diff --git a/.github/ISSUE_TEMPLATE/bug.yml b/.github/ISSUE_TEMPLATE/bug.yml
index d39a437..b750958 100644
--- a/.github/ISSUE_TEMPLATE/bug.yml
+++ b/.github/ISSUE_TEMPLATE/bug.yml
@@ -33,12 +33,12 @@ body:
     id: stack_trace
     attributes:
       label: Stack Trace / Error Logs
-      description: paste full stack trace or logs
+      description: Provide full stack trace or logs
   - type: input
     id: version
     attributes:
       label: Version / Commit
-      description: git SHA or package version
+      description: Provide git SHA or package version
   - type: checkboxes
     id: env
     attributes:
diff --git a/.github/workflows/ci.yml b/.github/workflows/ci.yml
index 58e148b..cd9b19f 100644
--- a/.github/workflows/ci.yml
+++ b/.github/workflows/ci.yml
@@ -57,6 +57,25 @@ jobs:
       - name: PRNG golden regression (rmg-core)
         run: cargo test -p rmg-core --features golden_prng -- tests::next_int_golden_regression
 
+  test-musl:
+    name: Tests (musl)
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v4
+        with:
+          submodules: false
+      - uses: dtolnay/rust-toolchain@1.90.0
+        with:
+          targets: x86_64-unknown-linux-musl
+      - name: Install musl tools
+        run: sudo apt-get update && sudo apt-get install -y musl-tools
+      - uses: Swatinem/rust-cache@v2
+        with:
+          workspaces: |
+            .
+      - name: cargo test (rmg-core, musl)
+        run: cargo test -p rmg-core --target x86_64-unknown-linux-musl
+
   docs:
     name: Docs Guard
     runs-on: ubuntu-latest
diff --git a/.github/workflows/macos-local.yml b/.github/workflows/macos-local.yml
new file mode 100644
index 0000000..77f0133
--- /dev/null
+++ b/.github/workflows/macos-local.yml
@@ -0,0 +1,24 @@
+name: CI (macOS — manual)
+
+on:
+  workflow_dispatch:
+
+jobs:
+  test-macos:
+    name: Tests (macOS local only)
+    runs-on: macos-latest
+    steps:
+      - uses: actions/checkout@v4
+        with:
+          submodules: false
+      - uses: dtolnay/rust-toolchain@1.90.0
+      - uses: Swatinem/rust-cache@v2
+        with:
+          workspaces: |
+            .
+      - name: cargo fmt
+        run: cargo fmt --all -- --check
+      - name: cargo clippy
+        run: cargo clippy --all-targets -- -D warnings -D missing_docs
+      - name: cargo test (workspace)
+        run: cargo test --workspace
diff --git a/Cargo.lock b/Cargo.lock
index 160776d..07d3f53 100644
--- a/Cargo.lock
+++ b/Cargo.lock
@@ -14,6 +14,33 @@ version = "0.7.6"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "7c02d123df017efcdfbd739ef81735b36c5ba83ec3c59c80a9d7ecc718f92e50"
 
+[[package]]
+name = "autocfg"
+version = "1.5.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "c08606f8c3cbf4ce6ec8e28fb0014a2c086708fe954eaa885384a6165172e7e8"
+
+[[package]]
+name = "bit-set"
+version = "0.8.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "08807e080ed7f9d5433fa9b275196cfc35414f66a0c79d864dc51a0d825231a3"
+dependencies = [
+ "bit-vec",
+]
+
+[[package]]
+name = "bit-vec"
+version = "0.8.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "5e764a1d40d510daf35e07be9eb06e75770908c27d411ee6c92109c9840eaaf7"
+
+[[package]]
+name = "bitflags"
+version = "2.10.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "812e12b5285cc515a9c72a5c1d3b6d46a19dac5acfef5265968c166106e31dd3"
+
 [[package]]
 name = "blake3"
 version = "1.8.2"
@@ -71,12 +98,46 @@ version = "0.3.1"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "7c74b8349d32d297c9134b8c88677813a227df8f779daa29bfc29c183fe3dca6"
 
+[[package]]
+name = "errno"
+version = "0.3.14"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "39cab71617ae0d63f51a36d69f866391735b51691dbda63cf6f96d042b63efeb"
+dependencies = [
+ "libc",
+ "windows-sys",
+]
+
+[[package]]
+name = "fastrand"
+version = "2.3.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "37909eebbb50d72f9059c3b6d82c0463f2ff062c9e95845c43a6c9c0355411be"
+
 [[package]]
 name = "find-msvc-tools"
 version = "0.1.4"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "52051878f80a721bb68ebfbc930e07b65ba72f2da88968ea5c06fd6ca3d3a127"
 
+[[package]]
+name = "fnv"
+version = "1.0.7"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "3f9eec918d3f24069decb9af1554cad7c880e2da24a9afd88aca000531ab82c1"
+
+[[package]]
+name = "getrandom"
+version = "0.3.4"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "899def5c37c4fd7b2664648c28120ecec138e4d395b459e5ca34f9cce2dd77fd"
+dependencies = [
+ "cfg-if",
+ "libc",
+ "r-efi",
+ "wasip2",
+]
+
 [[package]]
 name = "hex"
 version = "0.4.3"
@@ -99,6 +160,18 @@ dependencies = [
  "wasm-bindgen",
 ]
 
+[[package]]
+name = "libc"
+version = "0.2.177"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "2874a2af47a2325c2001a6e6fad9b16a53b802102b528163885171cf92b15976"
+
+[[package]]
+name = "linux-raw-sys"
+version = "0.11.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "df1d3c3b53da64cf5760482273a98e575c651a67eec7f77df96b5b642de8f039"
+
 [[package]]
 name = "memchr"
 version = "2.7.6"
@@ -115,12 +188,30 @@ dependencies = [
  "walkdir",
 ]
 
+[[package]]
+name = "num-traits"
+version = "0.2.19"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "071dfc062690e90b734c0b2273ce72ad0ffa95f0c74596bc250dcfd960262841"
+dependencies = [
+ "autocfg",
+]
+
 [[package]]
 name = "once_cell"
 version = "1.21.3"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "42f5e15c9953c5e4ccceeb2e7382a716482c34515315f7b03532b8b4e8393d2d"
 
+[[package]]
+name = "ppv-lite86"
+version = "0.2.21"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "85eae3c4ed2f50dcfe72643da4befc30deadb458a9b590d720cde2f2b1e97da9"
+dependencies = [
+ "zerocopy",
+]
+
 [[package]]
 name = "proc-macro2"
 version = "1.0.103"
@@ -130,6 +221,31 @@ dependencies = [
  "unicode-ident",
 ]
 
+[[package]]
+name = "proptest"
+version = "1.9.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "bee689443a2bd0a16ab0348b52ee43e3b2d1b1f931c8aa5c9f8de4c86fbe8c40"
+dependencies = [
+ "bit-set",
+ "bit-vec",
+ "bitflags",
+ "num-traits",
+ "rand",
+ "rand_chacha",
+ "rand_xorshift",
+ "regex-syntax",
+ "rusty-fork",
+ "tempfile",
+ "unarray",
+]
+
+[[package]]
+name = "quick-error"
+version = "1.2.3"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "a1d01941d82fa2ab50be1e79e6714289dd7cde78eba4c074bc5a4374f650dfe0"
+
 [[package]]
 name = "quote"
 version = "1.0.41"
@@ -139,6 +255,56 @@ dependencies = [
  "proc-macro2",
 ]
 
+[[package]]
+name = "r-efi"
+version = "5.3.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "69cdb34c158ceb288df11e18b4bd39de994f6657d83847bdffdbd7f346754b0f"
+
+[[package]]
+name = "rand"
+version = "0.9.2"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "6db2770f06117d490610c7488547d543617b21bfa07796d7a12f6f1bd53850d1"
+dependencies = [
+ "rand_chacha",
+ "rand_core",
+]
+
+[[package]]
+name = "rand_chacha"
+version = "0.9.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "d3022b5f1df60f26e1ffddd6c66e8aa15de382ae63b3a0c1bfc0e4d3e3f325cb"
+dependencies = [
+ "ppv-lite86",
+ "rand_core",
+]
+
+[[package]]
+name = "rand_core"
+version = "0.9.3"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "99d9a13982dcf210057a8a78572b2217b667c3beacbf3a0d8b454f6f82837d38"
+dependencies = [
+ "getrandom",
+]
+
+[[package]]
+name = "rand_xorshift"
+version = "0.4.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "513962919efc330f829edb2535844d1b912b0fbe2ca165d613e4e8788bb05a5a"
+dependencies = [
+ "rand_core",
+]
+
+[[package]]
+name = "regex-syntax"
+version = "0.8.8"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "7a2d987857b319362043e95f5353c0535c1f58eec5336fdfcf626430af7def58"
+
 [[package]]
 name = "rmg-cli"
 version = "0.1.0"
@@ -151,6 +317,7 @@ dependencies = [
  "bytes",
  "hex",
  "once_cell",
+ "proptest",
  "serde",
  "serde_json",
  "thiserror",
@@ -181,12 +348,37 @@ dependencies = [
  "wasm-bindgen-test",
 ]
 
+[[package]]
+name = "rustix"
+version = "1.1.2"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "cd15f8a2c5551a84d56efdc1cd049089e409ac19a3072d5037a17fd70719ff3e"
+dependencies = [
+ "bitflags",
+ "errno",
+ "libc",
+ "linux-raw-sys",
+ "windows-sys",
+]
+
 [[package]]
 name = "rustversion"
 version = "1.0.22"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "b39cdef0fa800fc44525c84ccb54a029961a8215f9619753635a9c0d2538d46d"
 
+[[package]]
+name = "rusty-fork"
+version = "0.3.1"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "cc6bf79ff24e648f6da1f8d1f011e9cac26491b619e6b9280f2b47f1774e6ee2"
+dependencies = [
+ "fnv",
+ "quick-error",
+ "tempfile",
+ "wait-timeout",
+]
+
 [[package]]
 name = "ryu"
 version = "1.0.20"
@@ -262,6 +454,19 @@ dependencies = [
  "unicode-ident",
 ]
 
+[[package]]
+name = "tempfile"
+version = "3.23.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "2d31c77bdf42a745371d260a26ca7163f1e0924b64afa0b688e61b5a9fa02f16"
+dependencies = [
+ "fastrand",
+ "getrandom",
+ "once_cell",
+ "rustix",
+ "windows-sys",
+]
+
 [[package]]
 name = "thiserror"
 version = "1.0.69"
@@ -282,12 +487,27 @@ dependencies = [
  "syn",
 ]
 
+[[package]]
+name = "unarray"
+version = "0.1.4"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "eaea85b334db583fe3274d12b4cd1880032beab409c0d774be044d4480ab9a94"
+
 [[package]]
 name = "unicode-ident"
 version = "1.0.20"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "462eeb75aeb73aea900253ce739c8e18a67423fadf006037cd3ff27e82748a06"
 
+[[package]]
+name = "wait-timeout"
+version = "0.2.1"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "09ac3b126d3914f9849036f826e054cbabdc8519970b8998ddaf3b5bd3c65f11"
+dependencies = [
+ "libc",
+]
+
 [[package]]
 name = "walkdir"
 version = "2.5.0"
@@ -298,6 +518,15 @@ dependencies = [
  "winapi-util",
 ]
 
+[[package]]
+name = "wasip2"
+version = "1.0.1+wasi-0.2.4"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "0562428422c63773dad2c345a1882263bbf4d65cf3f42e90921f787ef5ad58e7"
+dependencies = [
+ "wit-bindgen",
+]
+
 [[package]]
 name = "wasm-bindgen"
 version = "0.2.105"
@@ -413,3 +642,29 @@ checksum = "ae137229bcbd6cdf0f7b80a31df61766145077ddf49416a728b02cb3921ff3fc"
 dependencies = [
  "windows-link",
 ]
+
+[[package]]
+name = "wit-bindgen"
+version = "0.46.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "f17a85883d4e6d00e8a97c586de764dabcc06133f7f1d55dce5cdc070ad7fe59"
+
+[[package]]
+name = "zerocopy"
+version = "0.8.27"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "0894878a5fa3edfd6da3f88c4805f4c8558e2b996227a3d864f47fe11e38282c"
+dependencies = [
+ "zerocopy-derive",
+]
+
+[[package]]
+name = "zerocopy-derive"
+version = "0.8.27"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "88d2b8d9c68ad2b9e4340d7832716a4d21a22a1154777ad56ea55c51a9cf3831"
+dependencies = [
+ "proc-macro2",
+ "quote",
+ "syn",
+]
diff --git a/crates/rmg-core/Cargo.toml b/crates/rmg-core/Cargo.toml
index 8f87bcd..1f51fc6 100644
--- a/crates/rmg-core/Cargo.toml
+++ b/crates/rmg-core/Cargo.toml
@@ -23,6 +23,7 @@ once_cell = "1.19"
 [dev-dependencies]
 serde = { version = "1.0", features = ["derive"] }
 serde_json = "1.0"
+proptest = { version = "1.5" }
 
 [features]
 default = []
diff --git a/crates/rmg-core/tests/proptest_seed_pinning.rs b/crates/rmg-core/tests/proptest_seed_pinning.rs
new file mode 100644
index 0000000..7954d6c
--- /dev/null
+++ b/crates/rmg-core/tests/proptest_seed_pinning.rs
@@ -0,0 +1,72 @@
+#![allow(missing_docs)]
+use proptest::prelude::*;
+use proptest::test_runner::{Config as PropConfig, RngAlgorithm, TestRng, TestRunner};
+
+use rmg_core::{
+    decode_motion_payload, encode_motion_payload, make_node_id, make_type_id, ApplyResult, Engine,
+    GraphStore, NodeRecord, MOTION_RULE_NAME,
+};
+
+// Demonstrates how to pin a deterministic seed for property tests so failures
+// are reproducible across machines and CI.
+//
+// To re-run with a different seed locally, you can set PROPTEST_SEED, e.g.:
+//   PROPTEST_SEED=0000000000000000000000000000000000000000000000000000000000000042 cargo test -p rmg-core -- proptest_seed_pinned_motion_updates
+// Or update the `SEED_BYTES` below for a committed example.
+
+#[test]
+fn proptest_seed_pinned_motion_updates() {
+    // Pin a seed for deterministic case generation. Using a small numeric
+    // value is enough; TestRng::from_seed expects 32 bytes.
+    const SEED_BYTES: [u8; 32] = [
+        0x42, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
+        0, 0, 0,
+    ];
+
+    let rng = TestRng::from_seed(RngAlgorithm::ChaCha, &SEED_BYTES);
+    let mut runner = TestRunner::new_with_rng(PropConfig::default(), rng);
+
+    // Strategy: finite f32 in a sane range to avoid infinities/NaNs.
+    let scalar = any::<f32>().prop_filter("finite", |v| v.is_finite() && v.abs() < 1.0e6);
+    let vec3 = prop::array::uniform3(scalar.clone());
+
+    let prop = (vec3.clone(), vec3).prop_map(|(pos, vel)| (pos, vel));
+
+    runner
+        .run(&prop, |(pos, vel)| {
+            // Build a fresh engine for each case (property tests are short).
+            let entity = make_node_id("prop-entity");
+            let entity_ty = make_type_id("entity");
+
+            let mut store = GraphStore::default();
+            store.insert_node(
+                entity,
+                NodeRecord {
+                    ty: entity_ty,
+                    payload: Some(encode_motion_payload(pos, vel)),
+                },
+            );
+
+            let mut engine = Engine::new(store, entity);
+            engine
+                .register_rule(rmg_core::motion_rule())
+                .expect("register motion rule");
+
+            let tx = engine.begin();
+            let res = engine.apply(tx, MOTION_RULE_NAME, &entity).expect("apply");
+            prop_assert!(matches!(res, ApplyResult::Applied));
+            engine.commit(tx).expect("commit");
+
+            let node = engine.node(&entity).expect("node exists");
+            let (new_pos, new_vel) =
+                decode_motion_payload(node.payload.as_ref().expect("payload")).expect("decode");
+
+            // Velocity is preserved; position += vel * dt (dt = 1.0).
+            for i in 0..3 {
+                prop_assert_eq!(new_vel[i].to_bits(), vel[i].to_bits());
+                prop_assert_eq!(new_pos[i].to_bits(), (pos[i] + vel[i]).to_bits());
+            }
+            Ok(())
+        })
+        .expect("proptest with pinned seed should complete");
+}
diff --git a/docs/decision-log.md b/docs/decision-log.md
index 6bfb7f8..9a481a2 100644
--- a/docs/decision-log.md
+++ b/docs/decision-log.md
@@ -24,6 +24,9 @@ The following entries use a heading + bullets format for richer context.
 | 2025-10-30 | Templates PR scope | Clean `echo/pr-templates-and-project` to contain only templates + docs notes; remove unrelated files pulled in by merge; fix YAML lint (trailing blanks; quote placeholder) | Keep PRs reviewable and single-purpose; satisfy CI Docs Guard | Easier review; no runtime impact |
 | 2025-10-30 | Docs lint | Fix MD022 (blank line after headings) in `docs/spec-deterministic-math.md` on branch `echo/docs-math-harness-notes` | Keep markdown lint clean; improve readability | No content change; unblock future docs PRs |
 | 2025-10-30 | Bug template triage | Add optional `stack_trace` and `version` fields to `.github/ISSUE_TEMPLATE/bug.yml` | Capture logs and version/SHA up front to speed debugging | Better triage signal without burdening reporters |
+| 2025-10-30 | Bug template wording | Standardize bug template descriptions to imperative capitalization ("Provide …") | Consistent style and clearer prompts | Improved reporter guidance |
+| 2025-10-30 | Proptest seed pinning | Add dev‑dep `proptest` and a pinned‑seed property test for motion rule (`proptest_seed_pinning.rs`) | Establish deterministic, reproducible property tests and document seed‑pinning pattern | Tests‑only; no runtime impact |
+| 2025-10-30 | CI matrix | Add musl tests job (rmg-core; x86_64-unknown-linux-musl) and a manual macOS workflow for local runs | Cover glibc + musl in CI while keeping macOS optional to control costs | Determinism coverage improves; CI footprint remains lean |
 | 2025-10-28 | PR #7 merged | Reachability-only snapshot hashing; ports demo registers rule; guarded ports footprint; scheduler `finalize_tx()` clears `pending`; `PortKey` u30 mask; hooks+CI hardened (toolchain pin, rustdoc fixes). | Determinism + memory hygiene; remove test footguns; pass CI with stable toolchain while keeping rmg-core MSRV=1.68. | Queued follow-ups: #13 (Mat4 canonical zero + MulAssign), #14 (geom train), #15 (devcontainer). |
 | 2025-10-27 | MWMR reserve gate | Engine calls `scheduler.finalize_tx()` at commit; compact rule id used on execute path; per‑tx telemetry summary behind feature. | Enforce independence and clear active frontier deterministically; keep ordering stable with `(scope_hash, family_id)`. | Toolchain pinned to Rust 1.68; add design note for telemetry graph snapshot replay. |
  
diff --git a/docs/execution-plan.md b/docs/execution-plan.md
index 8c0a895..140c050 100644
--- a/docs/execution-plan.md
+++ b/docs/execution-plan.md
@@ -59,6 +59,19 @@ This is Codex’s working map for building Echo. Update it relentlessly—each s
 
 - Enhanced `.github/ISSUE_TEMPLATE/bug.yml` with optional fields for `Stack Trace / Error Logs` and `Version / Commit` to improve first‑pass triage quality.
 
+> 2025-10-30 — Bug template wording consistency
+
+- Standardized description capitalization in bug template to imperative form ("Provide …") for consistency with existing fields.
+
+> 2025-10-30 — PR-03: proptest seed pinning (tests-only)
+
+- Added `proptest` as a dev‑dependency in `rmg-core` and a single example test `proptest_seed_pinning.rs` that pins a deterministic RNG seed and validates the motion rule under generated inputs. This demonstrates how to reproduce failures via a fixed seed across CI and local runs (no runtime changes).
+
+> 2025-10-30 — PR-04: CI matrix (glibc + musl; macOS manual)
+
+- CI: Added a musl job (`Tests (musl)`) that installs `musl-tools`, adds target `x86_64-unknown-linux-musl`, and runs `cargo test -p rmg-core --target x86_64-unknown-linux-musl`.
+- CI: Added a separate macOS workflow (`CI (macOS — manual)`) triggered via `workflow_dispatch` to run fmt/clippy/tests on `macos-latest` when needed, avoiding default macOS runner costs.
+
 
 > 2025-10-29 — Geom fat AABB midpoint sampling (merge-train)