diff --git a/frontend/src/main.tsx b/frontend/src/main.tsx
index edc1fca..a9582e8 100644
--- a/frontend/src/main.tsx
+++ b/frontend/src/main.tsx
@@ -1,4 +1,46 @@
 import ReactDOM from "react-dom/client";
 import App from "./App";
 
+const backendBase =
+  (import.meta.env.VITE_BACKEND_URL as string | undefined) ?? "http://localhost:8000";
+
+const sendFrontLog = (message: string, level: "info" | "warn" | "error" = "info") => {
+  fetch(`${backendBase}/logs`, {
+    method: "POST",
+    headers: { "Content-Type": "application/json" },
+    body: JSON.stringify({ message, level, source: "frontend" }),
+  }).catch(() => {});
+};
+
+window.addEventListener("error", (event) => {
+  const err = event.error instanceof Error ? event.error : null;
+  const details = err?.stack || err?.message || String(event.message || "unknown error");
+  sendFrontLog(`window.error: ${details}`, "error");
+});
+
+window.addEventListener("unhandledrejection", (event) => {
+  const reason = event.reason instanceof Error ? event.reason.stack || event.reason.message : String(event.reason);
+  sendFrontLog(`unhandledrejection: ${reason}`, "error");
+});
+
+const _consoleError = console.error.bind(console);
+console.error = (...args: unknown[]) => {
+  try {
+    sendFrontLog(`console.error: ${args.map(String).join(" ")}`, "error");
+  } catch {
+    // ignore
+  }
+  _consoleError(...args);
+};
+
+const _consoleWarn = console.warn.bind(console);
+console.warn = (...args: unknown[]) => {
+  try {
+    sendFrontLog(`console.warn: ${args.map(String).join(" ")}`, "warn");
+  } catch {
+    // ignore
+  }
+  _consoleWarn(...args);
+};
+
 ReactDOM.createRoot(document.getElementById("root") as HTMLElement).render(<App />);
diff --git a/gnss/__main__.py b/gnss/__main__.py
index 125ad7c..bcd7e52 100644
--- a/gnss/__main__.py
+++ b/gnss/__main__.py
@@ -1,5 +1,7 @@
 import argparse
 import os
+import sys
+from pathlib import Path
 from typing import Optional
 
 import uvicorn
@@ -12,19 +14,80 @@ def _env(name: str, default: str) -> str:
     return v if v is not None and v != "" else default
 
 
+class _TeeStream:
+    def __init__(self, primary, secondary):
+        self._primary = primary
+        self._secondary = secondary
+
+    def write(self, data):
+        try:
+            self._primary.write(data)
+        except Exception:
+            pass
+        try:
+            self._secondary.write(data)
+        except Exception:
+            pass
+        return len(data)
+
+    def flush(self):
+        try:
+            self._primary.flush()
+        except Exception:
+            pass
+        try:
+            self._secondary.flush()
+        except Exception:
+            pass
+
+    def isatty(self):
+        try:
+            return self._primary.isatty()
+        except Exception:
+            return False
+
+
+def _ensure_uvicorn_logs_to_file(log_path: Path) -> None:
+    import logging
+
+    log_path.parent.mkdir(parents=True, exist_ok=True)
+    file_handler = logging.FileHandler(log_path, encoding="utf-8")
+    file_handler.setLevel(logging.INFO)
+    file_handler.setFormatter(logging.Formatter("%(asctime)s [%(levelname)s] %(name)s: %(message)s"))
+
+    for name in ("uvicorn", "uvicorn.error", "uvicorn.access"):
+        logger = logging.getLogger(name)
+        logger.setLevel(logging.INFO)
+        if not any(
+            isinstance(h, logging.FileHandler) and getattr(h, "baseFilename", None) == str(log_path)
+            for h in logger.handlers
+        ):
+            logger.addHandler(file_handler)
+        logger.propagate = True
+
+
 def main(argv: Optional[list[str]] = None) -> int:
     parser = argparse.ArgumentParser(prog="gnss", description="GNSS Backend (FastAPI)")
     parser.add_argument("--host", default=_env("GNSS_HOST", "0.0.0.0"))
     parser.add_argument("--port", type=int, default=int(_env("GNSS_PORT", "8000")))
     parser.add_argument("--log-level", default=_env("GNSS_LOG_LEVEL", "info"))
+    parser.add_argument("--log-file", default=_env("GNSS_BACKEND_LOG_FILE", "logs/backend.log"))
     args = parser.parse_args(argv)
 
+    log_path = Path(args.log_file).expanduser()
+    log_path.parent.mkdir(parents=True, exist_ok=True)
+    backend_log_file = log_path.open("a", encoding="utf-8", buffering=1)
+    sys.stdout = _TeeStream(sys.stdout, backend_log_file)  # type: ignore[assignment]
+    sys.stderr = _TeeStream(sys.stderr, backend_log_file)  # type: ignore[assignment]
+    _ensure_uvicorn_logs_to_file(log_path)
+
     uvicorn.run(
         app,
         host=args.host,
         port=args.port,
         log_level=args.log_level,
         access_log=True,
+        log_config=None,
         workers=1,
     )
     return 0