diff --git a/packages/opencode/test/bus/bus-effect.test.ts b/packages/opencode/test/bus/bus-effect.test.ts
index 101d3be72b..377c541096 100644
--- a/packages/opencode/test/bus/bus-effect.test.ts
+++ b/packages/opencode/test/bus/bus-effect.test.ts
@@ -2,9 +2,8 @@ import { describe, expect } from "bun:test"
 import { Deferred, Effect, Layer, Schema, Stream } from "effect"
 import { Bus } from "../../src/bus"
 import { BusEvent } from "../../src/bus/bus-event"
-import { Instance } from "../../src/project/instance"
 import { CrossSpawnSpawner } from "@opencode-ai/core/cross-spawn-spawner"
-import { disposeAllInstances, provideInstance, provideTmpdirInstance, tmpdirScoped } from "../fixture/fixture"
+import { disposeAllInstances, provideInstance, tmpdirScoped } from "../fixture/fixture"
 import { testEffect } from "../lib/effect"
 
 const TestEvent = {
@@ -19,111 +18,103 @@ const live = Layer.mergeAll(Bus.layer, node)
 const it = testEffect(live)
 
 describe("Bus (Effect-native)", () => {
-  it.live("publish + subscribe stream delivers events", () =>
-    provideTmpdirInstance(() =>
-      Effect.gen(function* () {
-        const bus = yield* Bus.Service
-        const received: number[] = []
-        const done = yield* Deferred.make<void>()
+  it.instance("publish + subscribe stream delivers events", () =>
+    Effect.gen(function* () {
+      const bus = yield* Bus.Service
+      const received: number[] = []
+      const done = yield* Deferred.make<void>()
 
-        yield* Stream.runForEach(bus.subscribe(TestEvent.Ping), (evt) =>
-          Effect.sync(() => {
-            received.push(evt.properties.value)
-            if (received.length === 2) Deferred.doneUnsafe(done, Effect.void)
-          }),
-        ).pipe(Effect.forkScoped)
+      yield* Stream.runForEach(bus.subscribe(TestEvent.Ping), (evt) =>
+        Effect.sync(() => {
+          received.push(evt.properties.value)
+          if (received.length === 2) Deferred.doneUnsafe(done, Effect.void)
+        }),
+      ).pipe(Effect.forkScoped)
 
-        yield* Effect.sleep("10 millis")
-        yield* bus.publish(TestEvent.Ping, { value: 1 })
-        yield* bus.publish(TestEvent.Ping, { value: 2 })
-        yield* Deferred.await(done)
+      yield* Effect.sleep("10 millis")
+      yield* bus.publish(TestEvent.Ping, { value: 1 })
+      yield* bus.publish(TestEvent.Ping, { value: 2 })
+      yield* Deferred.await(done)
 
-        expect(received).toEqual([1, 2])
-      }),
-    ),
+      expect(received).toEqual([1, 2])
+    }),
   )
 
-  it.live("subscribe filters by event type", () =>
-    provideTmpdirInstance(() =>
-      Effect.gen(function* () {
-        const bus = yield* Bus.Service
-        const pings: number[] = []
-        const done = yield* Deferred.make<void>()
+  it.instance("subscribe filters by event type", () =>
+    Effect.gen(function* () {
+      const bus = yield* Bus.Service
+      const pings: number[] = []
+      const done = yield* Deferred.make<void>()
 
-        yield* Stream.runForEach(bus.subscribe(TestEvent.Ping), (evt) =>
-          Effect.sync(() => {
-            pings.push(evt.properties.value)
-            Deferred.doneUnsafe(done, Effect.void)
-          }),
-        ).pipe(Effect.forkScoped)
+      yield* Stream.runForEach(bus.subscribe(TestEvent.Ping), (evt) =>
+        Effect.sync(() => {
+          pings.push(evt.properties.value)
+          Deferred.doneUnsafe(done, Effect.void)
+        }),
+      ).pipe(Effect.forkScoped)
 
-        yield* Effect.sleep("10 millis")
-        yield* bus.publish(TestEvent.Pong, { message: "ignored" })
-        yield* bus.publish(TestEvent.Ping, { value: 42 })
-        yield* Deferred.await(done)
+      yield* Effect.sleep("10 millis")
+      yield* bus.publish(TestEvent.Pong, { message: "ignored" })
+      yield* bus.publish(TestEvent.Ping, { value: 42 })
+      yield* Deferred.await(done)
 
-        expect(pings).toEqual([42])
-      }),
-    ),
+      expect(pings).toEqual([42])
+    }),
   )
 
-  it.live("subscribeAll receives all types", () =>
-    provideTmpdirInstance(() =>
-      Effect.gen(function* () {
-        const bus = yield* Bus.Service
-        const types: string[] = []
-        const done = yield* Deferred.make<void>()
+  it.instance("subscribeAll receives all types", () =>
+    Effect.gen(function* () {
+      const bus = yield* Bus.Service
+      const types: string[] = []
+      const done = yield* Deferred.make<void>()
 
-        yield* Stream.runForEach(bus.subscribeAll(), (evt) =>
-          Effect.sync(() => {
-            types.push(evt.type)
-            if (types.length === 2) Deferred.doneUnsafe(done, Effect.void)
-          }),
-        ).pipe(Effect.forkScoped)
+      yield* Stream.runForEach(bus.subscribeAll(), (evt) =>
+        Effect.sync(() => {
+          types.push(evt.type)
+          if (types.length === 2) Deferred.doneUnsafe(done, Effect.void)
+        }),
+      ).pipe(Effect.forkScoped)
 
-        yield* Effect.sleep("10 millis")
-        yield* bus.publish(TestEvent.Ping, { value: 1 })
-        yield* bus.publish(TestEvent.Pong, { message: "hi" })
-        yield* Deferred.await(done)
+      yield* Effect.sleep("10 millis")
+      yield* bus.publish(TestEvent.Ping, { value: 1 })
+      yield* bus.publish(TestEvent.Pong, { message: "hi" })
+      yield* Deferred.await(done)
 
-        expect(types).toContain("test.effect.ping")
-        expect(types).toContain("test.effect.pong")
-      }),
-    ),
+      expect(types).toContain("test.effect.ping")
+      expect(types).toContain("test.effect.pong")
+    }),
   )
 
-  it.live("multiple subscribers each receive the event", () =>
-    provideTmpdirInstance(() =>
-      Effect.gen(function* () {
-        const bus = yield* Bus.Service
-        const a: number[] = []
-        const b: number[] = []
-        const doneA = yield* Deferred.make<void>()
-        const doneB = yield* Deferred.make<void>()
+  it.instance("multiple subscribers each receive the event", () =>
+    Effect.gen(function* () {
+      const bus = yield* Bus.Service
+      const a: number[] = []
+      const b: number[] = []
+      const doneA = yield* Deferred.make<void>()
+      const doneB = yield* Deferred.make<void>()
 
-        yield* Stream.runForEach(bus.subscribe(TestEvent.Ping), (evt) =>
-          Effect.sync(() => {
-            a.push(evt.properties.value)
-            Deferred.doneUnsafe(doneA, Effect.void)
-          }),
-        ).pipe(Effect.forkScoped)
+      yield* Stream.runForEach(bus.subscribe(TestEvent.Ping), (evt) =>
+        Effect.sync(() => {
+          a.push(evt.properties.value)
+          Deferred.doneUnsafe(doneA, Effect.void)
+        }),
+      ).pipe(Effect.forkScoped)
 
-        yield* Stream.runForEach(bus.subscribe(TestEvent.Ping), (evt) =>
-          Effect.sync(() => {
-            b.push(evt.properties.value)
-            Deferred.doneUnsafe(doneB, Effect.void)
-          }),
-        ).pipe(Effect.forkScoped)
+      yield* Stream.runForEach(bus.subscribe(TestEvent.Ping), (evt) =>
+        Effect.sync(() => {
+          b.push(evt.properties.value)
+          Deferred.doneUnsafe(doneB, Effect.void)
+        }),
+      ).pipe(Effect.forkScoped)
 
-        yield* Effect.sleep("10 millis")
-        yield* bus.publish(TestEvent.Ping, { value: 99 })
-        yield* Deferred.await(doneA)
-        yield* Deferred.await(doneB)
+      yield* Effect.sleep("10 millis")
+      yield* bus.publish(TestEvent.Ping, { value: 99 })
+      yield* Deferred.await(doneA)
+      yield* Deferred.await(doneB)
 
-        expect(a).toEqual([99])
-        expect(b).toEqual([99])
-      }),
-    ),
+      expect(a).toEqual([99])
+      expect(b).toEqual([99])
+    }),
   )
 
   it.live("subscribeAll stream sees InstanceDisposed on disposal", () =>
diff --git a/packages/opencode/test/fixture/fixture.ts b/packages/opencode/test/fixture/fixture.ts
index 23dd61d880..9beb1b3c60 100644
--- a/packages/opencode/test/fixture/fixture.ts
+++ b/packages/opencode/test/fixture/fixture.ts
@@ -5,10 +5,12 @@ import path from "path"
 import { Effect, Context } from "effect"
 import type * as PlatformError from "effect/PlatformError"
 import type * as Scope from "effect/Scope"
+import { CrossSpawnSpawner } from "@opencode-ai/core/cross-spawn-spawner"
 import { ChildProcess, ChildProcessSpawner } from "effect/unstable/process"
 import type { Config } from "@/config/config"
 import { InstanceRef } from "../../src/effect/instance-ref"
 import { Instance } from "../../src/project/instance"
+import { InstanceStore } from "../../src/project/instance-store"
 import { TestLLMServer } from "../lib/llm-server"
 
 // Re-export for test ergonomics. The implementation lives next to the runtime
@@ -160,6 +162,18 @@ export function provideTmpdirInstance<A, E, R>(
   })
 }
 
+export class TestInstance extends Context.Service<TestInstance, { readonly directory: string }>()("@test/Instance") {}
+
+export const withTmpdirInstance =
+  (options?: { git?: boolean; config?: Partial<Config.Info> }) =>
+  <A, E, R>(self: Effect.Effect<A, E, R>) =>
+    Effect.gen(function* () {
+      const directory = yield* tmpdirScoped(options)
+      return yield* InstanceStore.Service.use((store) =>
+        store.provide({ directory }, self.pipe(Effect.provideService(TestInstance, { directory }))),
+      )
+    }).pipe(Effect.provide(InstanceStore.defaultLayer), Effect.provide(CrossSpawnSpawner.defaultLayer))
+
 export function provideTmpdirServer<A, E, R>(
   self: (input: { dir: string; llm: TestLLMServer["Service"] }) => Effect.Effect<A, E, R>,
   options?: { git?: boolean; config?: (url: string) => Partial<Config.Info> },
diff --git a/packages/opencode/test/lib/effect.ts b/packages/opencode/test/lib/effect.ts
index 131ec5cc6b..66c865190e 100644
--- a/packages/opencode/test/lib/effect.ts
+++ b/packages/opencode/test/lib/effect.ts
@@ -3,8 +3,11 @@ import { Cause, Effect, Exit, Layer } from "effect"
 import type * as Scope from "effect/Scope"
 import * as TestClock from "effect/testing/TestClock"
 import * as TestConsole from "effect/testing/TestConsole"
+import type { Config } from "@/config/config"
+import { TestInstance, withTmpdirInstance } from "../fixture/fixture"
 
 type Body<A, E, R> = Effect.Effect<A, E, R> | (() => Effect.Effect<A, E, R>)
+type InstanceOptions = { git?: boolean; config?: Partial<Config.Info> }
 
 const body = <A, E, R>(value: Body<A, E, R>) => Effect.suspend(() => (typeof value === "function" ? value() : value))
 
@@ -38,7 +41,28 @@ const make = <R, E>(testLayer: Layer.Layer<R, E>, liveLayer: Layer.Layer<R, E>)
   live.skip = <A, E2>(name: string, value: Body<A, E2, R | Scope.Scope>, opts?: number | TestOptions) =>
     test.skip(name, () => run(value, liveLayer), opts)
 
-  return { effect, live }
+  const instance = <A, E2>(
+    name: string,
+    value: Body<A, E2, R | TestInstance | Scope.Scope>,
+    instanceOptions?: InstanceOptions,
+    opts?: number | TestOptions,
+  ) => test(name, () => run(body(value).pipe(withTmpdirInstance(instanceOptions)), liveLayer), opts)
+
+  instance.only = <A, E2>(
+    name: string,
+    value: Body<A, E2, R | TestInstance | Scope.Scope>,
+    instanceOptions?: InstanceOptions,
+    opts?: number | TestOptions,
+  ) => test.only(name, () => run(body(value).pipe(withTmpdirInstance(instanceOptions)), liveLayer), opts)
+
+  instance.skip = <A, E2>(
+    name: string,
+    value: Body<A, E2, R | TestInstance | Scope.Scope>,
+    instanceOptions?: InstanceOptions,
+    opts?: number | TestOptions,
+  ) => test.skip(name, () => run(body(value).pipe(withTmpdirInstance(instanceOptions)), liveLayer), opts)
+
+  return { effect, live, instance }
 }
 
 // Test environment with TestClock and TestConsole