feat(observability): 트레이스에 model(metadata) + 사용 태그 — skill:<이름> / wiki / mcp:<함수>

Co-Authored-By: Claude Opus 5.5 (1M context) <noreply@anthropic.com>

5_django_backend/apps/chat/stream.py

@@ -228,6 +228,7 @@ async def _finalize(session: ChatSession, state: TurnState, started: float, *, f
     usage: dict | None = None
     title = state.title
     tool_parts: list[dict] = []
+    model = ""
     try:
         msgs = await opencode_service.list_messages_a(session.id) or []
         assistant = [m for m in msgs if (m.get("info") or {}).get("role") == "assistant"]
@@ -236,6 +237,7 @@ async def _finalize(session: ChatSession, state: TurnState, started: float, *, f
             parts = assistant[-1].get("parts") or []
             # 이 턴의 assistant 메시지가 여러 개(도구 왕복마다 하나)라 도구 파트는 전부 모음
             tool_parts = [p for m in assistant for p in (m.get("parts") or []) if p.get("type") == "tool"]
+            model = info.get("modelID") or ""
             full = "".join(p.get("text", "") for p in parts if p.get("type") == "text" and not p.get("synthetic"))
             if full:
                 content = full
@@ -276,9 +278,9 @@ async def _finalize(session: ChatSession, state: TurnState, started: float, *, f
         t0 = datetime.fromtimestamp(started, timezone.utc).isoformat()
         root = langfuse.trace(
             tid, "chat", userId=user_email, sessionId=session.id, input=state.user_text, output=content,
-            tags=["codeassist"], start=t0, end=langfuse.now_iso(),
-            usage=langfuse.usage_of(usage["input"], usage["output"]) if usage else None,
-            metadata={"elapsed_ms": usage["elapsed_ms"]} if usage else {}, error=failed,
+            tags=["codeassist", *langfuse.usage_tags(tool_parts)], start=t0, end=langfuse.now_iso(),
+            usage=langfuse.usage_of(usage["input"], usage["output"]) if usage else None, model=model,
+            metadata={"model": model, **({"elapsed_ms": usage["elapsed_ms"]} if usage else {})}, error=failed,
         )
         langfuse.send_later([root, *_tool_spans(tid, root, tool_parts)])
     return usage, title