diff --git a/packages/compiler/src/backend/llvm/lib-shared.ts b/packages/compiler/src/backend/llvm/lib-shared.ts
index 1c7604c34..9d85547eb 100644
--- a/packages/compiler/src/backend/llvm/lib-shared.ts
+++ b/packages/compiler/src/backend/llvm/lib-shared.ts
@@ -1754,6 +1754,9 @@ export const USES_TIMERS_LIB_FNS = new Set<string>([
   "timers.setImmediateFnValue",
   "timers.immediatePromise",
   "dyn.builtinFunction",
-  // An asynchronous call into Node needs the loop to settle.
+  // A call into Node needs the loop: an asynchronous one to settle, and
+  // either kind may leave Node with ref'd timers or I/O, which the loop
+  // drives (scr_node_island.c) before the program exits.
   "nodeIsland.call",
+  "nodeIsland.callSync",
 ]);
diff --git a/packages/compiler/src/index.ts b/packages/compiler/src/index.ts
index c66e37901..0571b04b0 100644
--- a/packages/compiler/src/index.ts
+++ b/packages/compiler/src/index.ts
@@ -108,7 +108,7 @@ import {
   nodeIslandNodeDiag,
   type ScrDiagnostic,
 } from "./diagnostics/diagnostic.js";
-import { libnodeRecord } from "./node-islands/libnode.js";
+import { libnodeCacheKey, libnodeRecord } from "./node-islands/libnode.js";
 import { loadLibraryProfile, type LibraryProfile } from "./library/library-profile.js";
 import { clearFenceEvalCaches, decorateLibraryRefusals } from "./library/fence-eval.js";
 import {
@@ -1375,8 +1375,8 @@ async function compileTracked(
   if (outputKind === "exe") {
     const helperObjectRoute =
       opts.nativeProgramObject === true || usesPrecompiledRuntimePack(opts, "llvm");
-    // Calls into Node record the libnode pack (node-islands/libnode.ts).
-    const libnodeKey = opts.libnode ?? process.env["SCRIPTC_LIBNODE"];
+    // Calls into Node record the libnode pack, keyed by its manifest (node-islands/libnode.ts).
+    const libnodeKey = libnodeCacheKey(opts.libnode);
     const routeOptions: Omit<
       EarlyExecutableCacheOptions,
       "implementation" | "implementationDependencies" | "nativeEnvironment"
@@ -1446,6 +1446,17 @@ async function compileTracked(
     if (earlyCacheOptions === null) {
       throw new InternalCompilerError("executable cache hit without executable cache options");
     }
+    // The pack a --libnode=beside build places next to the executable is an output of the
+    // build, like the executable: a restored executable that calls into Node gets it again.
+    if (earlyHit.native.nodeIsland === true && opts.libnode === "beside") {
+      const recorded = libnodeRecord(opts.libnode, opts.outPath);
+      if (typeof recorded === "string")
+        return {
+          ok: false,
+          diagnostics: [nodeIslandNodeDiag(recorded, entryPath)],
+          sourceTexts: new Map(),
+        };
+    }
     const executableCacheOptions = earlyCacheOptions;
     // Route/proof metadata is independently evictable. A full-compiler
     // fallback that still finds the validated payload repairs that lightweight
diff --git a/packages/compiler/src/node-islands/libnode.test.ts b/packages/compiler/src/node-islands/libnode.test.ts
index 107e4aceb..6fadedcec 100644
--- a/packages/compiler/src/node-islands/libnode.test.ts
+++ b/packages/compiler/src/node-islands/libnode.test.ts
@@ -1,8 +1,9 @@
-import { existsSync, mkdirSync, mkdtempSync, readFileSync, writeFileSync } from "node:fs";
+import { existsSync, mkdirSync, mkdtempSync, readFileSync, rmSync, writeFileSync } from "node:fs";
 import { tmpdir } from "node:os";
 import { join } from "node:path";
 import { describe, expect, test } from "vitest";
-import { libnodeRecord, NODE_BRIDGE_ABI } from "./libnode.js";
+import { USES_TIMERS_LIB_FNS } from "../backend/llvm/lib-shared.js";
+import { libnodeCacheKey, libnodeRecord, NODE_BRIDGE_ABI } from "./libnode.js";
 
 function pack(nodeVersion: string, bridgeAbi = NODE_BRIDGE_ABI): string {
   const dir = mkdtempSync(join(tmpdir(), "scriptc-libnode-"));
@@ -55,6 +56,19 @@ describe("the recorded libnode pack", () => {
     expect(existsSync(join(out, "app.libnode/manifest.json"))).toBe(true);
   });
 
+  test("beside places the pack again after the outputs were deleted", () => {
+    // A cached executable restored without its pack gets it again (compile, index.ts).
+    const dir = pack("24.22.0");
+    const out = mkdtempSync(join(tmpdir(), "scriptc-libnode-out-"));
+    libnodeRecord("beside", join(out, "app"), { SCRIPTC_LIBNODE: dir });
+    rmSync(join(out, "app.libnode"), { recursive: true, force: true });
+    expect(libnodeRecord("beside", join(out, "app"), { SCRIPTC_LIBNODE: dir })).toEqual({
+      libnode: "$ORIGIN/app.libnode",
+      nodeVersion: "24.22.0",
+    });
+    expect(readFileSync(join(out, "app.libnode/libscr_node_bridge.so"), "utf8")).toBe("bridge");
+  });
+
   test("a pack the deployment places beside the executable needs no manifest at build time", () => {
     expect(libnodeRecord("$ORIGIN/node", "/out/app", {})).toEqual({
       libnode: "$ORIGIN/node",
@@ -62,3 +76,35 @@ describe("the recorded libnode pack", () => {
     });
   });
 });
+
+describe("the libnode pack in an executable's cache key", () => {
+  test("is absent without --libnode or SCRIPTC_LIBNODE", () => {
+    expect(libnodeCacheKey(undefined, {})).toBeUndefined();
+  });
+
+  test("changes when the pack in the same directory is upgraded", () => {
+    const dir = pack("24.22.0");
+    const before = libnodeCacheKey(dir, {});
+    expect(libnodeCacheKey(dir, {})).toBe(before);
+    writeFileSync(
+      join(dir, "manifest.json"),
+      JSON.stringify({ nodeVersion: "24.23.0", bridgeAbi: NODE_BRIDGE_ABI, files: {} }),
+    );
+    expect(libnodeCacheKey(dir, {})).not.toBe(before);
+  });
+
+  test("names the pack beside copies from", () => {
+    const a = pack("24.22.0");
+    const b = pack("24.22.0");
+    expect(libnodeCacheKey("beside", { SCRIPTC_LIBNODE: a })).not.toBe(
+      libnodeCacheKey("beside", { SCRIPTC_LIBNODE: b }),
+    );
+    expect(libnodeCacheKey("beside", { SCRIPTC_LIBNODE: a })).not.toBe(libnodeCacheKey(a, {}));
+  });
+});
+
+test("calls into Node keep the program's event loop running", () => {
+  // Node's ref'd timers and I/O run on the program's loop (scr_node_island.c).
+  expect(USES_TIMERS_LIB_FNS.has("nodeIsland.call")).toBe(true);
+  expect(USES_TIMERS_LIB_FNS.has("nodeIsland.callSync")).toBe(true);
+});
diff --git a/packages/compiler/src/node-islands/libnode.ts b/packages/compiler/src/node-islands/libnode.ts
index defb13869..2ba056023 100644
--- a/packages/compiler/src/node-islands/libnode.ts
+++ b/packages/compiler/src/node-islands/libnode.ts
@@ -12,6 +12,7 @@
  * as `<output>.libnode/`, recorded as `$ORIGIN/<output>.libnode`, so the
  * executable and its Node travel together; a recorded `$ORIGIN/` path is
  * also the hook for bundling Node into the executable itself later. */
+import { createHash } from "node:crypto";
 import { copyFileSync, linkSync, mkdirSync, readFileSync, rmSync, statSync } from "node:fs";
 import { basename, isAbsolute, join, resolve } from "node:path";
 
@@ -109,3 +110,28 @@ export function libnodeRecord(
   placeBeside(source, manifest, `${outPath}.libnode`);
   return { libnode: `${ORIGIN}${name}`, nodeVersion: manifest.nodeVersion };
 }
+
+/** The part of an executable's cache key that names its libnode pack, or
+ * undefined when neither --libnode nor SCRIPTC_LIBNODE is set. It holds the
+ * option, the pack directory and a digest of the pack's manifest.json, so
+ * that a pack upgraded in place (another Node version, bridge ABI or file
+ * list) gives cached executables a new key instead of their old record. */
+export function libnodeCacheKey(
+  option: string | undefined,
+  env: NodeJS.ProcessEnv = process.env,
+): string | undefined {
+  const fromEnv = env["SCRIPTC_LIBNODE"];
+  if (option === undefined && fromEnv === undefined) return undefined;
+  const source = option !== undefined && option !== "beside" ? option : (fromEnv ?? "");
+  let manifest = "none";
+  if (isAbsolute(source)) {
+    try {
+      manifest = createHash("sha256")
+        .update(readFileSync(join(source, "manifest.json")))
+        .digest("hex");
+    } catch {
+      // A missing pack fails the build that records it (libnodeRecord).
+    }
+  }
+  return `${option ?? ""}|${source}|${manifest}`;
+}
diff --git a/packages/runtime/src/scr_runtime.h b/packages/runtime/src/scr_runtime.h
index bf01a4a9b..79c4a105f 100644
--- a/packages/runtime/src/scr_runtime.h
+++ b/packages/runtime/src/scr_runtime.h
@@ -77,5 +77,6 @@
 #include "scr_fs_cp.h"
 #include "scr_wasm_abi.h"
 #include "scr_wasm.h"
+#include "scr_node_island.h"
 
 #endif /* SCR_RUNTIME_H */
diff --git a/tests/harness/corpus-costs/6800-node-call-sync/main.ts.json b/tests/harness/corpus-costs/6800-node-call-sync/main.ts.json
new file mode 100644
index 000000000..3ca32050d
--- /dev/null
+++ b/tests/harness/corpus-costs/6800-node-call-sync/main.ts.json
@@ -0,0 +1 @@
+{ "plain": 2856, "san": 39153 }
diff --git a/tests/harness/corpus-costs/6801-node-call-errors/main.ts.json b/tests/harness/corpus-costs/6801-node-call-errors/main.ts.json
new file mode 100644
index 000000000..6583fe71c
--- /dev/null
+++ b/tests/harness/corpus-costs/6801-node-call-errors/main.ts.json
@@ -0,0 +1 @@
+{ "plain": 1928, "san": 35656 }
diff --git a/tests/harness/corpus-costs/6802-node-call-async/main.ts.json b/tests/harness/corpus-costs/6802-node-call-async/main.ts.json
new file mode 100644
index 000000000..3aa5290bd
--- /dev/null
+++ b/tests/harness/corpus-costs/6802-node-call-async/main.ts.json
@@ -0,0 +1 @@
+{ "plain": 3224, "san": 32694 }
diff --git a/tests/harness/corpus-costs/6803-node-call-exit/main.ts.json b/tests/harness/corpus-costs/6803-node-call-exit/main.ts.json
new file mode 100644
index 000000000..134fe7954
--- /dev/null
+++ b/tests/harness/corpus-costs/6803-node-call-exit/main.ts.json
@@ -0,0 +1 @@
+{ "plain": 2860, "san": 20343 }