diff --git a/packages/opencode/src/bus/index.ts b/packages/opencode/src/bus/index.ts
index b10c299665..49b2a2335d 100644
--- a/packages/opencode/src/bus/index.ts
+++ b/packages/opencode/src/bus/index.ts
@@ -1,11 +1,10 @@
 import z from "zod"
-import { Effect, Fiber, Layer, PubSub, ServiceMap, Stream } from "effect"
+import { Effect, Layer, PubSub, ServiceMap, Stream } from "effect"
 import { Log } from "../util/log"
 import { Instance } from "../project/instance"
 import { BusEvent } from "./bus-event"
 import { GlobalBus } from "./global"
-import { registerDisposer } from "../effect/instance-registry"
-import { forkInstance, runCallbackInstance, runPromiseInstance } from "../effect/runtime"
+import { runCallbackInstance, runPromiseInstance } from "../effect/runtime"
 
 export namespace Bus {
   const log = Log.create({ service: "bus" })
@@ -109,33 +108,22 @@ export namespace Bus {
 
   export function subscribeAll(callback: (event: any) => void) {
     const directory = Instance.directory
-    let manualUnsub = false
 
-    const fiber = forkInstance(
-      Service.use((svc) =>
-        svc.subscribeAll().pipe(Stream.runForEach((msg) => Effect.sync(() => callback(msg)))),
-      ).pipe(
-        Effect.ensuring(
-          Effect.sync(() => {
-            if (!manualUnsub) {
-              callback({ type: InstanceDisposed.type, properties: { directory } })
-            }
-          }),
-        ),
-      ),
-    )
-
-    // Interrupt the fiber before the layer is invalidated, awaiting
-    // completion so the refCount drops and the scope can close.
-    const unregister = registerDisposer(
-      (dir) => (dir !== directory ? Promise.resolve() : Effect.runPromise(Fiber.interrupt(fiber))),
-      -1,
-    )
+    // InstanceDisposed is delivered via GlobalBus because the sync
+    // callback API can't wait for async layer acquisition. The Effect
+    // service's stream ending IS the disposal signal for Effect consumers.
+    const onDispose = (evt: { directory?: string; payload: any }) => {
+      if (evt.payload.type !== InstanceDisposed.type) return
+      if (evt.directory !== directory) return
+      callback(evt.payload)
+      GlobalBus.off("event", onDispose)
+    }
+    GlobalBus.on("event", onDispose)
 
+    const interrupt = runStream((svc) => svc.subscribeAll(), callback)
     return () => {
-      manualUnsub = true
-      unregister()
-      fiber.interruptUnsafe()
+      GlobalBus.off("event", onDispose)
+      interrupt()
     }
   }
 }
diff --git a/packages/opencode/src/effect/instance-registry.ts b/packages/opencode/src/effect/instance-registry.ts
index 49b4abe137..59c556e044 100644
--- a/packages/opencode/src/effect/instance-registry.ts
+++ b/packages/opencode/src/effect/instance-registry.ts
@@ -1,25 +1,12 @@
-const disposers = new Set<{
-  fn: (directory: string) => Promise<void>
-  priority: number
-}>()
+const disposers = new Set<(directory: string) => Promise<void>>()
 
-export function registerDisposer(disposer: (directory: string) => Promise<void>, priority = 0) {
-  const item = {
-    fn: disposer,
-    priority,
-  }
-  disposers.add(item)
+export function registerDisposer(disposer: (directory: string) => Promise<void>) {
+  disposers.add(disposer)
   return () => {
-    disposers.delete(item)
+    disposers.delete(disposer)
   }
 }
 
 export async function disposeInstance(directory: string) {
-  const list = [...disposers].sort((a, b) => a.priority - b.priority)
-  const seen = new Set<number>()
-  for (const item of list) {
-    if (seen.has(item.priority)) continue
-    seen.add(item.priority)
-    await Promise.allSettled(list.filter((x) => x.priority === item.priority).map((x) => x.fn(directory)))
-  }
+  await Promise.allSettled([...disposers].map((disposer) => disposer(directory)))
 }
diff --git a/packages/opencode/src/effect/runtime.ts b/packages/opencode/src/effect/runtime.ts
index 794e5978e9..4465b106f4 100644
--- a/packages/opencode/src/effect/runtime.ts
+++ b/packages/opencode/src/effect/runtime.ts
@@ -1,4 +1,4 @@
-import { Effect, Fiber, Layer, ManagedRuntime } from "effect"
+import { Effect, Layer, ManagedRuntime } from "effect"
 import { AccountEffect } from "@/account/effect"
 import { AuthEffect } from "@/auth/effect"
 import { Instances } from "@/effect/instances"
@@ -18,12 +18,6 @@ export function runPromiseInstance<A, E>(effect: Effect.Effect<A, E, InstanceSer
   return runtime.runPromise(effect.pipe(Effect.provide(Instances.get(Instance.directory))))
 }
 
-export function forkInstance<A, E>(
-  effect: Effect.Effect<A, E, InstanceServices>,
-): Fiber.Fiber<A, E> {
-  return runtime.runFork(effect.pipe(Effect.provide(Instances.get(Instance.directory))))
-}
-
 export function runCallbackInstance<A, E>(
   effect: Effect.Effect<A, E, InstanceServices>,
 ): (interruptor?: number) => void {
diff --git a/packages/opencode/test/bus/bus.test.ts b/packages/opencode/test/bus/bus.test.ts
index b3da0fc9ea..a8929aa1c9 100644
--- a/packages/opencode/test/bus/bus.test.ts
+++ b/packages/opencode/test/bus/bus.test.ts
@@ -4,6 +4,7 @@ import { Bus } from "../../src/bus"
 import { BusEvent } from "../../src/bus/bus-event"
 import { GlobalBus } from "../../src/bus/global"
 import { Instance } from "../../src/project/instance"
+import { Log } from "../../src/util/log"
 import { tmpdir } from "../fixture/fixture"
 
 // ---------------------------------------------------------------------------
@@ -190,6 +191,38 @@ describe("Bus", () => {
 
       expect(all).toEqual(["test.ping"])
     })
+
+    test("subscribeAll delivers InstanceDisposed via GlobalBus on disposal", async () => {
+      await using tmp = await tmpdir()
+      const all: string[] = []
+
+      await withInstance(tmp.path, async () => {
+        Bus.subscribeAll((evt) => {
+          all.push(evt.type)
+        })
+      })
+
+      await Instance.disposeAll()
+
+      expect(all).toContain(Bus.InstanceDisposed.type)
+    })
+
+    test("manual unsubscribe suppresses InstanceDisposed", async () => {
+      await using tmp = await tmpdir()
+      const all: string[] = []
+      let unsub = () => {}
+
+      await withInstance(tmp.path, async () => {
+        unsub = Bus.subscribeAll((evt) => {
+          all.push(evt.type)
+        })
+      })
+
+      unsub()
+      await Instance.disposeAll()
+
+      expect(all).not.toContain(Bus.InstanceDisposed.type)
+    })
   })
 
   describe("GlobalBus forwarding", () => {