# 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. **A plain rebuild does NOT fix it — TESTED 2026-06-30, dead end.** Ran
   `bash hosts/ocaml/browser/build-all.sh` with the current `wasm_of_ocaml 6.3.2`. The output
   `.wasm` units came out **byte-identical** to the Jun-29 backup (same content hashes, e.g.
   `dune__exe__Sx_browser-4878f9e1.wasm`; `diff -rq` clean). So 6.3.2 still emits the legacy
   `try` — rebuilding gains nothing. **The fix needs a newer `wasm_of_ocaml` (or a flag) that
   emits `try_table`** — a toolchain *upgrade* (`opam upgrade wasm_of_ocaml-compiler` to a
   version that defaults to `try_table`, or find the relevant `--enable` flag), then rebuild +
   verify. (Disassembly check note: apt's `wasm2wat`/wabt is too old for these wasm-GC binaries —
   `error: unexpected type form (got 0x5e)`; need `wasm-tools` for wasm-GC, or verify in a real
   up-to-date browser. Playwright's older chromium still accepts `try`, so it won't tell you.)
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.
