fix(nodes): Pair node fills the prompt's empty category and tags (#546)

The Pair node stored category and tags on the pair row only, so the Library
showed its prompt as Uncategorized. A save now fills the positive prompt's
category and tags where empty and never replaces a value.

TESTING.md

@@ -2888,6 +2888,13 @@ with its own negative, a self-pair, each drift, validation); `tests/test_library
 copy, the server after, archive-only, reset to Archive) and `library-delete-concept.spec.mjs`. A Python
 change: ComfyUI needs a restart.
 
+### Pair node fills the prompt's empty category and tags (#546)
+
+A Pair save fills the positive prompt's category and tags where each is empty and never replaces a value; a prompt
+with any tag keeps exactly those tags. The negative stays empty, the saved pair keeps its own metadata, and
+`save_prompt_pair` itself still writes no component metadata. There is no backfill: a prompt fills when a Pair node
+next executes. Tests: `tests/test_prompt_pair_node.py`. A Python change: ComfyUI needs a restart.
+
 ### Delete… on the archived shelf (#492)
 
 Extends **D160** (coordinator ruling 2026-10-29, cutover item): the archived shelf's bar reads "N selected · Restore ·

database/pairs.py

@@ -195,6 +195,43 @@ class PairOperations:
             self._sync_pair_tags(conn, pair_id, tags)
         return pair_id, True
 
+    def fill_empty_prompt_metadata(
+        self,
+        prompt_id: int,
+        category: Optional[str] = None,
+        tags: Optional[List[str]] = None,
+    ) -> bool:
+        """Give a prompt a category and tags where it has none (#546).
+
+        Each field fills on its own and never replaces a value already there.
+        Tags are not additive: a prompt with any tag keeps exactly those tags.
+        Returns True if the prompt changed.
+        """
+        tags = _validate_metadata(None, category, tags, None, None)
+        with self._pair_transaction() as conn:
+            changed = False
+            if category:
+                changed = (
+                    conn.execute(
+                        "UPDATE prompts SET category = ? WHERE id = ? "
+                        "AND (category IS NULL OR TRIM(category) = '')",
+                        (category, prompt_id),
+                    ).rowcount
+                    == 1
+                )
+            has_tags = conn.execute(
+                "SELECT 1 FROM prompt_tags WHERE prompt_id = ? LIMIT 1", (prompt_id,)
+            ).fetchone()
+            if tags and not has_tags:
+                self._sync_prompt_tags(conn, prompt_id, tags)
+                changed = True
+            if changed:
+                conn.execute(
+                    "UPDATE prompts SET updated_at = ? WHERE id = ?",
+                    (utc_now_iso(), prompt_id),
+                )
+            return changed
+
     def _read_pair_rows(
         self, conn: sqlite3.Connection, where: str, params: List[Any], suffix: str = ""
     ) -> List[Dict[str, Any]]:

prompt_manager_pair.py

@@ -233,6 +233,16 @@ class PromptManagerPair(PromptManagerFocused):
         )
         pair = self.db.get_prompt_pair(pair_id)
         prompt_id = pair["positive_prompt_id"]
+        # The Library shows the prompt's own category and tags, not the pair's.
+        # A failure here must not cost the run its count or image link.
+        try:
+            self.db.fill_empty_prompt_metadata(
+                prompt_id,
+                category=category.strip() or None,
+                tags=self._parse_tags(tags),
+            )
+        except Exception as error:
+            self.logger.warning(f"Could not fill prompt metadata: {error}")
         resolved_positive = (
             resolve_text_input(prompt, node_id, "text") if known else None
         )

tests/test_prompt_pair_node.py

@@ -13,6 +13,7 @@ except ImportError:  # discovered with tests/ as the top-level directory
 
 from database.operations import PromptDatabase
 from prompt_manager_pair import PromptManagerPair
+from utils.hashing import generate_prompt_hash
 from utils.usage_tracking import PendingFirstUse
 
 
@@ -109,14 +110,89 @@ class TestPromptPairNode(unittest.TestCase):
             ),
             ("cat", "blur", "Animals", ["studio"]),
         )
-        self.assertIsNone(
-            self.db.get_prompt_by_id(pair["positive_prompt_id"])["category"]
+        self.assertEqual(
+            self.db.get_prompt_by_id(pair["positive_prompt_id"])["category"],
+            "Animals",
         )
         tracked = self.node.prompt_tracker.set_current_prompt.call_args.kwargs
         self.assertEqual(tracked["additional_data"]["pair_id"], pair["id"])
         self.assertEqual(tracked["additional_data"]["negative_text"], " blur ")
         self.assertEqual(tracked["additional_data"]["positive_storage_text"], "cat")
 
+    def save(self, text="cat", negative="blur", **widgets):
+        self.node.encode_prompt(
+            self.clip,
+            text,
+            negative_text=negative,
+            prompt=pair_graph(text, negative),
+            unique_id="1",
+            **widgets,
+        )
+        hash_of = generate_prompt_hash
+        return (
+            self.db.get_prompt_by_hash(hash_of(text)),
+            self.db.get_prompt_by_hash(hash_of(negative)),
+        )
+
+    def test_first_save_gives_the_positive_its_category_and_tags(self):
+        positive, negative = self.save(category=" Animals ", tags="studio, macro")
+        self.assertEqual(positive["category"], "Animals")
+        self.assertCountEqual(positive["tags"], ["studio", "macro"])
+        self.assertIsNone(negative["category"])
+        self.assertEqual(negative["tags"], [])
+
+    def test_a_later_save_never_changes_a_category_or_tags_already_set(self):
+        self.save(category="Animals", tags="studio")
+        positive, _ = self.save(negative="noise", category="Pets", tags="other")
+        self.assertEqual(positive["category"], "Animals")
+        self.assertEqual(positive["tags"], ["studio"])
+
+    def test_a_save_keeps_metadata_a_person_set_on_the_prompt(self):
+        text = "cat"
+        self.db.save_prompt(
+            text,
+            category="Mine",
+            tags=["kept"],
+            prompt_hash=generate_prompt_hash(text),
+        )
+        positive, _ = self.save(category="Animals", tags="studio")
+        self.assertEqual(positive["category"], "Mine")
+        self.assertEqual(positive["tags"], ["kept"])
+
+    def test_category_and_tags_fill_independently_where_empty(self):
+        self.save(category="Animals")
+        positive, _ = self.save(negative="noise", category="Pets", tags="studio")
+        self.assertEqual(positive["category"], "Animals")
+        self.assertEqual(positive["tags"], ["studio"])
+
+    def test_blank_widgets_leave_the_prompt_empty(self):
+        positive, _ = self.save(category="  ", tags=" ")
+        self.assertIsNone(positive["category"])
+        self.assertEqual(positive["tags"], [])
+
+    def test_a_filled_prompt_does_not_change_the_saved_pair(self):
+        self.save(category="Animals", tags="studio")
+        positive, _ = self.save(category="Pets", tags="other")
+        pairs = self.db.list_prompt_pairs()["pairs"]
+        self.assertEqual(
+            [(pair["category"], pair["tags"]) for pair in pairs],
+            [("Animals", ["studio"])],
+        )
+        self.assertEqual(positive["category"], "Animals")
+
+    def test_a_failed_fill_still_tracks_the_run(self):
+        self.db.fill_empty_prompt_metadata = Mock(side_effect=RuntimeError("locked"))
+        self.save(category="Animals")
+        self.node.prompt_tracker.set_current_prompt.assert_called_once()
+
+    def test_library_shows_filled_metadata_without_repeating_a_tag(self):
+        self.save(category="Animals", tags="studio")
+        item = self.db.list_library()["items"][0]
+        self.assertEqual(item["category"], "Animals")
+        self.assertEqual(item["tags"], ["studio"])
+        tag = self.db.list_vocabulary_tags(limit=5)["tags"][0]
+        self.assertEqual(tag["prompt_count"], 1)
+
     def test_empty_negative_encodes_empty_text_and_stores_null_component(self):
         result = self.node.encode_prompt(self.clip, "cat", negative_text="")
         self.assertEqual(result[3], "")