fix(translation): openai-dialect responses without a wire body error loudly (critic-openai M3)

serialize_response fell through to the anthropic assembly when an
openai-dialect ChatResponse carried no wire body, silently serving a
wrong-shaped body if a future openai-dialect parser forgets to set
ChatResponse.wire (azure/azure_ai now extend exactly this path). The
function returns Body | TranslationError; both pipeline call sites lift
the error into the Result, and a regression test pins the loud error.

litellm/translation/engine/pipeline.py

@@ -180,11 +180,20 @@ def translate_chat_response(
             )
         )
     dialect = response_dialect(provider)
-    return parser(raw_response, request).map(
-        lambda response: serialize_response(response, deps, dialect)
+    return parser(raw_response, request).bind(
+        lambda response: _serialized_body(response, deps, dialect)
     )
 
 
+def _serialized_body(
+    response: ChatResponse, deps: TranslationDeps, dialect: ResponseDialect
+) -> TranslateResult:
+    body = serialize_response(response, deps, dialect)
+    if isinstance(body, TranslationError):
+        return Error(body)
+    return Ok(body)
+
+
 @dataclass(frozen=True)
 class PreparedRequest:
     """A request that passed the fail-closed translation; from here on the
@@ -268,9 +277,10 @@ async def send_prepared(
         )
     match parser(response.body, prepared.request):
         case Result(tag="ok", ok=chat_response):
-            return Ok(
-                serialize_response(chat_response, deps, response_dialect(provider))
-            )
+            body = serialize_response(chat_response, deps, response_dialect(provider))
+            if isinstance(body, TranslationError):
+                return Error(ExecuteError.of_translation(body))
+            return Ok(body)
         case Result(error=response_err):
             return Error(ExecuteError.of_translation(response_err))
 

litellm/translation/inbound/openai_chat/response.py

@@ -29,6 +29,7 @@ from expression import Option
 from expression.collections import Block
 
 from ...deps import TranslationDeps
+from ...errors import BoundaryError, TranslationError
 from ...ir import Body, ChatResponse, ContentBlock, PlainJson, ResponseUsage
 
 ResponseDialect = Literal["anthropic", "bedrock_converse", "openai", "gemini"]
@@ -38,13 +39,27 @@ def serialize_response(
     response: ChatResponse,
     deps: TranslationDeps,
     dialect: ResponseDialect = "anthropic",
-) -> Body:
+) -> Body | TranslationError:
     if dialect == "openai":
         match response.wire:
             case Option(tag="some", some=blob) if isinstance(blob.value, dict):
                 return blob.value
             case _:
-                pass  # no wire body: fall through to the anthropic assembly
+                # The openai dialect has no assembly of its own: the provider
+                # parser MUST ride the normalized body on ChatResponse.wire.
+                # A registered openai-dialect parser that does not is a
+                # wiring bug; serving the anthropic assembly here would put a
+                # wrong-shaped body on the wire silently (critic-openai M3).
+                return TranslationError.of_boundary(
+                    BoundaryError.of(
+                        Block.of_seq(
+                            [
+                                "openai-dialect response carries no wire body;"
+                                " the provider parser must set ChatResponse.wire"
+                            ]
+                        )
+                    )
+                )
     if dialect == "gemini":
         return _gemini_body(response)
     text = "".join(block.text.text for block in response.content if block.tag == "text")

tests/test_litellm/translation/test_differential_openai_response.py

@@ -345,3 +345,23 @@ def test_unreachable_response_shape_is_a_typed_error(name: str) -> None:
     result = parse_response(copy.deepcopy(raw), parsed.ok)
     assert result.is_error(), f"{name} unexpectedly parsed"
     assert reason_fragment in result.error.summary, result.error.summary
+
+
+def test_openai_dialect_without_wire_body_is_a_loud_error() -> None:
+    """An openai-dialect response whose parser failed to set
+    ChatResponse.wire must be a typed error, never a silently served
+    anthropic-shaped body (critic-openai M3)."""
+    import dataclasses
+
+    from expression import Nothing
+
+    from litellm.translation.errors import TranslationError
+
+    parsed = parse_request(copy.deepcopy(_REQUEST))
+    assert parsed.is_ok()
+    response = parse_response(copy.deepcopy(_RESPONSES["text"]), parsed.ok)
+    assert response.is_ok()
+    wireless = dataclasses.replace(response.ok, wire=Nothing)
+    body = serialize_response(wireless, build_translation_deps(), "openai")
+    assert isinstance(body, TranslationError)
+    assert "wire body" in body.summary