diff --git a/next-env.d.ts b/next-env.d.ts
index b87975d..9edff1c 100644
--- a/next-env.d.ts
+++ b/next-env.d.ts
@@ -1,6 +1,6 @@
 /// <reference types="next" />
 /// <reference types="next/image-types/global" />
-import "./dist/dev/types/routes.d.ts";
+import "./.next/types/routes.d.ts";
 
 // NOTE: This file should not be edited
 // see https://nextjs.org/docs/app/api-reference/config/typescript for more information.
diff --git a/src-tauri/src/downloader.rs b/src-tauri/src/downloader.rs
index 21d61c4..09dbd1a 100644
--- a/src-tauri/src/downloader.rs
+++ b/src-tauri/src/downloader.rs
@@ -308,40 +308,12 @@ impl Downloader {
       .resolve_download_url(browser_type.clone(), version, download_info)
       .await?;
 
-    // Check existing file size — if it matches the expected size, skip download
+    // Determine if we have a partial file to resume
     let mut existing_size: u64 = 0;
     if let Ok(meta) = std::fs::metadata(&file_path) {
       existing_size = meta.len();
     }
 
-    // Do a HEAD request to get the expected file size for skip/resume decisions
-    let head_response = self
-      .client
-      .head(&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
-      .ok();
-
-    let expected_size = head_response.as_ref().and_then(|r| r.content_length());
-
-    // If existing file matches expected size, skip download entirely
-    if existing_size > 0 {
-      if let Some(expected) = expected_size {
-        if existing_size == expected {
-          log::info!(
-            "Archive {} already exists with correct size ({} bytes), skipping download",
-            file_path.display(),
-            existing_size
-          );
-          return Ok(file_path);
-        }
-      }
-    }
-
     // 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 = {
@@ -415,6 +387,20 @@ impl Downloader {
       existing_size = 0;
     }
 
+    // If the existing file already matches the total size, skip the download
+    if existing_size > 0 {
+      if let Some(total) = total_size {
+        if existing_size >= total {
+          log::info!(
+            "Archive {} already complete ({} bytes), skipping download",
+            file_path.display(),
+            existing_size
+          );
+          return Ok(file_path);
+        }
+      }
+    }
+
     let mut downloaded = existing_size;
     let start_time = std::time::Instant::now();
     let mut last_update = start_time;
diff --git a/src-tauri/src/lib.rs b/src-tauri/src/lib.rs
index 1dcf230..168d0a4 100644
--- a/src-tauri/src/lib.rs
+++ b/src-tauri/src/lib.rs
@@ -297,7 +297,7 @@ async fn fetch_dynamic_proxy(
     .fetch_dynamic_proxy(&url, &format)
     .await?;
 
-  // Validate the proxy actually works by routing through a temporary local proxy
+  // Validate the proxy actually works by connecting through it
   crate::proxy_manager::PROXY_MANAGER
     .check_proxy_validity("_dynamic_test", &settings)
     .await
diff --git a/src-tauri/src/proxy_manager.rs b/src-tauri/src/proxy_manager.rs
index e84c66d..0103bba 100644
--- a/src-tauri/src/proxy_manager.rs
+++ b/src-tauri/src/proxy_manager.rs
@@ -907,6 +907,63 @@ impl ProxyManager {
       .map(|p| p.proxy_settings.clone())
   }
 
+  fn classify_proxy_error(raw_error: &str, settings: &ProxySettings) -> String {
+    let err = raw_error.to_lowercase();
+    let proxy_addr = format!("{}:{}", settings.host, settings.port);
+
+    if err.contains("connection refused") {
+      return format!(
+        "Connection refused by {proxy_addr}. The proxy server is not accepting connections."
+      );
+    }
+    if err.contains("connection reset") {
+      return format!(
+        "Connection reset by {proxy_addr}. The proxy server closed the connection unexpectedly."
+      );
+    }
+    if err.contains("timed out") || err.contains("deadline has elapsed") {
+      return format!("Connection to {proxy_addr} timed out. The proxy server is not responding.");
+    }
+    if err.contains("no such host") || err.contains("dns") || err.contains("resolve") {
+      return format!(
+        "Could not resolve proxy host '{}'. Check that the hostname is correct.",
+        settings.host
+      );
+    }
+    if err.contains("authentication") || err.contains("407") || err.contains("proxy auth") {
+      return format!(
+        "Proxy authentication failed for {proxy_addr}. Check your username and password."
+      );
+    }
+    if err.contains("403") || err.contains("forbidden") {
+      return format!("Access denied by {proxy_addr} (403 Forbidden).");
+    }
+    if err.contains("402") {
+      return format!(
+        "Payment required by {proxy_addr} (402). Your proxy subscription may have expired."
+      );
+    }
+    if err.contains("502") || err.contains("bad gateway") {
+      return format!(
+        "Bad gateway from {proxy_addr} (502). The upstream proxy server may be down."
+      );
+    }
+    if err.contains("503") || err.contains("service unavailable") {
+      return format!("Proxy {proxy_addr} is temporarily unavailable (503).");
+    }
+    if err.contains("socks") && err.contains("unreachable") {
+      return format!("SOCKS proxy {proxy_addr} could not reach the target. The proxy server may not have internet access.");
+    }
+    if err.contains("invalid proxy") || err.contains("unsupported proxy") {
+      return format!(
+        "Invalid proxy configuration for {proxy_addr}. Check the proxy type and address."
+      );
+    }
+
+    // Generic fallback — still show the proxy address for context
+    format!("Proxy check failed for {proxy_addr}. Could not connect through the proxy.")
+  }
+
   // Build proxy URL string from ProxySettings
   fn build_proxy_url(proxy_settings: &ProxySettings) -> String {
     let mut url = format!("{}://", proxy_settings.proxy_type);
@@ -928,9 +985,8 @@ impl ProxyManager {
     url
   }
 
-  // Check if a proxy is valid by routing through a temporary local donut-proxy.
-  // This tests the exact same code path the browser uses, ensuring that if the
-  // check passes, the browser connection will work too.
+  // Check if a proxy is valid by routing through a temporary in-process donut-proxy.
+  // This tests the same code path the browser uses (local proxy -> upstream).
   pub async fn check_proxy_validity(
     &self,
     proxy_id: &str,
@@ -938,19 +994,41 @@ impl ProxyManager {
   ) -> Result<ProxyCheckResult, String> {
     let upstream_url = Self::build_proxy_url(proxy_settings);
 
-    // Start a temporary local proxy that tunnels through the upstream
-    let proxy_config = crate::proxy_runner::start_proxy_process(Some(upstream_url), None)
+    // Bind a temporary local proxy server in-process (no child process needed)
+    let listener = tokio::net::TcpListener::bind("127.0.0.1:0")
       .await
-      .map_err(|e| format!("Failed to start test proxy: {e}"))?;
+      .map_err(|e| format!("Failed to bind test proxy: {e}"))?;
+    let local_port = listener
+      .local_addr()
+      .map_err(|e| format!("Failed to get local address: {e}"))?
+      .port();
 
-    let local_url = format!("http://127.0.0.1:{}", proxy_config.local_port.unwrap_or(0));
-    let proxy_id_clone = proxy_config.id.clone();
+    let upstream_for_task = upstream_url.clone();
+    let proxy_task = tokio::spawn(async move {
+      use crate::proxy_server::BypassMatcher;
+      let bypass_matcher = BypassMatcher::new(&[]);
+      let upstream = Some(upstream_for_task);
+      // Accept up to 10 connections (enough for IP check which tries multiple endpoints)
+      for _ in 0..10 {
+        let accept =
+          tokio::time::timeout(std::time::Duration::from_secs(15), listener.accept()).await;
+        match accept {
+          Ok(Ok((stream, _))) => {
+            let upstream = upstream.clone();
+            let matcher = bypass_matcher.clone();
+            tokio::spawn(async move {
+              crate::proxy_server::handle_proxy_connection(stream, upstream, matcher).await;
+            });
+          }
+          _ => break,
+        }
+      }
+    });
 
-    // Fetch public IP through the local proxy (same path the browser uses)
+    let local_url = format!("http://127.0.0.1:{local_port}");
     let ip_result = ip_utils::fetch_public_ip(Some(&local_url)).await;
 
-    // Stop the temporary proxy regardless of result
-    let _ = crate::proxy_runner::stop_proxy_process(&proxy_id_clone).await;
+    proxy_task.abort();
 
     let ip = match ip_result {
       Ok(ip) => ip,
@@ -964,7 +1042,10 @@ impl ProxyManager {
           is_valid: false,
         };
         let _ = self.save_proxy_check_cache(proxy_id, &failed_result);
-        return Err(format!("Failed to fetch public IP: {e}"));
+
+        let err_str = e.to_string();
+        let user_message = Self::classify_proxy_error(&err_str, proxy_settings);
+        return Err(user_message);
       }
     };
 
diff --git a/src-tauri/src/proxy_server.rs b/src-tauri/src/proxy_server.rs
index 5b0eed7..6852ea4 100644
--- a/src-tauri/src/proxy_server.rs
+++ b/src-tauri/src/proxy_server.rs
@@ -883,6 +883,87 @@ fn build_reqwest_client_with_proxy(
   Ok(client_builder.proxy(proxy).build()?)
 }
 
+/// Handle a single proxy connection (used by both the proxy worker and in-process proxy checks).
+pub async fn handle_proxy_connection(
+  mut stream: tokio::net::TcpStream,
+  upstream_url: Option<String>,
+  bypass_matcher: BypassMatcher,
+) {
+  let _ = stream.set_nodelay(true);
+
+  if stream.readable().await.is_err() {
+    return;
+  }
+
+  let mut peek_buffer = [0u8; 16];
+  match stream.read(&mut peek_buffer).await {
+    Ok(0) => {}
+    Ok(n) => {
+      let request_start_upper = String::from_utf8_lossy(&peek_buffer[..n.min(7)]).to_uppercase();
+      let is_connect = request_start_upper.starts_with("CONNECT");
+
+      if is_connect {
+        let mut full_request = Vec::with_capacity(4096);
+        full_request.extend_from_slice(&peek_buffer[..n]);
+
+        let mut remaining = [0u8; 4096];
+        let mut total_read = n;
+        let max_reads = 100;
+        let mut reads = 0;
+
+        loop {
+          if reads >= max_reads {
+            break;
+          }
+          match stream.read(&mut remaining).await {
+            Ok(0) => {
+              if full_request.ends_with(b"\r\n\r\n")
+                || full_request.ends_with(b"\n\n")
+                || total_read > 0
+              {
+                break;
+              }
+              return;
+            }
+            Ok(m) => {
+              reads += 1;
+              total_read += m;
+              full_request.extend_from_slice(&remaining[..m]);
+              if full_request.ends_with(b"\r\n\r\n") || full_request.ends_with(b"\n\n") {
+                break;
+              }
+            }
+            Err(_) => {
+              if total_read > 0 {
+                break;
+              }
+              return;
+            }
+          }
+        }
+
+        let _ =
+          handle_connect_from_buffer(stream, full_request, upstream_url, bypass_matcher).await;
+        return;
+      }
+
+      // Non-CONNECT: prepend consumed bytes and pass to hyper
+      let prepended_bytes = peek_buffer[..n].to_vec();
+      let prepended_reader = PrependReader {
+        prepended: prepended_bytes,
+        prepended_pos: 0,
+        inner: stream,
+      };
+      let io = TokioIo::new(prepended_reader);
+      let service =
+        service_fn(move |req| handle_request(req, upstream_url.clone(), bypass_matcher.clone()));
+
+      let _ = http1::Builder::new().serve_connection(io, service).await;
+    }
+    Err(_) => {}
+  }
+}
+
 pub async fn run_proxy_server(config: ProxyConfig) -> Result<(), Box<dyn std::error::Error>> {
   log::error!(
     "Proxy worker starting, looking for config id: {}",
@@ -1052,145 +1133,11 @@ pub async fn run_proxy_server(config: ProxyConfig) -> Result<(), Box<dyn std::er
   // This ensures the process doesn't exit even if there are no active connections
   loop {
     match listener.accept().await {
-      Ok((mut stream, peer_addr)) => {
-        // Enable TCP_NODELAY to ensure small packets are sent immediately
-        // This is critical for CONNECT responses to be sent before tunneling begins
-        let _ = stream.set_nodelay(true);
-        log::error!("DEBUG: Accepted connection from {:?}", peer_addr);
-
+      Ok((stream, _peer_addr)) => {
         let upstream = upstream_url.clone();
         let matcher = bypass_matcher.clone();
-
         tokio::task::spawn(async move {
-          // Wait for the stream to have readable data before attempting to read.
-          // This prevents read() from returning 0 on a fresh connection before
-          // the client's data arrives.
-          if stream.readable().await.is_err() {
-            return;
-          }
-
-          let mut peek_buffer = [0u8; 16];
-          match stream.read(&mut peek_buffer).await {
-            Ok(0) => {}
-            Ok(n) => {
-              // Check if this looks like a CONNECT request
-              // Be more lenient - check if the first bytes match "CONNECT" (case-insensitive)
-              let request_start_upper =
-                String::from_utf8_lossy(&peek_buffer[..n.min(7)]).to_uppercase();
-              let is_connect = request_start_upper.starts_with("CONNECT");
-
-              log::error!(
-                "DEBUG: Read {} bytes, starts with: {:?}, is_connect: {}",
-                n,
-                String::from_utf8_lossy(&peek_buffer[..n.min(20)]),
-                is_connect
-              );
-
-              if is_connect {
-                // Handle CONNECT request manually for tunneling
-                let mut full_request = Vec::with_capacity(4096);
-                full_request.extend_from_slice(&peek_buffer[..n]);
-
-                // Read the rest of the CONNECT request until we have the full headers
-                // CONNECT requests end with \r\n\r\n (or \n\n)
-                let mut remaining = [0u8; 4096];
-                let mut total_read = n;
-                let max_reads = 100; // Prevent infinite loop
-                let mut reads = 0;
-
-                loop {
-                  if reads >= max_reads {
-                    log::error!("DEBUG: Max reads reached, breaking");
-                    break;
-                  }
-
-                  match stream.read(&mut remaining).await {
-                    Ok(0) => {
-                      // Connection closed, but we might have a complete request
-                      if full_request.ends_with(b"\r\n\r\n") || full_request.ends_with(b"\n\n") {
-                        break;
-                      }
-                      // If we have some data, try to process it anyway
-                      if total_read > 0 {
-                        break;
-                      }
-                      return; // No data at all
-                    }
-                    Ok(m) => {
-                      reads += 1;
-                      total_read += m;
-                      full_request.extend_from_slice(&remaining[..m]);
-
-                      // Check if we have complete headers
-                      if full_request.ends_with(b"\r\n\r\n") || full_request.ends_with(b"\n\n") {
-                        break;
-                      }
-
-                      // Also check if we have enough to parse (at least "CONNECT host:port HTTP/1.x")
-                      if total_read >= 20 {
-                        // Check if we have a newline that might indicate end of request line
-                        if let Some(pos) = full_request.iter().position(|&b| b == b'\n') {
-                          if pos < full_request.len() - 1 {
-                            // We have at least the request line, check if we have headers
-                            let request_str = String::from_utf8_lossy(&full_request);
-                            if request_str.contains("\r\n\r\n") || request_str.contains("\n\n") {
-                              break;
-                            }
-                          }
-                        }
-                      }
-                    }
-                    Err(e) => {
-                      log::error!("DEBUG: Error reading CONNECT request: {:?}", e);
-                      // If we have some data, try to process it
-                      if total_read > 0 {
-                        break;
-                      }
-                      return;
-                    }
-                  }
-                }
-
-                // Handle CONNECT manually
-                log::error!(
-                  "DEBUG: Handling CONNECT manually for: {}",
-                  String::from_utf8_lossy(&full_request[..full_request.len().min(200)])
-                );
-                if let Err(e) =
-                  handle_connect_from_buffer(stream, full_request, upstream, matcher).await
-                {
-                  log::error!("Error handling CONNECT request: {:?}", e);
-                } else {
-                  log::error!("DEBUG: CONNECT handled successfully");
-                }
-                return;
-              }
-
-              // Not CONNECT (or partial read) - reconstruct stream with consumed bytes prepended
-              // This is critical: we MUST prepend any bytes we consumed, even if < 7 bytes
-              log::error!(
-                "DEBUG: Non-CONNECT request, first {} bytes: {:?}",
-                n,
-                String::from_utf8_lossy(&peek_buffer[..n.min(50)])
-              );
-              let prepended_bytes = peek_buffer[..n].to_vec();
-              let prepended_reader = PrependReader {
-                prepended: prepended_bytes,
-                prepended_pos: 0,
-                inner: stream,
-              };
-              let io = TokioIo::new(prepended_reader);
-              let service =
-                service_fn(move |req| handle_request(req, upstream.clone(), matcher.clone()));
-
-              if let Err(err) = http1::Builder::new().serve_connection(io, service).await {
-                log::error!("Error serving connection: {:?}", err);
-              }
-            }
-            Err(e) => {
-              log::error!("Error reading from connection: {:?}", e);
-            }
-          }
+          handle_proxy_connection(stream, upstream, matcher).await;
         });
       }
       Err(e) => {