@@ -256,6 +256,24 @@ private static List<StarType> defaultStarTypes() {
      * The stock galaxy table. Weights are the real abundance ordering — dwarfs outnumber giants by two
      * orders — so a spiral is something a player FINDS rather than the default sky.
      */
+    /**
+     * The stock SPIRAL archetype — the type every partially-specified {@code <galaxyType>} inherits
+     * its unwritten attributes from.
+     *
+     * <p>It exists so those defaults are not a second copy of the numbers below. They were, and the
+     * copy went stale the moment the galaxy scale moved: a pack writing
+     * {@code <galaxyType thickness="0.05"/>} got a "spiral" 900&ndash;2 200 ly across, an order and a
+     * half under every real one, silently and only in the authored path.</p>
+     */
+    public static GalaxyType stockSpiral() {
+        for (GalaxyType t : defaultGalaxyTypes()) {
+            if ("Spiral".equals(t.name)) {
+                return t;
+            }
+        }
+        throw new IllegalStateException("the stock galaxy table must contain a Spiral");
+    }
+
     private static List<GalaxyType> defaultGalaxyTypes() {
         // The bands are REAL radii, read off a catalogue and stated in light years so they can be
         // checked against one — never a multiple of UniverseScale.REFERENCE_GALAXY_RADIUS_LY. They
 
@@ -329,12 +329,16 @@ private GalaxyGenConfig readGalaxyGen(Node node) {
      * Parse one {@code <galaxyType>} element into a galaxy archetype.
      *
      * <pre>{@code
-     * <galaxyType name="Spiral" profile="DISC" minRadius="900" maxRadius="2200"
+     * <galaxyType name="Spiral" profile="DISC" minRadius="15000" maxRadius="60000"
      *             thickness="0.02" arms="2" rotationSpeed="220" coreFraction="0.08" weight="7"/>
      * }</pre>
      *
-     * <p>Every attribute defaults to the stock spiral's value, so a pack that wants to change only
-     * how flat a disc is writes only {@code thickness}.</p>
+     * <p>Every SHAPE attribute defaults to the stock spiral's value, so a pack that wants to change
+     * only how flat a disc is writes only {@code thickness}. Those defaults are READ OFF
+     * {@link GalaxyGenConfig#stockSpiral()} rather than written here: they were literals once, and the
+     * copy went stale the moment the galaxy scale moved. {@code weight} is the deliberate exception —
+     * it defaults to {@code 1}, the rarest, because a type a pack did not weight should not silently
+     * inherit a spiral's abundance.</p>
      */
     private static GalaxyGenConfig.GalaxyType readGalaxyType(Node node) {
         String profileName = attr(node, ATTR_PROFILE);
@@ -348,15 +352,16 @@ private static GalaxyGenConfig.GalaxyType readGalaxyType(Node node) {
             }
         }
         String name = attr(node, ATTR_NAME);
+        GalaxyGenConfig.GalaxyType stock = GalaxyGenConfig.stockSpiral();
         return new GalaxyGenConfig.GalaxyType(
                 (name == null || name.trim().isEmpty()) ? "Galaxy" : name.trim(),
                 profile,
-                attrDouble(node, ATTR_MINRADIUS, 900d),
-                attrDouble(node, ATTR_MAXRADIUS, 2200d),
-                attrDouble(node, ATTR_THICKNESS, 0.02d),
-                attrInt(node, ATTR_ARMS, 2),
-                attrDouble(node, ATTR_ROTATIONSPEED, 220d),
-                attrDouble(node, ATTR_COREFRACTION, 0.08d),
+                attrDouble(node, ATTR_MINRADIUS, stock.minRadiusLy),
+                attrDouble(node, ATTR_MAXRADIUS, stock.maxRadiusLy),
+                attrDouble(node, ATTR_THICKNESS, stock.scaleHeightRatio),
+                attrInt(node, ATTR_ARMS, stock.armCount),
+                attrDouble(node, ATTR_ROTATIONSPEED, stock.rotationSpeedKmS),
+                attrDouble(node, ATTR_COREFRACTION, stock.coreRadiusFraction),
                 attrInt(node, ATTR_WEIGHT, 1));
     }
 
 
@@ -558,6 +558,32 @@ public void galaxyTypeChildrenReplaceTheStockTable() throws Exception {
         assertEquals(5, t.weight);
     }
 
+    @Test
+    public void aPartiallySpecifiedGalaxyTypeInheritsTheSTOCKspiralNotAFrozenCopyOfIt()
+            throws Exception {
+        // The reason this test exists: the reader's defaults used to be literals — 900 / 2200 ly — and
+        // they went stale the moment the galaxy scale moved, so a pack that wrote only `thickness` got
+        // a "spiral" an order and a half under every real one, silently and only in the authored path.
+        // A pack writing one attribute must get the SHIPPED spiral for the rest.
+        GalaxyGenConfig.GalaxyType stock = GalaxyGenConfig.stockSpiral();
+        DimensionPropertyCoupling c = parse(galaxy(
+                "<galaxyGen>\n"
+                        + "  <galaxyType name=\"Fat Disc\" thickness=\"0.25\"/>\n"
+                        + "</galaxyGen>\n"));
+        assertNotNull(c.galaxyGenConfig);
+        GalaxyGenConfig.GalaxyType t = c.galaxyGenConfig.galaxyTypes.get(0);
+
+        assertEquals("thickness is what the pack asked for", 0.25d, t.scaleHeightRatio, 1e-9);
+        assertEquals("and the radius band is the SHIPPED spiral's", stock.minRadiusLy,
+                t.minRadiusLy, 1e-9);
+        assertEquals(stock.maxRadiusLy, t.maxRadiusLy, 1e-9);
+        assertEquals(stock.armCount, t.armCount);
+        assertEquals(stock.rotationSpeedKmS, t.rotationSpeedKmS, 1e-9);
+        assertEquals(stock.coreRadiusFraction, t.coreRadiusFraction, 1e-9);
+        assertEquals("weight is the deliberate exception: an unweighted type is the rarest", 1,
+                t.weight);
+    }
+
     @Test
     public void galaxyTypesRoundTripThroughWriteXml() throws IOException {
         // This file is REWRITTEN on every world save, so a table the writer does not emit is a table a