otel: waterfall prefers newest multi-span trace (real page render)

lib/host/otel.sx

@@ -399,18 +399,28 @@
 (define otel/recent-traces
   (fn () (reverse (map otel/trace-summary (otel/-trace-ids)))))
 ;; the dashboard's own endpoints — excluded from the "latest trace" so the
-;; waterfall shows the latest REAL request (a page) instead of the 3s poll.
+;; waterfall shows a real request, not the 3s poll.
 (define otel/-self-route?
   (fn (route)
     (or (= route "/otel") (= route "/otel/fragment") (= route "/otel/stream"))))
-;; the most recent NON-self trace (fall back to any trace if all are self).
+(define otel/-trace-route
+  (fn (trace-id)
+    (let ((roots (filter (fn (s) (nil? (get s :parent))) (otel/trace-spans trace-id))))
+      (if (empty? roots) nil (get (get (first roots) :attrs) :http.route)))))
+;; which trace the waterfall shows: prefer the newest MULTI-span trace (an
+;; instrumented page render — the interesting one), else the newest non-self trace
+;; (skip the poll), else the newest trace. Single-span assets/polls lose to a real
+;; page render even when they're more recent.
 (define otel/latest-trace
   (fn ()
-    (let ((real (filter (fn (s) (not (otel/-self-route? (get (get s :attrs) :http.route)))) (otel/recent))))
-      (cond
-        ((not (empty? real)) (get (last real) :trace))
-        ((not (empty? (otel/recent))) (get (last (otel/recent)) :trace))
-        (else nil)))))
+    (let ((newest-first (reverse (otel/-trace-ids))))
+      (let ((multi (filter (fn (tid) (> (len (otel/trace-spans tid)) 1)) newest-first))
+            (real  (filter (fn (tid) (not (otel/-self-route? (otel/-trace-route tid)))) newest-first)))
+        (cond
+          ((not (empty? multi)) (first multi))
+          ((not (empty? real)) (first real))
+          ((not (empty? newest-first)) (first newest-first))
+          (else nil))))))
 
 ;; ── SSE span events (SXTP) ────────────────────────────────────────────
 (define otel/span-event