component_modeler_def import (
     make_basic_filter_terminals,
     make_coaxial_component_modeler,
@@ -521,14 +521,16 @@ def test_ab_to_s_component_modeler():
     assert np.isclose(S_matrix, b_matrix).all()
 
 
-def test_port_snapping(tmp_path):
+def test_port_snapping():
     """Make sure that the snapping behavior of the load resistor is mirrored
     by all other components in the modeler simulations with rectangular ports.
     """
     y_z_grid = td.UniformGrid(dl=0.1 * 1e3)
     x_grid = td.UniformGrid(dl=11 * 1e3)
     grid_spec = td.GridSpec(grid_x=x_grid, grid_y=y_z_grid, grid_z=y_z_grid)
-    modeler = make_component_modeler(planar_pec=True, port_refinement=False, grid_spec=grid_spec)
+    modeler = make_component_modeler(
+        planar_pec=True, port_refinement=False, port_snapping=False, grid_spec=grid_spec
+    )
     check_lumped_port_components_snapped_correctly(modeler=modeler)
 
 
@@ -548,7 +550,7 @@ def test_coaxial_port_source_size(axis):
     assert np.isclose(source.size[axis], 0)
 
 
-def test_coarse_grid_at_port(monkeypatch, tmp_path):
+def test_coarse_grid_at_port(monkeypatch):
     modeler = make_component_modeler(planar_pec=True, port_refinement=False, port_snapping=False)
     # Without port refinement the grid is much too coarse for these port sizes
     with pytest.raises(SetupError):
@@ -823,8 +825,7 @@ def test_make_coaxial_component_modeler_with_wave_ports(tmp_path):
     xy_grid = td.UniformGrid(dl=0.1 * 1e3)
     grid_spec = td.GridSpec(grid_x=xy_grid, grid_y=xy_grid, grid_z=z_grid)
     _ = make_coaxial_component_modeler(
-        port_types=(WavePort, WavePort),
-        grid_spec=grid_spec,
+        port_types=(WavePort, WavePort), grid_spec=grid_spec, port_refinement=False
     )
 
 
@@ -844,6 +845,7 @@ def test_run_coaxial_component_modeler_with_wave_ports(
                 grid_spec=grid_spec,
                 use_voltage=voltage_enabled,
                 use_current=current_enabled,
+                port_refinement=False,
             )
         return
 
@@ -852,6 +854,7 @@ def test_run_coaxial_component_modeler_with_wave_ports(
         grid_spec=grid_spec,
         use_voltage=voltage_enabled,
         use_current=current_enabled,
+        port_refinement=False,
     )
     s_matrix = get_terminal_port_data_array(monkeypatch, modeler)
 
@@ -895,7 +898,9 @@ def test_run_mixed_component_modeler_with_wave_ports(monkeypatch, tmp_path):
     xy_grid = td.UniformGrid(dl=0.1 * 1e3)
     grid_spec = td.GridSpec(grid_x=xy_grid, grid_y=xy_grid, grid_z=z_grid)
     modeler = make_coaxial_component_modeler(
-        port_types=(CoaxialLumpedPort, WavePort), grid_spec=grid_spec
+        port_types=(CoaxialLumpedPort, WavePort),
+        grid_spec=grid_spec,
+        port_refinement=False,
     )
     s_matrix = get_terminal_port_data_array(monkeypatch, modeler)
 
@@ -1363,7 +1368,9 @@ def test_run_only_and_element_mappings(monkeypatch, tmp_path):
     xy_grid = td.UniformGrid(dl=0.1 * 1e3)
     grid_spec = td.GridSpec(grid_x=xy_grid, grid_y=xy_grid, grid_z=z_grid)
     modeler = make_coaxial_component_modeler(
-        port_types=(CoaxialLumpedPort, CoaxialLumpedPort), grid_spec=grid_spec
+        port_types=(CoaxialLumpedPort, CoaxialLumpedPort),
+        grid_spec=grid_spec,
+        port_refinement=False,
     )
     port0_idx = modeler.network_index(modeler.ports[0])
     port1_idx = modeler.network_index(modeler.ports[1])
@@ -1677,7 +1684,11 @@ def test_S_parameter_deembedding(monkeypatch, tmp_path):
     z_grid = td.UniformGrid(dl=1 * 1e3)
     xy_grid = td.UniformGrid(dl=0.1 * 1e3)
     grid_spec = td.GridSpec(grid_x=xy_grid, grid_y=xy_grid, grid_z=z_grid)
-    modeler = make_coaxial_component_modeler(port_types=(WavePort, WavePort), grid_spec=grid_spec)
+    modeler = make_coaxial_component_modeler(
+        port_types=(WavePort, WavePort),
+        grid_spec=grid_spec,
+        port_refinement=False,
+    )
 
     # Make sure the smatrix and impedance calculations work for reduced simulations
     modeler_data = run_component_modeler(monkeypatch, modeler)
@@ -1977,7 +1988,11 @@ def test_validate_run_only_with_wave_ports():
     z_grid = td.UniformGrid(dl=1 * 1e3)
     xy_grid = td.UniformGrid(dl=0.1 * 1e3)
     grid_spec = td.GridSpec(grid_x=xy_grid, grid_y=xy_grid, grid_z=z_grid)
-    modeler = make_coaxial_component_modeler(port_types=(WavePort, WavePort), grid_spec=grid_spec)
+    modeler = make_coaxial_component_modeler(
+        port_types=(WavePort, WavePort),
+        grid_spec=grid_spec,
+        port_refinement=False,
+    )
 
     port0_idx = modeler.network_index(modeler.ports[0], 0)
     port1_idx = modeler.network_index(modeler.ports[1], 0)
@@ -2212,6 +2227,7 @@ def test_wave_port_mode_index_with_modeler():
         mode_spec=mode_spec,
         direction="+",
         mode_selection=(0, 2),  # Only modes 0 and 2
+        num_grid_cells=None,
     )
 
     # Verify the port has only the selected modes
@@ -2232,6 +2248,8 @@ def test_wave_port_mode_index_with_modeler():
         size=(1, 1, 0),
         voltage_axis=0,  # x-direction since port is in x-y plane
         name="lumped_port",
+        num_grid_cells=None,
+        enable_snapping_points=False,
     )
 
     modeler = TerminalComponentModeler(
@@ -2306,3 +2324,12 @@ def test_get_task_name():
     # Test with wave port (no mode_index) - should work
     task_name = TerminalComponentModeler.get_task_name(port=wave_port)
     assert task_name == "wave@1"
+
+
+def test_validate_port_refinement_with_uniform_grid():
+    """Test that port refinement options raise error with uniform grid."""
+    uniform_grid = td.GridSpec.uniform(dl=0.5 * mm)
+    with AssertLogLevel("WARNING", contains_str="mesh refinement options enabled"):
+        make_coaxial_component_modeler(
+            port_types=(CoaxialLumpedPort, WavePort), grid_spec=uniform_grid
+        )
diff --git a/tidy3d/plugins/smatrix/component_modelers/terminal.py b/tidy3d/plugins/smatrix/component_modelers/terminal.py
index ccc2de5f22..f865286c4e 100644
--- a/tidy3d/plugins/smatrix/component_modelers/terminal.py
+++ b/tidy3d/plugins/smatrix/component_modelers/terminal.py
@@ -742,6 +742,31 @@ def _validate_3d_simulation(cls, val):
             )
         return val
 
+    @pd.validator("ports")
+    @skip_if_fields_missing(["simulation"])
+    def _validate_port_refinement_usage(cls, val, values):
+        """Warn if port refinement options are enabled, but the supplied simulation
+        does not contain a grid type that will make use of them."""
+
+        sim: Simulation = values.get("simulation")
+        # If grid spec is using AutoGrid
+        # then set up is acceptable
+        if sim.grid_spec.auto_grid_used:
+            return val
+
+        for port in val:
+            if port._is_using_mesh_refinement:
+                log.warning(
+                    f"A port with name '{port.name}' has mesh refinement options enabled, but the "
+                    "'Simulation' passed to the 'TerminalComponentModeler' was setup with a 'GridSpec' which "
+                    "does not support mesh refinement. For accurate simulations, please setup the "
+                    "'Simulation' to use an 'AutoGrid'. To suppress this warning, please explicitly disable "
+                    "mesh refinement options in the port, which are by default enabled. For example, set "
+                    "the 'enable_snapping_points=False' and 'num_grid_cells=None' for lumped ports."
+                )
+
+        return val
+
     @pd.validator("radiation_monitors")
     @skip_if_fields_missing(["freqs"])
     def _validate_radiation_monitors(cls, val, values):
diff --git a/tidy3d/plugins/smatrix/ports/base_lumped.py b/tidy3d/plugins/smatrix/ports/base_lumped.py
index 0e4516aa69..4582773128 100644
--- a/tidy3d/plugins/smatrix/ports/base_lumped.py
+++ b/tidy3d/plugins/smatrix/ports/base_lumped.py
@@ -94,3 +94,11 @@ def to_monitors(
     @abstractmethod
     def _check_grid_size(self, yee_grid: YeeGrid) -> None:
         """Raises :class:`SetupError` if the grid is too coarse at port locations."""
+
+    @property
+    def _is_using_mesh_refinement(self) -> bool:
+        """Check if this lumped port is using any mesh refinement options.
+
+        Returns ``True`` if snapping points are enabled or custom grid cell count is specified.
+        """
+        return self.enable_snapping_points or self.num_grid_cells is not None
diff --git a/tidy3d/plugins/smatrix/ports/wave.py b/tidy3d/plugins/smatrix/ports/wave.py
index aea67192bb..8b160c3bdc 100644
--- a/tidy3d/plugins/smatrix/ports/wave.py
+++ b/tidy3d/plugins/smatrix/ports/wave.py
@@ -365,3 +365,11 @@ def _validate_mode_index(cls, val, values):
                 f"'mode_spec.num_modes' ({num_modes}). Valid range is 0 to {num_modes - 1}."
             )
         return val
+
+    @property
+    def _is_using_mesh_refinement(self) -> bool:
+        """Check if this wave port is using mesh refinement options.
+
+        Returns ``True`` if a custom grid cell count is specified.
+        """
+        return self.num_grid_cells is not None