diff --git a/run.sh b/run.sh
index d65fa970..bd2a6751 100755
--- a/run.sh
+++ b/run.sh
@@ -204,11 +204,13 @@ start_backend() {
     if [ -f ".env" ]; then
         uvicorn_env_args=(--env-file .env)
     fi
-    # Use a subshell to prefix output
-    # NOTE: --reload breaks stderr capture (subprocess child loses the 2>&1 pipe).
+    # PYTHONUNBUFFERED=1 prevents stderr buffering when piped through sed.
+    # Without it, JSON logs from superset_tools_app get stuck in the buffer
+    # and never appear in real time (or at all, for small log lines).
+    # NOTE: --reload also breaks stderr capture (subprocess child loses the pipe).
     # For hot-reload during development, run uvicorn directly instead:
     #   cd backend && source .venv/bin/activate && uvicorn src.app:app --reload --port 8000
-    python3 -m uvicorn src.app:app --port "$BACKEND_PORT" "${uvicorn_env_args[@]}" 2>&1 | sed "s/^/$(echo -e '\033[0;34m[Backend]\033[0m ') /" &
+    PYTHONUNBUFFERED=1 python3 -m uvicorn src.app:app --port "$BACKEND_PORT" "${uvicorn_env_args[@]}" 2>&1 | sed "s/^/$(echo -e '\033[0;34m[Backend]\033[0m ') /" &
     BACKEND_PID=$!
     cd ..
 }