fix(bedrock): forward the per-turn-control beta to Bedrock Invoke

Claude Code sends `anthropic-beta: per-turn-control-2026-07-01` together
with a mid-conversation `role: system` message carrying a message-level
`output_config` (for example an effort change). The beta header config
mapped the beta to null for `bedrock`, so LiteLLM dropped it while
keeping the message in place on models flagged
`supports_mid_conversation_system`, and Bedrock Invoke rejected the turn
with "messages.N.output_config: Extra inputs are not permitted".

Direct Bedrock InvokeModel probes with a synthetic request show Claude
Opus 5.5 accepts that message shape only with this beta, and that Claude
Haiku 4.5, Sonnet 4.6, Opus 4.8, Opus 5, and Sonnet 5 accept the beta on
a plain request, so map it to itself for `bedrock`. `bedrock_converse`
is unchanged.

Generated with AI

Co-Authored-By: Claude Code

litellm/anthropic_beta_headers_config.json

@@ -124,7 +124,7 @@
     "mcp-servers-2025-12-04": null,
     "output-128k-2025-02-19": null,
     "structured-output-2024-03-01": null,
-    "per-turn-control-2026-07-01": null,
+    "per-turn-control-2026-07-01": "per-turn-control-2026-07-01",
     "prompt-caching-scope-2026-01-05": null,
     "skills-2025-10-02": null,
     "structured-outputs-2025-11-13": null,

tests/test_litellm/llms/bedrock/messages/invoke_transformations/test_anthropic_claude3_transformation.py

@@ -2359,6 +2359,37 @@ def test_bedrock_invoke_transform_hoists_only_leading_system_run(local_model_cos
     ]
 
 
+def test_bedrock_invoke_transform_forwards_per_turn_control_beta_with_message_output_config(
+    local_model_cost_map, local_beta_headers_config
+):
+    """Claude Code's per-turn control sends a mid-conversation ``role: "system"``
+    message carrying a message-level ``output_config`` together with the
+    per-turn-control-2026-07-01 beta. Bedrock Invoke rejects that message with
+    "messages.N.output_config: Extra inputs are not permitted" unless the beta
+    is present, so the beta must reach ``anthropic_beta`` and the message must
+    stay in place with its ``output_config``."""
+    from litellm.types.router import GenericLiteLLMParams
+
+    cfg = AmazonAnthropicClaudeMessagesConfig()
+    messages = [
+        {"role": "user", "content": "hi"},
+        {"role": "assistant", "content": "hello"},
+        {"role": "system", "content": [], "output_config": {"effort": "low"}},
+        {"role": "user", "content": "continue"},
+    ]
+
+    result = cfg.transform_anthropic_messages_request(
+        model="us.anthropic.claude-opus-5-5",
+        messages=copy.deepcopy(messages),
+        anthropic_messages_optional_request_params={"max_tokens": 256, "stream": False},
+        litellm_params=GenericLiteLLMParams(),
+        headers={"anthropic-beta": "per-turn-control-2026-07-01"},
+    )
+
+    assert result["messages"] == messages
+    assert result["anthropic_beta"].count("per-turn-control-2026-07-01") == 1
+
+
 def test_bedrock_invoke_transform_converts_mid_conversation_system_for_older_claude(local_model_cost_map):
     """Invoke rejects ``role: "system"`` in every position on Opus 4.7, Sonnet
     4.6, Haiku 4.5, etc. ("role 'system' is not supported on this model"), but

tests/test_litellm/test_anthropic_beta_headers_filtering.py

@@ -458,6 +458,21 @@ class TestAnthropicBetaHeadersFiltering:
 
         assert filtered == ["dangerous-tool-use-2026-09-03"]
 
+    @pytest.mark.parametrize("provider", ["anthropic", "bedrock", "bedrock_mantle"])
+    def test_per_turn_control_forwarded(self, provider):
+        """Claude Code sends per-turn-control-2026-07-01 together with a
+        mid-conversation `role: system` message that carries a message-level
+        `output_config` (e.g. an effort change). Bedrock Invoke accepts that
+        message only when the beta is present and otherwise answers
+        "messages.N.output_config: Extra inputs are not permitted", so dropping
+        the header (previously mapped to null) turned every such turn into a 400."""
+        filtered = filter_and_transform_beta_headers(
+            beta_headers=["per-turn-control-2026-07-01"],
+            provider=provider,
+        )
+
+        assert filtered == ["per-turn-control-2026-07-01"]
+
     def test_null_value_headers_filtered(self):
         """Test that headers with null values are always filtered out."""
         for provider in [