diff --git a/src-tauri/Cargo.lock b/src-tauri/Cargo.lock
index e7263b14..38ee99fc 100644
--- a/src-tauri/Cargo.lock
+++ b/src-tauri/Cargo.lock
@@ -1762,6 +1762,7 @@ dependencies = [
  "crossbeam-channel",
  "directories",
  "dirs 7.0.0",
+ "dunce",
  "env_logger",
  "flate2",
  "futures-util",
diff --git a/src-tauri/Cargo.toml b/src-tauri/Cargo.toml
index db927c56..b997d0cf 100644
--- a/src-tauri/Cargo.toml
+++ b/src-tauri/Cargo.toml
@@ -119,6 +119,7 @@ serde_yaml = "0.9"
 thiserror = "2.0"
 regex-lite = "0.1"
 tempfile = "3"
+dunce = "1"
 maxminddb = "0.32"
 quick-xml = { version = "0.42", features = ["serialize"] }
 
diff --git a/src-tauri/src/extension_manager.rs b/src-tauri/src/extension_manager.rs
index 4a760044..e8cfa424 100644
--- a/src-tauri/src/extension_manager.rs
+++ b/src-tauri/src/extension_manager.rs
@@ -683,7 +683,9 @@ impl ExtensionManager {
     dir: &Path,
     manifest: &serde_json::Value,
   ) -> Result<Extension, Box<dyn std::error::Error>> {
-    let absolute = dir.canonicalize()?;
+    // dunce, not std: on Windows std returns the `\\?\C:\...` form, which the
+    // Extensions page would show and `--load-extension` would be handed.
+    let absolute = dunce::canonicalize(dir)?;
     if !path_is_load_extension_safe(&absolute) {
       return Err(err_code("EXTENSION_PATH_HAS_COMMA"));
     }
@@ -956,7 +958,7 @@ impl ExtensionManager {
     manifest: &serde_json::Value,
     explicit_name_provided: bool,
   ) -> Result<(), Box<dyn std::error::Error>> {
-    let absolute = dir.canonicalize()?;
+    let absolute = dunce::canonicalize(dir)?;
     if !path_is_load_extension_safe(&absolute) {
       return Err(err_code("EXTENSION_PATH_HAS_COMMA"));
     }
@@ -2201,7 +2203,11 @@ mod tests {
 
     let mgr = ExtensionManager::new();
     let source = write_unpacked_fixture(&tmp.path().join("linked-extension"), "Linked Fixture");
-    let canonical = source.canonicalize().unwrap().to_string_lossy().to_string();
+    let canonical = dunce::canonicalize(&source)
+      .unwrap()
+      .to_string_lossy()
+      .to_string();
+    assert!(!canonical.starts_with(r"\\?\"), "{canonical}");
     let ext = mgr
       .add_unpacked_extension("Ignored".to_string(), &source, true)
       .unwrap();
diff --git a/src-tauri/src/mcp_integrations.rs b/src-tauri/src/mcp_integrations.rs
index c55e17fb..bcd85660 100644
--- a/src-tauri/src/mcp_integrations.rs
+++ b/src-tauri/src/mcp_integrations.rs
@@ -180,7 +180,10 @@ impl AgentEnv {
   pub fn from_process() -> Option<Self> {
     Some(Self {
       platform: Platform::current(),
-      home: dirs::home_dir()?,
+      // std, not `dirs`: on Windows `dirs` asks for the Profile known folder
+      // and ignores USERPROFILE, while the clients themselves (Node's
+      // os.homedir(), Rust's home_dir) follow USERPROFILE.
+      home: std::env::home_dir()?,
       appdata: env_path("APPDATA"),
       xdg_config_home: env_path("XDG_CONFIG_HOME"),
       codex_home: env_path("CODEX_HOME"),