fix(bedrock): send compaction only with its beta, and add the beta for an adopted block

Follow-ups to forwarding the compact-2026-09-04 `compaction` parameter on
Bedrock Invoke:

- `compaction` stays in the body only when it is an object and
  compact-2026-09-04 survives the route's beta filter. bedrock_mantle has no
  entry for that beta, so a mantle request keeps the earlier strip instead of
  reaching Bedrock with the field and no beta (400 "Extra inputs are not
  permitted"). A null or non-object value is dropped the same way.
- A request that adopts the signed compaction block now gets the beta even
  without a client anthropic-beta header, as the Anthropic route does
  (carries_signed_compaction_block).
- The compaction tests pin the bundled beta config (local_beta_headers_config)
  so they do not read the remote copy an earlier test left cached.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

litellm/llms/bedrock/messages/invoke_transformations/anthropic_claude_transformation.py

@@ -23,6 +23,7 @@ from litellm.llms.anthropic.common_utils import (
     OBJECT_MAPPING_ADAPTER,
     AnthropicModelInfo,
     carried_thinking_keys,
+    carries_signed_compaction_block,
     validated_object_mapping,
 )
 from litellm.llms.anthropic.messages.native.transformation import (
@@ -555,12 +556,15 @@ class AmazonAnthropicClaudeMessagesConfig(
         """
         A top-level ``compaction`` request needs the ``compact-2026-09-04``
         anthropic-beta; without it Bedrock answers 400 "compaction: Extra inputs
-        are not permitted". Later requests that adopt the returned block need the
-        same beta, which the caller sends as a header.
+        are not permitted". A later request that adopts the returned signed
+        block needs the same beta, so it is added for that block too, as the
+        Anthropic route does.
 
         Ref: https://docs.aws.amazon.com/bedrock/latest/userguide/claude-messages-compaction.html
         """
-        if isinstance(anthropic_messages_request.get("compaction"), dict):
+        if isinstance(anthropic_messages_request.get("compaction"), dict) or carries_signed_compaction_block(
+            anthropic_messages_request.get("messages") or ()
+        ):
             beta_set.add("compact-2026-09-04")
 
     def strips_beta_gated_fields_from_final_headers(self) -> bool:
@@ -843,6 +847,16 @@ class AmazonAnthropicClaudeMessagesConfig(
         if filtered_betas:
             anthropic_messages_request["anthropic_beta"] = filtered_betas
 
+        # ``compaction`` travels only with its beta. A beta map without compact-2026-09-04
+        # (bedrock_mantle) or a non-object value keeps the earlier strip instead of a 400.
+        if "compaction" in anthropic_messages_request and not (
+            isinstance(anthropic_messages_request["compaction"], dict) and "compact-2026-09-04" in filtered_betas
+        ):
+            verbose_logger.debug(
+                "Bedrock Invoke: dropping `compaction`; compact-2026-09-04 is not served on this route"
+            )
+            anthropic_messages_request.pop("compaction")
+
         final_request: Final = OBJECT_MAPPING_ADAPTER.validate_python(anthropic_messages_request)  # pyright: ignore[reportUnknownArgumentType]  # built from the base signature's bare dict
         gated: Final = strip_beta_gated_native_request(
             {},

tests/unit/llms/bedrock/messages/invoke_transformations/test_anthropic_claude_transformation.py

@@ -1547,6 +1547,7 @@ def test_bedrock_messages_preserves_compact_context_management_and_adds_beta():
     assert result["max_tokens"] == 4096
 
 
+@pytest.mark.usefixtures("local_beta_headers_config")
 def test_bedrock_messages_keeps_compaction_param_and_adds_beta():
     """
     The ``compact-2026-09-04`` beta uses a top-level ``compaction`` parameter, not a
@@ -1580,6 +1581,7 @@ def test_bedrock_messages_keeps_compaction_param_and_adds_beta():
     assert set(result).issubset(cfg.BEDROCK_INVOKE_ALLOWED_TOP_LEVEL_FIELDS)
 
 
+@pytest.mark.usefixtures("local_beta_headers_config")
 def test_bedrock_messages_keeps_compact_2026_09_04_beta_for_adopting_request():
     """
     A request that adopts the signed block sends it first in ``messages`` and must
@@ -1603,6 +1605,54 @@ def test_bedrock_messages_keeps_compact_2026_09_04_beta_for_adopting_request():
     assert result["messages"][0]["content"][0] == block
 
 
+@pytest.mark.usefixtures("local_beta_headers_config")
+def test_bedrock_messages_adds_compact_2026_09_04_beta_for_signed_block_without_client_header():
+    """
+    A client that adopts the signed block but sends no anthropic-beta header still
+    needs ``compact-2026-09-04``; the Anthropic route adds it for the block, and so
+    does Bedrock Invoke.
+    """
+    from litellm.types.router import GenericLiteLLMParams
+
+    cfg = AmazonAnthropicClaudeMessagesConfig()
+    block = {"type": "compaction", "content": "<summary>TR-TITCK: Type IB.</summary>", "signature": "sig"}
+    messages = [{"role": "user", "content": [block, {"type": "text", "text": "Now KR-MFDS."}]}]
+
+    result = cfg.transform_anthropic_messages_request(
+        model="anthropic.claude-opus-5",
+        messages=messages,
+        anthropic_messages_optional_request_params={"max_tokens": 512},
+        litellm_params=GenericLiteLLMParams(),
+        headers={},
+    )
+
+    assert result["anthropic_beta"] == ["compact-2026-09-04"]
+    assert result["messages"][0]["content"][0] == block
+
+
+@pytest.mark.usefixtures("local_beta_headers_config")
+@pytest.mark.parametrize("compaction", [None, "summarize", []])
+def test_bedrock_messages_drops_compaction_that_is_not_an_object(compaction):
+    """
+    Only an object ``compaction`` gets the beta. Any other value is dropped, as it
+    was before the field was allowed, instead of reaching Bedrock without its beta.
+    """
+    from litellm.types.router import GenericLiteLLMParams
+
+    cfg = AmazonAnthropicClaudeMessagesConfig()
+
+    result = cfg.transform_anthropic_messages_request(
+        model="anthropic.claude-opus-5",
+        messages=[{"role": "user", "content": [{"type": "text", "text": "Hi"}]}],
+        anthropic_messages_optional_request_params={"max_tokens": 512, "compaction": compaction},
+        litellm_params=GenericLiteLLMParams(),
+        headers={},
+    )
+
+    assert "compaction" not in result
+    assert "compact-2026-09-04" not in result.get("anthropic_beta", [])
+
+
 def test_bedrock_messages_filters_unsupported_context_management_edits():
     """
     Mixed edit lists must drop the LiteLLM-internal ``clear_thinking_20251015``

tests/unit/llms/bedrock/test_mantle.py

@@ -796,3 +796,26 @@ async def test_mantle_anthropic_messages_streaming_sends_stream_and_passes_throu
     assert "event: message_start" in text
     assert '"text": "pong"' in text
     assert "event: message_stop" in text
+
+
+@pytest.mark.usefixtures("local_beta_headers_config")
+def test_mantle_messages_drops_compaction_without_its_beta():
+    """
+    The bedrock_mantle beta map has no compact-2026-09-04, so the beta is filtered
+    out on this route. ``compaction`` must go with it, or the body carries a field
+    that Bedrock refuses without the beta.
+    """
+    from litellm.types.router import GenericLiteLLMParams
+
+    config = AmazonMantleMessagesConfig()
+    headers: dict = {}
+    request = config.transform_anthropic_messages_request(
+        model="mantle/anthropic.claude-mythos-preview",
+        messages=[{"role": "user", "content": "Hello"}],
+        anthropic_messages_optional_request_params={"max_tokens": 100, "compaction": {"type": "summarize"}},
+        litellm_params=GenericLiteLLMParams(),
+        headers=headers,
+    )
+
+    assert "compaction" not in request
+    assert "compact-2026-09-04" not in headers.get("anthropic-beta", "")