fix(memory): typed Prisma error + explicit-null metadata on PUT

Two more greptile threads from the last review:

- Unique-violation detection was string-matching "Unique"/"UniqueViolation"
  in the exception message, fragile across Prisma/driver versions. Now
  check the typed error `code == "P2002"` first, with string fallback.

- PUT could not distinguish "metadata omitted" from "metadata: null" —
  both parsed as `None`, so callers had no way to clear stored metadata.
  Switch to Pydantic v2's `model_fields_set` to tell which fields the
  caller actually sent; explicit null now clears the column.

New tests:
- explicit null clears metadata
- omitted metadata preserves existing value

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

litellm/proxy/memory/memory_endpoints.py

@@ -87,9 +87,20 @@ def _require_prisma():
 
 
 def _is_unique_violation(exc: Exception) -> bool:
-    """Best-effort detection of a Prisma unique-constraint violation."""
+    """
+    Detect a Prisma unique-constraint violation.
+
+    Prefer the typed error code `P2002` from `PrismaClientKnownRequestError`;
+    fall back to string matching so we stay robust across Prisma versions
+    where the typed class may be unavailable or differently named.
+    """
+    code = getattr(exc, "code", None)
+    if code == "P2002":
+        return True
     msg = str(exc)
-    return "Unique" in msg or "unique" in msg or "UniqueViolation" in msg
+    return (
+        "P2002" in msg or "Unique" in msg or "unique" in msg or "UniqueViolation" in msg
+    )
 
 
 def _resolve_scope(
@@ -292,10 +303,19 @@ async def upsert_memory(
     """
     prisma_client = _require_prisma()
 
+    # Distinguish "metadata omitted from request" from "metadata: null".
+    # Omitted → don't touch the existing field. Explicit null → clear to SQL NULL.
+    # `model_fields_set` (Pydantic v2) only contains field names the caller
+    # actually sent in the payload.
+    fields_sent = body.model_fields_set
+    metadata_explicit = "metadata" in fields_sent
+
     data: dict = {}
     if body.value is not None:
         data["value"] = body.value
-    if body.metadata is not None:
+    if metadata_explicit:
+        # body.metadata may be None here — Prisma update accepts None on a
+        # nullable Json? field and sets the column to SQL NULL.
         data["metadata"] = body.metadata
     if not data:
         raise HTTPException(

tests/test_litellm/proxy/memory/test_memory_endpoints.py

@@ -427,6 +427,48 @@ class TestMemoryEndpoints:
         assert resp.json()["value"] == "new"
         assert len(table.rows) == 1
 
+    def test_put_memory_explicit_null_metadata_clears_field(self):
+        """PUT with `metadata: null` should clear the metadata column (not silently drop the field)."""
+        table = self.prisma.db.litellm_memorytable
+        table.rows.append(
+            _make_row(
+                memory_id="m1",
+                key="notes",
+                value="v",
+                user_id="user-a",
+                team_id="team-a",
+                metadata={"tag": "old"},
+            )
+        )
+        client = _make_client(_user_auth("user-a", "team-a"))
+        with _patch_prisma(self.prisma):
+            resp = client.put("/v1/memory/notes", json={"metadata": None})
+        assert resp.status_code == 200, resp.text
+        body = resp.json()
+        assert body["metadata"] is None
+        assert table.rows[0].metadata is None
+
+    def test_put_memory_omitted_metadata_preserves_field(self):
+        """PUT without a metadata field should NOT touch the stored metadata."""
+        table = self.prisma.db.litellm_memorytable
+        table.rows.append(
+            _make_row(
+                memory_id="m1",
+                key="notes",
+                value="old",
+                user_id="user-a",
+                team_id="team-a",
+                metadata={"tag": "keep"},
+            )
+        )
+        client = _make_client(_user_auth("user-a", "team-a"))
+        with _patch_prisma(self.prisma):
+            resp = client.put("/v1/memory/notes", json={"value": "new"})
+        assert resp.status_code == 200, resp.text
+        body = resp.json()
+        assert body["value"] == "new"
+        assert body["metadata"] == {"tag": "keep"}
+
     def test_put_memory_empty_body_returns_400(self):
         client = _make_client(_user_auth("user-a", "team-a"))
         with _patch_prisma(self.prisma):