diff --git a/langfuse/_client/client.py b/langfuse/_client/client.py
index d262f5047..c46278180 100644
--- a/langfuse/_client/client.py
+++ b/langfuse/_client/client.py
@@ -160,8 +160,24 @@ def __init__(
         sample_rate: Optional[float] = None,
         mask: Optional[MaskFunction] = None,
     ):
-        debug = debug if debug else (os.getenv(LANGFUSE_DEBUG, "False") == "True")
+        self._host = host or os.environ.get(LANGFUSE_HOST, "https://cloud.langfuse.com")
+        self._environment = environment or os.environ.get(LANGFUSE_TRACING_ENVIRONMENT)
+        self._mask = mask
+        self._project_id = None
+        sample_rate = sample_rate or float(os.environ.get(LANGFUSE_SAMPLE_RATE, 1.0))
+        if not 0.0 <= sample_rate <= 1.0:
+            raise ValueError(f"Sample rate must be between 0.0 and 1.0, got {sample_rate}")
 
+        self._tracing_enabled = (
+            tracing_enabled
+            and os.environ.get(LANGFUSE_TRACING_ENABLED, "True") != "False"
+        )
+        if not self._tracing_enabled:
+            langfuse_logger.info(
+                "Configuration: Langfuse tracing is explicitly disabled. No data will be sent to the Langfuse API."
+            )
+
+        debug = debug if debug else (os.getenv(LANGFUSE_DEBUG, "False") == "True")
         if debug:
             logging.basicConfig(
                 format="%(asctime)s - %(name)s - %(levelname)s - %(message)s"
@@ -188,23 +204,6 @@ def __init__(
             self._otel_tracer = otel_trace_api.NoOpTracer()
             return
 
-        self._host = host or os.environ.get(LANGFUSE_HOST, "https://cloud.langfuse.com")
-        self._environment = environment or os.environ.get(LANGFUSE_TRACING_ENVIRONMENT)
-        sample_rate = sample_rate or float(os.environ.get(LANGFUSE_SAMPLE_RATE, 1.0))
-
-        self._tracing_enabled = (
-            tracing_enabled
-            and os.environ.get(LANGFUSE_TRACING_ENABLED, "True") != "False"
-        )
-
-        if not self._tracing_enabled:
-            langfuse_logger.info(
-                "Configuration: Langfuse tracing is explicitly disabled. No data will be sent to the Langfuse API."
-            )
-
-        self._mask = mask
-        self._project_id = None
-
         # Initialize api and tracer if requirements are met
         self._resources = LangfuseResourceManager(
             public_key=public_key,
diff --git a/langfuse/_client/observe.py b/langfuse/_client/observe.py
index 8416ffd46..cdfb04d7b 100644
--- a/langfuse/_client/observe.py
+++ b/langfuse/_client/observe.py
@@ -145,10 +145,9 @@ def sub_process():
             - For async functions, the decorator returns an async function wrapper.
             - For sync functions, the decorator returns a synchronous wrapper.
         """
-        function_io_capture_enabled = (
-            os.environ.get(LANGFUSE_OBSERVE_DECORATOR_IO_CAPTURE_ENABLED, "True")
-            .lower() not in ("false", "0")
-        )
+        function_io_capture_enabled = os.environ.get(
+            LANGFUSE_OBSERVE_DECORATOR_IO_CAPTURE_ENABLED, "True"
+        ).lower() not in ("false", "0")
 
         def decorator(func: F) -> F:
             return (