diff --git a/native/lgj-abi/src/exports.rs b/native/lgj-abi/src/exports.rs
index 15558d5..f02e961 100644
--- a/native/lgj-abi/src/exports.rs
+++ b/native/lgj-abi/src/exports.rs
@@ -1756,7 +1756,12 @@ fn exec_error_to_status(e: ExecError) -> i32 {
         | ExecError::BlendNeedsOut
         | ExecError::TerminalNeedsOut { .. }
         | ExecError::GateAliasesDst { .. }
-        | ExecError::RangeOutOfBounds { .. } => LGJ_ERR_ALLOCATION_FAILED,
+        | ExecError::RangeOutOfBounds { .. }
+        // Raised only by `execute_extent` over a PARTIAL extent. Every call in
+        // this file executes the whole population, so reaching either would
+        // be a bug here, exactly like the arms above.
+        | ExecError::ExtentOutOfRange { .. }
+        | ExecError::ExtentUnsupported { .. } => LGJ_ERR_ALLOCATION_FAILED,
     }
 }
 
diff --git a/native/lgj-abi/src/exports/tests/group_sum.rs b/native/lgj-abi/src/exports/tests/group_sum.rs
index c322b37..51a21a3 100644
--- a/native/lgj-abi/src/exports/tests/group_sum.rs
+++ b/native/lgj-abi/src/exports/tests/group_sum.rs
@@ -256,7 +256,10 @@ fn the_tiled_executor_and_the_scalar_reference_agree_on_the_lowered_program() {
         for key in keys {
             let program =
                 plan_lower::lower_group_sum(&ops, n as u32, key, LANE_VALUES as u16).unwrap();
-            let tile = tile_words_for(n as usize);
+            // An explicit narrow tile, not `tile_words_for`: the default tile
+            // is a performance setting (256 words since lance-graph #1281) and
+            // must not decide whether this fixture spans several tiles.
+            let tile = (n.div_ceil(64) as usize).min(8);
             let need = scratch_words_for(tile, plan_lower::SLOTS as usize).unwrap();
             let mut buf = vec![0u64; need];
             let mut scratch = Scratch::over(&mut buf, tile, plan_lower::SLOTS as usize).unwrap();