Merge remote-tracking branch 'origin/main' into t1181-step-canvas

server/src/atlas/layer_proxy.rs

@@ -3830,6 +3830,20 @@ mod tests {
         assert_eq!(ta_pass1.water_dist, ta_pass2.water_dist);
         assert_eq!(ta_pass1.slope_deg, ta_pass2.slope_deg);
         assert_eq!(ta_pass1.elev_pct, ta_pass2.elev_pct);
+        // T-1184: two independent hydrology solves (each run_layer1 call
+        // solves fresh — no shared HydrologyResult) must also agree
+        // byte-for-byte, extending this test's own "weakest link in the
+        // determinism chain" rationale to the newest field on TerrainAnalysis.
+        let hydro1 = ta_pass1
+            .hydrology
+            .as_ref()
+            .expect("run_layer1 must populate hydrology");
+        let hydro2 = ta_pass2
+            .hydrology
+            .as_ref()
+            .expect("run_layer1 must populate hydrology");
+        assert_eq!(hydro1.elevation, hydro2.elevation);
+        assert_eq!(hydro1.filled, hydro2.filled);
 
         // Now the FULL path: pack a DistrictWindowLayer from each independent
         // TerrainAnalysis and confirm the complete served payload agrees.