Root cause: when perform fires inside a VM closure chain (call_closure_reuse),
the caller frames are saved to reuse_stack on the ACTIVE VM. But the
_cek_io_suspend_hook and _cek_eval_lambda_ref create a NEW stub VM for the
VmSuspended exception. On resume, resume_vm runs on the STUB VM which has
an empty reuse_stack — the caller frames are orphaned on the original VM.
Fix: transfer reuse_stack from _active_vm to the stub VM before raising
VmSuspended. This ensures resume_vm -> restore_reuse can find and restore
the caller's frames after async resume via _driveAsync/setTimeout.
Also restore step_limit/step_count refs dropped by bootstrap.py regeneration.
Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>
Root cause: sx_browser.ml registered all HTML tags (a, b, i, p, s, u, g, etc.)
as custom special forms. The evaluator's step_eval_list checked custom special
forms BEFORE checking local env bindings. So (let ((a (fn () 42))) (a))
matched the HTML tag <a> instead of calling the local function a.
Fix: skip custom special forms AND render-check when the symbol is bound in
the local env. Added (not (env-has? env name)) guard to both checks in
step-eval-list (spec/evaluator.sx and transpiled sx_ref.ml).
This was the root cause of "[sx] resume: Not callable: nil" — after hs-wait
resumed, calling letrec-bound functions like wait-boot (which is not an HTML
tag) worked, but any function whose name collided with an HTML tag failed.
Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>
The previous commit accidentally lost ~1100 lines from sx_server.ml
due to a git stash conflict resolution that silently deleted the
hash-index, manifest generation, and /sx/h/ route handler code.
Restored from 97818c6d. Only change: added host-* platform primitive
stubs (host-get, host-set!, host-call, etc.) needed because the
callable? fix in boot-helpers.sx now properly loads code paths that
reference these browser-only functions.
Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>
callable? in boot-helpers.sx checked for "native-fn" but type-of returns
"function" for NativeFn — broke make-spread and all native fn dispatch
in aser. Restore 20 behavioral tests replaced with NOT IMPLEMENTED stubs
by the test regeneration commit. Add host-* platform primitive stubs to
sx_server.ml so boot-helpers.sx loads without errors server-side.
Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>
The _cek_io_suspend_hook creates a stub VM to carry the suspended CEK
state. Previously used empty globals, which caused "Not callable: nil"
when the CEK resume needed platform functions. Now uses _default_vm_globals
(set to _vm_globals by sx_browser.ml) so all platform functions and
definitions are available during resume.
Remaining issue: still getting "resume: Not callable: nil" — the CEK
continuation env may not include letrec bindings from the island body.
The suspension point is inside reload-frame → hs-wait, and the resume
needs to call wait-boot (a letrec binding).
Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>
The _cek_io_suspend_hook was only added to cek_run_iterative (line 986)
but the actual code path went through cek_run (line 624). Added the hook
check to both functions.
This fixes the "IO suspension in non-IO context" error that blocked
hs-wait/perform from propagating through event handler → trampoline →
eval_expr call chains. IO suspension now converts to VmSuspended via the
hook, which the value_to_js wrapper catches and drives with _driveAsync.
+42 OCaml test passes (3924→3966). IO suspension verified working in
browser WASM: dom-on click handler → hs-wait → perform → suspend →
_driveAsync → setTimeout → resume.
Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>
Root cause: cek_run_iterative (used by eval_expr/trampoline) raised
"IO suspension in non-IO context" when the CEK hit a perform. This
blocked IO suspension from propagating through nested eval_expr calls
(event handler → trampoline → eval_expr → for-each callback → hs-wait).
Fix: added _cek_io_suspend_hook (Sx_types) that converts CEK suspension
to VmSuspended, set by sx_vm.ml at init. cek_run_iterative now calls the
hook instead of erroring. The VmSuspended propagates to the value_to_js
wrapper which has _driveAsync handling.
+42 test passes (3924→3966), zero regressions.
Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>
Root cause found: when the click handler calls run-all → for-each → callback → hs-wait → perform,
the perform raises VmSuspended. But the call path goes through sx_apply_cek
(from the call-lambda CALL_PRIM) which converts VmSuspended → CekPerformRequest.
The inner CEK context has no IO handler, so it raises "IO suspension in non-IO context"
instead of propagating the suspension to the outer context.
Fix needed: either (a) make sx_apply_cek NOT convert VmSuspended when in a context
that supports IO suspension, or (b) ensure the inner CEK from call-lambda propagates
perform as a suspension state rather than erroring.
Debug logging still present in sx_browser.ml (js_to_value traces).
Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>
runner.sx: Converted define forms inside island body to letrec. Multiple
define forms in a let body cause render-to-dom to fall back to eval-expr
for the whole body, which evaluates (div ...) as a list instead of
rendering it to DOM. letrec keeps the last body expression (div) as the
render target.
sx_browser.ml: js_to_value now stores plain JS functions as host objects
(Dict with __host_handle) instead of wrapping as NativeFn. This preserves
the original JS function identity through the SX→JS round-trip, keeping
_driveAsync wrappers from host-callback intact when passed to
addEventListener via host-call.
Remaining: IO suspension in click handler is caught as "IO suspension in
non-IO context" instead of being driven by _driveAsync. The host-callback
wrapper creates the right JS function, but the event dispatch path doesn't
go through K.callFn.
Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>
VM frame merging bug: call_closure_reuse now saves caller continuations
on a reuse_stack instead of merging frames. resume_vm restores them in
innermost-first order. Fixes frame count corruption when nested closures
suspend via OP_PERFORM. Zero test regressions (3924/3924).
Island hydration: hydrate-island now looks up components from (global-env)
instead of render-env, triggering the symbol resolve hook. Added JS-level
preload-island-defs that scans DOM for data-sx-island and loads definitions
from the content-addressed manifest BEFORE hydration — avoids K.load
reentrancy when the resolve hook fires inside env_get.
loadDefinitionByHash: fixed isMultiDefine check — defcomp/defisland bodies
containing nested (define ...) forms no longer suppress name insertion.
Added K.load return value checking for silent error string returns.
sx_browser.ml: resolve hook falls back to global_env.bindings when
_vm_globals miss (sync gap). Snapshot reuse_stack alongside pending_cek.
Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>
- htmx-boot-subtree! wired into process-elements for auto-activation
- Fixed cond compilation bug in hx-verb-info (Clojure-style flat cond)
- Platform io-fetch upgraded: method/body/headers support, full response dict
- Replaced perform IO ops with browser primitives (set-timeout, browser-confirm, etc)
- SX→HTML rendering in hx-do-swap with OOB section filtering
- hx-collect-params: collects input name/value for all methods
- Handler naming: ex-{slug} convention, removed perform IO dependencies
- Test runner page at (test.(applications.(htmx))) with iframe-based runner
- Header "test" link on every page linking to test URL
- Page file restructure: 285 files moved to URL-matching paths (a/b/c/index.sx)
- page-functions.sx: ~100 component name references updated
- _test added to skip_dirs, test- file prefix convention for test files
Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>
- sx_vm.ml: VM timeout now compares vm_insn_count > step_limit instead of
unconditionally throwing after 65536 instructions when limit > 0
- sx_browser.ml: Expose setStepLimit/resetStepCount APIs on SxKernel;
callFn now returns {__sx_error, message} on Eval_error instead of null
- compiler.sx: emit-set handles array-index targets (host-set! instead of
nth) and 'of' property chains (dom-set-prop with chain navigation)
- hs-run-fast.js: New Node.js test runner with step-limit timeouts,
SX-level guard for error detection, insertAdjacentHTML mock,
range selection (HS_START/HS_END), wall-clock timeout in driveAsync
- hs-debug-test.js: Single-test debugger with DOM state inspection
- hs-verify.js: Assertion verification (proves pass/fail detection works)
Test results: 415/831 (50%), up from 408/831 (49%) baseline.
Fixes: set my style["color"], set X of Y, put at end of (insertAdjacentHTML).
Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>
When innerHTML is set on a mock element, textContent now updates to
match (with HTML tags stripped). Many HS tests do `put "foo" into me`
(which sets innerHTML) then check textContent. Previously textContent
stayed empty because only innerHTML was updated.
Also fixes innerHTML="" to fully detach children from parent.
393 → 408/831 HS tests (+15).
Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>
Setting innerHTML="" on a mock element now detaches and removes all
children, matching browser behavior. Previously hs-cleanup! (which
sets body.innerHTML="") left stale children attached, causing
querySelector to find elements from prior tests.
Also clears children when textContent is set (browser behavior).
375 → 393/831 HS tests (+18).
Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>
In a real browser, innerHTML/textContent/value are always strings.
The mock was storing raw SX values (Number, Bool, Nil), causing type
mismatches like "Expected 1, got 1" where the value was correct but
Number 1.0 != String "1".
Now coerces to string on host-set! for innerHTML, textContent, value,
outerHTML, innerText. Fixes 10 increment tests that were doing
`put value into me` with numeric results.
367 → 375/831 HS tests (+8 net, +10 new passes, -2 regressions).
Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>
The infinite loops in the HS parser are in transpiled native OCaml code,
not in the VM or CEK step loop. Neither step counters (in cek_step_loop,
cek_step, trampoline) nor VM instruction checks caught them because
the loops are in direct OCaml recursion.
Fix: SIGALRM handler raises Eval_error to break out of native loops.
Also sets step_limit flag to catch VM loops. Combined approach handles
both native OCaml recursion (alarm+raise) and VM bytecode (step check).
The alarm+raise can become unreliable after ~13 timeouts in a single
process, but handles the common case well. Reverts the fork-based
approach which lost inter-test state.
Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>
Two critical fixes for the mock DOM test runner:
1. host-get returns truthy for DOM method names on mock elements.
dom.sx guards like `(and el (host-get el "setAttribute"))` were
silently skipping setAttribute/getAttribute calls because the mock
dict had no "setAttribute" key. Now returns Bool true for known
DOM method names, fixing hs-activate! → dom-set-attr → dom-get-attr
chain. Also adds firstElementChild, nextElementSibling, etc. as
computed properties.
2. Fork-based per-test timeout (5 seconds). The HS parser has infinite
loops on certain syntax ([@attr], complex put targets). Signal-based
alarm doesn't work reliably in OCaml 5. Fork + waitpid + select
gives hard OS-level timeout protection.
Also adds step_limit/step_count to sx_ref.ml trampoline (currently
unused but available for future CEK-level timeout).
Result: 525/963 total, up from 498. Many more add/remove/toggle/set
tests now pass because hs-activate! actually wires up event handlers.
Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>
Replace the monolithic 500KB <script data-components> block with a 25KB
JSON manifest mapping names to content hashes. Every definition —
components, islands, macros, client libraries, bytecode modules, and
WASM binaries — is now content-addressed and loaded on demand.
Server (sx_server.ml):
- build_hash_index: Merkle DAG over all definitions — topological sort,
hash leaves first, component refs become @h:{hash} in instantiated form
- /sx/h/{hash} endpoint: serves definitions with Cache-Control: immutable
- Per-page manifest in <script data-sx-manifest> with defs + modules + boot
- Client library .sx files hashed as whole units (tw.sx, tw-layout.sx, etc.)
- .sxbc modules and WASM kernel hashed individually
Browser (sx-platform.js):
- Content-addressed boot: inline script loads kernel + platform by hash
- loadDefinitionByHash: recursive dep resolution with @h: rewriting
- resolveHash: 3-tier cache (memory → localStorage → fetch /sx/h/{hash})
- __resolve-symbol extended for manifest-based component + library loading
- Cache API wrapper intercepts .wasm fetches for offline caching
- Eager pre-loading of plain symbol deps for CEK evaluator compatibility
Shell template (shell.sx):
- Monolithic <script data-components> removed
- data-sx-manifest script with full hash manifest
- Inline bootstrap replaces <script src="...?v="> with CID-based loading
Second visit loads zero bytes from network. Changed content gets a new
hash — only that item refetched (Merkle propagation).
Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>
Add mock DOM layer to run_tests.ml so hyperscript behavioral tests
(spec/tests/test-hyperscript-behavioral.sx) can run in the OCaml test
runner without a browser. Previously these tests required Playwright
which crashed after 10 minutes from WASM page reboots.
Mock DOM implementation:
- host-global, host-get, host-set!, host-call, host-new, host-callback,
host-typeof, host-await — OCaml primitives operating on SX Dict elements
- Mock elements with classList, style, attributes, event dispatch + bubbling
- querySelector/querySelectorAll with #id, .class, tag, [attr] selectors
- Load web/lib/dom.sx and web/lib/browser.sx for dom-* wrappers
- eval-hs function for expression-only tests (comparisonOperator, etc.)
Result: 367/831 HS tests pass in ~30 seconds (was: Playwright crash).
14 suites at 100%: live, component, liveTemplate, scroll, call, go,
focus, log, reactive-properties, resize, measure, attributeRef,
objectLiteral, queryRef.
Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>
Root cause: sx_insert_near placed break-lines-greedy, pretext-position-line,
pretext-layout-lines OUTSIDE the define-library begin block. The bytecode
compiler only compiles forms inside begin as STORE_GLOBAL — forms outside
are invisible to the browser VM.
Fix: moved all function definitions inside (begin ...) of (define-library).
Bytecode now includes all 17 functions (11K compiled, was 9K).
Browser load-sxbc: simplified VmSuspended handling — just catch and
continue, since STORE_GLOBAL ops already ran before the import OP_PERFORM.
sync_vm_to_env copies them to global_env.
Island now calls break-lines and pretext-layout-lines from bytecode-compiled
library — runs on VM, not CEK interpreter.
Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>
- text-layout.sx added to WASM bytecode pipeline (9K compiled)
- Fix multi-list map calls (map-indexed + nth instead of map fn list1 list2)
- pretext-layout-lines and pretext-position-line moved to library exports
- Browser load-sxbc: handle VmSuspended for import, copy library exports
to global_env after module load (define-library export fix)
- compile-modules.js: text-layout in SOURCE_MAP, FILES, and entry deps
- Island uses library functions (break-lines, pretext-layout-lines)
instead of inlining — runs on bytecode VM when exports resolve
Known issue: define-library exports don't propagate to browser global env
yet. The load-sxbc import suspension handler resumes correctly but
bind_import_set doesn't fire. Needs deeper investigation into how the
WASM kernel's define-library registers exports vs how other libraries
(adapter-html, tw) make their exports available.
Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>
Parser/compiler/runtime for focus command. Tokenizer: focus, blur,
precedes, follows, ignoring, case keywords. Test spec: per-test
failure output for diagnosis.
374/831 (45%)
Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>
The previous K.eval() approach double-escaped backslashes in SX source
strings, breaking the \/ → / unescaping that the server serializer adds
for HTML safety. Using K.callFn() passes strings directly as arguments,
bypassing the escaping problem entirely.
Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>
stream-colors dict had green/blue keys but data used emerald/violet — all three
slots now render with correct Tailwind color classes. Platform: resolveSuspense
must not exist on Sx until boot completes, otherwise bootstrap __sxResolve calls
it before web stack loads and resolves silently fail. Moved to post-boot setup
so all pre-boot resolves queue in __sxPending and drain correctly.
Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>
Streaming chunked transfer with shell-first suspense and resolve scripts.
Hyperscript parser/compiler/runtime expanded for conformance. WASM static
assets added to OCaml host. Playwright streaming and page-level test suites.
Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>
The shell HTML included closing </body></html> tags. Resolve script
chunks arrived AFTER the document end — browser ignored them
(ERR_INCOMPLETE_CHUNKED_ENCODING). Now strips </body></html> from
shell, sends resolve scripts inside the body, closes document last.
Added live server Playwright tests that hit the actual streaming
endpoint and verify suspense slots resolve with content.
Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>
The streaming render matched `List items` but SX's `(list ...)` produces
`ListRef` (mutable list) in the OCaml runtime. Data items were rejected
with "returned list, expected dict or list" — 0 resolve chunks sent.
Fixed both streaming render and AJAX paths to handle ListRef.
Added sandbox test for streaming-demo-data return type validation.
Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>
Server (sx_server.ml):
- eval_with_io: CEK evaluator with IO suspension handling (io-sleep, import)
- io-sleep platform primitive: raises CekPerformRequest, resolved by eval_with_io
- Streaming render uses eval_with_io for data + content evaluation
- Data items with "delay" field sleep before resolving (async streaming)
- Removed hardcoded streaming-demo-data — application logic belongs in .sx
Application (streaming-demo.sx):
- streaming-demo-data defined in SX: 3 items with 1s/3s/5s delays
- Each item has delay, stream-id, and display data fields
- Shell renders instantly, slots fill progressively as IO completes
Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>
compile-let now handles dict destructuring patterns:
(let {:key1 var1 :key2 var2} source body). This unblocked core-signals.sx
(deref uses dict destructuring) which was the sole bytecode skip.
Rewrote stripLibraryWrapper from line-based to paren-aware extraction.
The old regex missed (define-library on its own line (no trailing space),
silently passing the full wrapper to the compiler.
Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>
bytecode-serialize/deserialize: sxbc v2 format wrapping compiled code
dicts. cek-serialize/deserialize: cek-state v1 format wrapping suspended
CEK state (phase, request, env, kont). Both use SX s-expression
round-trip via inspect/parse. lib/serialize.sx has pure SX versions.
Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>
Three changes to eliminate the stepper flash:
1. home-stepper.sx: server path reads cookie via (get-cookie) for
step-idx initial value. Client path reads document.cookie via
def-store. Both default to 0 when no cookie exists.
2. sx_server.ml: bypass response cache when sx-home-stepper cookie
is present. Render on main thread (not worker) so get-cookie
sees the parsed request cookies.
3. site-full.spec.js: flash detection test sets cookie=7 via
Playwright context, checks SSR HTML matches hydrated state.
Test: "No flash: SSR=7 hydrated=7 (cookie=7)" — passes.
Tested on fresh stack=site server subprocess.
Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>
The value_to_js resume handler was calling _driveAsync on re-suspension,
but the JS driveAsync caller also processes the returned suspension.
This caused the second wait in each iteration to fire immediately (0ms)
instead of respecting the delay.
Fix: resume handler just returns the suspension object, lets the JS
driveAsync handle scheduling via setTimeout.
Verified: repeat 3 times add/wait 300ms/remove/wait 300ms produces
6 transitions at correct 300ms intervals (1504ms total).
Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>
The resume callback in the value_to_js VmSuspended handler now catches
VmSuspended recursively, building a new suspension object and calling
_driveAsync for each iteration. Fixes repeat N times ... wait ... end
which produces N sequential suspensions.
Bounce works on repeated clicks. 4/4 regression tests pass.
Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>
Reverts the source-loading workaround. Bytecode modules go through the
VM which handles IO suspension (perform/wait/fetch) correctly. The
endModuleLoad sync copies VM globals to CEK env, so eval-expr-cek in
hs-handler can find hs-on/hs-toggle-class!/etc.
All three HS examples fully working on live site:
Toggle Color — toggle classes on click
Bounce — add class, wait 1s (IO suspend+resume), remove class
Count Clicks — increment counter, update innerHTML
Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>
- sx-platform.js: add _driveAsync to platform (was sandbox-only) for
driving wait/fetch IO suspension chains in live site
- sx-platform.js: host-callback wrapper calls _driveAsync on callFn result
- sx_browser.ml: value_to_js callable wrapper catches VmSuspended, builds
suspension object, and calls _driveAsync directly
Toggle and count clicks work fully. Bounce adds class but wait/remove
requires IO suspension in CEK context (eval-expr-cek doesn't support
perform — needs VM-path evaluation in hs-handler).
Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>
- sx_browser.ml: restore VmSuspended handler in api_call_fn with
make_js_callFn_suspension for IO suspension chains (wait, fetch)
- runtime.sx: delete host-get stub that shadowed platform native —
hs-toggle-class! now uses real FFI host-get for classList access
All three live demo examples work:
Toggle Color — classList.toggle on click
Bounce — add .animate-bounce, wait 1s suspend, remove
Count Clicks — increment @data-count, put into innerHTML
4/4 bytecode regression tests pass (was 0/4 without VmSuspended).
Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>
Three bugs fixed:
1. host-get in sx-platform.js: return true for function-valued properties
so dom-get-attr/dom-set-attr guards pass (functions can't cross WASM boundary)
2. hs-runtime.sx: renamed host-get→hs-host-get and dom-query→hs-dom-query to
stop shadowing platform natives when loaded as .sx source
3. compile-modules.js: HS dependency chain (integration→runtime→compiler→parser→tokenizer)
so lazy loading pulls in all deps. Non-library modules load as .sx source
for CEK env visibility.
Result: 8/8 elements activate, hs-on attaches listeners. Click handler needs
IO suspension support (VmSuspended in sx_browser.ml) to fire — next step.
Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>
- orchestration.sx: add hs-boot-subtree! call to process-elements
- integration.sx: remove load-library! calls (browser loads via manifest)
- sx_vm.ml: add __resolve-symbol hook to OP_GLOBAL_GET for lazy loading
- compile-modules.js: add HS modules as lazy_deps in manifest
HS compilation works in browser (tokenize→parse→compile verified).
Activation pipeline partially working — hs-activate! needs debugging
(dom-get-data/dom-set-data interaction with WASM host-get on functions).
Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>
Reset to last known-good state (908f4f80) where links, stepper, and
islands all work, then recovered all hyperscript implementation,
conformance tests, behavioral tests, Playwright specs, site sandbox,
IO-aware server loading, and upstream test suite from f271c88a.
Excludes runtime changes (VM resolve hook, VmSuspended browser handler,
sx_ref.ml guard recovery) that need careful re-integration.
Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>
When cek_call_or_suspend runs a CEK machine for a non-bytecoded Lambda
(e.g. a thunk), _active_vm still pointed to the caller's VM. VmClosure
calls inside the CEK (e.g. hs-wait) would merge their frames with the
caller's VM via call_closure_reuse, causing the VM to skip the CEK's
remaining continuation on resume — producing wrong DOM mutation order
(+active, +active, -active instead of +active, -active, +active).
Fix: swap _active_vm with an empty isolation VM before running the CEK,
restore after. This keeps VmClosure calls on their own frame stack while
preserving js_of_ocaml exception identity (Some path, not None).
Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>
