diff --git a/src-tauri/src/browser_runner.rs b/src-tauri/src/browser_runner.rs
index 42ba6a7..f2bc706 100644
--- a/src-tauri/src/browser_runner.rs
+++ b/src-tauri/src/browser_runner.rs
@@ -1380,9 +1380,10 @@ impl BrowserRunner {
       return Err(error_details.into());
     }
 
-    registry
-      .mark_download_completed(&browser_str, &version)
-      .map_err(|e| format!("Failed to mark download as completed: {e}"))?;
+    // Mark completion in registry. If it fails (e.g., rare race during cleanup), log but continue.
+    if let Err(e) = registry.mark_download_completed(&browser_str, &version) {
+      eprintln!("Warning: Could not mark {browser_str} {version} as completed in registry: {e}");
+    }
     registry
       .save()
       .map_err(|e| format!("Failed to save registry: {e}"))?;
diff --git a/src-tauri/src/download.rs b/src-tauri/src/download.rs
index bca3e08..8c4ec9e 100644
--- a/src-tauri/src/download.rs
+++ b/src-tauri/src/download.rs
@@ -402,23 +402,44 @@ impl Downloader {
       existing_size = meta.len();
     }
 
-    // Build request, add Range only if we have bytes
-    let mut request = self
-      .client
-      .get(&download_url)
-      .header(
-        "User-Agent",
-        "Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/136.0.0.0 Safari/537.36",
-      );
+    // Build request, add Range only if we have bytes. If the server responds with 416 (Range Not
+    // Satisfiable), delete the partial file and retry once without the Range header.
+    let response = {
+      let mut request = self
+        .client
+        .get(&download_url)
+        .header(
+          "User-Agent",
+          "Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/136.0.0.0 Safari/537.36",
+        );
 
-    if existing_size > 0 {
-      request = request.header("Range", format!("bytes={existing_size}-"));
-    }
+      if existing_size > 0 {
+        request = request.header("Range", format!("bytes={existing_size}-"));
+      }
 
-    // Start download (or resume)
-    let response = request.send().await?;
+      let first = request.send().await?;
 
-    // Check if the response is successful
+      if first.status().as_u16() == 416 && existing_size > 0 {
+        // Partial file on disk is not acceptable to the server — remove it and retry from scratch
+        let _ = std::fs::remove_file(&file_path);
+        existing_size = 0;
+
+        let retry = self
+          .client
+          .get(&download_url)
+          .header(
+            "User-Agent",
+            "Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/136.0.0.0 Safari/537.36",
+          )
+          .send()
+          .await?;
+        retry
+      } else {
+        first
+      }
+    };
+
+    // Check if the response is successful (200 OK or 206 Partial Content)
     if !(response.status().is_success() || response.status().as_u16() == 206) {
       return Err(format!("Download failed with status: {}", response.status()).into());
     }
diff --git a/src-tauri/src/platform_browser.rs b/src-tauri/src/platform_browser.rs
index b42a74c..f72d019 100644
--- a/src-tauri/src/platform_browser.rs
+++ b/src-tauri/src/platform_browser.rs
@@ -727,41 +727,10 @@ pub mod windows {
       cmd.current_dir(parent_dir);
     }
 
-    let output = cmd.output()?;
-
-    if !output.status.success() {
-      // Try fallback without --new-window
-      let mut fallback_cmd = Command::new(&executable_path);
-      fallback_cmd.args([
-        &format!(
-          "--user-data-dir={}",
-          profile
-            .get_profile_data_path(profiles_dir)
-            .to_string_lossy()
-        ),
-        url,
-      ]);
-
-      if let Some(parent_dir) = browser_dir
-        .parent()
-        .or_else(|| browser_dir.ancestors().nth(1))
-      {
-        fallback_cmd.current_dir(parent_dir);
-      }
-
-      let fallback_output = fallback_cmd.output()?;
-
-      if !fallback_output.status.success() {
-        return Err(
-          format!(
-            "Failed to open URL in existing Chromium-based browser: {}",
-            String::from_utf8_lossy(&fallback_output.stderr)
-          )
-          .into(),
-        );
-      }
-    }
-
+    // Do not call output() to avoid blocking the UI thread while the browser processes the request.
+    // Spawn the helper process and return immediately. This applies to Chromium-based browsers
+    // including Brave to prevent UI freezes observed in production.
+    let _child = cmd.spawn()?;
     Ok(())
   }