diff --git a/src-tauri/src/sidecar/mod.rs b/src-tauri/src/sidecar/mod.rs
index bc4efc6..9d97ab5 100644
--- a/src-tauri/src/sidecar/mod.rs
+++ b/src-tauri/src/sidecar/mod.rs
@@ -463,11 +463,63 @@ impl SidecarManager {
             .take()
             .ok_or("Failed to capture sidecar stdout")?;
 
-        let port = Self::wait_for_ready(stdout)?;
+        // Capture stderr in a background thread so we can log it
+        let stderr = child
+            .stderr
+            .take()
+            .ok_or("Failed to capture sidecar stderr")?;
 
-        self.child = Some(child);
-        self.port = Some(port);
-        Ok(port)
+        let log_dir = DIRS.get().map(|d| d.data_dir.clone());
+        std::thread::spawn(move || {
+            use std::io::BufRead;
+            let reader = std::io::BufReader::new(stderr);
+            let mut log_file = log_dir.and_then(|d| {
+                std::fs::OpenOptions::new()
+                    .create(true)
+                    .append(true)
+                    .open(d.join("sidecar.log"))
+                    .ok()
+            });
+            for line in reader.lines() {
+                if let Ok(line) = line {
+                    eprintln!("[sidecar-stderr] {}", line);
+                    if let Some(ref mut f) = log_file {
+                        use std::io::Write;
+                        let _ = writeln!(f, "{}", line);
+                    }
+                }
+            }
+        });
+
+        match Self::wait_for_ready(stdout) {
+            Ok(port) => {
+                self.child = Some(child);
+                self.port = Some(port);
+                Ok(port)
+            }
+            Err(e) => {
+                // Kill the child if ready failed
+                let _ = child.kill();
+                let _ = child.wait();
+
+                // Read the sidecar.log for context
+                let log_hint = DIRS
+                    .get()
+                    .and_then(|d| std::fs::read_to_string(d.data_dir.join("sidecar.log")).ok())
+                    .and_then(|s| {
+                        let lines: Vec<&str> = s.lines().collect();
+                        let tail: Vec<&str> = lines.iter().rev().take(10).rev().cloned().collect();
+                        if tail.is_empty() { None } else { Some(tail.join("\n")) }
+                    })
+                    .unwrap_or_default();
+
+                if log_hint.is_empty() {
+                    Err(e)
+                } else {
+                    Err(format!("{e}\n\nSidecar stderr (last 10 lines):\n{log_hint}"))
+                }
+            }
+        }
     }
 
     /// Stop the sidecar process if running.