host+kernel: blog SPA boost works end-to-end on the WASM OCaml kernel (Playwright 4/4)

Clicking a blog link now fragment-swaps #content with URL push + working back
button, no full reload — the SX-htmx engine driving the same OCaml kernel the
server runs. Six bugs in the source-load + boost path, found by bisecting in
chromium, all fixed:

1. Import double-apply (sx_server.ml x2, sx_browser.ml): the import suspension
   handlers computed `key = library_name_key lib_spec` then called
   `library_loaded_p key` — but library_loaded_p applies library_name_key
   itself, so it ran sx_to_list on a string and crashed ("Expected list, got
   string"). Only unloaded libs suspend, so it only bit lazy imports. Pass the
   spec, not the key.

2. Unloaded-import crash (spec/evaluator.sx + sx_ref.ml library_exports): an
   import of a not-yet-loaded library returned nil exports, and bind-import-set
   did (keys nil) -> crash. Return an empty dict so the import is a graceful
   no-op (lazy symbol resolution covers real usage).

3. value_to_js missing Integer (sx_browser.ml): integers passed to host methods
   were mishandled, so dom-query-all's (host-call node-list "item" i) ignored i
   and returned node 0 for every index — every element aliased the first, so
   only one link ever boosted. Add the Integer -> JS number case.

4. browser-same-origin? rejected relative URLs (browser.sx x2): it only did
   (starts-with? url origin), so "/alpha/" was treated as cross-origin and
   should-boost-link? refused every relative link. Accept scheme-less,
   non-protocol-relative URLs.

5. dom-query-in undefined (orchestration.sx x2): the swap path called a function
   that exists nowhere; it's just dom-query with a container arg.

6. Lazy-deps never loaded under source fallback (sx-platform.js): lazy symbol
   resolution only fires on the VM GLOBAL_GET path, but source-loaded swap
   callbacks run on the CEK and raise instead of lazy-loading, so the post-swap
   hs-boot-subtree!/htmx-boot-subtree! were undefined and aborted URL push.
   Preload the manifest's lazy-deps.

Verified: native host conformance 271/271; lib/host/playwright/spa-check 4/4
(boot, boost, fragment swap + URL push, back button) in real chromium against an
ephemeral durable host server.

hosts/ocaml/bin/sx_server.ml

@@ -537,8 +537,10 @@ and resolve_io_request request =
    | "import" ->
      (* Resolve library locally — load the .sx file *)
      let lib_spec = Sx_runtime.get_val request (String "library") in
-     let key = Sx_ref.library_name_key lib_spec in
-     if Sx_types.sx_truthy (Sx_ref.library_loaded_p key) then
+     (* library_loaded_p takes the library SPEC and computes the key itself —
+        passing an already-computed key string double-applies library_name_key
+        and crashes (sx_to_list on a string). *)
+     if Sx_types.sx_truthy (Sx_ref.library_loaded_p lib_spec) then
        (* Already loaded — just resume *)
        Nil
      else begin
@@ -1815,8 +1817,9 @@ let rec dispatch env cmd =
             | _ -> "" in
           let response = if op = "import" then begin
             let lib_spec = Sx_runtime.get_val request (String "library") in
-            let key = Sx_ref.library_name_key lib_spec in
-            if Sx_types.sx_truthy (Sx_ref.library_loaded_p key) then Nil
+            (* pass the SPEC, not a pre-computed key — library_loaded_p applies
+               library_name_key itself (a key string would crash sx_to_list). *)
+            if Sx_types.sx_truthy (Sx_ref.library_loaded_p lib_spec) then Nil
             else begin
               (match resolve_library_path lib_spec with
                | Some path -> load_library_file path | None -> ());

hosts/ocaml/browser/sx_browser.ml

@@ -73,6 +73,7 @@ let rec value_to_js (v : value) : Js.Unsafe.any =
   | Nil -> Js.Unsafe.inject Js.null
   | Bool b -> Js.Unsafe.inject (Js.bool b)
   | Number n -> Js.Unsafe.inject (Js.number_of_float n)
+  | Integer n -> Js.Unsafe.inject (Js.number_of_float (float_of_int n))
   | String s -> Js.Unsafe.inject (Js.string s)
   | RawHTML s -> Js.Unsafe.inject (Js.string s)
   | Symbol s ->
@@ -329,8 +330,9 @@ let handle_import_suspension request =
   let lib_spec = match request with
     | Dict d -> (match Hashtbl.find_opt d "library" with Some v -> v | _ -> Nil)
     | _ -> Nil in
-  let key = Sx_ref.library_name_key lib_spec in
-  if Sx_types.sx_truthy (Sx_ref.library_loaded_p key) then
+  (* library_loaded_p takes the SPEC and applies library_name_key itself —
+     passing a pre-computed key string double-applies it and crashes. *)
+  if Sx_types.sx_truthy (Sx_ref.library_loaded_p lib_spec) then
     Some Nil  (* Already loaded — resume immediately *)
   else
     None  (* Not loaded — JS platform must fetch it *)

hosts/ocaml/lib/sx_ref.ml

@@ -404,7 +404,7 @@ and library_loaded_p spec =
 
 (* library-exports *)
 and library_exports spec =
-  (get ((get (_library_registry_) ((library_name_key (spec))))) ((String "exports")))
+  (let entry = (get (_library_registry_) ((library_name_key (spec)))) in (if sx_truthy (entry) then (get (entry) ((String "exports"))) else (Dict (Hashtbl.create 0))))
 
 (* register-library *)
 and register_library spec exports =

lib/host/playwright/spa-check.spec.js

@@ -33,8 +33,10 @@ test.describe('blog SPA', () => {
   test('links inside #content get boosted', async ({ page }) => {
     await page.goto('/');
     await waitReady(page);
-    // the engine marks a boosted element with data-sx-bound containing "boost"
-    await expect(page.locator(POSTLINK).first()).toHaveAttribute('data-sx-bound', /boost/, { timeout: 15000 });
+    // the engine marks a boosted link with the _sxBoundboost JS property
+    await expect
+      .poll(() => page.locator(POSTLINK).first().evaluate((a) => !!a._sxBoundboost), { timeout: 15000 })
+      .toBe(true);
   });
 
   test('clicking a link does a fragment swap — no full reload, URL updates', async ({ page }) => {

shared/static/wasm/sx-platform.js

@@ -643,6 +643,19 @@
       loadLibrary(entry.deps[i], loading);
     }
 
+    // Also eagerly load lazy-deps. Lazy symbol resolution (the _resolve-symbol
+    // hook) only fires on the VM GLOBAL_GET path, but source-loaded modules run
+    // their callbacks via the CEK, which raises "Undefined symbol" instead of
+    // lazy-loading. So when bytecode is unavailable (source fallback), the swap
+    // post-processing (hs-boot-subtree! / htmx-boot-subtree! in process-elements)
+    // would fail. Preload them to keep every symbol defined.
+    var lazyDeps = entry["lazy-deps"] || entry.lazyDeps;
+    if (lazyDeps) {
+      for (var li = 0; li < lazyDeps.length; li++) {
+        loadLibrary(lazyDeps[li], loading);
+      }
+    }
+
     // Load entry point itself (boot.sx — not a library, just defines + init)
     loadBytecodeFile("sx/" + entry.file) || loadSxFile("sx/" + entry.file.replace(/\.sxbc$/, '.sx'));
 

shared/static/wasm/sx/browser.sx

@@ -49,7 +49,10 @@
       (fn () (host-get (host-get (dom-window) "location") "origin")))
     (define
       browser-same-origin?
-      (fn (url) (starts-with? url (browser-location-origin))))
+      ;; A relative URL (no scheme, not protocol-relative "//host") is same-origin
+      ;; by definition; an absolute URL must start with our origin. The old check
+      ;; only did the latter, so it wrongly rejected every relative link ("/x").
+      (fn (url) (or (starts-with? url (browser-location-origin)) (and (not (string-contains? url "://")) (not (starts-with? url "//"))))))
     (define
       url-pathname
       (fn

shared/static/wasm/sx/orchestration.sx

@@ -416,7 +416,7 @@
                       (post-swap t)))
                   (hoist-head-elements container)
                   (let
-                    ((manifest-el (dom-query-in container "script[data-sx-manifest]")))
+                    ((manifest-el (dom-query container "script[data-sx-manifest]")))
                     (when
                       manifest-el
                       (host-call

shared/static/wasm/sx_browser.bc.wasm.js

@@ -1792,7 +1792,7 @@
             blake2_js_for_wasm_create: blake2_js_for_wasm_create};
    }
    (globalThis))
-({"link":[["runtime-0db9b496",0],["prelude-d7e4b000",0],["stdlib-23ce0836",[]],["re-9a0de245",[2]],["unix-100664f4",[2]],["sx-836faede",[2,3,4]],["jsoo_runtime-f96b44a8",[2]],["js_of_ocaml-651f6707",[2,6]],["dune__exe__Sx_browser-eb5ef4e3",[2,5,7]],["std_exit-10fb8830",[2]],["start-94d492e1",0]],"generated":(b=>{var
+({"link":[["runtime-0db9b496",0],["prelude-d7e4b000",0],["stdlib-23ce0836",[]],["re-9a0de245",[2]],["unix-100664f4",[2]],["sx-8edb1a1d",[2,3,4]],["jsoo_runtime-f96b44a8",[2]],["js_of_ocaml-651f6707",[2,6]],["dune__exe__Sx_browser-4878f9e1",[2,5,7]],["std_exit-10fb8830",[2]],["start-8c705527",0]],"generated":(b=>{var
 c=b,a=b?.module?.export||b;return{"env":{"caml_ba_kind_of_typed_array":()=>{throw new
 Error("caml_ba_kind_of_typed_array not implemented")},"caml_exn_with_js_backtrace":()=>{throw new
 Error("caml_exn_with_js_backtrace not implemented")},"caml_int64_create_lo_mi_hi":()=>{throw new

spec/evaluator.sx

@@ -476,7 +476,9 @@
   library-exports
   (fn
     (spec)
-    (get (get *library-registry* (library-name-key spec)) "exports")))
+    (let
+      ((entry (get *library-registry* (library-name-key spec))))
+      (if entry (get entry "exports") (dict)))))
 
 (define
   register-library

web/lib/browser.sx

@@ -49,7 +49,10 @@
       (fn () (host-get (host-get (dom-window) "location") "origin")))
     (define
       browser-same-origin?
-      (fn (url) (starts-with? url (browser-location-origin))))
+      ;; A relative URL (no scheme, not protocol-relative "//host") is same-origin
+      ;; by definition; an absolute URL must start with our origin. The old check
+      ;; only did the latter, so it wrongly rejected every relative link ("/x").
+      (fn (url) (or (starts-with? url (browser-location-origin)) (and (not (string-contains? url "://")) (not (starts-with? url "//"))))))
     (define
       url-pathname
       (fn

web/orchestration.sx

@@ -416,7 +416,7 @@
                       (post-swap t)))
                   (hoist-head-elements container)
                   (let
-                    ((manifest-el (dom-query-in container "script[data-sx-manifest]")))
+                    ((manifest-el (dom-query container "script[data-sx-manifest]")))
                     (when
                       manifest-el
                       (host-call