docs: adjudicate #165 — enter-sync-call's unbracketed gate is accepted

docs/architecture.md

@@ -380,6 +380,34 @@ the site (`runtime/src/intrinsics/async_builtins.ts`, the determinacy park
 in `createSubtaskCancel`); regression pinned across seeds by
 `runtime/tests/cancel_bracket_race_test.ts`.
 
+Named divergence (2026-08-20, [#165](https://github.com/lann/deltic/issues/165),
+adjudicated-accept): **`enter-sync-call` checks the callee's reentrance gate
+but does not take it.** A FACT sync guest→guest call performs the
+reference's `trap_if(not may_enter_from(caller))` and stops — the
+`enter_from`/`leave_to` bracket around the call body (`Store.lift`,
+definitions.py:578-585) is deliberately omitted, so *host-mediated* reentry
+into the callee while the call is in flight (host → A.f → C.g → host import
+→ host re-enters C.g) is admitted where the pinned reference traps. Pure
+guest→guest cycles remain statically impossible (FACT compile-time traps;
+the instance-import DAG, [#99](https://github.com/lann/deltic/issues/99)/
+[#101](https://github.com/lann/deltic/issues/101)). Accepted on three
+grounds: **wasmtime parity** (`enter_guest_sync_call` performs no reentrance
+check at all, and fused adapters elide it); **architecture** — taking the
+bracket would create a guest→guest lock spanning suspension points,
+reintroducing the await-spanning-lock class that
+[#156](https://github.com/lann/deltic/issues/156)/[#160](https://github.com/lann/deltic/issues/160)
+eliminated; and **upstream trajectory** — CM PR
+[#705](https://github.com/WebAssembly/component-model/pull/705) ("CABI:
+remove the may_enter flag/trap") deletes the trap from the `canon lift`,
+`resource.drop`, and `subtask.cancel` paths and makes previously-trapping
+reentrance valid, retaining only run-to-completion serialization of async
+callback turns. This divergence is therefore a trailing indicator of the
+upstream removal and self-resolves when the submodule pin advances past
+#705; the pin-advance migration map is
+[#173](https://github.com/lann/deltic/issues/173). Until that advance the
+pinned definitions.py remains the tie-breaker everywhere else — every
+reentrance check deltic does enforce stays in force.
+
 ## 7. Canonical ABI decisions
 
 Authority: [CanonicalABI.md] and its executable reference

runtime/src/intrinsics/mod.ts

@@ -514,12 +514,20 @@ function createTrampolineBody(
         // Deliberately *not* done here: `enter_from` / `leave_to` around the
         // bracket. The reference locks the callee for the duration, which
         // would additionally trap host-mediated reentrance (host -> A.f ->
-        // C.g -> host import -> host invokes C.g). Doing it needs the trap /
-        // capability-signal distinction that only `exec/boundary.ts` has
-        // (a `NeedsJspi` bail out of a sync callee skips `exit-sync-call`
-        // and would poison a healthy instance), and the general form of that
-        // hole is the missing `ComponentInstance.parent` chain already
-        // recorded in `task/mod.ts` `enteringSet`. Reported, not smuggled in.
+        // C.g -> host import -> host invokes C.g).
+        //
+        // ADJUDICATED 2026-08-20 (deltic#165; named divergence in
+        // docs/architecture.md section 6): accepted — the bracket stays
+        // omitted. Three grounds: wasmtime parity (`enter_guest_sync_call`
+        // checks nothing); taking the bracket would create a guest-to-guest
+        // lock spanning suspension points, reintroducing the await-spanning
+        // -lock class removed by #156/#160; and upstream is deleting the
+        // trap outright — CM PR #705 ("CABI: remove the may_enter
+        // flag/trap") makes previously-trapping reentrance valid, so this
+        // divergence is a trailing indicator of the removal and
+        // self-resolves at the submodule pin advance (migration map:
+        // deltic#173). Until that pin advance the reference's checks deltic
+        // DOES enforce stay in force.
         if (
           typeof callerInstance === "number" &&
           typeof calleeInstance === "number"