diff --git a/src/anthropic/_base_client.py b/src/anthropic/_base_client.py
index 9e215f57..46cf5e0b 100644
--- a/src/anthropic/_base_client.py
+++ b/src/anthropic/_base_client.py
@@ -956,6 +956,11 @@ def _request(
         stream: bool,
         stream_cls: type[_StreamT] | None,
     ) -> ResponseT | _StreamT:
+        # create a copy of the options we were given so that if the
+        # options are mutated later & we then retry, the retries are
+        # given the original options
+        input_options = model_copy(options)
+
         cast_to = self._maybe_override_cast_to(cast_to, options)
         self._prepare_options(options)
 
@@ -980,7 +985,7 @@ def _request(
 
             if retries > 0:
                 return self._retry_request(
-                    options,
+                    input_options,
                     cast_to,
                     retries,
                     stream=stream,
@@ -995,7 +1000,7 @@ def _request(
 
             if retries > 0:
                 return self._retry_request(
-                    options,
+                    input_options,
                     cast_to,
                     retries,
                     stream=stream,
@@ -1023,7 +1028,7 @@ def _request(
             if retries > 0 and self._should_retry(err.response):
                 err.response.close()
                 return self._retry_request(
-                    options,
+                    input_options,
                     cast_to,
                     retries,
                     err.response.headers,
@@ -1532,6 +1537,11 @@ async def _request(
             # execute it earlier while we are in an async context
             self._platform = await asyncify(get_platform)()
 
+        # create a copy of the options we were given so that if the
+        # options are mutated later & we then retry, the retries are
+        # given the original options
+        input_options = model_copy(options)
+
         cast_to = self._maybe_override_cast_to(cast_to, options)
         await self._prepare_options(options)
 
@@ -1554,7 +1564,7 @@ async def _request(
 
             if retries > 0:
                 return await self._retry_request(
-                    options,
+                    input_options,
                     cast_to,
                     retries,
                     stream=stream,
@@ -1569,7 +1579,7 @@ async def _request(
 
             if retries > 0:
                 return await self._retry_request(
-                    options,
+                    input_options,
                     cast_to,
                     retries,
                     stream=stream,
@@ -1592,7 +1602,7 @@ async def _request(
             if retries > 0 and self._should_retry(err.response):
                 await err.response.aclose()
                 return await self._retry_request(
-                    options,
+                    input_options,
                     cast_to,
                     retries,
                     err.response.headers,