# Follow-up: WASM kernel uses deprecated `try` exception instruction (+ sync XHR)

**Found:** 2026-06-30, from a real browser console on `blog.rose-ash.com` (modern Chrome/Firefox).
**Severity:** not yet breaking — *deprecation warnings*. The SPA still boots (a hard refresh
cleared a stale cached loader, which was the day's actual symptom). But when browsers **remove**
the legacy `try` instruction, the WASM kernel will fail to instantiate → "SxKernel not found
after 5s" → no SPA (server-rendered pages + native-form writes still work; only SPA nav + the
interactive picker need the kernel).

## The two warnings

1. **`WebAssembly exception handling 'try' instruction is deprecated … use 'try_table' instead`**
   (×6). The kernel `shared/static/wasm/sx_browser.bc.wasm.assets/*.wasm` was compiled (Jun-29
   artifact) with the legacy exception-handling encoding. wasm_of_ocaml standardized on
   `try_table`; current toolchain is **6.3.2**.
2. **`Synchronous XMLHttpRequest on the main thread is deprecated`** — `sx-platform.js:575`,
   `loadManifest()` does `xhr.open("GET", …module-manifest.sx…, false)` (sync). Browsers
   increasingly restrict sync XHR.

## Fix

1. **Rebuild the kernel with the current toolchain.** `bash hosts/ocaml/browser/build-all.sh`
   (dune builds `browser/sx_browser.bc.wasm.js`), then `bundle.sh` syncs to
   `shared/static/wasm/`. Modern wasm_of_ocaml 6.x *may* emit `try_table` by default → a fresh
   rebuild alone could fix #1. **Verify:** disassemble a `.wasm` unit (`wasm-tools print` / grep
   for `try_table` vs `try`), then boot it in a REAL up-to-date browser (not just the older
   Playwright chromium, which still accepts `try`) and confirm no deprecation warning + SxKernel
   registers. If 6.3.2 still emits legacy `try`, check for a wasm_of_ocaml flag or bump the
   compiler.
2. **`loadManifest` → async.** Change to an async fetch and restructure the boot so the manifest
   is awaited before module loading (it's currently consumed synchronously). Contained to
   `hosts/ocaml/browser/sx-platform.js` + its copy in `shared/static/wasm/`.

## Scope / ownership

`hosts/ocaml/browser/` is the OCaml→WASM toolchain — generally out of the host loop's lane, though
the host loop has committed there for the blog SPA (b21ae05e, 689dae7d). A kernel rebuild affects
the LIVE SPA, so do it when the box is quiet, with real-browser verification, and a quick rollback
path (the Jun-29 `.assets` are the known-good artifact — keep a copy before overwriting). Not
urgent; schedule rather than rush.