diff --git a/packages/opencode/src/util/rpc.ts b/packages/opencode/src/util/rpc.ts
index 02586ebcfc60..a86540ca664e 100644
--- a/packages/opencode/src/util/rpc.ts
+++ b/packages/opencode/src/util/rpc.ts
@@ -10,6 +10,7 @@ export function listen(rpc: Definition) {
       postMessage(JSON.stringify({ type: "rpc.result", result, id: parsed.id }))
     }
   }
+  postMessage(JSON.stringify({ type: "rpc.ready" }))
 }
 
 export function emit(event: string, data: unknown) {
@@ -23,8 +24,13 @@ export function client<T extends Definition>(target: {
   const pending = new Map<number, (result: any) => void>()
   const listeners = new Map<string, Set<(data: any) => void>>()
   let id = 0
+  // Bun drops messages that reach a worker before its module (which may have a
+  // top-level await) has set onmessage, so requests wait for the worker to say it listens.
+  let markReady!: () => void
+  const ready = new Promise<void>((resolve) => (markReady = resolve))
   target.onmessage = async (evt) => {
     const parsed = JSON.parse(evt.data)
+    if (parsed.type === "rpc.ready") markReady()
     if (parsed.type === "rpc.result") {
       const resolve = pending.get(parsed.id)
       if (resolve) {
@@ -46,7 +52,7 @@ export function client<T extends Definition>(target: {
       const requestId = id++
       return new Promise((resolve) => {
         pending.set(requestId, resolve)
-        target.postMessage(JSON.stringify({ type: "rpc.request", method, input, id: requestId }))
+        ready.then(() => target.postMessage(JSON.stringify({ type: "rpc.request", method, input, id: requestId })))
       })
     },
     on<Data>(event: string, handler: (data: Data) => void) {
diff --git a/packages/opencode/test/fixture/rpc-worker.ts b/packages/opencode/test/fixture/rpc-worker.ts
new file mode 100644
index 000000000000..0e17d37b3469
--- /dev/null
+++ b/packages/opencode/test/fixture/rpc-worker.ts
@@ -0,0 +1,8 @@
+import { Rpc } from "../../src/util/rpc"
+
+Rpc.emit("started", undefined)
+await new Promise((resolve) => setTimeout(resolve, 300))
+
+Rpc.listen({
+  echo: (input: string) => input,
+})
diff --git a/packages/opencode/test/util/rpc.test.ts b/packages/opencode/test/util/rpc.test.ts
new file mode 100644
index 000000000000..341e1249c40f
--- /dev/null
+++ b/packages/opencode/test/util/rpc.test.ts
@@ -0,0 +1,15 @@
+import { describe, expect, test } from "bun:test"
+import { Rpc } from "../../src/util/rpc"
+
+describe("util.rpc", () => {
+  test("delivers calls made while the worker is still in its top-level await", async () => {
+    const worker = new Worker(new URL("../fixture/rpc-worker.ts", import.meta.url).href)
+    try {
+      const client = Rpc.client<{ echo: (input: string) => string }>(worker)
+      await new Promise<void>((resolve) => client.on("started", () => resolve()))
+      expect(await client.call("echo", "hello")).toBe("hello")
+    } finally {
+      worker.terminate()
+    }
+  })
+})