Fix client routing: fall through to server on layout/section change

Client-side routing was only swapping #main-panel content without
updating OOB headers (nav rows, sub-rows). Now each page entry in the
registry includes a layout identity (e.g. "sx-section:Testing") and
try-client-route falls through to server when layout changes, so OOB
header updates are applied correctly.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

shared/sx/helpers.py

@@ -704,6 +704,31 @@ def _build_pages_sx(service: str) -> str:
             if io_deps else "()"
         )
 
+        # Extract layout identity for client-side routing.
+        # When layout changes between pages, client routing falls through
+        # to server so OOB header updates are applied.
+        layout_id = ""
+        if isinstance(page_def.layout, str):
+            layout_id = page_def.layout
+        elif isinstance(page_def.layout, list):
+            from .types import Keyword as _Kw, Symbol as _Sym
+            first = page_def.layout[0]
+            if isinstance(first, _Kw):
+                layout_id = first.name
+            elif isinstance(first, _Sym):
+                layout_id = first.name
+            else:
+                layout_id = str(first)
+            # Append section kwarg to distinguish same-layout-type
+            # with different sections (e.g. sx-section+Docs vs sx-section+Testing)
+            raw_layout = page_def.layout
+            for li in range(1, len(raw_layout) - 1):
+                if isinstance(raw_layout[li], _Kw) and raw_layout[li].name == "section":
+                    val = raw_layout[li + 1]
+                    if val is not None:
+                        layout_id = f"{layout_id}:{val}"
+                    break
+
         # Build closure as SX dict
         closure_parts: list[str] = []
         for k, v in page_def.closure.items():
@@ -719,6 +744,7 @@ def _build_pages_sx(service: str) -> str:
             + " :auth " + _sx_literal(auth)
             + " :has-data " + has_data
             + " :stream " + stream
+            + " :layout " + _sx_literal(layout_id)
             + " :io-deps " + io_deps_sx
             + " :content " + _sx_literal(content_src)
             + " :deps " + deps_sx

shared/sx/ref/orchestration.sx

@@ -593,7 +593,14 @@
 ;; Client-side routing
 ;; --------------------------------------------------------------------------
 
-;; No app-specific nav update here — apps handle sx:clientRoute event.
+(define current-page-layout
+  (fn ()
+    ;; Find the layout name of the currently displayed page by matching
+    ;; the browser URL against the page route table.
+    (let ((pathname (url-pathname (browser-location-href)))
+          (match (find-matching-route pathname _page-routes)))
+      (if (nil? match) ""
+        (or (get match "layout") "")))))
 
 
 (define swap-rendered-content
@@ -634,20 +641,25 @@
     ;; Try to render a page client-side. Returns true if successful, false otherwise.
     ;; target-sel is the CSS selector for the swap target (from sx-boost value).
     ;; For pure pages: renders immediately. For :data pages: fetches data then renders.
+    ;; Falls through to server when layout changes (needs OOB header update).
     (let ((match (find-matching-route pathname _page-routes)))
       (if (nil? match)
         (do (log-info (str "sx:route no match (" (len _page-routes) " routes) " pathname)) false)
-        (let ((content-src (get match "content"))
-              (closure (or (get match "closure") {}))
-              (params (get match "params"))
-              (page-name (get match "name")))
-          (if (or (nil? content-src) (empty? content-src))
-            (do (log-warn (str "sx:route no content for " pathname)) false)
-            (let ((target (resolve-route-target target-sel)))
-              (if (nil? target)
-                (do (log-warn (str "sx:route target not found: " target-sel)) false)
-                (if (not (deps-satisfied? match))
-                  (do (log-info (str "sx:route deps miss for " page-name)) false)
+        (let ((target-layout (or (get match "layout") ""))
+              (cur-layout (current-page-layout)))
+          (if (not (= target-layout cur-layout))
+            (do (log-info (str "sx:route server (layout: " cur-layout " -> " target-layout ") " pathname)) false)
+            (let ((content-src (get match "content"))
+                  (closure (or (get match "closure") {}))
+                  (params (get match "params"))
+                  (page-name (get match "name")))
+              (if (or (nil? content-src) (empty? content-src))
+                (do (log-warn (str "sx:route no content for " pathname)) false)
+                (let ((target (resolve-route-target target-sel)))
+                  (if (nil? target)
+                    (do (log-warn (str "sx:route target not found: " target-sel)) false)
+                    (if (not (deps-satisfied? match))
+                      (do (log-info (str "sx:route deps miss for " page-name)) false)
                   (let ((io-deps (get match "io-deps"))
                         (has-io (and io-deps (not (empty? io-deps)))))
                     ;; Ensure IO deps are registered as proxied primitives
@@ -715,7 +727,7 @@
                             (do (log-info (str "sx:route server (eval failed) " pathname)) false)
                             (do
                               (swap-rendered-content target rendered pathname)
-                              true)))))))))))))))
+                              true)))))))))))))))))
 
 
 (define bind-client-route-link