From 27537e0718f9105781cfe37dbd2da52151b7cf4d Mon Sep 17 00:00:00 2001
From: Eli Sterling <eli@eliware.org>
Date: Mon, 10 Aug 2026 05:10:25 +0000
Subject: [PATCH] Fix dynamic promise runtime gating

---
 packages/compiler/src/ir/nodes.ts |  8 ++++++++
 tests/harness/island.test.ts      | 10 ++++++++++
 2 files changed, 18 insertions(+)

diff --git a/packages/compiler/src/ir/nodes.ts b/packages/compiler/src/ir/nodes.ts
index 54ea11bc1..6736c4677 100644
--- a/packages/compiler/src/ir/nodes.ts
+++ b/packages/compiler/src/ir/nodes.ts
@@ -6074,6 +6074,14 @@ export function moduleUsesDynAsync(mod: IrModule): boolean {
       found = true;
       return;
     }
+    // Promise values crossing the checked-dynamic boundary are boxed by
+    // emit-walkers through scr_dyn_new_promise_adapting(). That constructor
+    // lives in scr_async_dyn.c, so promise-typed IR must pull that TU in even
+    // when the program never awaits a dyn value.
+    if (node.type !== undefined && node.type.kind === "promise") {
+      found = true;
+      return;
+    }
     for (const key of Object.keys(v)) visit((v as Record<string, unknown>)[key]);
   };
   visit(mod);
diff --git a/tests/harness/island.test.ts b/tests/harness/island.test.ts
index f7be561e8..0ef62ee65 100644
--- a/tests/harness/island.test.ts
+++ b/tests/harness/island.test.ts
@@ -338,6 +338,16 @@ console.log(__island_eval("Promise.reject(new TypeError('island second')); 'arme
     expect(r.stderr).toBe("Unhandled promise rejection: RangeError: static first\n");
   });
 
+  test("links the dynamic promise adapter for typed promises crossing a dynamic callback", async () => {
+    await build(
+      "typed-promise-dynamic-boundary",
+      `async function typed(): Promise<number> { return 1; }
+function invoke(fn: () => unknown): unknown { return fn(); }
+console.log(invoke(typed));
+`,
+    );
+  });
+
   test("--dynamic does not change emitted C for island-free programs", async () => {
     const source = `function greet(who: string): string {
   return "hello " + who;