diff --git a/nanobot/providers/anthropic_provider.py b/nanobot/providers/anthropic_provider.py
index 0625d23b7..00a7f8271 100644
--- a/nanobot/providers/anthropic_provider.py
+++ b/nanobot/providers/anthropic_provider.py
@@ -49,6 +49,8 @@ class AnthropicProvider(LLMProvider):
             client_kw["base_url"] = api_base
         if extra_headers:
             client_kw["default_headers"] = extra_headers
+        # Keep retries centralized in LLMProvider._run_with_retry to avoid retry amplification.
+        client_kw["max_retries"] = 0
         self._client = AsyncAnthropic(**client_kw)
 
     @staticmethod
diff --git a/nanobot/providers/openai_compat_provider.py b/nanobot/providers/openai_compat_provider.py
index 10323d0ae..4fa057b90 100644
--- a/nanobot/providers/openai_compat_provider.py
+++ b/nanobot/providers/openai_compat_provider.py
@@ -135,6 +135,7 @@ class OpenAICompatProvider(LLMProvider):
             api_key=api_key or "no-key",
             base_url=effective_base,
             default_headers=default_headers,
+            max_retries=0,
         )
 
     def _setup_env(self, api_key: str, api_base: str | None) -> None:
diff --git a/tests/providers/test_provider_sdk_retry_defaults.py b/tests/providers/test_provider_sdk_retry_defaults.py
new file mode 100644
index 000000000..4c79febc4
--- /dev/null
+++ b/tests/providers/test_provider_sdk_retry_defaults.py
@@ -0,0 +1,20 @@
+from unittest.mock import patch
+
+from nanobot.providers.anthropic_provider import AnthropicProvider
+from nanobot.providers.openai_compat_provider import OpenAICompatProvider
+
+
+def test_openai_compat_disables_sdk_retries_by_default() -> None:
+    with patch("nanobot.providers.openai_compat_provider.AsyncOpenAI") as mock_client:
+        OpenAICompatProvider(api_key="sk-test", default_model="gpt-4o")
+
+    kwargs = mock_client.call_args.kwargs
+    assert kwargs["max_retries"] == 0
+
+
+def test_anthropic_disables_sdk_retries_by_default() -> None:
+    with patch("anthropic.AsyncAnthropic") as mock_client:
+        AnthropicProvider(api_key="sk-test", default_model="claude-sonnet-4-5")
+
+    kwargs = mock_client.call_args.kwargs
+    assert kwargs["max_retries"] == 0