fix: improve daemon startup error handling and diagnostics (#337)

* fixes

* add debugging

cli/src/connection.rs

@@ -239,6 +239,37 @@ pub fn ensure_daemon(
             .map_err(|e| format!("Failed to create socket directory: {}", e))?;
     }
 
+    // Pre-flight check: Validate socket path length (Unix limit is 104 bytes including null terminator)
+    #[cfg(unix)]
+    {
+        let socket_path = get_socket_path(session);
+        let path_len = socket_path.as_os_str().len();
+        if path_len > 103 {
+            return Err(format!(
+                "Session name '{}' is too long. Socket path would be {} bytes (max 103).\n\
+                 Use a shorter session name or set AGENT_BROWSER_SOCKET_DIR to a shorter path.",
+                session, path_len
+            ));
+        }
+    }
+
+    // Pre-flight check: Verify socket directory is writable
+    {
+        let test_file = socket_dir.join(".write_test");
+        match fs::write(&test_file, b"") {
+            Ok(_) => {
+                let _ = fs::remove_file(&test_file);
+            }
+            Err(e) => {
+                return Err(format!(
+                    "Socket directory '{}' is not writable: {}",
+                    socket_dir.display(),
+                    e
+                ));
+            }
+        }
+    }
+
     let exe_path = env::current_exe().map_err(|e| e.to_string())?;
     // Canonicalize to resolve symlinks (e.g., npm global bin symlink -> actual binary)
     let exe_path = exe_path.canonicalize().unwrap_or(exe_path);
@@ -400,7 +431,10 @@ pub fn ensure_daemon(
         thread::sleep(Duration::from_millis(100));
     }
 
-    Err("Daemon failed to start".to_string())
+    Err(format!(
+        "Daemon failed to start (socket: {})",
+        get_socket_dir().join(format!("{}.sock", session)).display()
+    ))
 }
 
 fn connect(session: &str) -> Result<Connection, String> {

cli/src/main.rs

@@ -443,13 +443,33 @@ fn main() {
             launch_cmd["ignoreHTTPSErrors"] = json!(true);
         }
 
-        if let Err(e) = send_command(launch_cmd, &flags.session) {
-            if !flags.json {
-                eprintln!(
-                    "{} Could not configure browser: {}",
-                    color::warning_indicator(),
-                    e
-                );
+        match send_command(launch_cmd, &flags.session) {
+            Ok(resp) if !resp.success => {
+                // Launch command failed (e.g., invalid state file, profile error)
+                let error_msg = resp
+                    .error
+                    .unwrap_or_else(|| "Browser launch failed".to_string());
+                if flags.json {
+                    println!(r#"{{"success":false,"error":"{}"}}"#, error_msg);
+                } else {
+                    eprintln!("{} {}", color::error_indicator(), error_msg);
+                }
+                exit(1);
+            }
+            Err(e) => {
+                if flags.json {
+                    println!(r#"{{"success":false,"error":"{}"}}"#, e);
+                } else {
+                    eprintln!(
+                        "{} Could not configure browser: {}",
+                        color::error_indicator(),
+                        e
+                    );
+                }
+                exit(1);
+            }
+            Ok(_) => {
+                // Launch succeeded
             }
         }
     }