api.py: async chat-turn push to Graphiti

After chat() returns, fire-and-forget background thread POSTs the (user
message + assistant response) as one episode to /episodes. Default extraction
(Sonnet). Errors logged, never raised — chat is not gated on the write.

Wall-clock cost in the background is ~20 min per episode against the
current ~4,300-entity graph. The chat experience is unaffected; the graph
catches up with a delay. Search_facts queries reflect new turns once the
sidecar has finished processing them.

Kill-switch: SKIP_GRAPHITI_CHAT_PUSH=1 in the api service environment
disables the push without code changes. Useful if dedup contention surfaces
under sustained load.

Companions to this commit: search_facts tool (e96bf40), orientation indexer
worker (e96bf40), FalkorDB vector index patches (d2ec20e, 313c0f0).

scripts/api.py

@@ -488,6 +488,47 @@ SEARCH_FACTS_TOOL = {
 }
 
 
+def _push_chat_turn_to_graphiti(conversation_id, user_message, assistant_message):
+    """Async fire-and-forget push of a chat turn into Graphiti. Single episode,
+    default extraction, no custom_extraction_instructions. Takes ~20 min in
+    the background against the current ~4,300-entity graph; the chat caller
+    is not gated on this. Errors are logged, never raised."""
+    if os.getenv("SKIP_GRAPHITI_CHAT_PUSH"):
+        return
+    if not (user_message or "").strip() and not (assistant_message or "").strip():
+        return
+    import threading
+    from datetime import datetime as _dt
+
+    def _work():
+        try:
+            episode_name = f"chat-{conversation_id[:8]}-{_dt.now().strftime('%Y%m%dT%H%M%S')}"
+            content = (
+                f"User: {user_message}\n\n"
+                f"Assistant: {assistant_message}"
+            )
+            payload = {
+                "name": episode_name,
+                "content": content,
+                "source_description": f"chat turn (conversation {conversation_id})",
+                "timestamp": _dt.now().isoformat(),
+                "group_id": GRAPHITI_GROUP_ID,
+            }
+            # Long timeout — sidecar add_episode against the current graph
+            # is empirically ~20 min wall-clock. We're patient; chat isn't.
+            r = requests.post(f"{GRAPHITI_URL}/episodes", json=payload, timeout=1800)
+            if r.status_code == 200:
+                print(f"[graphiti-push] turn ingested: {episode_name}")
+            else:
+                print(f"[graphiti-push] non-200 ({r.status_code}) for {episode_name}: {r.text[:200]}")
+        except requests.RequestException as e:
+            print(f"[graphiti-push] request failed: {e}")
+        except Exception as e:
+            print(f"[graphiti-push] unexpected error: {e}")
+
+    threading.Thread(target=_work, daemon=True).start()
+
+
 def _execute_search_facts(tool_input):
     """Hit Graphiti /search, format the results as text for Claude."""
     query = (tool_input or {}).get("query", "").strip()
@@ -775,6 +816,11 @@ def chat(user_message, conversation_id, settings, client_time=None):
             for block in response.content:
                 if hasattr(block, "text"):
                     assistant_message += block.text
+            # Async fire-and-forget into Graphiti so the turn lands in the
+            # graph as a single episode for future search_facts queries to
+            # find. Takes ~20 min wall-clock in the background; chat returns
+            # immediately. Disable via SKIP_GRAPHITI_CHAT_PUSH=1 if needed.
+            _push_chat_turn_to_graphiti(conversation_id, user_message, assistant_message)
             # Cap citations: accumulated_sources can grow large across multiple
             # retrieve_documents calls and not every chunk that came back was
             # actually used in the answer. Insertion order preserves rank