diff --git a/cognite/extractorutils/unstable/core/base.py b/cognite/extractorutils/unstable/core/base.py
index d01b1f3b..6e38b9c9 100644
--- a/cognite/extractorutils/unstable/core/base.py
+++ b/cognite/extractorutils/unstable/core/base.py
@@ -784,9 +784,9 @@ def _handle_custom_action(self, action: Action) -> None:
                         external_id=action.external_id,
                         status=completed_status,
                         result_message=truncate_message(
-                            f"Action '{custom.name}' {outcome}, but metadata field(s) "
-                            f"{', '.join(oversized_fields)} exceeded the {MAX_METADATA_VALUE_BYTES}-byte-per-value "
-                            f"limit and were dropped from the reported result"
+                            f"Action '{custom.name}' {outcome}, but {len(oversized_fields)} metadata field(s) "
+                            f"exceeded the {MAX_METADATA_VALUE_BYTES}-byte-per-value limit and were dropped from "
+                            f"the reported result: {', '.join(oversized_fields)}"
                         ),
                         result_metadata=filtered_metadata,
                     )
@@ -813,8 +813,10 @@ def _handle_custom_action(self, action: Action) -> None:
                         str(e)
                         if not oversized_fields
                         else truncate_message(
-                            f"{e} (additionally, metadata field(s) {', '.join(oversized_fields)} exceeded "
-                            f"the {MAX_METADATA_VALUE_BYTES}-byte-per-value limit and were dropped)"
+                            f"{len(oversized_fields)} metadata field(s) exceeded the "
+                            f"{MAX_METADATA_VALUE_BYTES}-byte-per-value limit and were dropped. "
+                            f"Action failed: {truncate_message(str(e), max_length=500)}. "
+                            f"Dropped fields: {', '.join(oversized_fields)}"
                         )
                     ),
                     result_metadata=filtered_metadata,
diff --git a/tests/test_unstable/test_action_dispatch.py b/tests/test_unstable/test_action_dispatch.py
index 1d29dddc..635f1e6a 100644
--- a/tests/test_unstable/test_action_dispatch.py
+++ b/tests/test_unstable/test_action_dispatch.py
@@ -407,6 +407,10 @@ def target(ctx: ActionContext) -> None:
     assert final.result_message is not None
     assert len(final.result_message) <= MAX_MESSAGE_LENGTH
     assert final.result_message.endswith("...")
+    # Regression: the explanation, including the count, must survive truncation even when the
+    # field-name list doesn't.
+    assert "45 metadata field(s) exceeded" in final.result_message
+    assert "dropped" in final.result_message
 
 
 def test_oversized_action_error_with_long_message_truncates_instead_of_crashing() -> None:
@@ -427,7 +431,13 @@ def target(ctx: ActionContext) -> None:
     assert failed.result_metadata == {"error_type": "invalid_parameter"}
     assert failed.result_message is not None
     assert len(failed.result_message) <= MAX_MESSAGE_LENGTH
-    assert failed.result_message.endswith("...")
+    # Regression: the metadata-dropped explanation must survive truncation even when the
+    # ActionError message itself is long enough to need truncating on its own.
+    assert "exceeded" in failed.result_message
+    assert "dropped" in failed.result_message
+    # Regression: str(e) is bounded before combining, so there's still room left for the
+    # dropped-field-name list even when the ActionError message alone is very long.
+    assert "error_detail" in failed.result_message
 
 
 def test_custom_action_receives_call_metadata_in_context() -> None: