Log the 2026-08-24 session: F3 fix live, audit filled, corpus re-ingest scoped

apps/ai-service/routers/rag.py

@@ -1,5 +1,6 @@
 from __future__ import annotations
 
+import json
 import uuid
 from typing import Annotated, Any, Literal, Protocol
 
@@ -161,6 +162,18 @@ def _section_retriever(request: Request) -> SectionListRetriever:
 router = APIRouter(prefix="/v1/rag", tags=["rag"])
 
 
+def _json_attr(text: str) -> str:
+    """Langfuse expects `observation.input`/`output` as a JSON string.
+
+    Passing raw text silently maps to nothing: verified live 2026-08-21, the
+    span carried the attribute and Langfuse showed empty input/output columns
+    while `langfuse.session.id` -- a plain string by contract -- mapped fine
+    from the same annotate call. No error anywhere; the field simply stays
+    blank, which is the failure mode worth remembering.
+    """
+    return json.dumps(text, ensure_ascii=False)
+
+
 def _clip(text: str | None, limit: int = 2000) -> str:
     """Bounded text for a span attribute.
 
@@ -686,8 +699,8 @@ def query_rag(
             # exposure is bounded -- but it is a change, not an oversight, and
             # the text is truncated rather than unbounded.
             "langfuse.trace.name": f"rag.{decision}",
-            "langfuse.observation.input": _clip(payload.query),
-            "langfuse.observation.output": _clip(answer),
+            "langfuse.observation.input": _json_attr(_clip(payload.query)),
+            "langfuse.observation.output": _json_attr(_clip(answer)),
             "langfuse.trace.metadata.decision": decision,
             "langfuse.trace.metadata.reason": reason,
             "langfuse.trace.metadata.resolved_drug_id": resolved_drug_id or "",