fix(test): run the all-beta-headers bedrock cases on Claude Fable 5.1

Backport of #42048 to stable/1.101.x.
Cherry-picked from 7966f50c34 (main). The safeguards backport maps the dangerous-tool-use-2026-09-03 beta for Bedrock, which Claude Opus 4.5 on Bedrock Invoke rejects as an invalid beta flag, so the all-beta-headers Bedrock cases run on Claude Fable 5.1 as they do on main.

tests/proxy_e2e_anthropic_messages_tests/test_all_beta_headers.py

@@ -101,8 +101,8 @@ async def test_anthropic_messages_with_all_beta_headers(model_name, provider_nam
 @pytest.mark.parametrize(
     "model_name,provider_name",
     [
-        ("bedrock-claude-opus-4.5", "bedrock"),
-        ("bedrock-converse-claude-sonnet-4.5", "bedrock_converse"),
+        ("bedrock-claude-fable-5.1", "bedrock"),
+        ("bedrock-converse-claude-fable-5.1", "bedrock_converse"),
     ],
 )
 async def test_bedrock_invoke_messages_with_all_beta_headers(model_name, provider_name):

tests/proxy_e2e_anthropic_messages_tests/test_config.yaml

@@ -25,6 +25,11 @@ model_list:
       model: "bedrock/us.anthropic.claude-opus-4-5-20251101-v1:0"
       aws_region_name: "us-east-1"
 
+  - model_name: bedrock-claude-fable-5.1
+    litellm_params:
+      model: "bedrock/us.anthropic.claude-fable-5-1"
+      aws_region_name: "us-east-1"
+
   - model_name: bedrock-nova-pro
     litellm_params:
       model: "bedrock/us.amazon.nova-pro-v1:0"
@@ -35,6 +40,11 @@ model_list:
     litellm_params:
       model: "bedrock/converse/us.anthropic.claude-sonnet-4-5-20250929-v1:0"
       aws_region_name: "us-east-1"
+
+  - model_name: bedrock-converse-claude-fable-5.1
+    litellm_params:
+      model: "bedrock/converse/us.anthropic.claude-fable-5-1"
+      aws_region_name: "us-east-1"
   
   # Azure AI models
   - model_name: azure-ai-claude-opus-4.5