fix(anthropic): stop SDK retries from resending a rejected block or clearing the global num_retries

A transient 429 or 500 on a /v1/messages turn that carries a replayed encrypted
block was retried by an SDK call's num_retries loop, which sent the block again
until every retry was rejected. On async calls the loop then raised the first
transient error, so the turn failed instead of being sent again without the
block. The retry loop now stops at that rejection and passes it on, so the turn
is sent again once without encrypted blocks.

A rejected first try on a sync call also cleared the process-wide
litellm.num_retries, so later calls in the process were no longer retried. That
setting now stays as configured.

litellm/main.py

@@ -27,6 +27,7 @@ from functools import partial
 from types import MappingProxyType
 from typing import TYPE_CHECKING, Any, Final, Literal, Optional, Protocol, Union, cast, get_args
 
+from litellm._internal_context import is_resent_failure
 from litellm._logging import redact_string
 from litellm._uuid import uuid
 
@@ -6242,6 +6243,10 @@ def completion(
         )
 
 
+def _is_not_resent_failure(error: BaseException) -> bool:
+    return not (isinstance(error, Exception) and is_resent_failure(error))
+
+
 def completion_with_retries(*args, **kwargs):
     """
     Executes a litellm.completion() with 3 retries
@@ -6261,10 +6266,15 @@ def completion_with_retries(*args, **kwargs):
         retryer = tenacity.Retrying(
             wait=tenacity.wait_exponential(multiplier=1, max=10),
             stop=tenacity.stop_after_attempt(num_retries),
+            retry=tenacity.retry_if_exception(_is_not_resent_failure),
             reraise=True,
         )
     else:
-        retryer = tenacity.Retrying(stop=tenacity.stop_after_attempt(num_retries), reraise=True)
+        retryer = tenacity.Retrying(
+            stop=tenacity.stop_after_attempt(num_retries),
+            retry=tenacity.retry_if_exception(_is_not_resent_failure),
+            reraise=True,
+        )
     return retryer(original_function, *args, **kwargs)
 
 
@@ -6287,10 +6297,15 @@ async def acompletion_with_retries(*args, **kwargs):
         retryer = tenacity.AsyncRetrying(
             wait=tenacity.wait_exponential(multiplier=1, max=10),
             stop=tenacity.stop_after_attempt(num_retries),
+            retry=tenacity.retry_if_exception(_is_not_resent_failure),
             reraise=True,
         )
     else:
-        retryer = tenacity.AsyncRetrying(stop=tenacity.stop_after_attempt(num_retries), reraise=True)
+        retryer = tenacity.AsyncRetrying(
+            stop=tenacity.stop_after_attempt(num_retries),
+            retry=tenacity.retry_if_exception(_is_not_resent_failure),
+            reraise=True,
+        )
     return await retryer(original_function, *args, **kwargs)
 
 
@@ -6315,10 +6330,15 @@ def responses_with_retries(*args, **kwargs):
         retryer = tenacity.Retrying(
             wait=tenacity.wait_exponential(multiplier=1, max=10),
             stop=tenacity.stop_after_attempt(num_retries),
+            retry=tenacity.retry_if_exception(_is_not_resent_failure),
             reraise=True,
         )
     else:
-        retryer = tenacity.Retrying(stop=tenacity.stop_after_attempt(num_retries), reraise=True)
+        retryer = tenacity.Retrying(
+            stop=tenacity.stop_after_attempt(num_retries),
+            retry=tenacity.retry_if_exception(_is_not_resent_failure),
+            reraise=True,
+        )
     return retryer(original_function, *args, **kwargs)
 
 
@@ -6342,10 +6362,15 @@ async def aresponses_with_retries(*args, **kwargs):
         retryer = tenacity.AsyncRetrying(
             wait=tenacity.wait_exponential(multiplier=1, max=10),
             stop=tenacity.stop_after_attempt(num_retries),
+            retry=tenacity.retry_if_exception(_is_not_resent_failure),
             reraise=True,
         )
     else:
-        retryer = tenacity.AsyncRetrying(stop=tenacity.stop_after_attempt(num_retries), reraise=True)
+        retryer = tenacity.AsyncRetrying(
+            stop=tenacity.stop_after_attempt(num_retries),
+            retry=tenacity.retry_if_exception(_is_not_resent_failure),
+            reraise=True,
+        )
     return await retryer(original_function, *args, **kwargs)
 
 

litellm/utils.py

@@ -1980,7 +1980,8 @@ def client(original_function):
                         retry_policy=kwargs.get("retry_policy"),
                     )
                     kwargs["retry_policy"] = reset_retry_policy()  # prevent infinite loops
-                litellm.num_retries = None  # set retries to None to prevent infinite loops
+                if not is_resent_failure(e):
+                    litellm.num_retries = None  # set retries to None to prevent infinite loops
                 context_window_fallback_dict: Final = kwargs.get("context_window_fallback_dict", {})
 
                 is_completion_litellm_router_call: Final = _is_litellm_router_call(kwargs, is_async=False)
@@ -2015,7 +2016,8 @@ def client(original_function):
                         retry_policy=kwargs.get("retry_policy"),
                     )
                     kwargs["retry_policy"] = reset_retry_policy()  # prevent infinite loops
-                litellm.num_retries = None  # set retries to None to prevent infinite loops
+                if not is_resent_failure(e):
+                    litellm.num_retries = None  # set retries to None to prevent infinite loops
 
                 is_responses_litellm_router_call: Final = _is_litellm_router_call(kwargs, is_async=False)
                 if (
@@ -2314,8 +2316,9 @@ def client(original_function):
                         elif isinstance(e, openai.APIError):  # generic api error
                             kwargs["retry_strategy"] = "constant_retry"
                         result = await litellm.acompletion_with_retries(*args, **kwargs)
-                    except Exception:
-                        pass
+                    except Exception as retry_error:
+                        if is_resent_failure(retry_error):
+                            raise
                     else:
                         return result
                 elif (
@@ -2348,8 +2351,9 @@ def client(original_function):
                         elif isinstance(e, openai.APIError):  # generic api error
                             kwargs["retry_strategy"] = "constant_retry"
                         result = await litellm.aresponses_with_retries(*args, **kwargs)
-                    except Exception:
-                        pass
+                    except Exception as retry_error:
+                        if is_resent_failure(retry_error):
+                            raise
                     else:
                         return result
 

tests/unit/llms/anthropic/pass_through/adapters/test_anthropic_experimental_pass_through_adapters_transformation.py

@@ -5608,9 +5608,10 @@ async def test_async_messages_with_num_retries_send_the_rejected_reasoning_only_
 
 
 @pytest.mark.usefixtures("_chat_bridge_httpx")
-def test_sync_messages_with_num_retries_send_the_rejected_reasoning_only_once(
-    respx_mock: respx.MockRouter,
+def test_sync_messages_with_global_num_retries_send_the_rejected_reasoning_once_and_keep_the_setting(
+    respx_mock: respx.MockRouter, monkeypatch: pytest.MonkeyPatch
 ) -> None:
+    monkeypatch.setattr(litellm, "num_retries", 2)
     route: Final = respx_mock.post(url__regex=_RETRY_URL).mock(
         side_effect=[_RETRY_REJECTION, httpx.Response(200, json=_RETRY_REPLY)]
     )
@@ -5623,10 +5624,62 @@ def test_sync_messages_with_num_retries_send_the_rejected_reasoning_only_once(
         max_tokens=64,
         tools=_RETRY_TOOLS,
         messages=_history_with_foreign_reasoning(),
-        num_retries=2,
     )
 
     assert [len(_sent_reasoning_items(call.request)) for call in route.calls] == [1, 0]
+    assert litellm.num_retries == 2
+
+
+_SERVER_ERROR: Final = httpx.Response(
+    500, json={"error": {"message": "The server had an error while processing your request.", "type": "server_error"}}
+)
+
+
+@pytest.mark.asyncio
+@pytest.mark.usefixtures("_chat_bridge_httpx")
+async def test_async_messages_retry_a_server_error_with_the_reasoning_and_drop_it_only_once_rejected(
+    respx_mock: respx.MockRouter,
+) -> None:
+    route: Final = respx_mock.post(url__regex=_RETRY_URL).mock(
+        side_effect=[_SERVER_ERROR, _RETRY_REJECTION, httpx.Response(200, json=_RETRY_REPLY)]
+    )
+
+    response: Final = await litellm.anthropic.messages.acreate(
+        model="azure/gpt-5.4-nano",
+        api_base=_RETRY_API_BASE,
+        api_key="fake-key",
+        api_version="2025-04-01-preview",
+        max_tokens=64,
+        tools=_RETRY_TOOLS,
+        messages=_history_with_foreign_reasoning(),
+        num_retries=2,
+    )
+
+    assert [len(_sent_reasoning_items(call.request)) for call in route.calls] == [1, 1, 0]
+    assert [block["text"] for block in response["content"] if block["type"] == "text"] == ["Oslo"]
+
+
+@pytest.mark.usefixtures("_chat_bridge_httpx")
+def test_sync_messages_retry_a_server_error_with_the_reasoning_and_drop_it_only_once_rejected(
+    respx_mock: respx.MockRouter,
+) -> None:
+    route: Final = respx_mock.post(url__regex=_RETRY_URL).mock(
+        side_effect=[_SERVER_ERROR, _RETRY_REJECTION, httpx.Response(200, json=_RETRY_REPLY)]
+    )
+
+    response: Final = litellm.anthropic.messages.create(
+        model="azure/gpt-5.4-nano",
+        api_base=_RETRY_API_BASE,
+        api_key="fake-key",
+        api_version="2025-04-01-preview",
+        max_tokens=64,
+        tools=_RETRY_TOOLS,
+        messages=_history_with_foreign_reasoning(),
+        num_retries=2,
+    )
+
+    assert [len(_sent_reasoning_items(call.request)) for call in route.calls] == [1, 1, 0]
+    assert [block["text"] for block in response["content"] if block["type"] == "text"] == ["Oslo"]
 
 
 class _FailureLog(CustomLogger):

tests/unit/llms/anthropic/pass_through/responses_adapters/test_responses_adapters_handler.py

@@ -747,6 +747,12 @@ def _replayed_reasoning_counts(upstream: respx.Route) -> list[int]:
 
 
 def _upstream(respx_mock: respx.MockRouter, monkeypatch: pytest.MonkeyPatch, first: httpx.Response, stream: bool):
+    return _upstream_after(respx_mock, monkeypatch, (first,), stream)
+
+
+def _upstream_after(
+    respx_mock: respx.MockRouter, monkeypatch: pytest.MonkeyPatch, failures: tuple[httpx.Response, ...], stream: bool
+) -> respx.Route:
     monkeypatch.setenv("OPENAI_API_KEY", "sk-replay-test")
     monkeypatch.setenv("DISABLE_AIOHTTP_TRANSPORT", "True")
     litellm.in_memory_llm_clients_cache.flush_cache()
@@ -755,7 +761,7 @@ def _upstream(respx_mock: respx.MockRouter, monkeypatch: pytest.MonkeyPatch, fir
         if stream
         else httpx.Response(200, json=TEXT_RESPONSE)
     )
-    return respx_mock.post("https://api.openai.com/v1/responses").mock(side_effect=[first, served])
+    return respx_mock.post("https://api.openai.com/v1/responses").mock(side_effect=[*failures, served])
 
 
 @pytest.mark.asyncio
@@ -817,9 +823,10 @@ async def test_openai_turn_with_num_retries_sends_the_rejected_reasoning_only_on
     assert _replayed_reasoning_counts(upstream) == [1, 0]
 
 
-def test_sync_openai_turn_with_num_retries_sends_the_rejected_reasoning_only_once(
+def test_sync_openai_turn_with_global_num_retries_sends_the_rejected_reasoning_once_and_keeps_the_setting(
     respx_mock: respx.MockRouter, monkeypatch: pytest.MonkeyPatch
 ) -> None:
+    monkeypatch.setattr(litellm, "num_retries", 2)
     upstream: Final = _upstream(respx_mock, monkeypatch, httpx.Response(400, json=REJECTED_REPLAYED_REASONING), False)
 
     litellm.anthropic.messages.create(
@@ -827,10 +834,60 @@ def test_sync_openai_turn_with_num_retries_sends_the_rejected_reasoning_only_onc
         messages=_history(replayed_reasoning=True),
         model="openai/gpt-5.6-luna",
         tools=[dict(BASH_TOOL)],
-        num_retries=2,
     )
 
     assert _replayed_reasoning_counts(upstream) == [1, 0]
+    assert litellm.num_retries == 2
+
+
+_SERVER_ERROR: Final = {
+    "error": {"message": "The server had an error while processing your request.", "type": "server_error"}
+}
+
+
+@pytest.mark.asyncio
+async def test_openai_turn_retries_a_server_error_with_the_reasoning_and_drops_it_only_once_rejected(
+    respx_mock: respx.MockRouter, monkeypatch: pytest.MonkeyPatch
+) -> None:
+    upstream: Final = _upstream_after(
+        respx_mock,
+        monkeypatch,
+        (httpx.Response(500, json=_SERVER_ERROR), httpx.Response(400, json=REJECTED_REPLAYED_REASONING)),
+        False,
+    )
+
+    response: Final = await litellm.anthropic.messages.acreate(
+        max_tokens=64,
+        messages=_history(replayed_reasoning=True),
+        model="openai/gpt-5.6-luna",
+        tools=[dict(BASH_TOOL)],
+        num_retries=2,
+    )
+
+    assert _replayed_reasoning_counts(upstream) == [1, 1, 0]
+    assert cast(Mapping[str, object], response)["content"] == [{"type": "text", "text": "done"}]
+
+
+def test_sync_openai_turn_retries_a_server_error_with_the_reasoning_and_drops_it_only_once_rejected(
+    respx_mock: respx.MockRouter, monkeypatch: pytest.MonkeyPatch
+) -> None:
+    upstream: Final = _upstream_after(
+        respx_mock,
+        monkeypatch,
+        (httpx.Response(500, json=_SERVER_ERROR), httpx.Response(400, json=REJECTED_REPLAYED_REASONING)),
+        False,
+    )
+
+    response: Final = litellm.anthropic.messages.create(
+        max_tokens=64,
+        messages=_history(replayed_reasoning=True),
+        model="openai/gpt-5.6-luna",
+        tools=[dict(BASH_TOOL)],
+        num_retries=2,
+    )
+
+    assert _replayed_reasoning_counts(upstream) == [1, 1, 0]
+    assert cast(Mapping[str, object], response)["content"] == [{"type": "text", "text": "done"}]
 
 
 class _FailureLog(CustomLogger):