fix(retry): reject negative retry counts

src/agents/retry.py

@@ -210,7 +210,7 @@ def retry_policy_retries_all_transient_errors(policy: RetryPolicy | None) -> boo
 class ModelRetrySettings:
     """Opt-in runner-managed retry settings for model calls."""
 
-    max_retries: int | None = None
+    max_retries: int | None = Field(default=None, ge=0)
     """Retries allowed after the initial model request."""
 
     backoff: ModelRetryBackoffInput | None = None

tests/test_retry_count_validation.py

@@ -0,0 +1,16 @@
+from __future__ import annotations
+
+import pytest
+from pydantic import ValidationError
+
+from agents.retry import ModelRetrySettings
+
+
+def test_model_retry_settings_rejects_negative_max_retries() -> None:
+    with pytest.raises(ValidationError):
+        ModelRetrySettings(max_retries=-1)
+
+
+def test_model_retry_settings_allows_zero_max_retries() -> None:
+    settings = ModelRetrySettings(max_retries=0)
+    assert settings.max_retries == 0