diff --git a/.packwizignore b/.packwizignore
index ee0f592..ce94ef8 100644
--- a/.packwizignore
+++ b/.packwizignore
@@ -65,3 +65,8 @@ config/paxi/datapacks/*
 # Default Options copies them into place client-side, only when the target is absent.
 !config/defaultoptions
 !config/defaultoptions/**
+# Server spawn tuning (analysis/client-perf/SPAWN-TUNING.md); partial files, the mods
+# fill in defaults for every other key. Enforced: the server reads them from here.
+!config/alexsmobs-common.toml
+!config/fowlplay.json5
+!config/crittersandcompanions-common.json5
diff --git a/config/alexsmobs-common.toml b/config/alexsmobs-common.toml
new file mode 100644
index 0000000..2bd64f1
--- /dev/null
+++ b/config/alexsmobs-common.toml
@@ -0,0 +1,13 @@
+# Onion MC spawn tuning (analysis/client-perf/SPAWN-TUNING.md). Partial file: NeoForge
+# fills every other key with its default on load. Halves only the common mobs that are
+# heavy by weight x hard-coded group size; rare mobs keep their defaults.
+[spawning]
+	gazelleSpawnWeight = 20
+	capuchinMonkeySpawnWeight = 14
+	elephantSpawnWeight = 15
+	straddlerSpawnWeight = 35
+	rockyRollerSpawnWeight = 30
+	underminerSpawnWeight = 25
+	blobfishSpawnWeight = 15
+	mudskipperSpawnWeight = 14
+	caimanSpawnWeight = 15
diff --git a/config/crittersandcompanions-common.json5 b/config/crittersandcompanions-common.json5
new file mode 100644
index 0000000..259a191
--- /dev/null
+++ b/config/crittersandcompanions-common.json5
@@ -0,0 +1,51 @@
+// Onion MC spawn tuning (analysis/client-perf/SPAWN-TUNING.md). Partial file: YACL keeps
+// defaults for missing keys. Each listed rule list REPLACES that mob's defaults, so every
+// biome rule of a changed mob is listed. configVersion 2 skips the v1->v2 migration.
+{
+  "configVersion": 2,
+  "spawning": {
+    "leafInsect": [
+      {"biomeSpec": "#c:is_jungle", "weight": 8, "min": 1, "max": 1},
+      {"biomeSpec": "#c:is_forest", "weight": 4, "min": 1, "max": 1}
+    ],
+    "seaBunny": [
+      {"biomeSpec": "minecraft:ocean", "weight": 10, "min": 1, "max": 2},
+      {"biomeSpec": "minecraft:deep_ocean", "weight": 10, "min": 1, "max": 2},
+      {"biomeSpec": "minecraft:warm_ocean", "weight": 20, "min": 1, "max": 3},
+      {"biomeSpec": "minecraft:lukewarm_ocean", "weight": 10, "min": 1, "max": 3},
+      {"biomeSpec": "minecraft:deep_lukewarm_ocean", "weight": 10, "min": 1, "max": 3}
+    ],
+    "dragonfly": [
+      {"biomeSpec": "#c:is_river", "weight": 4, "min": 1, "max": 1},
+      {"biomeSpec": "#c:is_swamp", "weight": 5, "min": 1, "max": 1},
+      {"biomeSpec": "#c:is_lush", "weight": 6, "min": 1, "max": 1}
+    ],
+    "ladybug": [
+      {"biomeSpec": "#c:is_forest", "weight": 4, "min": 1, "max": 3},
+      {"biomeSpec": "#c:is_lush", "weight": 6, "min": 1, "max": 2},
+      {"biomeSpec": "#c:is_floral", "weight": 7, "min": 1, "max": 2}
+    ],
+    "stagBeetle": [
+      {"biomeSpec": "#c:is_forest", "weight": 3, "min": 1, "max": 2},
+      {"biomeSpec": "#c:is_lush", "weight": 6, "min": 1, "max": 2}
+    ],
+    "rolyPoly": [
+      {"biomeSpec": "#c:is_forest", "weight": 3, "min": 1, "max": 3},
+      {"biomeSpec": "#c:is_lush", "weight": 6, "min": 1, "max": 2},
+      {"biomeSpec": "#c:is_swamp", "weight": 6, "min": 1, "max": 2}
+    ],
+    "snail": [
+      {"biomeSpec": "#c:is_forest", "weight": 3, "min": 1, "max": 2},
+      {"biomeSpec": "#c:is_lush", "weight": 5, "min": 1, "max": 2},
+      {"biomeSpec": "#c:is_swamp", "weight": 6, "min": 1, "max": 2}
+    ],
+    "stickBug": [
+      {"biomeSpec": "#c:is_forest", "weight": 3, "min": 1, "max": 2},
+      {"biomeSpec": "#c:is_lush", "weight": 6, "min": 1, "max": 2}
+    ],
+    "weevil": [
+      {"biomeSpec": "#c:is_forest", "weight": 3, "min": 1, "max": 3},
+      {"biomeSpec": "#c:is_lush", "weight": 6, "min": 1, "max": 2}
+    ]
+  }
+}
diff --git a/config/fowlplay.json5 b/config/fowlplay.json5
new file mode 100644
index 0000000..79d66b1
--- /dev/null
+++ b/config/fowlplay.json5
@@ -0,0 +1,13 @@
+// Onion MC spawn tuning (analysis/client-perf/SPAWN-TUNING.md). Partial file: YACL keeps
+// defaults for every missing key and re-saves. Targets the waterfowl/gull/sparrow flocks
+// behind Fowl Play #214; songbirds and raptors keep their defaults.
+{
+  "duckSpawnWeight": 2,
+  "duckMaxGroupSize": 4,
+  "gooseSpawnWeight": 2,
+  "gooseMaxGroupSize": 3,
+  "gullSpawnWeight": 3,
+  "gullMaxGroupSize": 5,
+  "sparrowSpawnWeight": 12,
+  "sparrowMaxGroupSize": 4
+}
diff --git a/index.toml b/index.toml
index 44c617a..3fb9d14 100644
--- a/index.toml
+++ b/index.toml
@@ -4,6 +4,14 @@ hash-format = "sha256"
 file = "config/akashictome-common.toml"
 hash = "4e479c86ddfec0c5e28f07034f033a10abae404309f38ccc4bfc15da9de2dfa2"
 
+[[files]]
+file = "config/alexsmobs-common.toml"
+hash = "bc47ee67032ceab8b2b408819ce9b268812f37da8f13b9b7efeae0deed607c4b"
+
+[[files]]
+file = "config/crittersandcompanions-common.json5"
+hash = "a00a9fe09ce5b469247f757e780b5faf74191f5cfef158d999c4d7a1e203f420"
+
 [[files]]
 file = "config/defaultoptions/extra/config/DistantHorizons.toml"
 hash = "8949bf3c7a43df7a7ae384213db0985425db3559219c29cb63eaef45c7962dcc"
@@ -36,6 +44,10 @@ hash = "9b75828543ed2b8cc5804eabecdc28262297a90d6f0e8e771d64ff779a69e3c9"
 file = "config/defaultoptions/options.txt"
 hash = "62034e0589087dab02d1a15192ad313a57f907d5ee9ebbf8853151f7831851a1"
 
+[[files]]
+file = "config/fowlplay.json5"
+hash = "09ad767a358310e9d38e632ba0e670b0afd1554c162eadb6928d106df17b66c3"
+
 [[files]]
 file = "config/paxi/datapacks/onion-fixes/data/adorablehamsterpets/recipe/cucumber_crate.json"
 hash = "21b11674b18c3fb0d8292095cf7c12bca82ef4054ec3f1cd8d1e0222d1655629"
diff --git a/pack.toml b/pack.toml
index 3ba347e..8d23c93 100644
--- a/pack.toml
+++ b/pack.toml
@@ -6,7 +6,7 @@ pack-format = "packwiz:1.1.0"
 [index]
 file = "index.toml"
 hash-format = "sha256"
-hash = "50d97b070e620b4e850df2feb7a07b11bf7a90cab87efa96219a217b9586446d"
+hash = "3c17e58506c00f8c5aba5151afa765fdd68245c384293a017a5e2062ac35afbe"
 
 [versions]
 minecraft = "1.21.1"