fix: prevent duplicate LLM stream snapshots

assistant_agent.py

@@ -6,6 +6,8 @@ import urllib.request
 from collections.abc import Iterator
 from typing import Any
 
+from llm_stream import OpenAIStreamAccumulator
+
 
 class ReviewAssistantError(RuntimeError):
     pass
@@ -41,6 +43,7 @@ def stream_review_assistant(
     try:
         with urllib.request.urlopen(request, timeout=timeout) as response:
             yielded = False
+            accumulator = OpenAIStreamAccumulator()
             for raw_line in response:
                 line = raw_line.decode("utf-8", errors="replace").strip()
                 if not line or line.startswith(":"):
@@ -57,10 +60,7 @@ def stream_review_assistant(
                 if not choices:
                     continue
                 choice = choices[0] or {}
-                delta = choice.get("delta") or {}
-                content = delta.get("content")
-                if content is None:
-                    content = (choice.get("message") or {}).get("content")
+                content = accumulator.feed(choice)
                 if content:
                     yielded = True
                     yield str(content)