# Host blog → SPA via the SX-htmx engine (WASM OCaml kernel) Turn the blog (lib/host/blog.sx) into a single-page app using the in-repo SX hypermedia engine (web/engine.sx — "our htmx"): boot the **WASM OCaml kernel** (the same evaluator the server runs) in the browser, and `sx-boost` every link/form into a fragment swap into `#content` — no full reloads, history kept, graceful degradation to plain server-rendered pages with no JS. ## Status **DONE — server side (verified, all green):** - `lib/host/static.sx` — `GET /static/**` serves files under `shared/static` via the `file-read` primitive (content-type by extension, path-traversal guarded, 404 on missing). Mounted in serve.sh + the route list. Tested: kernel JS 200 + correct ctype + exact bytes; `.wasm` binary-exact with `application/wasm`; traversal/missing → 404. - `lib/host/blog.sx` `host/blog--page` is now the SPA shell: full page = WASM boot scripts (`/static/wasm/sx_browser.bc.wasm.js` + `sx-platform.js`) + a `sx-boost="#content"` wrapper div + `#content`. On the `SX-Request: true` header (a boosted nav) it returns ONLY the inner content (fragment) so the engine swaps it into `#content`. All 13 page handlers thread `req`. Tested: full page carries scripts+boost+#content; `SX-Request` returns the bare fragment. - `docker-compose.dev-sx-host.yml` mounts `./shared/static` so the live container can serve the kernel. - `lib/host/playwright/spa-check.spec.js` + `run-spa-check.sh` — browser check (boot, boost, fragment swap, back button). **DONE — client side, partial:** - The WASM kernel BOOTS in a headless browser: `globalThis.SxKernel` is an object, `` is set, the web-stack modules load. - Fixed: this worktree's `shared/static/wasm/sx_browser.bc.wasm.assets/` was missing 5 of 11 `.wasm` units (`sx-`, `unix-`, `re-`, `start-`, `dune__exe__Sx_browser-`); copied the complete set from the main worktree. **BLOCKER — boost does not activate (`boosted links: 0 / N`):** - The bundled `.sxbc` bytecode throws `VM: unknown opcode 0` against this worktree's `sx_browser.bc.wasm.js` kernel, so sx-platform.js falls back to `.sx` source for every web-stack module. Source fallback works for all modules EXCEPT `boot.sx`, which then fails with `Expected list, got string` — so the boot sequence that wires `process-elements → process-boosted` doesn't complete and no link gets `_sxBoundboost`. - Root cause: the `.sxbc` in `shared/static/wasm/sx/` are out of sync with the WASM kernel (sx.rose-ash.com avoids this because its Docker image ships a consistent bundle and it navigates via client-router page-routes, not boost). ## UPDATE 2026-06-29 — kernel BOOT crash fixed (crypto WASM-safe) The boot crash was NOT the build pipeline — it was the kernel's crypto stack assuming 63-bit native int. On the web targets (js_of_ocaml 32-bit, wasm_of_ocaml 31-bit) sha2/cbor/cid/ed25519 truncated, and ed25519 precomputes `sqrtm1` + `base_point` AT MODULE INIT via a base-2^26 bignum whose 52-bit products overflow → `Char.chr(-4)` crash on load. Fixed in `fce9e0c6` (sx_sha2 Int32 rounds + Int64 length, sx_cbor Int64 width-select, sx_cid bounded base32, sx_ed25519 Int64 bignum mul/div_small). Verified: NIST/CID vectors match native↔js↔wasm; native conformance 271/271; **the freshly-built browser kernel now BOOTS** (SxKernel live, data-sx-ready=true, crypto-sha256 correct on js + wasm). REMAINING for boost (separate layer — web-stack loading, NOT crypto). Two compounding roots, both fully diagnosed: 1. **`.sxbc` carry NIL bytecode.** `compile-modules.js` (via the native binary) emits `:bytecode (nil nil nil …)` placeholders, not real bytecode — so the SX-level `vm.sx` interpreter reads nil → `VM: unknown opcode 0`, and the web stack falls back to `.sx` source for every module. (Confirmed by inspecting a freshly-compiled `dom.sxbc`.) The native compiler isn't producing bytecode in this path. 2. **Source-fallback can't resolve manifest-mapped libraries.** With imports stripped, all 23 `boot.sx` body forms load clean — the `Expected list, got string` is from an `import`. `boot.sx` imports `(sx signals-web)`, but that library is *defined inside `signals.sx`* (the file→library names don't match; the module-manifest maps `"sx signals-web" → signals.sxbc`). The `.sx` source-fallback resolver maps a library to a like-named FILE, looks for a non-existent `signals-web.sx`, and the failed resolution returns a string into a list op → the error → `boot.sx` never loads → `process-boosted` never runs → boost 0/N. (A `signals-web.sx` bridge that imports signals was NOT sufficient — there is at least one more such mismatch among the imports.) THE CLEAN FIX is a proper bundle rebuild via `scripts/sx-build-all.sh` so the `.sxbc` carry real bytecode and the manifest-driven path loads everything (no source fallback, so root #2 never triggers) — gated on fixing root #1 (why `compile-modules.js` emits nil bytecode). Alternatively, make the source-fallback resolver manifest-aware. Neither is a quick edit; it's a web-stack build-tooling sub-project. The kernel itself is now correct and boots. ## Rebuild attempt (2026-06-28) — FAILED, reverted (superseded by the fix above) Tried it: `dune build browser/sx_browser.bc.wasm.js` succeeded (with many `integer-overflow` warnings — "generated code might be incorrect"), and `node hosts/ocaml/browser/compile-modules.js shared/static/wasm` recompiled all 35 `.sxbc` cleanly. But the freshly-built kernel **crashes on init** in the browser: `Fatal error: exception Invalid_argument("Char.chr")` — so `SxKernel` never initialises (worse than before). The integer-overflow truncation during wasm codegen is the likely culprit (a SHA/char constant). Reverted `shared/static/wasm/` to the main-worktree bundle (which boots cleanly — verified SxKernel + data-sx-ready). So a naive in-worktree rebuild is NOT the fix; the wasm build itself needs investigating (wasm_of_ocaml version? the merged sx-vm-extensions/resolver changes interacting with codegen?). ## Next step — rebuild a consistent WASM bundle `scripts/sx-build-all.sh` does: build the browser wasm target → sync web `.sx` into `hosts/ocaml/browser/dist/sx/` → `node hosts/ocaml/browser/compile-modules.js` (recompiles `.sxbc` via the native sx_server binary) → copy into `shared/static/wasm/`. The browser wasm target is NOT built in this worktree (`hosts/ocaml/_build/default/browser/` is empty), so this needs the `wasm_of_ocaml` toolchain set up first. Once the `.sxbc` match the kernel, the bytecode path loads (no source fallback), `boot.sx` runs, and `process-boosted` binds the links — then the SPA Playwright check should pass. Alternatively: build the browser kernel in the main worktree (which has the pipeline) and copy a consistent `sx_browser.bc.wasm.js` + assets + `.sxbc` set into this worktree's `shared/static/wasm/`. ## Deploy note The live container is NOT redeployed with the SPA shell yet — it keeps running the pre-SPA `blog.sx` in memory (the native host doesn't hot-reload). Don't recreate the container until the bundle is consistent and the SPA Playwright check is green, to avoid shipping a kernel that boots but doesn't boost. (Even if it is recreated, pages degrade gracefully: links still do normal full-page nav.)