diff --git a/src/mxpak/config/toml_reader.gleam b/src/mxpak/config/toml_reader.gleam
index 9cee153..1b1378a 100644
--- a/src/mxpak/config/toml_reader.gleam
+++ b/src/mxpak/config/toml_reader.gleam
@@ -2,6 +2,7 @@
 ////
 
 import gleam/dict
+import gleam/list
 import gleam/option
 import gleam/result
 import mxpak/error
@@ -93,6 +94,7 @@ fn extract_project_config(
     Ok(widgets_table) -> parse_widgets(widgets_table)
     Error(_) -> dict.new()
   }
+  use _ <- result.try(validate_widget_names(widgets))
   Ok(ProjectConfig(
     mendix_version: mendix_version,
     mode: mode,
@@ -101,6 +103,14 @@ fn extract_project_config(
   ))
 }
 
+fn validate_widget_names(
+  widgets: dict.Dict(String, WidgetConfig),
+) -> Result(Nil, error.Error) {
+  widgets
+  |> dict.keys
+  |> list.try_each(widget.validate_name)
+}
+
 fn parse_widgets(
   table: dict.Dict(String, tom.Toml),
 ) -> dict.Dict(String, WidgetConfig) {
diff --git a/src/mxpak/downloader.gleam b/src/mxpak/downloader.gleam
index 4f0a48f..2f16392 100644
--- a/src/mxpak/downloader.gleam
+++ b/src/mxpak/downloader.gleam
@@ -39,6 +39,7 @@ pub fn download_and_extract(
   content_id content_id: option.Option(Int),
   project_root project_root: String,
 ) -> Result(DownloadResult, error.Error) {
+  use _ <- result.try(widget.validate_name(name))
   let cache_dir = project_root <> "/build/widgets/" <> name
   use zip_data <- result.try(download_binary(url))
   let hash = integrity.sha256(zip_data)
@@ -92,6 +93,7 @@ pub fn download_mpk(
   content_id content_id: option.Option(Int),
   target_path target_path: String,
 ) -> Result(DownloadResult, error.Error) {
+  use _ <- result.try(widget.validate_name(name))
   use zip_data <- result.try(download_binary(url))
   let hash = integrity.sha256(zip_data)
   use cached <- result.try(cache.has(hash))
@@ -134,6 +136,7 @@ pub fn restore_from_cache(
   content_id content_id: option.Option(Int),
   project_root project_root: String,
 ) -> Result(DownloadResult, error.Error) {
+  use _ <- result.try(widget.validate_name(name))
   let cache_dir = project_root <> "/build/widgets/" <> name
   use _ <- result.try(cache.restore(hash, cache_dir))
   use has_mjs <- result.try(has_mjs_in_dir(cache_dir))
diff --git a/src/mxpak/widget.gleam b/src/mxpak/widget.gleam
index 291f255..d2b1e95 100644
--- a/src/mxpak/widget.gleam
+++ b/src/mxpak/widget.gleam
@@ -1,6 +1,9 @@
 //// Models the runtime kind of a Mendix widget package.
 ////
 
+import gleam/string
+import mxpak/error
+
 /// Represents whether a widget uses the classic or pluggable runtime.
 pub type Kind {
   /// A modern pluggable widget containing JavaScript modules.
@@ -16,3 +19,33 @@ pub fn is_classic(kind kind: Kind) -> Bool {
     Pluggable -> False
   }
 }
+
+/// Validates a configured widget name before it is used in a file path.
+///
+/// Widget names originate in project TOML files, so they are untrusted path
+/// segments. Dotted names remain valid because they are legal TOML section
+/// names and safe single path segments.
+pub fn validate_name(name name: String) -> Result(Nil, error.Error) {
+  case name {
+    "" ->
+      Error(error.configuration(
+        "Widget name must not be empty when it is used in a file path",
+      ))
+    "." | ".." ->
+      Error(error.configuration(
+        "Widget name must not be a relative directory reference: " <> name,
+      ))
+    _ ->
+      case
+        string.contains(name, "/")
+        || string.contains(name, "\\")
+        || string.contains(name, "\u{0000}")
+      {
+        True ->
+          Error(error.configuration(
+            "Widget name must not contain path separators or NUL: " <> name,
+          ))
+        False -> Ok(Nil)
+      }
+  }
+}
diff --git a/test/config_test.gleam b/test/config_test.gleam
index 56f2428..93b821d 100644
--- a/test/config_test.gleam
+++ b/test/config_test.gleam
@@ -2,6 +2,7 @@
 ////
 
 import gleam/dict
+import gleam/list
 import gleam/option
 import gleam/string
 import gleeunit
@@ -376,6 +377,50 @@ pub fn env_reader_missing_file_test() -> Nil {
   Nil
 }
 
+/// Verifies traversal widget names are rejected at the configuration boundary.
+pub fn read_config_rejects_path_traversal_names_test() -> Nil {
+  let cases = [
+    #("../../evil", "parent"),
+    #("/absolute/evil", "absolute"),
+    #("..", "dot"),
+    #("nested/evil", "nested"),
+    #("nested\\evil", "backslash"),
+  ]
+  list.each(cases, fn(pair) {
+    let #(name, slug) = pair
+    let dir = "build/test_tmp/traversal_" <> slug
+    simplifile.create_directory_all(dir)
+    |> should.be_ok
+    simplifile.write(
+      dir <> "/gleam.toml",
+      "[tools.mxpak.widgets.\"" <> name <> "\"]\nversion = \"1.0.0\"\n",
+    )
+    |> should.be_ok
+    toml_reader.read_config(dir)
+    |> should.be_error
+    simplifile.delete(dir)
+    |> should.be_ok
+  })
+  Nil
+}
+
+/// Verifies legal dotted widget names remain accepted.
+pub fn read_config_accepts_dotted_names_test() -> Nil {
+  let dir = "build/test_tmp/dotted_name"
+  simplifile.create_directory_all(dir)
+  |> should.be_ok
+  simplifile.write(
+    dir <> "/gleam.toml",
+    "[tools.mxpak.widgets.\"com.example.Widget\"]\nversion = \"1.0.0\"\n",
+  )
+  |> should.be_ok
+  toml_reader.read_config(dir)
+  |> should.be_ok
+  simplifile.delete(dir)
+  |> should.be_ok
+  Nil
+}
+
 fn contains(haystack: String, needle: String) -> Bool {
   string.contains(haystack, needle)
 }
diff --git a/test/mxpak_test.gleam b/test/mxpak_test.gleam
index 6230eeb..5377df2 100644
--- a/test/mxpak_test.gleam
+++ b/test/mxpak_test.gleam
@@ -1,9 +1,11 @@
 //// Tests mxpak behavior for mxpak.
 ////
 
+import gleam/list
 import gleeunit
 import gleeunit/should
 import mxpak/cli
+import mxpak/widget
 
 /// Runs this module's test suite.
 pub fn main() -> Nil {
@@ -24,6 +26,18 @@ pub fn parse_version_test() -> Nil {
   Nil
 }
 
+/// Verifies widget names are safe path segments.
+pub fn widget_validate_name_test() -> Nil {
+  ["DataGrid", "com.example.Widget", "Chart 2"]
+  |> list.each(fn(name) { widget.validate_name(name) |> should.be_ok })
+  [
+    "", ".", "..", "../sibling", "nested/evil", "nested\\evil", "/absolute/evil",
+    "a\u{0000}b",
+  ]
+  |> list.each(fn(name) { widget.validate_name(name) |> should.be_error })
+  Nil
+}
+
 /// Verifies parse version short behavior.
 pub fn parse_version_short_test() -> Nil {
   cli.parse(["-v"])