diff --git a/packages/runtime-core/src/project/compose/mod.rs b/packages/runtime-core/src/project/compose/mod.rs
index ca8d52f57..be2935aa0 100644
--- a/packages/runtime-core/src/project/compose/mod.rs
+++ b/packages/runtime-core/src/project/compose/mod.rs
@@ -3,6 +3,7 @@ use serde_json::{Map, Value};
 mod dependency_cache;
 mod fields;
 mod graph;
+mod ownership_labels;
 pub(super) mod routing;
 mod service;
 use fields::*;
diff --git a/packages/runtime-core/src/project/compose/ownership_labels.rs b/packages/runtime-core/src/project/compose/ownership_labels.rs
new file mode 100644
index 000000000..198c72317
--- /dev/null
+++ b/packages/runtime-core/src/project/compose/ownership_labels.rs
@@ -0,0 +1,63 @@
+//! Label namespaces that Hack writes as resource ownership evidence.
+
+/// Container, network and volume label namespaces that Hack writes to prove
+/// which resources it owns. This mirrors `HACK_OWNERSHIP_LABEL_NAMESPACES` in
+/// `src/lib/hack-ownership-labels.ts`, the source of truth;
+/// `tests/hack-ownership-labels.test.ts` fails when the two lists differ.
+///
+/// A project must not declare a label in these namespaces, because the native
+/// runtime and native-config Compose trust them as ownership evidence. The
+/// TypeScript classifier rejects such labels first; the candidate's own label
+/// review rejects them again so a bypassed classifier cannot pass one through.
+pub(super) const HACK_OWNERSHIP_LABEL_NAMESPACES: [&str; 4] = [
+    "io.hack-local.",
+    "io.hack.native-config.",
+    "io.hack.native-file.",
+    "io.hack.storage-witness.",
+];
+
+/// Whether `key` is inside a Hack ownership namespace or is a namespace root
+/// without its trailing dot (for example `io.hack-local`).
+pub(super) fn is_hack_ownership_label(key: &str) -> bool {
+    HACK_OWNERSHIP_LABEL_NAMESPACES
+        .iter()
+        .any(|namespace| key.starts_with(namespace) || namespace.strip_suffix('.') == Some(key))
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn ownership_namespaces_and_roots_are_hack_ownership_labels() {
+        for key in [
+            "io.hack-local.owner",
+            "io.hack-local",
+            "io.hack.native-config.owner",
+            "io.hack.native-config",
+            "io.hack.native-file.token",
+            "io.hack.native-file",
+            "io.hack.storage-witness.carrier",
+            "io.hack.storage-witness",
+        ] {
+            assert!(is_hack_ownership_label(key), "{key}");
+        }
+    }
+
+    #[test]
+    fn near_miss_keys_are_not_hack_ownership_labels() {
+        for key in [
+            "io.hack",
+            "io.hack.",
+            "io.hacker.owner",
+            "io.hack-localx.owner",
+            "io.hack.native-configx",
+            "io.hack.storage",
+            "io.hack.custom",
+            "example.io.hack-local.owner",
+            "IO.HACK-LOCAL.OWNER",
+        ] {
+            assert!(!is_hack_ownership_label(key), "{key}");
+        }
+    }
+}
diff --git a/packages/runtime-core/src/project/compose/service.rs b/packages/runtime-core/src/project/compose/service.rs
index 875c562a6..5cc51846a 100644
--- a/packages/runtime-core/src/project/compose/service.rs
+++ b/packages/runtime-core/src/project/compose/service.rs
@@ -805,11 +805,14 @@ pub(super) fn compile(
         }
         if routing_invalid
             || labels.keys().any(|key| {
-                !(dependency_cache.is_some() && super::dependency_cache::recognized(key))
-                    && !(routing.is_some() && super::routing::recognized(key))
-                    && ["caddy", "traefik", "hack", "com.docker.compose"]
-                        .iter()
-                        .any(|prefix| key == prefix || key.starts_with(&format!("{prefix}.")))
+                // Hack's ownership namespaces are never exempt: no routing or
+                // dependency cache declaration may carry ownership evidence.
+                super::ownership_labels::is_hack_ownership_label(key)
+                    || (!(dependency_cache.is_some() && super::dependency_cache::recognized(key))
+                        && !(routing.is_some() && super::routing::recognized(key))
+                        && ["caddy", "traefik", "hack", "com.docker.compose"]
+                            .iter()
+                            .any(|prefix| key == prefix || key.starts_with(&format!("{prefix}."))))
             })
         {
             diagnostics.push(Diagnostic::error(
diff --git a/packages/runtime-core/tests/project_contract.rs b/packages/runtime-core/tests/project_contract.rs
index 00199a38b..440cf3217 100644
--- a/packages/runtime-core/tests/project_contract.rs
+++ b/packages/runtime-core/tests/project_contract.rs
@@ -523,6 +523,61 @@ fn unsupported_privileged_external_and_unknown_fields_block_enrollment() {
     assert!(fixture.codes().contains(&"external_network".into()));
 }
 
+/// The candidate's own label review rejects Hack's ownership namespaces (the
+/// list `HACK_OWNERSHIP_LABEL_NAMESPACES` declares in TypeScript), so a
+/// project cannot carry ownership evidence even when the TypeScript classifier
+/// is bypassed. Routing and dependency cache declarations never exempt them.
+#[test]
+fn hack_ownership_label_namespaces_block_enrollment() {
+    let owner_label = |fixture: &Fixture| {
+        fixture
+            .codes()
+            .iter()
+            .any(|code| code == "external_route_or_owner_label")
+    };
+    for key in [
+        "io.hack-local.owner",
+        "io.hack.native-config.owner",
+        "io.hack.native-file.token",
+        "io.hack.storage-witness.carrier",
+    ] {
+        for labels in [
+            format!("    labels: {{'{key}': owner-canary}}\n"),
+            format!("    labels: ['{key}=owner-canary']\n"),
+            format!(
+                "    labels:\n      caddy: web.hack\n      caddy.reverse_proxy: '{{{{upstreams 3000}}}}'\n      caddy.tls: internal\n      '{key}': owner-canary\n"
+            ),
+        ] {
+            let fixture = Fixture::new(&format!("{BASIC}{labels}"));
+            let plan = fixture.plan();
+            assert!(owner_label(&fixture), "{key}: {labels}");
+            assert!(!plan.plan.enrollment_compatible, "{key}");
+            assert!(
+                !serde_json::to_string(&plan)
+                    .unwrap()
+                    .contains("owner-canary")
+            );
+            assert_eq!(
+                project::enroll(&fixture.candidate, fixture.options(), &plan.plan_id)
+                    .unwrap_err()
+                    .code,
+                "incompatible_compose"
+            );
+            assert!(!fixture.candidate.state_root.exists());
+        }
+    }
+    // Near misses outside every ownership namespace stay reviewable. Closer
+    // misses (a longer first segment, or another segment under the same
+    // reverse-DNS root) are pinned by the `ownership_labels` unit tests; they
+    // stay out of this file because the TypeScript parity scan reads every
+    // such key here as a label Hack writes.
+    let fixture = Fixture::new(&format!(
+        "{BASIC}    labels: {{example.io.hack-local.owner: a, io-hack-local.owner: b, io_hack.native-config.owner: c}}\n"
+    ));
+    assert!(!owner_label(&fixture));
+    assert!(fixture.plan().plan.enrollment_compatible);
+}
+
 #[test]
 fn explicit_external_network_replacement_is_owned_internal_and_review_bound() {
     let original =
diff --git a/src/lib/hack-ownership-labels.ts b/src/lib/hack-ownership-labels.ts
index 2cbc1d146..2bfd5e94a 100644
--- a/src/lib/hack-ownership-labels.ts
+++ b/src/lib/hack-ownership-labels.ts
@@ -18,7 +18,11 @@
  *   (`owner`, `generation`, `helper`, `carrier`).
  *
  * A project must not declare a label in these namespaces, because their
- * consumers trust them as ownership evidence. Add a namespace here before
+ * consumers trust them as ownership evidence. The TypeScript Compose
+ * classifier rejects them, and runtime-core's own label review rejects them
+ * again from a Rust mirror of this list
+ * (`packages/runtime-core/src/project/compose/ownership_labels.rs`) that the
+ * same test keeps identical. Add a namespace here, and to the mirror, before
  * writing a label in it.
  */
 export const HACK_OWNERSHIP_LABEL_NAMESPACES = [
diff --git a/tests/hack-ownership-labels.test.ts b/tests/hack-ownership-labels.test.ts
index dea0628c5..47901d64c 100644
--- a/tests/hack-ownership-labels.test.ts
+++ b/tests/hack-ownership-labels.test.ts
@@ -5,9 +5,10 @@ import { HACK_OWNERSHIP_LABEL_NAMESPACES } from "../src/lib/hack-ownership-label
 
 /**
  * Pins `HACK_OWNERSHIP_LABEL_NAMESPACES` to the label keys Hack actually
- * writes and verifies. The scan reads the TypeScript CLI and the Rust
- * runtime-core sources (read-only); the two files that only restate the list
- * are left out, so the list cannot satisfy itself.
+ * writes and verifies, and to runtime-core's Rust mirror of the list. The scan
+ * reads the TypeScript CLI and the Rust runtime-core sources (read-only); the
+ * files that only restate the list are left out, so the list cannot satisfy
+ * itself.
  */
 
 const REPO = resolve(import.meta.dir, "..");
@@ -17,9 +18,12 @@ const PATTERNS = [
   "packages/*/src/**/*.rs",
   "packages/*/tests/**/*.rs",
 ];
+const RUST_MIRROR =
+  "packages/runtime-core/src/project/compose/ownership_labels.rs";
 const RESTATEMENTS = new Set([
   "src/lib/hack-ownership-labels.ts",
   "src/lib/native-compose-backend-features.ts",
+  RUST_MIRROR,
 ]);
 const KEY = /\bio\.hack[A-Za-z0-9._-]*/g;
 
@@ -62,3 +66,27 @@ test("every declared ownership namespace is written or verified somewhere", asyn
   );
   expect(unused).toEqual([]);
 });
+
+/** The string literals of the Rust `HACK_OWNERSHIP_LABEL_NAMESPACES` array. */
+async function rustMirrorNamespaces(): Promise<readonly string[]> {
+  const text = await readFile(join(REPO, RUST_MIRROR), "utf8");
+  const body =
+    /const HACK_OWNERSHIP_LABEL_NAMESPACES: \[&str; (\d+)\] = \[([^\]]*)\];/.exec(
+      text
+    );
+  expect(body).not.toBeNull();
+  // Line comments are not entries, even when they quote a namespace.
+  const entries = (body?.[2] ?? "").replace(/\/\/[^\n]*/g, "");
+  const literals = [...entries.matchAll(/"([^"]*)"/g)].map(
+    (match) => match[1] ?? ""
+  );
+  // The declared array length must agree with the literals that were read.
+  expect(literals.length).toBe(Number(body?.[1]));
+  return literals;
+}
+
+test("runtime-core's label review rejects exactly the declared ownership namespaces", async () => {
+  expect(await rustMirrorNamespaces()).toEqual([
+    ...HACK_OWNERSHIP_LABEL_NAMESPACES,
+  ]);
+});