diff --git a/Cargo.lock b/Cargo.lock
index 86d9293..6741883 100644
--- a/Cargo.lock
+++ b/Cargo.lock
@@ -1189,7 +1189,7 @@ dependencies = [
  "glam",
  "itertools",
  "libm",
- "rand",
+ "rand 0.10.2",
  "rand_distr",
  "serde",
  "thiserror 2.0.18",
@@ -2825,6 +2825,17 @@ dependencies = [
  "windows-link",
 ]
 
+[[package]]
+name = "getrandom"
+version = "0.2.17"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "ff2abc00be7fca6ebc474524697ae276ad847ad0a6b3faa4bcb027e9a4614ad0"
+dependencies = [
+ "cfg-if",
+ "libc",
+ "wasi",
+]
+
 [[package]]
 name = "getrandom"
 version = "0.3.4"
@@ -2904,7 +2915,7 @@ dependencies = [
  "bytemuck",
  "encase",
  "libm",
- "rand",
+ "rand 0.10.2",
  "serde_core",
 ]
 
@@ -4482,6 +4493,15 @@ dependencies = [
  "unicode-xid",
 ]
 
+[[package]]
+name = "ppv-lite86"
+version = "0.2.21"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "85eae3c4ed2f50dcfe72643da4befc30deadb458a9b590d720cde2f2b1e97da9"
+dependencies = [
+ "zerocopy",
+]
+
 [[package]]
 name = "presser"
 version = "0.3.1"
@@ -4560,6 +4580,17 @@ version = "0.1.1"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "019b4b213425016d7d84a153c4c73afb0946fbb4840e4eece7ba8848b9d6da22"
 
+[[package]]
+name = "rand"
+version = "0.8.7"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "22f6172bdec972074665ed81ed53b71da00bfc44b65a753cfde883ec4c702a1a"
+dependencies = [
+ "libc",
+ "rand_chacha",
+ "rand_core 0.6.4",
+]
+
 [[package]]
 name = "rand"
 version = "0.10.2"
@@ -4567,7 +4598,26 @@ source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "c7f5fa3a058cd35567ef9bfa5e75732bee0f9e4c55fa90477bef2dfcdbc4be80"
 dependencies = [
  "getrandom 0.4.3",
- "rand_core",
+ "rand_core 0.10.1",
+]
+
+[[package]]
+name = "rand_chacha"
+version = "0.3.1"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "e6c10a63a0fa32252be49d21e7709d4d4baf8d231c2dbce1eaa8141b9b127d88"
+dependencies = [
+ "ppv-lite86",
+ "rand_core 0.6.4",
+]
+
+[[package]]
+name = "rand_core"
+version = "0.6.4"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "ec0be4795e2f6a28069bec0b5ff3e2ac9bafc99e6a9a7dc3547996c5c816922c"
+dependencies = [
+ "getrandom 0.2.17",
 ]
 
 [[package]]
@@ -4583,7 +4633,7 @@ source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "4d431c2703ccf129de4d45253c03f49ebb22b97d6ad79ee3ecfc7e3f4862c1d8"
 dependencies = [
  "num-traits",
- "rand",
+ "rand 0.10.2",
 ]
 
 [[package]]
@@ -4911,6 +4961,8 @@ dependencies = [
  "bevy",
  "bevy_egui",
  "js-sys",
+ "rand 0.8.7",
+ "rand_chacha",
  "wasm-bindgen",
  "web-sys",
 ]
@@ -5526,6 +5578,12 @@ dependencies = [
  "winapi-util",
 ]
 
+[[package]]
+name = "wasi"
+version = "0.11.1+wasi-snapshot-preview1"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "ccf3ec651a847eb01de73ccad15eb7d99f80485de043efb2f370cd654f4ea44b"
+
 [[package]]
 name = "wasip2"
 version = "1.0.4+wasi-0.2.12"
diff --git a/Cargo.toml b/Cargo.toml
index 2e6c3bb..62ea2fb 100644
--- a/Cargo.toml
+++ b/Cargo.toml
@@ -10,6 +10,11 @@ path = "src/lib.rs"
 [dependencies]
 bevy = "0.19"
 bevy_egui = "0.41"
+# Deterministic PRNG for planet seeding (ChaCha8Rng). `rand` is a transitive
+# dep via bevy_math but not declared directly; `rand_chacha` ships ChaCha8Rng.
+# Pinned to 0.8/0.3 (LTS, API-compatible with the Bevy 0.19 ecosystem).
+rand = "0.8"
+rand_chacha = "0.3"
 
 # Web-only deps for WebGPU detection + fallback message.
 [target.'cfg(target_arch = "wasm32")'.dependencies]