From ca077b429bf0f36a4ef04603a9baf23e05d7359d Mon Sep 17 00:00:00 2001
From: giles <giles.bradshaw@rose-ash.com>
Date: Thu, 16 Apr 2026 13:35:45 +0000
Subject: [PATCH] hydrate-island: clear-and-replace instead of hydration walk

Islands now clear SSR children before render-to-dom and append the
fresh DOM result. Avoids hydrate-mismatch errors from SSR/client
attribute differences (~tw generates different class strings).

The hydrating scope is set to nil (no cursor walk) so render-to-dom
creates new DOM nodes instead of trying to reuse SSR elements.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>
---
 shared/static/wasm/sx/boot.sx | 11 ++++++++---
 web/boot.sx                   | 11 ++++++++---
 2 files changed, 16 insertions(+), 6 deletions(-)

diff --git a/shared/static/wasm/sx/boot.sx b/shared/static/wasm/sx/boot.sx
index a5b319d1..6cb0f604 100644
--- a/shared/static/wasm/sx/boot.sx
+++ b/shared/static/wasm/sx/boot.sx
@@ -332,20 +332,25 @@
                 (component-params comp))
               (let
                 ((cursor (dict "parent" el "index" 0)))
-                (scope-push! "sx-hydrating" cursor)
+                (host-call el "replaceChildren")
+                (scope-push! "sx-hydrating" nil)
                 (cek-try
                   (fn
                     ()
                     (with-island-scope
                       (fn (disposable) (append! disposers disposable))
-                      (fn () (render-to-dom (component-body comp) local nil))))
+                      (fn
+                        ()
+                        (let
+                          ((result (render-to-dom (component-body comp) local el)))
+                          (when result (dom-append el result))))))
                   (fn
                     (err)
                     (scope-pop! "sx-hydrating")
                     (log-warn
                       (str "hydrate fallback: " comp-name " — " err))
                     (let
-                      ((fallback (cek-try (fn () (with-island-scope (fn (d) (append! disposers d)) (fn () (render-to-dom (component-body comp) local nil)))) (fn (err2) (let ((e (dom-create-element "div" nil))) (dom-set-text-content e (str "Island error: " comp-name "\n" err2)) e)))))
+                      ((fallback (dom-create-text (str "Island error: " comp-name " " err))))
                       (host-call el "replaceChildren" fallback)
                       nil)))
                 (scope-pop! "sx-hydrating")
diff --git a/web/boot.sx b/web/boot.sx
index a5b319d1..6cb0f604 100644
--- a/web/boot.sx
+++ b/web/boot.sx
@@ -332,20 +332,25 @@
                 (component-params comp))
               (let
                 ((cursor (dict "parent" el "index" 0)))
-                (scope-push! "sx-hydrating" cursor)
+                (host-call el "replaceChildren")
+                (scope-push! "sx-hydrating" nil)
                 (cek-try
                   (fn
                     ()
                     (with-island-scope
                       (fn (disposable) (append! disposers disposable))
-                      (fn () (render-to-dom (component-body comp) local nil))))
+                      (fn
+                        ()
+                        (let
+                          ((result (render-to-dom (component-body comp) local el)))
+                          (when result (dom-append el result))))))
                   (fn
                     (err)
                     (scope-pop! "sx-hydrating")
                     (log-warn
                       (str "hydrate fallback: " comp-name " — " err))
                     (let
-                      ((fallback (cek-try (fn () (with-island-scope (fn (d) (append! disposers d)) (fn () (render-to-dom (component-body comp) local nil)))) (fn (err2) (let ((e (dom-create-element "div" nil))) (dom-set-text-content e (str "Island error: " comp-name "\n" err2)) e)))))
+                      ((fallback (dom-create-text (str "Island error: " comp-name " " err))))
                       (host-call el "replaceChildren" fallback)
                       nil)))
                 (scope-pop! "sx-hydrating")