From 35b2427451814dcdc3dd8ca3addaba4181e75c5a Mon Sep 17 00:00:00 2001
From: Erik van Sebille <erikvansebille@gmail.com>
Date: Tue, 16 Jun 2026 09:27:28 +0200
Subject: [PATCH 1/2] Changing OUT_OF_BOUNDS error codes to be extremely large

In the previous implementation, the GRID_SEARCH_ERROR, LEFT_OUT_OF_BOUNDS and RIGHT_OUT_OF_BOUNDS were negative values, but this could create confusion when a user would then use particles.ei (as negative values are wrapped in the array). See also #2629
---
 src/parcels/_core/index_search.py | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/src/parcels/_core/index_search.py b/src/parcels/_core/index_search.py
index 5e84eee2e..6c75fa080 100644
--- a/src/parcels/_core/index_search.py
+++ b/src/parcels/_core/index_search.py
@@ -12,9 +12,9 @@
     from parcels._core.xgrid import XGrid
 
 
-GRID_SEARCH_ERROR = -3
-LEFT_OUT_OF_BOUNDS = -2
-RIGHT_OUT_OF_BOUNDS = -1
+GRID_SEARCH_ERROR = np.iinfo(np.int32).max - 3
+LEFT_OUT_OF_BOUNDS = np.iinfo(np.int32).max - 2
+RIGHT_OUT_OF_BOUNDS = np.iinfo(np.int32).max - 1
 
 
 def _search_1d_array(

From b49ee3473042d1f98732516864219b15ee7a964f Mon Sep 17 00:00:00 2001
From: Erik van Sebille <erikvansebille@gmail.com>
Date: Tue, 16 Jun 2026 09:37:45 +0200
Subject: [PATCH 2/2] Adding unit test for OutOfBounds field.eval

---
 tests/test_field.py | 16 ++++++++++++++++
 1 file changed, 16 insertions(+)

diff --git a/tests/test_field.py b/tests/test_field.py
index 5e57c43cb..587a39a57 100644
--- a/tests/test_field.py
+++ b/tests/test_field.py
@@ -5,6 +5,7 @@
 
 from parcels import Field, UxGrid, VectorField, XGrid
 from parcels._core.fieldset import FieldSet
+from parcels._datasets.structured.generated import simple_UV_dataset
 from parcels._datasets.structured.generic import T as T_structured
 from parcels._datasets.structured.generic import datasets as datasets_structured
 from parcels._datasets.unstructured.generic import datasets as datasets_unstructured
@@ -270,6 +271,21 @@ def test_field_constant_in_time():
     assert np.isclose(P1, P2)
 
 
+def test_field_eval_out_of_bounds():
+    """Test that Field.eval returns IndexError when queried outside the grid boundaries."""
+    ds = simple_UV_dataset(mesh="flat")
+    fieldset = FieldSet.from_sgrid_conventions(ds, mesh="flat")
+
+    with pytest.raises(IndexError, match=".* is out of bounds.*"):
+        fieldset.U.eval(0.0, 0.0, 0.0, 5e6)
+
+    with pytest.raises(IndexError, match=".* is out of bounds.*"):
+        fieldset.U.eval(0.0, 0.0, 5e6, 0.0)
+
+    with pytest.raises(IndexError, match=".* is out of bounds.*"):
+        fieldset.U.eval(0.0, 5e6, 0.0, 0.0)
+
+
 def test_field_unstructured_grid_creation(): ...