From 9dfc77630ef6154c127a7f2384c9c4eca9f7a227 Mon Sep 17 00:00:00 2001
From: javierdejesusda <javier.dejesusj9@gmail.com>
Date: Wed, 25 Mar 2026 00:17:16 +0100
Subject: [PATCH] fix(bedrock): retry transient 400 errors from Bedrock

Bedrock can return transient errors like ThrottlingException with HTTP
400 status codes. The base retry logic only retries on 408, 409, 429,
and 5xx, so these transient 400s were not retried.

Override _should_retry in BaseBedrockClient to check the
x-amzn-errortype response header for known transient error types.

closes #940
---
 src/anthropic/lib/bedrock/_client.py | 21 +++++++
 tests/lib/test_bedrock.py            | 93 +++++++++++++++++++++++++++-
 2 files changed, 113 insertions(+), 1 deletion(-)

diff --git a/src/anthropic/lib/bedrock/_client.py b/src/anthropic/lib/bedrock/_client.py
index 013d2702..f53a8aa4 100644
--- a/src/anthropic/lib/bedrock/_client.py
+++ b/src/anthropic/lib/bedrock/_client.py
@@ -91,6 +91,27 @@ def _infer_region() -> str:
 
 
 class BaseBedrockClient(BaseClient[_HttpxClientT, _DefaultStreamT]):
+    @override
+    def _should_retry(self, response: httpx.Response) -> bool:
+        if super()._should_retry(response):
+            return True
+
+        if response.status_code == 400:
+            error_type = response.headers.get("x-amzn-errortype", "")
+            if any(
+                exc in error_type
+                for exc in (
+                    "ThrottlingException",
+                    "TooManyRequestsException",
+                    "ModelTimeoutException",
+                    "ServiceUnavailableException",
+                )
+            ):
+                log.debug("Retrying due to Bedrock transient error: %s", error_type)
+                return True
+
+        return False
+
     @override
     def _make_status_error(
         self,
diff --git a/tests/lib/test_bedrock.py b/tests/lib/test_bedrock.py
index fe62da43..ea7bb565 100644
--- a/tests/lib/test_bedrock.py
+++ b/tests/lib/test_bedrock.py
@@ -8,7 +8,7 @@
 import pytest
 from respx import MockRouter
 
-from anthropic import AnthropicBedrock, AsyncAnthropicBedrock
+from anthropic import BadRequestError, AnthropicBedrock, AsyncAnthropicBedrock
 
 sync_client = AnthropicBedrock(
     aws_region="us-east-1",
@@ -195,3 +195,94 @@ def test_region_infer_from_specified_profile(
     client = AnthropicBedrock()
 
     assert client.aws_region == next(profile for profile in profiles if profile["name"] == aws_profile)["region"]
+
+
+@pytest.mark.filterwarnings("ignore::DeprecationWarning")
+@pytest.mark.respx()
+def test_retries_on_bedrock_throttling_error(respx_mock: MockRouter) -> None:
+    respx_mock.post(re.compile(r"https://bedrock-runtime\.us-east-1\.amazonaws\.com/model/.*/invoke")).mock(
+        side_effect=[
+            httpx.Response(
+                400,
+                json={"message": "Too many requests, please wait before trying again."},
+                headers={"x-amzn-errortype": "ThrottlingException", "retry-after-ms": "10"},
+            ),
+            httpx.Response(200, json={"foo": "bar"}),
+        ]
+    )
+
+    sync_client.messages.create(
+        max_tokens=1024,
+        messages=[
+            {
+                "role": "user",
+                "content": "Say hello there!",
+            }
+        ],
+        model="anthropic.claude-3-5-sonnet-20241022-v2:0",
+    )
+
+    calls = cast("list[MockRequestCall]", respx_mock.calls)
+
+    assert len(calls) == 2
+
+
+@pytest.mark.filterwarnings("ignore::DeprecationWarning")
+@pytest.mark.respx()
+@pytest.mark.asyncio()
+async def test_retries_on_bedrock_throttling_error_async(respx_mock: MockRouter) -> None:
+    respx_mock.post(re.compile(r"https://bedrock-runtime\.us-east-1\.amazonaws\.com/model/.*/invoke")).mock(
+        side_effect=[
+            httpx.Response(
+                400,
+                json={"message": "Too many requests, please wait before trying again."},
+                headers={"x-amzn-errortype": "ThrottlingException", "retry-after-ms": "10"},
+            ),
+            httpx.Response(200, json={"foo": "bar"}),
+        ]
+    )
+
+    await async_client.messages.create(
+        max_tokens=1024,
+        messages=[
+            {
+                "role": "user",
+                "content": "Say hello there!",
+            }
+        ],
+        model="anthropic.claude-3-5-sonnet-20241022-v2:0",
+    )
+
+    calls = cast("list[MockRequestCall]", respx_mock.calls)
+
+    assert len(calls) == 2
+
+
+@pytest.mark.filterwarnings("ignore::DeprecationWarning")
+@pytest.mark.respx()
+def test_no_retry_on_bedrock_validation_error(respx_mock: MockRouter) -> None:
+    respx_mock.post(re.compile(r"https://bedrock-runtime\.us-east-1\.amazonaws\.com/model/.*/invoke")).mock(
+        side_effect=[
+            httpx.Response(
+                400,
+                json={"message": "Invalid input"},
+                headers={"x-amzn-errortype": "ValidationException"},
+            ),
+        ]
+    )
+
+    with pytest.raises(BadRequestError):
+        sync_client.messages.create(
+            max_tokens=1024,
+            messages=[
+                {
+                    "role": "user",
+                    "content": "Say hello there!",
+                }
+            ],
+            model="anthropic.claude-3-5-sonnet-20241022-v2:0",
+        )
+
+    calls = cast("list[MockRequestCall]", respx_mock.calls)
+
+    assert len(calls) == 1