@@ -38,6 +38,15 @@ changes:
     description: This feature is no longer experimental.
 -->
 
+<!-- worker-execargv-permission-ceiling -->
+When the Permission Model is enabled in the parent process, creating a
+`worker_threads.Worker` with an explicit `execArgv` option (including an empty
+array) no longer allows the worker to obtain a wider permission-related grant
+set than the parent. Non-permission `execArgv` flags are unaffected. This is a
+breaking change relative to earlier releases where `execArgv: []` could drop
+the parent's Permission Model grants.
+
+
 > Stability: 2 - Stable
 
 The Node.js Permission Model is a mechanism for restricting access to specific
 
@@ -1605,6 +1605,13 @@ changes:
     description: The `resourceLimits` option was introduced.
 -->
 
+<!-- worker-execargv-permission-ceiling -->
+**Permission Model (breaking):** If the parent process runs with the
+Permission Model enabled, an explicit `execArgv` (including `[]`) does not
+disable or exceed the parent's permission-related grants. See the
+[Permission Model](permissions.md#permission-model) documentation.
+
+
 * `filename` {string|URL} The path to the Worker's main script or module. Must
   be either an absolute path or a relative path (i.e. relative to the
   current working directory) starting with `./` or `../`, or a WHATWG `URL`
 
@@ -11,6 +11,7 @@
 #include "node_profiling.h"
 #include "node_snapshot_builder.h"
 #include "permission/permission.h"
+#include "path.h"
 #include "util-inl.h"
 #include "v8-cppgc.h"
 #include "v8-profiler.h"
@@ -503,6 +504,235 @@ Worker::~Worker() {
   Debug(this, "Worker %llu destroyed", thread_id_.id);
 }
 
+
+
+// SEMVER-MAJOR: Permission ceiling for Worker when execArgv is explicit
+// (including []). Default Worker (no execArgv) is unchanged.
+
+namespace {
+
+#define PERMISSION_BOOL_FLAGS(V)                  \
+  V(allow_addons, "--allow-addons")               \
+  V(allow_inspector, "--allow-inspector")         \
+  V(allow_child_process, "--allow-child-process") \
+  V(allow_net, "--allow-net")                     \
+  V(allow_wasi, "--allow-wasi")                   \
+  V(allow_ffi, "--allow-ffi")                     \
+  V(allow_openssl_store, "--allow-openssl-store") \
+  V(allow_worker_threads, "--allow-worker")
+
+bool WorkerConfiguredPermission(const EnvironmentOptions* w) {
+  if (w == nullptr) return false;
+  if (w->permission || w->permission_audit) return true;
+  if (!w->allow_fs_read.empty() || !w->allow_fs_write.empty()) return true;
+#define V(field, flag) || w->field
+  return false PERMISSION_BOOL_FLAGS(V);
+#undef V
+}
+
+void ApplyParentPermissionCeiling(EnvironmentOptions* w,
+                                  const EnvironmentOptions* parent) {
+  w->permission = true;
+  w->permission_audit = parent->permission_audit;
+#define V(field, flag) w->field = parent->field;
+  PERMISSION_BOOL_FLAGS(V)
+#undef V
+  w->allow_fs_read = parent->allow_fs_read;
+  w->allow_fs_write = parent->allow_fs_write;
+}
+
+void NormalizePathForCompare(std::string* s) {
+  while (s->size() > 1 &&
+         (s->back() == '/' || s->back() == static_cast<char>(92))) {
+    s->pop_back();
+  }
+#ifdef _WIN32
+  for (char& c : *s) {
+    if (c >= 'A' && c <= 'Z') {
+      c = static_cast<char>(c - 'A' + 'a');
+    }
+    if (c == '/') c = static_cast<char>(92);
+  }
+#endif
+}
+
+std::string ResolveForCompare(Environment* env, const std::string& in) {
+  if (in.empty() || in == "*") return in;
+  std::string resolved =
+      PathResolve(env, std::vector<std::string_view>{std::string_view(in)});
+  if (resolved.empty()) resolved = in;
+  NormalizePathForCompare(&resolved);
+  return resolved;
+}
+
+bool ParentEntryCoversResolvedPath(Environment* env,
+                                   const std::string& parent_raw,
+                                   const std::string& resolved_requested) {
+  if (parent_raw == "*") return true;
+  const std::string parent = ResolveForCompare(env, parent_raw);
+  if (parent.empty()) return false;
+  if (resolved_requested == parent) return true;
+  if (resolved_requested.size() <= parent.size()) return false;
+  if (resolved_requested.compare(0, parent.size(), parent) != 0) return false;
+  const char next = resolved_requested[parent.size()];
+  return next == '/' || next == static_cast<char>(92);
+}
+
+bool ParentListHasWildcard(const std::vector<std::string>& parent) {
+  for (const std::string& entry : parent) {
+    if (entry == "*") return true;
+  }
+  return false;
+}
+
+void FilterPathListToParentSubset(Environment* env,
+                                  EnvironmentOptions* w,
+                                  std::vector<std::string>* worker,
+                                  const std::vector<std::string>& parent) {
+  if (worker == nullptr) return;
+  // Worker listed no fs paths → keep empty (restrict).
+  if (worker->empty()) return;
+  // Parent "*" → FS already unrestricted; worker paths cannot exceed parent.
+  if (ParentListHasWildcard(parent)) return;
+
+  std::vector<std::string> out;
+  out.reserve(worker->size());
+  bool saw_star = false;
+  for (const std::string& wpath : *worker) {
+    if (wpath == "*") {
+      saw_star = true;
+      continue;
+    }
+    const std::string resolved_wpath = ResolveForCompare(env, wpath);
+    for (const std::string& entry : parent) {
+      if (ParentEntryCoversResolvedPath(env, entry, resolved_wpath)) {
+        out.push_back(resolved_wpath);
+        break;
+      }
+    }
+  }
+  // "*" alone or combined with concrete paths still means "everything the
+  // parent allows" here, not "just the concrete paths that also matched" —
+  // treating it as a subset would silently grant *less* than requesting "*"
+  // by itself, which is backwards. See PR discussion for why this needs to
+  // be unconditional on saw_star, not just "saw_star && out.empty()".
+  if (saw_star) {
+    *worker = parent;
+    return;
+  }
+  *worker = std::move(out);
+}
+
+void IntersectPermissionGrants(Environment* env,
+                               EnvironmentOptions* w,
+                               const EnvironmentOptions* parent) {
+  w->permission = true;
+  w->permission_audit = w->permission_audit || parent->permission_audit;
+#define V(field, flag) w->field = w->field && parent->field;
+  PERMISSION_BOOL_FLAGS(V)
+#undef V
+  FilterPathListToParentSubset(env, w, &w->allow_fs_read, parent->allow_fs_read);
+  FilterPathListToParentSubset(
+      env, w, &w->allow_fs_write, parent->allow_fs_write);
+}
+
+void ClampWorkerPermissionToParent(Environment* env,
+                                   PerIsolateOptions* worker_opts) {
+  if (worker_opts == nullptr || env == nullptr ||
+      !env->permission()->enabled()) {
+    return;
+  }
+  EnvironmentOptions* parent =
+      env->isolate_data()->options()->get_per_env_options();
+  EnvironmentOptions* w = worker_opts->get_per_env_options();
+  if (parent == nullptr || w == nullptr) return;
+
+  if (!WorkerConfiguredPermission(w)) {
+    ApplyParentPermissionCeiling(w, parent);
+  } else {
+    IntersectPermissionGrants(env, w, parent);
+  }
+}
+
+bool IsPermissionCliToken(const std::string& a) {
+  if (a == "--permission" || a == "--permission-audit") return true;
+  if (a == "--allow-fs-read" || a == "--allow-fs-write") return true;
+  if (a.rfind("--allow-fs-read=", 0) == 0) return true;
+  if (a.rfind("--allow-fs-write=", 0) == 0) return true;
+#define V(field, flag)                       \
+  if (a == flag) return true;                \
+  {                                          \
+    const size_t n = sizeof(flag) - 1;       \
+    if (a.size() > n && a.compare(0, n, flag) == 0 && a[n] == '=') \
+      return true;                           \
+  }
+  PERMISSION_BOOL_FLAGS(V)
+#undef V
+  return false;
+}
+
+bool PermissionFlagTakesNextArg(const std::string& a) {
+  return a == "--allow-fs-read" || a == "--allow-fs-write";
+}
+
+bool PathSafeForAllowFlag(const std::string& path) {
+  if (path.empty()) return false;
+  for (unsigned char c : path) {
+    if (c == 0 || c == 10 || c == 13) return false;
+  }
+  return true;
+}
+
+void RebuildExecArgvOutFromPermissionOptions(
+    PerIsolateOptions* worker_opts, std::vector<std::string>* exec_argv_out) {
+  if (worker_opts == nullptr || exec_argv_out == nullptr) return;
+  EnvironmentOptions* w = worker_opts->get_per_env_options();
+  if (w == nullptr || !w->permission) return;
+
+  std::vector<std::string> kept;
+  kept.reserve(exec_argv_out->size());
+  for (size_t i = 0; i < exec_argv_out->size(); ++i) {
+    const std::string& tok = (*exec_argv_out)[i];
+    if (tok.empty()) continue;
+    if (IsPermissionCliToken(tok)) {
+      // Space-form --allow-fs-read/--allow-fs-write always consume the next
+      // token as their argument, regardless of its first character — paths
+      // are legal starting with '-' on Unix, so gating on that would leave
+      // a stray token behind instead of consuming it as the flag's value.
+      if (PermissionFlagTakesNextArg(tok) && i + 1 < exec_argv_out->size()) {
+        ++i;
+      }
+      continue;
+    }
+    kept.push_back(tok);
+  }
+
+  std::vector<std::string> out;
+  out.reserve(kept.size() + 16 + w->allow_fs_read.size() +
+              w->allow_fs_write.size());
+  for (const std::string& tok : kept) out.push_back(tok);
+
+  out.push_back("--permission");
+  if (w->permission_audit) out.push_back("--permission-audit");
+#define V(field, flag) \
+  if (w->field) out.push_back(flag);
+  PERMISSION_BOOL_FLAGS(V)
+#undef V
+  for (const std::string& p : w->allow_fs_read) {
+    if (!PathSafeForAllowFlag(p)) continue;
+    out.push_back("--allow-fs-read=" + p);
+  }
+  for (const std::string& p : w->allow_fs_write) {
+    if (!PathSafeForAllowFlag(p)) continue;
+    out.push_back("--allow-fs-write=" + p);
+  }
+  *exec_argv_out = std::move(out);
+}
+
+#undef PERMISSION_BOOL_FLAGS
+
+}  // namespace
+
 void Worker::New(const FunctionCallbackInfo<Value>& args) {
   Environment* env = Environment::GetCurrent(args);
   THROW_IF_INSUFFICIENT_PERMISSIONS(
@@ -682,6 +912,14 @@ void Worker::New(const FunctionCallbackInfo<Value>& args) {
     per_isolate_opts = env->isolate_data()->options()->Clone();
   }
 
+  // Explicit execArgv only (including []). Default Worker path unchanged.
+  if (env->permission()->enabled() && per_isolate_opts &&
+      args[2]->IsArray()) {
+    ClampWorkerPermissionToParent(env, per_isolate_opts.get());
+    RebuildExecArgvOutFromPermissionOptions(per_isolate_opts.get(),
+                                            &exec_argv_out);
+  }
+
   // Internal workers should not wait for inspector frontend to connect or
   // break on the first line of internal scripts. Module loader threads are
   // essential to load user codes and must not be blocked by the inspector