diff --git a/restricted-execution/default.nix b/restricted-execution/default.nix
index c77c52d..a909585 100644
--- a/restricted-execution/default.nix
+++ b/restricted-execution/default.nix
@@ -41,6 +41,8 @@ let
       ''
         mkdir -p "$out/lib" "$out/bin"
         cp ${./service.mjs} "$out/lib/service.mjs"
+        cp ${../socket-address.mjs} "$out/lib/socket-address.mjs"
+        substituteInPlace "$out/lib/service.mjs" --replace-fail '../socket-address.mjs' './socket-address.mjs'
         cp ${./worker.mjs} "$out/lib/worker.mjs"
         makeWrapper ${pkgs.nodejs_24}/bin/node "$out/bin/quixos-restricted-registry" \
           --add-flags "$out/lib/service.mjs" \
@@ -48,6 +50,13 @@ let
           --set QUIXOS_RESTRICTED_SANDBOX ${sandbox}/bin/quixos-restricted-sandbox \
           --set QUIXOS_RESTRICTED_WORKER "$out/lib/worker.mjs"
       '';
+  qualificationSource = pkgs.lib.fileset.toSource {
+    root = ../.;
+    fileset = pkgs.lib.fileset.unions [
+      (pkgs.lib.fileset.fileFilter (file: file.hasExt "mjs") ./.)
+      ../socket-address.mjs
+    ];
+  };
   qualification =
     pkgs.runCommand "quixos-restricted-execution-qualification"
       {
@@ -56,7 +65,7 @@ let
         QUIXOS_TEST_SDK = "${sdk}/core.mjs";
       }
       ''
-        node --test ${./.}/service.test.mjs
+        node --test ${qualificationSource}/restricted-execution/service.test.mjs
         touch "$out"
       '';
 in
@@ -69,6 +78,7 @@ in
     nativeProbeSandbox
     sdk
     runtime
+    qualificationSource
     qualification
     ;
 }
diff --git a/restricted-execution/identity-launcher.nix b/restricted-execution/identity-launcher.nix
index 7cfdca1..f277cfc 100644
--- a/restricted-execution/identity-launcher.nix
+++ b/restricted-execution/identity-launcher.nix
@@ -12,17 +12,31 @@ assert builtins.match "[a-z][a-z0-9_-]{0,63}" authorityUser != null;
 assert builtins.match "/run/[a-zA-Z0-9_/-]+" engineDirectory != null;
 assert !(pkgs.lib.hasInfix ".." engineDirectory);
 assert !(pkgs.lib.hasSuffix "/" engineDirectory);
-assert builtins.stringLength engineDirectory < 80;
 assert builtins.isInt firstUid && builtins.isInt identityCount;
 assert firstUid >= 610000 && firstUid + identityCount <= 2147483647;
 assert identityCount >= 1 && identityCount <= 64;
-pkgs.runCommand "quixos-restricted-identity-launcher" { nativeBuildInputs = [ pkgs.stdenv.cc ]; } ''
-  mkdir -p "$out/bin"
-  $CC -O2 -Wall -Wextra -Werror ${./identity-launcher.c} \
-    -DSANDBOX_EXECUTABLE='"${sandbox}/bin/quixos-restricted-sandbox"' \
-    -DAUTHORITY_USER='"${authorityUser}"' \
-    -DENGINE_DIRECTORY='"${engineDirectory}"' \
-    -DENGINE_FIRST_UID=${toString firstUid} \
-    -DENGINE_IDENTITY_COUNT=${toString identityCount} \
-    -o "$out/bin/quixos-restricted-engine"
-''
+pkgs.runCommand "quixos-restricted-identity-launcher"
+  {
+    nativeBuildInputs = [
+      pkgs.stdenv.cc
+      pkgs.nodejs_24
+    ];
+    QUIXOS_RESTRICTED_ENGINE_DIRECTORY = engineDirectory;
+  }
+  ''
+    # Validate the complete generated filename with the shared UTF-8 policy,
+    # before compiling or installing a launcher for this configured /run root.
+    node --input-type=module <<'JS'
+    import { checkedSocketPath } from '${../socket-address.mjs}';
+    for (const filename of ["broker.sock", "engine.sock"])
+      checkedSocketPath(process.env.QUIXOS_RESTRICTED_ENGINE_DIRECTORY + "/qx-engine-XXXXXX/" + filename);
+    JS
+    mkdir -p "$out/bin"
+    $CC -O2 -Wall -Wextra -Werror ${./identity-launcher.c} \
+      -DSANDBOX_EXECUTABLE='"${sandbox}/bin/quixos-restricted-sandbox"' \
+      -DAUTHORITY_USER='"${authorityUser}"' \
+      -DENGINE_DIRECTORY='"${engineDirectory}"' \
+      -DENGINE_FIRST_UID=${toString firstUid} \
+      -DENGINE_IDENTITY_COUNT=${toString identityCount} \
+      -o "$out/bin/quixos-restricted-engine"
+  ''
diff --git a/restricted-execution/service.mjs b/restricted-execution/service.mjs
index 091b79e..a4140b9 100644
--- a/restricted-execution/service.mjs
+++ b/restricted-execution/service.mjs
@@ -6,6 +6,8 @@ import { constants } from "node:fs";
 import { tmpdir } from "node:os";
 import { join, dirname } from "node:path";
 
+import { checkedSocketPath } from "../socket-address.mjs";
+
 const abi = "quixos-transaction-ports-v1";
 /** Reserved supervisor faults are not authored domain rejections. A graph
  * transaction must roll back without recording a permanent rejected outcome
@@ -359,10 +361,16 @@ export async function serveRestrictedRegistry(config, io = process) {
       () => destroyEngine(engine),
     );
     if (!call.open) return;
+    if (config.sandboxIdentity) {
+      // The privileged helper owns a fixed explicit /run root and requires
+      // this exact basename. Keep its cross-UID ancestry and identity rules.
+      for (const filename of ["broker.sock", "engine.sock"])
+        checkedSocketPath(tmpdir() + "/qx-engine-XXXXXX/" + filename);
+    }
     engine.directory = await mkdtemp(join(tmpdir(), "qx-engine-"));
     if (!call.open) return;
-    const broker = join(engine.directory, "broker.sock");
-    engine.socket = join(engine.directory, "engine.sock");
+    const broker = checkedSocketPath(join(engine.directory, "broker.sock"));
+    engine.socket = checkedSocketPath(join(engine.directory, "engine.sock"));
     engine.server = createServer(async (request, response) => {
       const call = engine.current;
       const message = call?.message;
diff --git a/socket-address.mjs b/socket-address.mjs
index e75695b..57d866f 100644
--- a/socket-address.mjs
+++ b/socket-address.mjs
@@ -68,7 +68,8 @@ export function socketDirectory(identity, options) {
 }
 
 export function socketAddress(identity, role, options) {
-  if (typeof role !== "string" || !/^[a-z][a-z0-9-]{0,10}$/.test(role)) throw Error("Invalid bounded socket role");
+  if (typeof role !== "string" || role !== role.trim() || !/^[a-z][a-z0-9-]{0,10}$/.test(role))
+    throw Error("Invalid bounded socket role");
   return checkedSocketPath(path.join(socketDirectory(identity, options), role + ".sock"));
 }