diff --git a/packages/opencode/src/session/compaction.ts b/packages/opencode/src/session/compaction.ts
index c4934b625f..de0f8d0788 100644
--- a/packages/opencode/src/session/compaction.ts
+++ b/packages/opencode/src/session/compaction.ts
@@ -9,14 +9,12 @@ import z from "zod"
 import { Token } from "../util/token"
 import { Log } from "../util/log"
 import { SessionProcessor } from "./processor"
-import { fn } from "@/util/fn"
 import { Agent } from "@/agent/agent"
 import { Plugin } from "@/plugin"
 import { Config } from "@/config/config"
 import { NotFoundError } from "@/storage/db"
 import { ModelID, ProviderID } from "@/provider/schema"
 import { Effect, Layer, Context } from "effect"
-import { makeRuntime } from "@/effect/run-service"
 import { InstanceState } from "@/effect/instance-state"
 import { isOverflow as overflow } from "./overflow"
 
@@ -408,25 +406,4 @@ When constructing the summary, try to stick to this template:
       Layer.provide(Config.defaultLayer),
     ),
   )
-
-  const { runPromise } = makeRuntime(Service, defaultLayer)
-
-  export async function isOverflow(input: { tokens: MessageV2.Assistant["tokens"]; model: Provider.Model }) {
-    return runPromise((svc) => svc.isOverflow(input))
-  }
-
-  export async function prune(input: { sessionID: SessionID }) {
-    return runPromise((svc) => svc.prune(input))
-  }
-
-  export const create = fn(
-    z.object({
-      sessionID: SessionID.zod,
-      agent: z.string(),
-      model: z.object({ providerID: ProviderID.zod, modelID: ModelID.zod }),
-      auto: z.boolean(),
-      overflow: z.boolean().optional(),
-    }),
-    (input) => runPromise((svc) => svc.create(input)),
-  )
 }
diff --git a/packages/opencode/test/session/compaction.test.ts b/packages/opencode/test/session/compaction.test.ts
index 206f417d11..42511d2118 100644
--- a/packages/opencode/test/session/compaction.test.ts
+++ b/packages/opencode/test/session/compaction.test.ts
@@ -13,7 +13,7 @@ import { Instance } from "../../src/project/instance"
 import { Log } from "../../src/util/log"
 import { Permission } from "../../src/permission"
 import { Plugin } from "../../src/plugin"
-import { tmpdir } from "../fixture/fixture"
+import { provideTmpdirInstance, tmpdir } from "../fixture/fixture"
 import { Session } from "../../src/session"
 import { MessageV2 } from "../../src/session/message-v2"
 import { MessageID, PartID, SessionID } from "../../src/session/schema"
@@ -24,6 +24,8 @@ import type { Provider } from "../../src/provider/provider"
 import * as SessionProcessorModule from "../../src/session/processor"
 import { Snapshot } from "../../src/snapshot"
 import { ProviderTest } from "../fake/provider"
+import { testEffect } from "../lib/effect"
+import * as CrossSpawnSpawner from "../../src/effect/cross-spawn-spawner"
 
 Log.init({ print: false })
 
@@ -179,6 +181,23 @@ function runtime(result: "continue" | "compact", plugin = Plugin.defaultLayer, p
   )
 }
 
+const deps = Layer.mergeAll(
+  ProviderTest.fake().layer,
+  layer("continue"),
+  Agent.defaultLayer,
+  Plugin.defaultLayer,
+  Bus.layer,
+  Config.defaultLayer,
+)
+
+const env = Layer.mergeAll(
+  Session.defaultLayer,
+  CrossSpawnSpawner.defaultLayer,
+  SessionCompaction.layer.pipe(Layer.provide(Session.defaultLayer), Layer.provideMerge(deps)),
+)
+
+const it = testEffect(env)
+
 function llm() {
   const queue: Array<
     Stream.Stream<LLM.Event, unknown> | ((input: LLM.StreamInput) => Stream.Stream<LLM.Event, unknown>)
@@ -259,77 +278,77 @@ function autocontinue(enabled: boolean) {
 }
 
 describe("session.compaction.isOverflow", () => {
-  test("returns true when token count exceeds usable context", async () => {
-    await using tmp = await tmpdir()
-    await Instance.provide({
-      directory: tmp.path,
-      fn: async () => {
+  it.live(
+    "returns true when token count exceeds usable context",
+    provideTmpdirInstance(() =>
+      Effect.gen(function* () {
+        const compact = yield* SessionCompaction.Service
         const model = createModel({ context: 100_000, output: 32_000 })
         const tokens = { input: 75_000, output: 5_000, reasoning: 0, cache: { read: 0, write: 0 } }
-        expect(await SessionCompaction.isOverflow({ tokens, model })).toBe(true)
-      },
-    })
-  })
+        expect(yield* compact.isOverflow({ tokens, model })).toBe(true)
+      }),
+    ),
+  )
 
-  test("returns false when token count within usable context", async () => {
-    await using tmp = await tmpdir()
-    await Instance.provide({
-      directory: tmp.path,
-      fn: async () => {
+  it.live(
+    "returns false when token count within usable context",
+    provideTmpdirInstance(() =>
+      Effect.gen(function* () {
+        const compact = yield* SessionCompaction.Service
         const model = createModel({ context: 200_000, output: 32_000 })
         const tokens = { input: 100_000, output: 10_000, reasoning: 0, cache: { read: 0, write: 0 } }
-        expect(await SessionCompaction.isOverflow({ tokens, model })).toBe(false)
-      },
-    })
-  })
+        expect(yield* compact.isOverflow({ tokens, model })).toBe(false)
+      }),
+    ),
+  )
 
-  test("includes cache.read in token count", async () => {
-    await using tmp = await tmpdir()
-    await Instance.provide({
-      directory: tmp.path,
-      fn: async () => {
+  it.live(
+    "includes cache.read in token count",
+    provideTmpdirInstance(() =>
+      Effect.gen(function* () {
+        const compact = yield* SessionCompaction.Service
         const model = createModel({ context: 100_000, output: 32_000 })
         const tokens = { input: 60_000, output: 10_000, reasoning: 0, cache: { read: 10_000, write: 0 } }
-        expect(await SessionCompaction.isOverflow({ tokens, model })).toBe(true)
-      },
-    })
-  })
+        expect(yield* compact.isOverflow({ tokens, model })).toBe(true)
+      }),
+    ),
+  )
 
-  test("respects input limit for input caps", async () => {
-    await using tmp = await tmpdir()
-    await Instance.provide({
-      directory: tmp.path,
-      fn: async () => {
+  it.live(
+    "respects input limit for input caps",
+    provideTmpdirInstance(() =>
+      Effect.gen(function* () {
+        const compact = yield* SessionCompaction.Service
         const model = createModel({ context: 400_000, input: 272_000, output: 128_000 })
         const tokens = { input: 271_000, output: 1_000, reasoning: 0, cache: { read: 2_000, write: 0 } }
-        expect(await SessionCompaction.isOverflow({ tokens, model })).toBe(true)
-      },
-    })
-  })
+        expect(yield* compact.isOverflow({ tokens, model })).toBe(true)
+      }),
+    ),
+  )
 
-  test("returns false when input/output are within input caps", async () => {
-    await using tmp = await tmpdir()
-    await Instance.provide({
-      directory: tmp.path,
-      fn: async () => {
+  it.live(
+    "returns false when input/output are within input caps",
+    provideTmpdirInstance(() =>
+      Effect.gen(function* () {
+        const compact = yield* SessionCompaction.Service
         const model = createModel({ context: 400_000, input: 272_000, output: 128_000 })
         const tokens = { input: 200_000, output: 20_000, reasoning: 0, cache: { read: 10_000, write: 0 } }
-        expect(await SessionCompaction.isOverflow({ tokens, model })).toBe(false)
-      },
-    })
-  })
+        expect(yield* compact.isOverflow({ tokens, model })).toBe(false)
+      }),
+    ),
+  )
 
-  test("returns false when output within limit with input caps", async () => {
-    await using tmp = await tmpdir()
-    await Instance.provide({
-      directory: tmp.path,
-      fn: async () => {
+  it.live(
+    "returns false when output within limit with input caps",
+    provideTmpdirInstance(() =>
+      Effect.gen(function* () {
+        const compact = yield* SessionCompaction.Service
         const model = createModel({ context: 200_000, input: 120_000, output: 10_000 })
         const tokens = { input: 50_000, output: 9_999, reasoning: 0, cache: { read: 0, write: 0 } }
-        expect(await SessionCompaction.isOverflow({ tokens, model })).toBe(false)
-      },
-    })
-  })
+        expect(yield* compact.isOverflow({ tokens, model })).toBe(false)
+      }),
+    ),
+  )
 
   // ─── Bug reproduction tests ───────────────────────────────────────────
   // These tests demonstrate that when limit.input is set, isOverflow()
@@ -343,11 +362,11 @@ describe("session.compaction.isOverflow", () => {
   // Related issues: #10634, #8089, #11086, #12621
   // Open PRs: #6875, #12924
 
-  test("BUG: no headroom when limit.input is set — compaction should trigger near boundary but does not", async () => {
-    await using tmp = await tmpdir()
-    await Instance.provide({
-      directory: tmp.path,
-      fn: async () => {
+  it.live(
+    "BUG: no headroom when limit.input is set — compaction should trigger near boundary but does not",
+    provideTmpdirInstance(() =>
+      Effect.gen(function* () {
+        const compact = yield* SessionCompaction.Service
         // Simulate Claude with prompt caching: input limit = 200K, output limit = 32K
         const model = createModel({ context: 200_000, input: 200_000, output: 32_000 })
 
@@ -364,16 +383,16 @@ describe("session.compaction.isOverflow", () => {
 
         // With 198K used and only 2K headroom, the next turn will overflow.
         // Compaction MUST trigger here.
-        expect(await SessionCompaction.isOverflow({ tokens, model })).toBe(true)
-      },
-    })
-  })
+        expect(yield* compact.isOverflow({ tokens, model })).toBe(true)
+      }),
+    ),
+  )
 
-  test("BUG: without limit.input, same token count correctly triggers compaction", async () => {
-    await using tmp = await tmpdir()
-    await Instance.provide({
-      directory: tmp.path,
-      fn: async () => {
+  it.live(
+    "BUG: without limit.input, same token count correctly triggers compaction",
+    provideTmpdirInstance(() =>
+      Effect.gen(function* () {
+        const compact = yield* SessionCompaction.Service
         // Same model but without limit.input — uses context - output instead
         const model = createModel({ context: 200_000, output: 32_000 })
 
@@ -383,17 +402,17 @@ describe("session.compaction.isOverflow", () => {
         // usable = context - output = 200K - 32K = 168K
         // 198K > 168K = true → compaction correctly triggered
 
-        const result = await SessionCompaction.isOverflow({ tokens, model })
+        const result = yield* compact.isOverflow({ tokens, model })
         expect(result).toBe(true) // ← Correct: headroom is reserved
-      },
-    })
-  })
+      }),
+    ),
+  )
 
-  test("BUG: asymmetry — limit.input model allows 30K more usage before compaction than equivalent model without it", async () => {
-    await using tmp = await tmpdir()
-    await Instance.provide({
-      directory: tmp.path,
-      fn: async () => {
+  it.live(
+    "BUG: asymmetry — limit.input model allows 30K more usage before compaction than equivalent model without it",
+    provideTmpdirInstance(() =>
+      Effect.gen(function* () {
+        const compact = yield* SessionCompaction.Service
         // Two models with identical context/output limits, differing only in limit.input
         const withInputLimit = createModel({ context: 200_000, input: 200_000, output: 32_000 })
         const withoutInputLimit = createModel({ context: 200_000, output: 32_000 })
@@ -401,67 +420,66 @@ describe("session.compaction.isOverflow", () => {
         // 170K total tokens — well above context-output (168K) but below input limit (200K)
         const tokens = { input: 166_000, output: 10_000, reasoning: 0, cache: { read: 5_000, write: 0 } }
 
-        const withLimit = await SessionCompaction.isOverflow({ tokens, model: withInputLimit })
-        const withoutLimit = await SessionCompaction.isOverflow({ tokens, model: withoutInputLimit })
+        const withLimit = yield* compact.isOverflow({ tokens, model: withInputLimit })
+        const withoutLimit = yield* compact.isOverflow({ tokens, model: withoutInputLimit })
 
         // Both models have identical real capacity — they should agree:
         expect(withLimit).toBe(true) // should compact (170K leaves no room for 32K output)
         expect(withoutLimit).toBe(true) // correctly compacts (170K > 168K)
-      },
-    })
-  })
+      }),
+    ),
+  )
 
-  test("returns false when model context limit is 0", async () => {
-    await using tmp = await tmpdir()
-    await Instance.provide({
-      directory: tmp.path,
-      fn: async () => {
+  it.live(
+    "returns false when model context limit is 0",
+    provideTmpdirInstance(() =>
+      Effect.gen(function* () {
+        const compact = yield* SessionCompaction.Service
         const model = createModel({ context: 0, output: 32_000 })
         const tokens = { input: 100_000, output: 10_000, reasoning: 0, cache: { read: 0, write: 0 } }
-        expect(await SessionCompaction.isOverflow({ tokens, model })).toBe(false)
-      },
-    })
-  })
+        expect(yield* compact.isOverflow({ tokens, model })).toBe(false)
+      }),
+    ),
+  )
 
-  test("returns false when compaction.auto is disabled", async () => {
-    await using tmp = await tmpdir({
-      init: async (dir) => {
-        await Bun.write(
-          path.join(dir, "opencode.json"),
-          JSON.stringify({
-            compaction: { auto: false },
-          }),
-        )
+  it.live(
+    "returns false when compaction.auto is disabled",
+    provideTmpdirInstance(
+      () =>
+        Effect.gen(function* () {
+          const compact = yield* SessionCompaction.Service
+          const model = createModel({ context: 100_000, output: 32_000 })
+          const tokens = { input: 75_000, output: 5_000, reasoning: 0, cache: { read: 0, write: 0 } }
+          expect(yield* compact.isOverflow({ tokens, model })).toBe(false)
+        }),
+      {
+        config: {
+          compaction: { auto: false },
+        },
       },
-    })
-    await Instance.provide({
-      directory: tmp.path,
-      fn: async () => {
-        const model = createModel({ context: 100_000, output: 32_000 })
-        const tokens = { input: 75_000, output: 5_000, reasoning: 0, cache: { read: 0, write: 0 } }
-        expect(await SessionCompaction.isOverflow({ tokens, model })).toBe(false)
-      },
-    })
-  })
+    ),
+  )
 })
 
 describe("session.compaction.create", () => {
-  test("creates a compaction user message and part", async () => {
-    await using tmp = await tmpdir()
-    await Instance.provide({
-      directory: tmp.path,
-      fn: async () => {
-        const session = await Session.create({})
+  it.live(
+    "creates a compaction user message and part",
+    provideTmpdirInstance(() =>
+      Effect.gen(function* () {
+        const compact = yield* SessionCompaction.Service
+        const session = yield* Session.Service
 
-        await SessionCompaction.create({
-          sessionID: session.id,
+        const info = yield* session.create({})
+
+        yield* compact.create({
+          sessionID: info.id,
           agent: "build",
           model: ref,
           auto: true,
           overflow: true,
         })
 
-        const msgs = await Session.messages({ sessionID: session.id })
+        const msgs = yield* session.messages({ sessionID: info.id })
         expect(msgs).toHaveLength(1)
         expect(msgs[0].info.role).toBe("user")
         expect(msgs[0].parts).toHaveLength(1)
@@ -470,60 +488,190 @@ describe("session.compaction.create", () => {
           auto: true,
           overflow: true,
         })
-      },
-    })
-  })
+      }),
+    ),
+  )
 })
 
 describe("session.compaction.prune", () => {
-  test("compacts old completed tool output", async () => {
-    await using tmp = await tmpdir()
-    await Instance.provide({
-      directory: tmp.path,
-      fn: async () => {
-        const session = await Session.create({})
-        const a = await user(session.id, "first")
-        const b = await assistant(session.id, a.id, tmp.path)
-        await tool(session.id, b.id, "bash", "x".repeat(200_000))
-        await user(session.id, "second")
-        await user(session.id, "third")
+  it.live(
+    "compacts old completed tool output",
+    provideTmpdirInstance((dir) =>
+      Effect.gen(function* () {
+        const compact = yield* SessionCompaction.Service
+        const session = yield* Session.Service
+        const info = yield* session.create({})
+        const a = yield* session.updateMessage({
+          id: MessageID.ascending(),
+          role: "user",
+          sessionID: info.id,
+          agent: "build",
+          model: ref,
+          time: { created: Date.now() },
+        })
+        yield* session.updatePart({
+          id: PartID.ascending(),
+          messageID: a.id,
+          sessionID: info.id,
+          type: "text",
+          text: "first",
+        })
+        const b: MessageV2.Assistant = {
+          id: MessageID.ascending(),
+          role: "assistant",
+          sessionID: info.id,
+          mode: "build",
+          agent: "build",
+          path: { cwd: dir, root: dir },
+          cost: 0,
+          tokens: {
+            output: 0,
+            input: 0,
+            reasoning: 0,
+            cache: { read: 0, write: 0 },
+          },
+          modelID: ref.modelID,
+          providerID: ref.providerID,
+          parentID: a.id,
+          time: { created: Date.now() },
+          finish: "end_turn",
+        }
+        yield* session.updateMessage(b)
+        yield* session.updatePart({
+          id: PartID.ascending(),
+          messageID: b.id,
+          sessionID: info.id,
+          type: "tool",
+          callID: crypto.randomUUID(),
+          tool: "bash",
+          state: {
+            status: "completed",
+            input: {},
+            output: "x".repeat(200_000),
+            title: "done",
+            metadata: {},
+            time: { start: Date.now(), end: Date.now() },
+          },
+        })
+        for (const text of ["second", "third"]) {
+          const msg = yield* session.updateMessage({
+            id: MessageID.ascending(),
+            role: "user",
+            sessionID: info.id,
+            agent: "build",
+            model: ref,
+            time: { created: Date.now() },
+          })
+          yield* session.updatePart({
+            id: PartID.ascending(),
+            messageID: msg.id,
+            sessionID: info.id,
+            type: "text",
+            text,
+          })
+        }
 
-        await SessionCompaction.prune({ sessionID: session.id })
+        yield* compact.prune({ sessionID: info.id })
 
-        const msgs = await Session.messages({ sessionID: session.id })
+        const msgs = yield* session.messages({ sessionID: info.id })
         const part = msgs.flatMap((msg) => msg.parts).find((part) => part.type === "tool")
         expect(part?.type).toBe("tool")
         expect(part?.state.status).toBe("completed")
         if (part?.type === "tool" && part.state.status === "completed") {
           expect(part.state.time.compacted).toBeNumber()
         }
-      },
-    })
-  })
+      }),
+    ),
+  )
 
-  test("skips protected skill tool output", async () => {
-    await using tmp = await tmpdir()
-    await Instance.provide({
-      directory: tmp.path,
-      fn: async () => {
-        const session = await Session.create({})
-        const a = await user(session.id, "first")
-        const b = await assistant(session.id, a.id, tmp.path)
-        await tool(session.id, b.id, "skill", "x".repeat(200_000))
-        await user(session.id, "second")
-        await user(session.id, "third")
+  it.live(
+    "skips protected skill tool output",
+    provideTmpdirInstance((dir) =>
+      Effect.gen(function* () {
+        const compact = yield* SessionCompaction.Service
+        const session = yield* Session.Service
+        const info = yield* session.create({})
+        const a = yield* session.updateMessage({
+          id: MessageID.ascending(),
+          role: "user",
+          sessionID: info.id,
+          agent: "build",
+          model: ref,
+          time: { created: Date.now() },
+        })
+        yield* session.updatePart({
+          id: PartID.ascending(),
+          messageID: a.id,
+          sessionID: info.id,
+          type: "text",
+          text: "first",
+        })
+        const b: MessageV2.Assistant = {
+          id: MessageID.ascending(),
+          role: "assistant",
+          sessionID: info.id,
+          mode: "build",
+          agent: "build",
+          path: { cwd: dir, root: dir },
+          cost: 0,
+          tokens: {
+            output: 0,
+            input: 0,
+            reasoning: 0,
+            cache: { read: 0, write: 0 },
+          },
+          modelID: ref.modelID,
+          providerID: ref.providerID,
+          parentID: a.id,
+          time: { created: Date.now() },
+          finish: "end_turn",
+        }
+        yield* session.updateMessage(b)
+        yield* session.updatePart({
+          id: PartID.ascending(),
+          messageID: b.id,
+          sessionID: info.id,
+          type: "tool",
+          callID: crypto.randomUUID(),
+          tool: "skill",
+          state: {
+            status: "completed",
+            input: {},
+            output: "x".repeat(200_000),
+            title: "done",
+            metadata: {},
+            time: { start: Date.now(), end: Date.now() },
+          },
+        })
+        for (const text of ["second", "third"]) {
+          const msg = yield* session.updateMessage({
+            id: MessageID.ascending(),
+            role: "user",
+            sessionID: info.id,
+            agent: "build",
+            model: ref,
+            time: { created: Date.now() },
+          })
+          yield* session.updatePart({
+            id: PartID.ascending(),
+            messageID: msg.id,
+            sessionID: info.id,
+            type: "text",
+            text,
+          })
+        }
 
-        await SessionCompaction.prune({ sessionID: session.id })
+        yield* compact.prune({ sessionID: info.id })
 
-        const msgs = await Session.messages({ sessionID: session.id })
+        const msgs = yield* session.messages({ sessionID: info.id })
         const part = msgs.flatMap((msg) => msg.parts).find((part) => part.type === "tool")
         expect(part?.type).toBe("tool")
         if (part?.type === "tool" && part.state.status === "completed") {
           expect(part.state.time.compacted).toBeUndefined()
         }
-      },
-    })
-  })
+      }),
+    ),
+  )
 })
 
 describe("session.compaction.process", () => {