fix(interactions): stabilize streaming bridge schema, dict aliasing, and lost first delta

- Capture use_legacy_interactions_schema once at iterator construction so
  all events emitted by a single stream use a consistent schema, even if
  the global flag is mutated mid-stream.
- Check for the buffered interaction.complete/completed event before the
  finished check in __next__/__anext__ so the final completion event
  (which carries the full collected text in steps) is not dropped after
  self.finished is set.
- Copy text content entries before appending to both outputs and the
  steps content list to avoid shared mutable dict aliasing between the
  two response fields.

Co-authored-by: Yassin Kortam <yassin@berri.ai>

litellm/interactions/litellm_responses_transformation/streaming_iterator.py

@@ -47,6 +47,8 @@ class LiteLLMResponsesInteractionsStreamingIterator:
         custom_llm_provider: Optional[str] = None,
         litellm_metadata: Optional[Dict[str, Any]] = None,
     ):
+        import litellm
+
         self.model = model
         self.responses_stream_iterator = litellm_custom_stream_wrapper
         self.request_input = request_input
@@ -57,12 +59,10 @@ class LiteLLMResponsesInteractionsStreamingIterator:
         self.collected_text = ""
         self.sent_interaction_start = False
         self.sent_content_start = False
-
-    @property
-    def _use_legacy(self) -> bool:
-        import litellm
-
-        return litellm.use_legacy_interactions_schema
+        # Capture the schema flag once at construction time so all events
+        # emitted by this stream use a consistent schema, even if the global
+        # flag is mutated mid-stream (e.g. by a config reload).
+        self._use_legacy: bool = litellm.use_legacy_interactions_schema
 
     def _transform_responses_chunk_to_interactions_chunk(
         self,
@@ -201,10 +201,9 @@ class LiteLLMResponsesInteractionsStreamingIterator:
 
     def __next__(self) -> InteractionsAPIStreamingResponse:
         """Get next chunk in sync mode."""
-        if self.finished:
-            raise StopIteration
-
-        # Check if we have a pending interaction.complete to send
+        # Check for a pending interaction.complete/completed event BEFORE the
+        # finished check — otherwise the buffered completion event (which
+        # carries the full text) would be dropped after `self.finished` is set.
         if hasattr(self, "_pending_interaction_complete"):
             pending: InteractionsAPIStreamingResponse = getattr(
                 self, "_pending_interaction_complete"
@@ -212,6 +211,9 @@ class LiteLLMResponsesInteractionsStreamingIterator:
             delattr(self, "_pending_interaction_complete")
             return pending
 
+        if self.finished:
+            raise StopIteration
+
         # Use a loop instead of recursion to avoid stack overflow
         sync_iterator = cast(
             SyncResponsesAPIStreamingIterator, self.responses_stream_iterator
@@ -287,10 +289,9 @@ class LiteLLMResponsesInteractionsStreamingIterator:
 
     async def __anext__(self) -> InteractionsAPIStreamingResponse:
         """Get next chunk in async mode."""
-        if self.finished:
-            raise StopAsyncIteration
-
-        # Check if we have a pending interaction.complete to send
+        # Check for a pending interaction.complete/completed event BEFORE the
+        # finished check — otherwise the buffered completion event (which
+        # carries the full text) would be dropped after `self.finished` is set.
         if hasattr(self, "_pending_interaction_complete"):
             pending: InteractionsAPIStreamingResponse = getattr(
                 self, "_pending_interaction_complete"
@@ -298,6 +299,9 @@ class LiteLLMResponsesInteractionsStreamingIterator:
             delattr(self, "_pending_interaction_complete")
             return pending
 
+        if self.finished:
+            raise StopAsyncIteration
+
         # Use a loop instead of recursion to avoid stack overflow
         async_iterator = cast(
             ResponsesAPIStreamingIterator, self.responses_stream_iterator

litellm/interactions/litellm_responses_transformation/transformation.py

@@ -240,15 +240,16 @@ class LiteLLMResponsesInteractionsConfig:
                         # Check if content_item has text attribute
                         text = getattr(content_item, "text", None)
                         if text is not None:
-                            text_entry = {"type": "text", "text": text}
-                            outputs.append(text_entry)
-                            model_output_contents.append(text_entry)
+                            # Use independent dict instances so mutations to one
+                            # of `outputs` / `steps` don't leak into the other.
+                            outputs.append({"type": "text", "text": text})
+                            model_output_contents.append({"type": "text", "text": text})
                         elif (
                             isinstance(content_item, dict)
                             and content_item.get("type") == "text"
                         ):
-                            outputs.append(content_item)
-                            model_output_contents.append(content_item)
+                            outputs.append({**content_item})
+                            model_output_contents.append({**content_item})
                     if model_output_contents:
                         steps.append(
                             {