fix(determinism): asteroid roll keys on the saved world seed; stable audio hashes

TODO.md

@@ -7099,6 +7099,21 @@ is **pre-approved** (keys in `tools/ai-assets/.env`, run via `uv`).
 
 ---
 
+## ✅ Done (2026-08-04): seed-determinism fixes — asteroid roll keys on the saved seed; stable audio hashing (#719/#720)
+
+Two findings from a worldgen-determinism audit (world = seed-recomputed baseline + persisted deltas;
+the audit confirmed the model holds except for a few runtime-random systems):
+
+- **#719 (server)** — `SpawnAsteroid`'s family/size roll mixed **`_config.Seed`** (the launch flag,
+  0 on desktop singleplayer) instead of the persisted **`_meta.Seed`**. Desktop worlds therefore all
+  shared the same per-field family patterns, and relaunching a hosted world with a different/absent
+  `--seed` silently re-rolled every rock. One-line fix + regression test: reloading the same save
+  under a different launch-config seed must yield identical rocks.
+- **#720 (client)** — `ProceduralAudio` seeded its noise synthesis from `name.GetHashCode()` at 10
+  sites; string hash codes are per-process randomised on .NET Core and differ across runtimes, which
+  would re-roll every synthesized sound's noise character under a runtime/backend change. Replaced
+  with the codebase-standard stable order-dependent hash (NpcView/FloraTints convention).
+
 ## ✅ Done (2026-08-04): server test-writing guide + de-ghosted spec citations (#571 follow-up)
 
 A contributor stepped down from #571 ("not enough business-logic context to write meaningful

client/Assets/BlocksBeyondTheStars/Scripts/ProceduralAudio.cs

@@ -94,6 +94,20 @@ private static AudioClip Buf(string name, float seconds, System.Action<float[]>
             return clip;
         }
 
+        /// <summary>Order-dependent string hash that is stable across sessions, runtimes and machines —
+        /// .NET string hash codes are randomised per process, which would re-roll the noise character of
+        /// every synthesized sound between runs (#720; same convention as NpcView/FloraTints).</summary>
+        private static int StableHash(string s)
+        {
+            int h = 17;
+            foreach (char c in s ?? string.Empty)
+            {
+                h = unchecked(h * 31 + c);
+            }
+
+            return h;
+        }
+
         /// <summary>Crossfades the tail into the head so the clip loops without a click.</summary>
         private static void LoopFade(float[] d, int fade)
         {
@@ -141,7 +155,7 @@ private static AudioClip Arp(string name, float dur, float vol, bool up) => Buf(
 
         private static AudioClip NoiseHit(string name, float dur, float vol, float cutoff, float decay) => Buf(name, dur, d =>
         {
-            var rng = new System.Random(name.GetHashCode());
+            var rng = new System.Random(StableHash(name));
             float lp = 0f, a = Mathf.Clamp01(cutoff / Rate * 6f);
             for (int i = 0; i < d.Length; i++)
             {
@@ -154,7 +168,7 @@ private static AudioClip NoiseHit(string name, float dur, float vol, float cutof
 
         private static AudioClip Thud(string name, float dur, float vol) => Buf(name, dur, d =>
         {
-            var rng = new System.Random(name.GetHashCode());
+            var rng = new System.Random(StableHash(name));
             for (int i = 0; i < d.Length; i++)
             {
                 float t = i / (float)Rate;
@@ -182,7 +196,7 @@ private static AudioClip Clang(string name, float freq, float dur, float vol) =>
 
         private static AudioClip Explosion(string name, float dur, float vol) => Buf(name, dur, d =>
         {
-            var rng = new System.Random(name.GetHashCode());
+            var rng = new System.Random(StableHash(name));
             float lp = 0f;
             for (int i = 0; i < d.Length; i++)
             {
@@ -218,7 +232,7 @@ private static AudioClip Hurt(string name) => Buf(name, 0.3f, d =>
 
         private static AudioClip Thunder(string name, int variant) => Buf(name, 1.6f, d =>
         {
-            var rng = new System.Random(name.GetHashCode() + variant);
+            var rng = new System.Random(StableHash(name) + variant);
             float lp = 0f;
             for (int i = 0; i < d.Length; i++)
             {
@@ -286,7 +300,7 @@ private static AudioClip Shimmer(string name) => Buf(name, 0.6f, d =>
 
         private static AudioClip Roar(string name, bool rising) => Buf(name, 1.6f, d =>
         {
-            var rng = new System.Random(name.GetHashCode());
+            var rng = new System.Random(StableHash(name));
             float lp = 0f;
             for (int i = 0; i < d.Length; i++)
             {
@@ -304,7 +318,7 @@ private static AudioClip Roar(string name, bool rising) => Buf(name, 1.6f, d =>
 
         private static AudioClip WindLoop(string name, float dur, float vol, float cutoff, bool chirp = false, bool rumble = false) => Buf(name, dur, d =>
         {
-            var rng = new System.Random(name.GetHashCode());
+            var rng = new System.Random(StableHash(name));
             float lp = 0f, a = Mathf.Clamp01(cutoff * 0.02f + 0.01f);
             for (int i = 0; i < d.Length; i++)
             {
@@ -323,7 +337,7 @@ private static AudioClip WindLoop(string name, float dur, float vol, float cutof
 
         private static AudioClip RainLoop(string name, float vol) => Buf(name, 3f, d =>
         {
-            var rng = new System.Random(name.GetHashCode());
+            var rng = new System.Random(StableHash(name));
             float lp = 0f;
             for (int i = 0; i < d.Length; i++)
             {
@@ -337,7 +351,7 @@ private static AudioClip RainLoop(string name, float vol) => Buf(name, 3f, d =>
 
         private static AudioClip BubbleLoop(string name) => Buf(name, 3f, d =>
         {
-            var rng = new System.Random(name.GetHashCode());
+            var rng = new System.Random(StableHash(name));
             for (int i = 0; i < d.Length; i++)
             {
                 float t = i / (float)Rate;
@@ -351,7 +365,7 @@ private static AudioClip BubbleLoop(string name) => Buf(name, 3f, d =>
 
         private static AudioClip DrillLoop(string name) => Buf(name, 1f, d =>
         {
-            var rng = new System.Random(name.GetHashCode());
+            var rng = new System.Random(StableHash(name));
             for (int i = 0; i < d.Length; i++)
             {
                 float t = i / (float)Rate;
@@ -365,7 +379,7 @@ private static AudioClip DrillLoop(string name) => Buf(name, 1f, d =>
 
         private static AudioClip EngineLoop(string name) => Buf(name, 1.5f, d =>
         {
-            var rng = new System.Random(name.GetHashCode());
+            var rng = new System.Random(StableHash(name));
             float lp = 0f;
             for (int i = 0; i < d.Length; i++)
             {

src/BlocksBeyondTheStars.GameServer/GameServerSpaceStructure.cs

@@ -991,7 +991,8 @@ private static List<ItemAmount> AsteroidLoot(string family, int radius)
     /// <summary>Spawns one asteroid: a combat entity (for ship targeting/firing + respawn accounting) paired with
     /// a voxel ore structure of the same id (for rendering + EVA mining) — item 20 S3. The entity's hull tracks
     /// its block count so laser fire carves the rock down as it depletes. #687: the family/size roll is seeded
-    /// from the instance id + spawn <paramref name="ordinal"/>, so the same world always grows the same rocks;
+    /// from the world's saved seed + instance id + spawn <paramref name="ordinal"/>, so the same world always
+    /// grows the same rocks (#719: the SAVED seed, not the launch config's — those differ on name-seeded worlds);
     /// ordinal 0 is pinned to the classic metallic r=2 rock so every field guarantees one titanium core
     /// (mirrors the start-planet ring pin).</summary>
     private void SpawnAsteroid(SpaceInstance instance, Vector3f pos, int ordinal, bool broadcast)
@@ -1001,7 +1002,7 @@ private void SpawnAsteroid(SpaceInstance instance, Vector3f pos, int ordinal, bo
         if (ordinal > 0)
         {
             long h = WorldGenerator.StableHash(instance.Id);
-            uint state = (uint)(h ^ (h >> 32) ^ (_config.Seed * 397L) ^ (ordinal * 668265263L)) | 1u;
+            uint state = (uint)(h ^ (h >> 32) ^ (_meta.Seed * 397L) ^ (ordinal * 668265263L)) | 1u;
             family = PickWeighted(AsteroidFamilies, ref state);
             radius = PickWeighted(AsteroidSizes, ref state);
         }

tests/BlocksBeyondTheStars.Tests/SpaceCombatTests.cs

@@ -374,6 +374,10 @@ public void SpaceAsteroids_RollSeededFamiliesAndSizes()
         // The same world rolls the same rocks again (deterministic — restart-safe).
         Assert.Equal(first, Snapshot("astroll", 1));
 
+        // #719: the roll keys on the SAVED world seed, so reloading the same save under a different
+        // launch-config seed must not re-roll the rocks.
+        Assert.Equal(first, Snapshot("astroll", 999));
+
         // And across a handful of seeds the rolled rocks are NOT all clones of the classic one.
         var rolled = new List<(int Count, ushort Core)>();
         for (long seed = 2; seed <= 5; seed++)