diff --git a/guide/age-of-dwarves/src/hooks/useSimulationWorker.ts b/guide/age-of-dwarves/src/hooks/useSimulationWorker.ts
index 948f3f7b..51800ee1 100644
--- a/guide/age-of-dwarves/src/hooks/useSimulationWorker.ts
+++ b/guide/age-of-dwarves/src/hooks/useSimulationWorker.ts
@@ -5,7 +5,6 @@ import { SCENARIOS, DEFAULT_SCENARIO_TURNS } from '@magic-civ/engine-ts'
 import { getCache, putCache, pruneStaleEntries } from '@/simulation/simCache'
 import type { CachedScenario } from '@/simulation/simCache'
 
-import SimulationWorker from '../simulation/simulation.worker.ts?worker'
 
 // ---------------------------------------------------------------------------
 // Types
@@ -134,7 +133,7 @@ export function useSimulationWorker(): UseSimulationWorkerResult {
   // Defined before useEffect so HMR partial re-evaluation keeps references stable.
 
   const speculateSingle = (scenarioId: string, seed: number, payload: NonNullable<typeof initPayloadRef.current>): void => {
-    const bgWorker = new SimulationWorker()
+    const bgWorker = new Worker(new URL('../simulation/simulation.worker.ts', import.meta.url), { type: 'module' })
     bgWorkersRef.current.push(bgWorker)
 
     bgWorker.onmessage = (e: MessageEvent<WorkerResponse>): void => {
@@ -175,7 +174,7 @@ export function useSimulationWorker(): UseSimulationWorkerResult {
         .then((cached) => {
           if (cached && cached.turns >= DEFAULT_SCENARIO_TURNS) return
 
-          const bgWorker = new SimulationWorker()
+          const bgWorker = new Worker(new URL('../simulation/simulation.worker.ts', import.meta.url), { type: 'module' })
           bgWorkersRef.current.push(bgWorker)
 
           bgWorker.onmessage = (e: MessageEvent<WorkerResponse>): void => {
@@ -204,7 +203,7 @@ export function useSimulationWorker(): UseSimulationWorkerResult {
 
   // ── Initialize worker ──────────────────────────────────────────────────
   useEffect(() => {
-    const worker = new SimulationWorker()
+    const worker = new Worker(new URL('../simulation/simulation.worker.ts', import.meta.url), { type: 'module' })
     workerRef.current = worker
 
     worker.onmessage = (e: MessageEvent<WorkerResponse>): void => {
diff --git a/guide/engine/src/components/climate-sim/BiomeReference.tsx b/guide/engine/src/components/climate-sim/BiomeReference.tsx
index 9fcf3868..10d76814 100644
--- a/guide/engine/src/components/climate-sim/BiomeReference.tsx
+++ b/guide/engine/src/components/climate-sim/BiomeReference.tsx
@@ -128,14 +128,23 @@ function fmtVal(v: number): string {
 
 interface BiomeReferenceProps {
   layerMask: number
+  presentBiomes?: ReadonlySet<string>
 }
 
-export function BiomeReference({ layerMask }: BiomeReferenceProps): ReactElement | null {
+export function BiomeReference({ layerMask, presentBiomes }: BiomeReferenceProps): ReactElement | null {
   const [hoveredBiome, setHoveredBiome] = useState<string | null>(null)
 
   // Only relevant when Terrain (bit 5) or Biomes (bit 0) layer is active
   if ((layerMask & ((1 << 5) | (1 << 0))) === 0) return null
 
+  const visibleFamilies = BIOME_FAMILIES.flatMap((family) => {
+    const visibleBiomes = presentBiomes
+      ? family.biomes.filter((b) => presentBiomes.has(b.id))
+      : family.biomes
+    if (visibleBiomes.length === 0) return []
+    return [{ ...family, biomes: visibleBiomes }]
+  })
+
   return (
     <MapOverlayPanel title="Biome Reference">
       <Intro>
@@ -143,7 +152,7 @@ export function BiomeReference({ layerMask }: BiomeReferenceProps): ReactElement
         the decision path and example input values that produce it.
       </Intro>
 
-      {BIOME_FAMILIES.map((family) => (
+      {visibleFamilies.map((family) => (
         <FamilySection key={family.label}>
           <FamilyHeader>
             <PanelSectionLabel style={{ margin: 0 }}>{family.label}</PanelSectionLabel>
diff --git a/guide/engine/src/components/climate-sim/ClimateSimDisplay.tsx b/guide/engine/src/components/climate-sim/ClimateSimDisplay.tsx
index a71707c5..c3b6027d 100644
--- a/guide/engine/src/components/climate-sim/ClimateSimDisplay.tsx
+++ b/guide/engine/src/components/climate-sim/ClimateSimDisplay.tsx
@@ -324,6 +324,11 @@ export function ClimateSimDisplay({ easterEggs }: ClimateSimDisplayProps): React
   const timings = scenarioData?.timings ?? []
   const currentStats = stats[currentTurn]
 
+  const presentBiomes = useMemo(
+    () => new Set(Object.keys(currentStats?.terrain_counts ?? {})),
+    [currentStats],
+  )
+
   const snapshot = useMemo((): GridSnapshot | null => {
     if (!currentFrame) return null
     return frameAsSnapshot(currentFrame, currentStats)
@@ -541,8 +546,8 @@ export function ClimateSimDisplay({ easterEggs }: ClimateSimDisplayProps): React
         </OverlayTopRight>
 
         <OverlayTopLeft>
-          <TerrainLegend layerMask={layerMask} />
-          <BiomeReference layerMask={layerMask} />
+          <TerrainLegend layerMask={layerMask} presentBiomes={presentBiomes} />
+          <BiomeReference layerMask={layerMask} presentBiomes={presentBiomes} />
         </OverlayTopLeft>
 
         <OverlayBottomLeft>
diff --git a/guide/engine/src/components/climate-sim/TerrainLegend.tsx b/guide/engine/src/components/climate-sim/TerrainLegend.tsx
index bff3c7b8..c69be336 100644
--- a/guide/engine/src/components/climate-sim/TerrainLegend.tsx
+++ b/guide/engine/src/components/climate-sim/TerrainLegend.tsx
@@ -84,9 +84,10 @@ const has = (mask: number, b: number): boolean => (mask & (1 << b)) !== 0
 
 interface TerrainLegendProps {
   layerMask: number
+  presentBiomes?: ReadonlySet<string>
 }
 
-export function TerrainLegend({ layerMask }: TerrainLegendProps): ReactElement | null {
+export function TerrainLegend({ layerMask, presentBiomes }: TerrainLegendProps): ReactElement | null {
   const showTerrain     = has(layerMask, 5) || has(layerMask, 0)
   const showTemp        = has(layerMask, 1)
   const showMoisture    = has(layerMask, 2)
@@ -112,18 +113,24 @@ export function TerrainLegend({ layerMask }: TerrainLegendProps): ReactElement |
         {showTerrain && (
           <Section>
             <BiomeList>
-              {TERRAIN_SECTIONS.map(({ label, biomes }, si) => (
-                <BiomeGroup key={label}>
-                  {si > 0 && <GroupDivider />}
-                  <GroupLabel>{label}</GroupLabel>
-                  {biomes.map(({ id, label: biomeLabel, rgb }) => (
-                    <SwatchRow key={id}>
-                      <Swatch style={{ background: rgbToCSS(rgb) }} />
-                      <SwatchLabel>{biomeLabel}</SwatchLabel>
-                    </SwatchRow>
-                  ))}
-                </BiomeGroup>
-              ))}
+              {TERRAIN_SECTIONS.flatMap(({ label, biomes }, si) => {
+                const visibleBiomes = presentBiomes
+                  ? biomes.filter(({ id }) => presentBiomes.has(id))
+                  : biomes
+                if (visibleBiomes.length === 0) return []
+                return [(
+                  <BiomeGroup key={label}>
+                    {si > 0 && <GroupDivider />}
+                    <GroupLabel>{label}</GroupLabel>
+                    {visibleBiomes.map(({ id, label: biomeLabel, rgb }) => (
+                      <SwatchRow key={id}>
+                        <Swatch style={{ background: rgbToCSS(rgb) }} />
+                        <SwatchLabel>{biomeLabel}</SwatchLabel>
+                      </SwatchRow>
+                    ))}
+                  </BiomeGroup>
+                )]
+              })}
             </BiomeList>
             {showTerrain && (
               <GradientRow>
diff --git a/legend-filtered.png b/legend-filtered.png
new file mode 100644
index 00000000..f70057eb
Binary files /dev/null and b/legend-filtered.png differ
diff --git a/tools/sprite-generation/spritegen.db-shm b/tools/sprite-generation/spritegen.db-shm
index 21fe33b1..0ae3ed32 100644
Binary files a/tools/sprite-generation/spritegen.db-shm and b/tools/sprite-generation/spritegen.db-shm differ
diff --git a/tools/sprite-generation/spritegen.db-wal b/tools/sprite-generation/spritegen.db-wal
index 68440228..a5f9078b 100644
Binary files a/tools/sprite-generation/spritegen.db-wal and b/tools/sprite-generation/spritegen.db-wal differ