diff --git a/frontend/src/components/map/MapPage.tsx b/frontend/src/components/map/MapPage.tsx
index 2a014b3..ee9fd93 100644
--- a/frontend/src/components/map/MapPage.tsx
+++ b/frontend/src/components/map/MapPage.tsx
@@ -707,10 +707,7 @@ export default function MapPage({
   // link adds are blocked regardless of count, so don't auto-clear there — the user
   // dismisses it themselves. Prevents a stale flag from resurfacing spuriously.
   useEffect(() => {
-    if (
-      filtersUnlimited ||
-      (!lockFilterAdds && Object.keys(filters).length < effectiveFilterCap)
-    ) {
+    if (filtersUnlimited || (!lockFilterAdds && Object.keys(filters).length < effectiveFilterCap)) {
       setFilterLimitHit(false);
     }
   }, [filtersUnlimited, lockFilterAdds, effectiveFilterCap, filters]);
diff --git a/frontend/src/i18n/locales/en.ts b/frontend/src/i18n/locales/en.ts
index 8a27a76..a13b540 100644
--- a/frontend/src/i18n/locales/en.ts
+++ b/frontend/src/i18n/locales/en.ts
@@ -682,8 +682,7 @@ const en = {
     addFilter: 'Add filters',
     findingPerfectPostcode: 'Finding the Perfect Postcode',
     addFiltersHint: 'Add filters below to narrow the map to areas that match your criteria',
-    upgradePrompt:
-      'Go lifetime to stack unlimited filters across every postcode in England.',
+    upgradePrompt: 'Go lifetime to stack unlimited filters across every postcode in England.',
     oneTimeLifetime: 'One-time payment, lifetime access.',
     upgradeToFullMap: 'Upgrade to full map',
     registerPrompt:
diff --git a/frontend/src/i18n/locales/hi.ts b/frontend/src/i18n/locales/hi.ts
index 571014a..cbee11d 100644
--- a/frontend/src/i18n/locales/hi.ts
+++ b/frontend/src/i18n/locales/hi.ts
@@ -674,8 +674,7 @@ const hi: Translations = {
     addFilter: 'फ़िल्टर जोड़ें',
     findingPerfectPostcode: 'Perfect Postcode खोजा जा रहा है',
     addFiltersHint: 'अपनी शर्तों से मेल खाने वाले क्षेत्र पाने के लिए नीचे फ़िल्टर जोड़ें',
-    upgradePrompt:
-      'इंग्लैंड के हर पोस्टकोड में असीमित फ़िल्टर लगाने के लिए आजीवन पहुँच लें.',
+    upgradePrompt: 'इंग्लैंड के हर पोस्टकोड में असीमित फ़िल्टर लगाने के लिए आजीवन पहुँच लें.',
     oneTimeLifetime: 'एक बार भुगतान, आजीवन पहुँच.',
     upgradeToFullMap: 'पूरे मानचित्र पर अपग्रेड करें',
     registerPrompt:
diff --git a/frontend/src/i18n/locales/hu.ts b/frontend/src/i18n/locales/hu.ts
index 6bca033..ccc5abc 100644
--- a/frontend/src/i18n/locales/hu.ts
+++ b/frontend/src/i18n/locales/hu.ts
@@ -702,7 +702,8 @@ const hu: Translations = {
     upgradeToFullMap: 'Teljes térkép megnyitása',
     registerPrompt:
       'Hozz létre egy ingyenes fiókot, hogy akár 5 szűrőt kombinálhass, és menthess, megoszthass és exportálhass kereséseket.',
-    registerSubPrompt: 'Ingyenes – kártya nélkül. Korlátlan szűrők élethosszig tartó hozzáféréssel.',
+    registerSubPrompt:
+      'Ingyenes – kártya nélkül. Korlátlan szűrők élethosszig tartó hozzáféréssel.',
     registerCta: 'Ingyenes fiók létrehozása',
     chooseFilters:
       'Kattints a Hozzáadásra a szűréshez. A kis gombok adatokat mutatnak vagy színezik a térképet.',
diff --git a/frontend/src/lib/url-state.test.ts b/frontend/src/lib/url-state.test.ts
index c59ee96..3645bd1 100644
--- a/frontend/src/lib/url-state.test.ts
+++ b/frontend/src/lib/url-state.test.ts
@@ -2,6 +2,7 @@ import { beforeEach, describe, expect, it } from 'vitest';
 
 import type { FeatureMeta } from '../types';
 import { parseUrlState, stateToParams } from './url-state';
+import { DEFAULT_OVERLAY_IDS } from './overlays';
 import { INITIAL_VIEW_STATE } from './consts';
 import { createSchoolFilterKey } from './school-filter';
 import { createSpecificCrimeFilterKey } from './crime-filter';
@@ -199,10 +200,10 @@ describe('url-state', () => {
     expect(state.overlays).toEqual(new Set(['noise', 'crime-hotspots']));
   });
 
-  it('enables crime + trees overlays by default on a fresh visit', () => {
+  it('enables the default overlays on a fresh visit', () => {
     const state = parseUrlState();
 
-    expect(state.overlays).toEqual(new Set(['crime-hotspots', 'trees-outside-woodlands']));
+    expect(state.overlays).toEqual(new Set(DEFAULT_OVERLAY_IDS));
   });
 
   it('round-trips an explicit "all overlays off" via the __none sentinel', () => {
diff --git a/server-rs/src/data/crime_records.rs b/server-rs/src/data/crime_records.rs
index 8402ffb..3aa99d3 100644
--- a/server-rs/src/data/crime_records.rs
+++ b/server-rs/src/data/crime_records.rs
@@ -158,7 +158,10 @@ impl CrimeRecords {
             ParquetReader::new(file)
                 .get_metadata()
                 .with_context(|| {
-                    format!("Failed to read crime-records parquet metadata at {}", path.display())
+                    format!(
+                        "Failed to read crime-records parquet metadata at {}",
+                        path.display()
+                    )
                 })?
                 .clone()
         };
@@ -193,10 +196,18 @@ impl CrimeRecords {
         // the column builders' write order.
         let mut global_row: u32 = 0;
 
-        let columns: Vec<String> = ["postcode", "month_index", "crime_type", "location", "outcome", "lat", "lon"]
-            .iter()
-            .map(|s| s.to_string())
-            .collect();
+        let columns: Vec<String> = [
+            "postcode",
+            "month_index",
+            "crime_type",
+            "location",
+            "outcome",
+            "lat",
+            "lon",
+        ]
+        .iter()
+        .map(|s| s.to_string())
+        .collect();
 
         let mut offset = 0usize;
         while offset < n {
@@ -337,7 +348,10 @@ impl CrimeRecords {
         if let Some(prev) = cur_pc.take() {
             by_postcode.insert(prev, (cur_start, global_row - cur_start));
         }
-        debug_assert_eq!(global_row as usize, n, "streamed fewer rows than the parquet declares");
+        debug_assert_eq!(
+            global_row as usize, n,
+            "streamed fewer rows than the parquet declares"
+        );
 
         let records = Self {
             month: month.finish()?,
@@ -413,7 +427,7 @@ mod tests {
             .unwrap();
         assert_eq!(robbery.outcome, Some("Court result"));
         assert_eq!(robbery.location, None); // null location → None
-        // Two records have a null outcome (an AA1 Burglary and the BB2 Drugs).
+                                            // Two records have a null outcome (an AA1 Burglary and the BB2 Drugs).
         let null_outcomes = all
             .iter()
             .map(|&i| recs.view(i))
@@ -518,7 +532,10 @@ mod tests {
             rss_after,
         );
 
-        assert!(!recs.by_postcode.is_empty(), "expected at least one postcode");
+        assert!(
+            !recs.by_postcode.is_empty(),
+            "expected at least one postcode"
+        );
         assert!(total > 0, "expected at least one record");
         // The old `.collect()` decoded all rows' string columns at once (tens of
         // GB). Streaming must keep the peak growth far below that; a generous 20GiB
diff --git a/server-rs/src/data/postcode_population.rs b/server-rs/src/data/postcode_population.rs
index 928e4cf..1913b3f 100644
--- a/server-rs/src/data/postcode_population.rs
+++ b/server-rs/src/data/postcode_population.rs
@@ -82,10 +82,7 @@ impl PostcodePopulation {
             bail!("population parquet at {} produced no rows", path.display());
         }
 
-        info!(
-            postcodes = by_postcode.len(),
-            "Postcode population loaded"
-        );
+        info!(postcodes = by_postcode.len(), "Postcode population loaded");
         Ok(Self { by_postcode })
     }
 
diff --git a/server-rs/src/data/spill.rs b/server-rs/src/data/spill.rs
index 5468d31..a655cda 100644
--- a/server-rs/src/data/spill.rs
+++ b/server-rs/src/data/spill.rs
@@ -152,7 +152,10 @@ pub struct SpillVecBuilder<T: SpillElem> {
 }
 
 enum Builder<T: SpillElem> {
-    Owned { values: Vec<T>, len: usize },
+    Owned {
+        values: Vec<T>,
+        len: usize,
+    },
     Mapped {
         map: MmapMut,
         len: usize,
@@ -462,7 +465,9 @@ mod tests {
 
     #[test]
     fn builder_streams_identically_owned_and_mapped() {
-        let values: Vec<u32> = (0..50_000u32).map(|n| n.wrapping_mul(2_246_822_519)).collect();
+        let values: Vec<u32> = (0..50_000u32)
+            .map(|n| n.wrapping_mul(2_246_822_519))
+            .collect();
 
         // Owned path (no spill dir): pushes accumulate into a heap Vec.
         let mut owned = SpillVecBuilder::<u32>::with_len(values.len(), None, "u32_owned").unwrap();
@@ -497,7 +502,8 @@ mod tests {
 
         let dir = TempDir::new("builder-spur");
         let mut builder =
-            SpillVecBuilder::<lasso::Spur>::with_len(keys.len(), Some(dir.path()), "spurs").unwrap();
+            SpillVecBuilder::<lasso::Spur>::with_len(keys.len(), Some(dir.path()), "spurs")
+                .unwrap();
         for &k in &keys {
             builder.push(k);
         }
@@ -536,7 +542,8 @@ mod tests {
     #[should_panic(expected = "overflow")]
     fn builder_overfill_panics() {
         let dir = TempDir::new("builder-overfill");
-        let mut builder = SpillVecBuilder::<u32>::with_len(2, Some(dir.path()), "overfill").unwrap();
+        let mut builder =
+            SpillVecBuilder::<u32>::with_len(2, Some(dir.path()), "overfill").unwrap();
         builder.push(1);
         builder.push(2);
         builder.push(3); // one past the declared length
diff --git a/server-rs/src/routes/crime_records.rs b/server-rs/src/routes/crime_records.rs
index fd95cf7..3d698f3 100644
--- a/server-rs/src/routes/crime_records.rs
+++ b/server-rs/src/routes/crime_records.rs
@@ -99,7 +99,11 @@ pub async fn get_crime_records(
             .postcode_to_idx
             .get(&normalized)
             .ok_or_else(|| {
-                (StatusCode::NOT_FOUND, format!("Postcode not found: {normalized}")).into_response()
+                (
+                    StatusCode::NOT_FOUND,
+                    format!("Postcode not found: {normalized}"),
+                )
+                    .into_response()
             })?;
         Selection::Postcode(normalized)
     } else {
@@ -120,12 +124,9 @@ pub async fn get_crime_records(
                 let mut h3_cache: FxHashMap<u64, u64> = FxHashMap::default();
                 let mut seen: FxHashSet<&str> = FxHashSet::default();
                 let mut out: Vec<String> = Vec::new();
-                state.grid.for_each_in_bounds(
-                    min_lat,
-                    min_lon,
-                    max_lat,
-                    max_lon,
-                    |row_idx| {
+                state
+                    .grid
+                    .for_each_in_bounds(min_lat, min_lon, max_lat, max_lon, |row_idx| {
                         let row = row_idx as usize;
                         if cell_for_row_cached(
                             row,
@@ -140,8 +141,7 @@ pub async fn get_crime_records(
                                 out.push(pc.to_string());
                             }
                         }
-                    },
-                );
+                    });
                 out
             }
         };
@@ -177,6 +177,10 @@ pub async fn get_crime_records(
     .map_err(|error| (StatusCode::INTERNAL_SERVER_ERROR, error.to_string()).into_response())?
     .map_err(|error| (StatusCode::INTERNAL_SERVER_ERROR, error).into_response())?;
 
-    info!(total = result.total, returned = result.records.len(), "GET /api/crime-records");
+    info!(
+        total = result.total,
+        returned = result.records.len(),
+        "GET /api/crime-records"
+    );
     Ok(Json(result))
 }
diff --git a/server-rs/src/routes/stats.rs b/server-rs/src/routes/stats.rs
index bf1d4cf..d1a210a 100644
--- a/server-rs/src/routes/stats.rs
+++ b/server-rs/src/routes/stats.rs
@@ -11,8 +11,8 @@ use crate::data::{FeatureStats, PostcodePoiMetrics, PropertyData};
 use crate::utils::{postcode_outcode, postcode_sector};
 
 use super::hexagon_stats::{
-    CrimeAreaAverage, CrimeYearPoint, CrimeYearStats, EnumFeatureStats,
-    HistogramStats, NumericFeatureStats, PricePoint,
+    CrimeAreaAverage, CrimeYearPoint, CrimeYearStats, EnumFeatureStats, HistogramStats,
+    NumericFeatureStats, PricePoint,
 };
 
 /// Extract price history (year, price) pairs from matching rows, downsampled if needed.
@@ -398,7 +398,6 @@ pub fn compute_crime_by_year(
     out
 }
 
-
 /// Latest year present anywhere in the by-year crime dataset. The client
 /// compares each selection's last charted year against this to caption
 /// force-level publication gaps (e.g. Greater Manchester ends mid-2019) as
@@ -615,18 +614,12 @@ mod tests {
         assert_eq!(sector.as_deref(), Some("E14 2"));
         assert_eq!(out.len(), 2);
 
-        let burglary = out
-            .iter()
-            .find(|c| c.name == "Burglary (/yr, 7y)")
-            .unwrap();
+        let burglary = out.iter().find(|c| c.name == "Burglary (/yr, 7y)").unwrap();
         assert_eq!(burglary.national, Some(8.0));
         assert_eq!(burglary.outcode, Some(10.0));
         assert_eq!(burglary.sector, Some(5.0));
 
-        let robbery = out
-            .iter()
-            .find(|c| c.name == "Robbery (/yr, 7y)")
-            .unwrap();
+        let robbery = out.iter().find(|c| c.name == "Robbery (/yr, 7y)").unwrap();
         assert_eq!(robbery.national, Some(6.0));
         // The outcode value was NaN — dropped to None; the sector value is finite.
         assert_eq!(robbery.outcode, None);
@@ -637,9 +630,7 @@ mod tests {
     fn area_crime_averages_respect_fields_filter() {
         let avgs = sample_averages();
         // Area averages are keyed by the full crime-feature name.
-        let fields: HashSet<String> = ["Burglary (/yr, 7y)".to_string()]
-            .into_iter()
-            .collect();
+        let fields: HashSet<String> = ["Burglary (/yr, 7y)".to_string()].into_iter().collect();
         let (_, _, out) = area_crime_averages_for(Some("E14 2DG"), &avgs, true, &fields);
         assert_eq!(out.len(), 1);
         assert_eq!(out[0].name, "Burglary (/yr, 7y)");