refactor(guardrails): narrow the SSE error-frame helper to the input it actually takes

Both callers pass a string, so the Mapping overload and its json.dumps branch
were unreachable. Folds the block branch's narrative comment into the rebind
suppressions that already carry a reason.

litellm/proxy/guardrails/anthropic_sse.py

@@ -98,15 +98,13 @@ def model_response_text(response: ModelResponse) -> str:
     )
 
 
-def anthropic_sse_error_frames(message: str | Mapping[str, object]) -> tuple[bytes, ...]:
+def anthropic_sse_error_frames(message: str) -> tuple[bytes, ...]:
     """Anthropic error event, for a failure discovered after the response headers were flushed.
 
     Once a keepalive ping has been sent a raise cannot reach the client, so the failure has to
-    travel as a frame. A structured detail is JSON-serialized into the string so it stays machine
-    readable without violating the string-typed contract.
+    travel as a frame.
     """
-    text: Final = message if isinstance(message, str) else json.dumps(message, default=str)
-    body: Final = json.dumps(text)
+    body: Final = json.dumps(message)
     return (
         f'event: error\ndata: {{"type": "error", "error": {{"type": "guardrail_error", '
         f'"message": {body}}}}}\n\n'.encode(),

litellm/proxy/guardrails/guardrail_hooks/bedrock_guardrails.py

@@ -2639,13 +2639,9 @@ class BedrockGuardrail(CustomGuardrail, BaseAWSLLM):
                 return
             except ModifyResponseException as e:
                 if raw_sse:
-                    # the shared per-endpoint block builder the unified guardrail path uses; it
-                    # mints a fresh message id because the block is not the upstream message, but
-                    # it reports exc.model, which defaults to the guardrail name rather than the model
-                    e.model = _pre_block_response.model or e.model  # rebind-ok: local synthetic block payload
+                    e.model = _pre_block_response.model or e.model  # rebind-ok: exc.model defaults to the guardrail
                     if e.original_response is None:
-                        # the builder reads usage off this; the upstream call was already paid for
-                        e.original_response = _pre_block_response  # rebind-ok: local synthetic block payload
+                        e.original_response = _pre_block_response  # rebind-ok: the block builder reads usage off this
                     for block_chunk in AnthropicMessagesHandler().build_block_sse_chunks(e, stream_started=False):
                         yield block_chunk
                     return