feat(collections): the rules-Apply path seeds the reversed default too

The creation seed (d56031f3) covered born-smart collections; a STATIC
collection that becomes smart through the rules editor's Apply landed
without any curated order — its dropdown stayed "Feed order" while
every other podcast smart collection opened reversed. Same decision,
same guardrails (2026-11-01 user approved closing this gap): a PUT
carrying an episodes-scope tree seeds chain_order=reverse only when
neither the request NOR the stored view_settings names one — a
deliberate native (client-sent or saved) is never clobbered, and
books-scope trees seed nothing.

Pins: apply-seeds-when-unordered, respects-stored-native,
respects-client-native (TestSmartCollectionBornReversed now covers
both seed paths); changelogged in contract_pins.

cmd/server/tests/podcast_test.go

@@ -2414,6 +2414,43 @@ func TestSmartCollectionBornReversed(t *testing.T) {
 		assert.NotContains(t, string(body), `"chain_order"`,
 			"static collections get no chain_order seed")
 	})
+
+	// The creation seed's twin (2026-11-01): APPLYING an episodes tree
+	// to a collection with no curated order seeds reverse — a static
+	// collection becoming smart lands with the same default a
+	// born-smart one gets. Explicit values (client-sent or stored) are
+	// never clobbered.
+	t.Run("apply_path_seeds_when_unordered", func(t *testing.T) {
+		id := create(t, `{"name":"test BornRev Apply `+t.Name()+`"}`)
+		code, body := podcastAuthed(t, setup, regToken, "PUT", "/api/collections/"+id,
+			`{"name":"test BornRev Apply `+t.Name()+`","filter_tree":{"scope":"episodes","mode":"all","children":[]}}`)
+		require.Equal(t, http.StatusCreated, code, "%s", string(body))
+		_, body = podcastAuthed(t, setup, regToken, "GET", "/api/collections/"+id, "")
+		assert.Contains(t, string(body), `"chain_order":"reverse"`,
+			"applying an episodes tree to an unordered collection seeds reverse")
+	})
+
+	t.Run("apply_path_respects_stored_native", func(t *testing.T) {
+		id := create(t, `{"name":"test BornRev KeepNative `+t.Name()+`","view_settings":{"chain_order":"native"}}`)
+		code, body := podcastAuthed(t, setup, regToken, "PUT", "/api/collections/"+id,
+			`{"name":"test BornRev KeepNative `+t.Name()+`","filter_tree":{"scope":"episodes","mode":"all","children":[]}}`)
+		require.Equal(t, http.StatusCreated, code, "%s", string(body))
+		_, body = podcastAuthed(t, setup, regToken, "GET", "/api/collections/"+id, "")
+		assert.Contains(t, string(body), `"chain_order":"native"`,
+			"a stored explicit chain_order is never clobbered by the apply seed")
+		assert.NotContains(t, string(body), `"chain_order":"reverse"`)
+	})
+
+	t.Run("apply_path_respects_client_native", func(t *testing.T) {
+		id := create(t, `{"name":"test BornRev ClientNative `+t.Name()+`"}`)
+		code, body := podcastAuthed(t, setup, regToken, "PUT", "/api/collections/"+id,
+			`{"name":"test BornRev ClientNative `+t.Name()+`","filter_tree":{"scope":"episodes","mode":"all","children":[]},"view_settings":{"chain_order":"native"}}`)
+		require.Equal(t, http.StatusCreated, code, "%s", string(body))
+		_, body = podcastAuthed(t, setup, regToken, "GET", "/api/collections/"+id, "")
+		assert.Contains(t, string(body), `"chain_order":"native"`,
+			"the client's explicit chain_order wins over the apply seed")
+		assert.NotContains(t, string(body), `"chain_order":"reverse"`)
+	})
 }
 
 // ---- label endpoint: names id-kind values for client-held trees ----

docs/contract_pins.md

@@ -703,3 +703,14 @@ resolves through the endpoint and rebuilds the chips bar when labels
 land. Pinned (TestFilterLabelsEndpoint): a zero-episode feed resolves
 its title, comma-joined ids resolve together, an unsubscribed feed id
 stays unnamed (RLS), non-id fields are 400.
+
+## 2026-11-01 — the rules-Apply path seeds the reversed default too
+
+PUT /api/collections/:id carrying an EPISODES-scope filter_tree seeds
+`chain_order = "reverse"` when neither the request nor the stored
+view_settings names one — the creation seed's twin: a static collection
+becoming smart lands with the same default a born-smart one gets.
+Explicit values (client-sent or stored — e.g. a deliberate native)
+are never clobbered. Pinned (TestSmartCollectionBornReversed):
+apply-seeds-when-unordered, respects stored native, respects client
+native.

internal/handlers/collections.go

@@ -607,6 +607,27 @@ func (h *CollectionHandler) UpdateCollection(c *echo.Context) error {
 	if treeErr != nil {
 		return c.JSON(http.StatusBadRequest, map[string]string{"error": treeErr.Error()})
 	}
+	// Applying a tree to a collection with NO curated listening order
+	// seeds the reversed default (2026-11-01 — the creation seed's twin):
+	// a static collection becoming smart lands with the same default a
+	// born-smart one gets. Triple-guarded: the client's explicit
+	// chain_order wins, a STORED chain_order is never clobbered, and
+	// only episodes-scope trees seed (books have no episode chain).
+	if treeJSON != nil && (req.ViewSettings == nil || req.ViewSettings["chain_order"] == nil) {
+		if t, perr := services.ParseFilterTree(string(treeJSON)); perr == nil &&
+			t.FilterScope() == services.ScopeEpisodes {
+			if existing, gerr := h.collectionService.GetCollection(c.Request().Context(), collectionID); gerr == nil {
+				var stored map[string]interface{}
+				_ = json.Unmarshal(existing.ViewSettings, &stored)
+				if stored == nil || stored["chain_order"] == nil {
+					if req.ViewSettings == nil {
+						req.ViewSettings = map[string]interface{}{}
+					}
+					req.ViewSettings["chain_order"] = "reverse"
+				}
+			}
+		}
+	}
 	collection, err := h.collectionService.UpdateCollection(
 		c.Request().Context(),
 		collectionID,