diff --git a/litellm/integrations/generic_api/generic_api_callback.py b/litellm/integrations/generic_api/generic_api_callback.py
index dfedc3a3cc9..25648f82a03 100644
--- a/litellm/integrations/generic_api/generic_api_callback.py
+++ b/litellm/integrations/generic_api/generic_api_callback.py
@@ -7,6 +7,7 @@ Callback to log events to a Generic API Endpoint
 """
 
 import asyncio
+import contextlib
 import json
 import os
 import re
@@ -158,7 +159,7 @@ class GenericAPILogger(CustomBatchLogger):
                 "endpoint not set for GenericAPILogger, GENERIC_LOGGER_ENDPOINT not found in environment variables"
             )
 
-        self.headers: dict[str, str] = self._get_headers(headers)
+        self.headers: dict[str, str] = self.resolve_headers(headers)
         self.endpoint: str = endpoint
         self.event_types: list[API_EVENT_TYPES] | None = event_types
         self.callback_name: str | None = callback_name
@@ -190,10 +191,30 @@ class GenericAPILogger(CustomBatchLogger):
         #########################################################
         self.flush_lock = asyncio.Lock()
         super().__init__(**kwargs, flush_lock=self.flush_lock)
-        asyncio.create_task(self.periodic_flush())
+        self._flush_task = asyncio.create_task(self._run_periodic_flush())
         self.log_queue: list[dict | StandardLoggingPayload] = []
 
-    def _get_headers(self, headers: dict | None = None):
+    async def _run_periodic_flush(self) -> None:
+        """Run the periodic flush loop; on cancellation, make a best-effort final
+        flush of any buffered logs before exiting. Prevents dropping the last batch
+        when this logger is evicted from the cache and cancelled via shutdown()."""
+        try:
+            await self.periodic_flush()
+        except asyncio.CancelledError:
+            # suppress(Exception) leaves a nested CancelledError (a BaseException) free to
+            # propagate, so a second cancellation during the final flush is still honored.
+            with contextlib.suppress(Exception):
+                await self.flush_queue()
+            raise
+
+    def shutdown(self) -> None:
+        """Cancel the background flush task. Called by LoggingCallbackManager when this
+        logger is evicted from the cache so its periodic_flush task does not leak."""
+        if not self._flush_task.done():
+            self._flush_task.cancel()
+
+    @staticmethod
+    def resolve_headers(headers: dict | None = None) -> dict[str, str]:  # mutable-ok: caller owns the returned headers
         """
         Get headers for the Generic API Logger
 
diff --git a/litellm/litellm_core_utils/logging_callback_manager.py b/litellm/litellm_core_utils/logging_callback_manager.py
index 9b612993a69..423786e8850 100644
--- a/litellm/litellm_core_utils/logging_callback_manager.py
+++ b/litellm/litellm_core_utils/logging_callback_manager.py
@@ -204,15 +204,19 @@ class LoggingCallbackManager:
             if (
                 isinstance(cached_logger, GenericAPILogger)
                 and cached_logger.endpoint == endpoint
-                and cached_logger.headers == headers
+                and cached_logger.headers == GenericAPILogger.resolve_headers(headers)
                 and cached_logger.event_types == event_types
-                and cached_logger.log_format == log_format
+                and cached_logger.log_format == (log_format if log_format is not None else "json_array")
                 and cached_logger.max_retries == max_retries
                 and cached_logger.retry_delay == retry_delay
                 and cached_logger.timeout == timeout
             ):
                 return cached_logger
 
+            # Cache miss (config changed or first creation). Build the replacement
+            # first, so that an invalid config raising in the constructor cannot leave
+            # the still-cached logger cancelled. Only after a successful build do we
+            # retire the evicted logger's background flush task.
             new_logger = GenericAPILogger(
                 endpoint=endpoint,
                 headers=headers,
@@ -222,6 +226,8 @@ class LoggingCallbackManager:
                 retry_delay=retry_delay,
                 timeout=timeout,
             )
+            if isinstance(cached_logger, GenericAPILogger):
+                cached_logger.shutdown()
             _generic_api_logger_cache[callback] = new_logger
             return new_logger