test(asyncify): red-green race harness + ablation flags, unwind-catch shim, spec tightening, decisions docs

The asyncify single-slot work, executed red-green (full ledger:
docs/features/asyncify-arbiter/redgreen.md; decisions record:
docs/features/async/07-decisions-and-outcome.md):

- tests/apps/standalone/asyncify-races/ + tests/asyncify/ + dedicated
  playwright config: 8 scenarios reproducing the KiCad asyncify failure
  family with the kicad-faithful startup topology (pre-park fiber swap →
  park throw through the live trampoline). Built in 3 variants; the
  SHIM_DISABLE_TRAMPOLINE_HEAL / SHIM_DISABLE_HANDLESLEEP ablation builds
  keep the historical hang and index-out-of-bounds crash reproducible
  forever (mutation-style pins for the existing shims).
- scripts/common/shims/handlesleep.js: catch the "unwind" park sentinel
  in the wakeUp path — when main's last pre-park suspension was a sleep,
  the main-loop park throw escaped through that sleep's promise reaction
  as an uncaught rejection (the calculator/gerbview console errors).
- scripts/common/inject-dyncall-shims.sh: SHIM_DISABLE_* ablation knobs.
- Spec tightening (the acceptance bar): 'uncaught exception: unwind'
  tolerance DELETED from pcbnew/eeschema specs; load-pcb gained a hard
  clean-console gate over 5 asyncify corruption signatures.
- wxwidgets pointer bump: modal LIFO resolvers, pump resolve-on-error,
  sync clipboard IsSupported (014f67e6c1).

Final state: asyncify suite 7/7, wx e2e 291/292 (1 skip), KiCad e2e 40
passed / 2 skipped with ZERO corruption signatures in any log across all
six apps.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

docs/features/async/07-decisions-and-outcome.md

@@ -0,0 +1,155 @@
+# 07 — Decisions and outcome (2026-06-12)
+
+> The dossier (01–06) ended with designs and open questions. This file records what was
+> actually decided, built, and deliberately NOT built — and the trigger conditions for
+> revisiting each road not taken. Working artifacts: `docs/features/asyncify-arbiter/`
+> (baseline.md, redgreen.md), harness in `tests/apps/standalone/asyncify-races/` +
+> `tests/asyncify/`, runnable via `npm run test:asyncify:firefox`.
+
+## D1 — Root cause: the dossier's two hang mechanisms were ONE mechanism
+
+The §5 (doc 02) question "orphaned currData vs stuck trampoline guard" was settled by code
+trace, then pinned by a deterministic test. At the `emscripten_set_main_loop(...,1)`
+`throw "unwind"` park, Asyncify state is clean — but **any OnInit-era fiber swap means
+main() is, from then on, executing inside `Fibers.trampoline()`'s `do/while`** (resumed via
+`finishContextSwitch → doRewind`). The throw tears through that live frame; the
+`trampolineRunning = false` reset is skipped; the guard wedges forever; the first post-idle
+swap strands. "Orphaned currData" is structurally impossible (the throw only executes from
+straight-line Normal-state code). Corollary: when main's *last* pre-park suspension was a
+**sleep**, the same throw instead escapes through that sleep's wakeUp promise reaction —
+that was the long-standing `uncaught exception: unwind` rejection family.
+
+Consequence: the trampoline self-heal (`inject-dyncall-shims.sh` §3c, commit `18a9de0`)
+is the **structural cure** for the hang, not a band-aid (doc 04 had it demoted), and
+**de-parking (02 §7) is not needed for correctness.**
+
+## D2 — Red-green doctrine governed everything
+
+Rule applied throughout: *no fix lands before a test has been observed failing for the
+exact disease, and the failing run is recorded* (`asyncify-arbiter/redgreen.md`). Two red
+flavors: **natural red** (bug unfixed today) and **ablation red** (fix exists; rebuild the
+harness with `SHIM_DISABLE_TRAMPOLINE_HEAL=1` / `SHIM_DISABLE_HANDLESLEEP=1` to prove the
+test detects the disease the fix prevents — mutation-testing style). The ablation flags are
+permanent injector features; the diseases stay reproducible on demand.
+
+## D3 — Decision: the full Design-A arbiter was NOT built
+
+Doc 05's arbiter (central context registry + deferred-wakeup queue + single-owner
+transitions) was the plan. It was dropped because **no scenario could be made red that it
+would fix**: at production asyncify semantics (`-sASSERTIONS=0`), the pre-existing
+per-sleep capture in `scripts/common/shims/handlesleep.js` (commit `a4ad694`) already
+implements Design A's core invariant — *`Asyncify.currData` is a transient register; every
+parked context owns its buffer pointer elsewhere* (fibers: in the `wasm_fcontext` struct;
+sleeps: in per-sleep closures, restored immediately before that sleep's own rewind). The
+scenarios predicted to need the arbiter (`wakeup_during_transition`,
+`out_of_order_sleep_resolution`, `sleep_inside_fiber_inside_modal`) are green under the
+existing shim and are kept as regression pins.
+
+Why the residual race is structurally hard to hit: promise resolvers only queue
+microtasks; microtasks run only at JS-stack-empty; every transition (unwind chain,
+trampoline loop, rewind chain) completes synchronously within one task. The only mechanism
+that splits a transition across tasks is an `await` inside the chain — the async-ccall
+pumps — which are exactly what was hardened (D5).
+
+**Trigger to revisit:** any reappearance of a wakeup-during-transition signature in
+`tests/logs/` (e.g. handleSleep entered at `state=2`, `invalid state` aborts), or any new
+red the existing shims can't turn green. The arbiter design in doc 05 remains the blueprint;
+the deferred-wakeup queue alone is a ~50-line `handlesleep.js` extension.
+
+## D4 — Decision: keep the park throw (+ heal + sentinel catch); defer the asyncify-park
+
+The alternative discussed ("Option C": park main in a never-resolving `EM_ASYNC_JS` sleep
+instead of the throw — clean unwind, no exceptional control flow, explicit teardown owner,
+natural step one of Design B) was deliberately **deferred**. With the heal (§3c) covering
+the fiber face and the `handlesleep.js` sentinel catch covering the sleep face, both damage
+classes of the throw are individually fixed and pinned; the asyncify-park would have landed
+green-on-green. Costs it would incur now: wx lifecycle change + rebuild, `MainLoop.pause()`
+interplay (handleSleep auto-pauses the loop), a permanently-parked buffer, divergence from
+stock emscripten idiom.
+
+**Trigger to revisit:** recurring `"unwind"`-leak variants that the sentinel catch doesn't
+cover, or starting Design B (fiber-first runtime) in earnest.
+
+## D5 — wx-layer fixes (the bugs that were wx's, not the shim's)
+
+1. **`dialog.cpp` — modal resolver is a LIFO stack.** `Module._endModal` was a single slot
+   that deleted itself after use; with 3+ nested modals the middle `EndModal` resolved
+   nothing and its `ShowModal` parked forever. Found by the new `modal_in_modal_in_modal`
+   scenario — a previously unknown product bug (KiCad nests dialogs routinely). Now:
+   stable `Module._endModal` dispatcher popping `Module._wxModalResolvers` (LIFO — matches
+   wx modal discipline and c27's `_wxNestedLoopExit` convention). If programmatic
+   out-of-order EndModal ever matters, key the dispatcher per-dialog (small change, needs
+   its own red test first).
+2. **Pumps must never stop without resolving.** Both `startModal` (modal pump) and
+   `wxWasmRunNestedLoop` (c27 quasi-modal pump) caught ProcessEvents rejections and
+   silently stopped, leaving the suspended C++ stack parked forever. Now both resolve on
+   error, loudly (`console.error`): the modal cancels with `wxID_CANCEL` (passed in from
+   C++), the nested loop exits. Self-cancel paths splice their own resolver out of the
+   stack (they may not be topmost).
+3. **`clipbrd.cpp` — `IsSupported` is synchronous again.** It called the 2 s
+   permission-gated `js_clipboardHasText` EM_ASYNC_JS from a synchronous-by-contract
+   predicate on the idle path — creating the long-parked sleeps behind the
+   `index out of bounds` family. Now answers optimistically from the sync
+   `js_isClipboardAPIAvailable` probe; the real read stays in `GetData()` (user-gesture
+   gated).
+
+## D6 — Harness design decisions (tests/apps/standalone/asyncify-races/)
+
+- **KiCad-faithful topology is the point:** ≥1 fiber swap in `OnInit` so main is
+  trampoline-resumed at park time — the precondition `coroutine-nested` lacked, which is
+  why it never reproduced the hang. `#mode=sleep-park` flips the last pre-park suspension
+  to a sleep for the rejection face.
+- **`-sASSERTIONS=0` (LDFLAGS_RACES):** emscripten's debug assert ("cannot start an async
+  operation when one is already in flight") forbids the very multi-parked-sleep states the
+  production shims exist to handle; the harness must match production semantics.
+- **Params travel in the URL hash:** `npx serve`'s cleanUrls redirect for `*.html` drops
+  query strings.
+- **EM_JS bodies use C parameter NAMES** (`aToken`), not `$0` — that is EM_ASM syntax.
+- **To make a pump fail, throw from a PENDING EVENT** (`CallAfter` → ProcessPendingEvents
+  inside the pump's awaited ccall). wx timers fire via
+  `emscripten_async_call`/`callUserCallback` and bypass pumps entirely.
+- **Quiescence probe** (state==Normal, currData==null, nextFiber==0) is checked
+  synchronously between scenarios; `trampolineRunning` is deliberately excluded from the
+  sync check (code resumed via a fiber legitimately runs inside the trampoline do/while) —
+  a genuinely stuck guard is caught by the per-scenario JS watchdogs instead.
+- Wedge-prone scenarios run as `#only=` singles on separate page loads; the chained battery
+  holds only scenarios that can't kill the chain.
+
+## D7 — Attribution ledger (who fixed what, when)
+
+Pre-existing (earlier sessions): per-sleep buffer capture/restore in `handlesleep.js`
+(`a4ad694`); trampoline self-heal §3c (`18a9de0`); per-fiber buffers (stock emscripten +
+libcontext). This session's code: the 13-line `"unwind"` sentinel catch in
+`handlesleep.js`; the three wx fixes (D5); `SHIM_DISABLE_*` ablation flags; the harness +
+specs + config; spec tightening (D8). This session's *proof*: before it, the shim and heal
+were unverified folklore — nothing failed if you deleted them. Now their diseases reproduce
+on demand and their absence fails tests.
+
+## D8 — Acceptance bar moved into the specs
+
+`'uncaught exception: unwind'` tolerance filters DELETED from `pcbnew.spec.ts` /
+`eeschema.spec.ts`; `load-pcb.spec.ts` gained a hard clean-console gate over five
+signatures (`index out of bounds`, `indirect call to null`, `uncaught exception: unwind`,
+`invalid state`, `is not a function`) covering before AND after board render.
+
+## Outcome (final verification)
+
+- Harness: 7/7 green (battery of 4 + three singles); both ablation builds still reproduce
+  their diseases. wx e2e 291 passed / 1 skipped / 0 failed; coroutine 13/13.
+- KiCad e2e after rebuilding **all six apps**: 40 passed / 2 skipped / 0 failed / 0 flaky,
+  and a sweep of every `tests/logs/kicad/` log finds **zero** corruption signatures and
+  **zero** `.errors.log` files (baseline had load-pcb `index out of bounds` and
+  calculator/gerbview `uncaught exception: unwind`).
+- Upstream (researched): Fibers/Asyncify JS runtime unchanged since 2020; the single-slot
+  limitation family is WONTFIX (#9153, #12270, #13302, #16291, #18412). The §3c
+  try/finally heal is a good candidate for an upstream PR.
+
+## Roads not taken, with triggers
+
+| Option | Status | Revisit when |
+|---|---|---|
+| Full Design-A arbiter (registry + wakeup queue) | not built | any wakeup-during-transition signature in logs, or a red the shims can't fix |
+| Park-via-unresolved-sleep (no throw) | deferred | recurring unwind-leak variants, or Design B work starts |
+| De-parking (02 §7, lifecycle surgery) | rejected | only as part of Design B |
+| Design B (fiber-first runtime) | long-term option | architectural appetite, not correctness need |
+| Per-dialog-keyed modal resolvers | not needed | a real out-of-order EndModal use case (write the red first) |

docs/features/async/README.md

@@ -39,6 +39,7 @@ or **hang** (a swap unwinds but is never rewound).
 | [`04-decisions-tests-open-questions.md`](04-decisions-tests-open-questions.md) | How the fix options relate (what's subsumed vs. genuinely separate), the one diagnostic that decides scope, the combinatorial test matrix, and open questions. |
 | [`05-design-a-js-asyncify-arbiter.md`](05-design-a-js-asyncify-arbiter.md) | Incremental design: keep current `EM_ASYNC_JS` sleeps and fibers, but put one JS arbiter in charge of `currData`, transition queueing, and the trampoline. Includes concept explanations. |
 | [`06-design-b-fiber-first-runtime.md`](06-design-b-fiber-first-runtime.md) | Cleaner long-term design: make modals, clipboard, fonts, nested loops, and tools all scheduler-owned fiber-like contexts. Explains how this relates to de-parking and app lifetime. |
+| [`07-decisions-and-outcome.md`](07-decisions-and-outcome.md) | **What was decided and shipped (2026-06-12):** root cause, red-green ledger, the arbiter NOT built and why, roads not taken with revisit triggers. |
 
 ## The single decisive next step
 
@@ -47,3 +48,32 @@ Before designing anything, **measure whether `Asyncify.currData` is clean (null)
 post-startup `emscripten_fiber_swap`). That one fact determines whether the universal fix must
 also reshape the main loop ("de-parking") or whether a per-context `currData` authority alone
 suffices. Details in [`04-decisions-tests-open-questions.md`](04-decisions-tests-open-questions.md).
+
+---
+
+## RESOLUTION (2026-06-12) — see [`07-decisions-and-outcome.md`](07-decisions-and-outcome.md) and `docs/features/asyncify-arbiter/`
+
+The decisive measurement was answered **by code trace and then pinned by a deterministic
+test** (`tests/asyncify/asyncify-races.spec.ts` + `tests/apps/standalone/asyncify-races/`):
+
+- At the park throw, Asyncify state IS clean (`currData==null`, `state==Normal`) — **but the
+  JS stack is necessarily still inside `Fibers.trampoline()`'s `do/while`** (any OnInit-era
+  fiber swap means main is trampoline-resumed from then on). The throw skips the
+  `trampolineRunning = false` reset → the guard wedges → the first post-idle swap hangs.
+  That IS the §5 hang; "orphaned currData" (mechanism #1) is structurally impossible.
+  The self-heal (`inject-dyncall-shims.sh` §3c, commit `18a9de0`) is therefore the
+  *structural cure*, not a band-aid — **no de-parking needed**.
+- When main's last pre-park suspension is a *sleep*, the same throw instead escapes through
+  the sleep's wakeUp promise reaction → the long-mystifying `uncaught exception: unwind`
+  rejections. Fixed in `scripts/common/shims/handlesleep.js` (catches the sentinel like
+  `callMain` does).
+- The full Design-A arbiter was NOT needed: at production semantics (`-sASSERTIONS=0`),
+  out-of-order and overlapping-sleep scenarios are already handled by the per-sleep buffer
+  capture in `handlesleep.js`. The remaining bugs were wx-layer: single-slot
+  `Module._endModal` broke 3-deep nested modals (now a LIFO resolver stack), and the
+  modal/nested-loop pumps stalled silently on ProcessEvents rejection (now resolve-on-error).
+  Clipboard `IsSupported` no longer runs the 2 s async probe.
+- De-parking (02 §7) and Design B remain documented options, unneeded for correctness today.
+- Upstream status (researched): the Fibers/Asyncify code is unchanged since 2020; the
+  single-slot family is WONTFIX (#9153, #12270, #13302, #16291, #18412). The trampoline
+  try/finally would be a good upstream PR.