diff --git a/src/future/worker-bootstrap.ts b/src/future/worker-bootstrap.ts
index 0da500a..3392d14 100644
--- a/src/future/worker-bootstrap.ts
+++ b/src/future/worker-bootstrap.ts
@@ -7,6 +7,7 @@
 
 import { parentPort, workerData } from "node:worker_threads";
 import { Ok, Err, safeTry } from "slang-ts";
+import { parseBoxSize } from "./memory-pool";
 import type { Result } from "slang-ts";
 import type {
   ActorSelf, ActorContext, ActorCallback, ActorRef, FormatUtils,
@@ -154,7 +155,7 @@ function createActorContext(): ActorContext {
       const { msg, type, data, share = "owner" } = params;
       pendingWrite = {
         resolve: (lock) => {
-          const boxSize = Number(config.memory.boxSize);
+        const boxSize = parseBoxSize(config.memory.boxSize);
           const offset = lock.boxIndex * boxSize;
           const view = new Uint8Array(sab, offset, Math.min(data.length, boxSize));
           view.set(data.subarray(0, boxSize));
@@ -169,7 +170,7 @@ function createActorContext(): ActorContext {
     /** Sync read from SAB. Returns null for Tier 1 (no handle). */
     read: (msg: Message) => {
       if (!msg.handle) return null;
-      const boxSize = Number(config.memory.boxSize);
+      const boxSize = parseBoxSize(config.memory.boxSize);
       const offset = msg.handle.boxIndex * boxSize;
       const view = new Uint8Array(sab, offset, boxSize);
       /** Strip trailing null bytes for text/JSON decoding (SAB is zero-initialized) */
diff --git a/tests/future/supervisor.spec.ts b/tests/future/supervisor.spec.ts
index fe44816..55baac5 100644
--- a/tests/future/supervisor.spec.ts
+++ b/tests/future/supervisor.spec.ts
@@ -281,6 +281,63 @@ describe("tier 2 shared memory", () => {
 
     expect(stripNulls(data)).toBe("hello world");
   });
+
+  it("supports string boxSize in worker write/read operations", async () => {
+    const sup = createSupervisor({
+      maxActors: 5,
+      memory: { poolSize: 2, boxSize: "1KB" },
+      timeouts: { defaultLeaseMs: 2000 },
+    });
+
+    const actor = sup.spawn(async (self, _msg, ctx) => {
+      const result = await ctx.write({
+       msg: "string-box-size",
+       type: "json",
+       data: ctx.fmt.json.encode({ ok: true, value: 42 }),
+       share: "owner",
+      });
+
+      if (result.isOk) {
+       self.send("string-box-size", { handle: result.value });
+      } else {
+       self.send("write-error", { error: result.error });
+      }
+    });
+
+    const data = await new Promise<unknown>((resolve, reject) => {
+      const timeout = setTimeout(() => {
+       reject(new Error("Timeout waiting for string boxSize write"));
+      }, 3000);
+
+      actor.subscribe((msg) => {
+       const m = msg as Message;
+
+       if (m.msg === "write-error" && m.data) {
+         clearTimeout(timeout);
+         reject(new Error((m.data as { error: string }).error));
+       }
+
+       if (m.msg === "string-box-size" && m.data) {
+         clearTimeout(timeout);
+          const handle = (m.data as { handle: Lock }).handle;
+          const reader = actor.read({ ...m, handle });
+
+          if (!reader) {
+           reject(new Error("Expected reader for string boxSize message"));
+           return;
+          }
+
+           resolve(reader.json());
+       }
+      });
+
+      actor.receive("write");
+    });
+
+    expect(data).toEqual({ ok: true, value: 42 });
+
+    await sup.shutdown();
+  });
 });
 
 // ============================================================================