diff --git a/packages/opencode/src/control-plane/workspace.ts b/packages/opencode/src/control-plane/workspace.ts
index fe8046ba9c..7f9d078bb7 100644
--- a/packages/opencode/src/control-plane/workspace.ts
+++ b/packages/opencode/src/control-plane/workspace.ts
@@ -169,6 +169,7 @@ export const layer = Layer.effect(
     const auth = yield* Auth.Service
     const session = yield* Session.Service
     const http = yield* HttpClient.HttpClient
+    const sync = yield* SyncEvent.Service
     const connections = new Map<WorkspaceID, ConnectionStatus>()
     const syncFibers = yield* FiberMap.make<WorkspaceID, void, SyncLoopError>()
 
@@ -307,25 +308,30 @@ export const layer = Layer.effect(
         events: events.length,
       })
 
-      yield* Effect.sync(() =>
-        WorkspaceContext.provide({
+      yield* Effect.promise(async () => {
+        await WorkspaceContext.provide({
           workspaceID: space.id,
-          fn: () => {
-            for (const event of events) {
-              SyncEvent.replay(
-                {
-                  id: event.id,
-                  aggregateID: event.aggregate_id,
-                  seq: event.seq,
-                  type: event.type,
-                  data: event.data,
-                },
-                { publish: true },
-              )
-            }
+          async fn() {
+            await Effect.runPromise(
+              Effect.forEach(
+                events,
+                (event) =>
+                  sync.replay(
+                    {
+                      id: event.id,
+                      aggregateID: event.aggregate_id,
+                      seq: event.seq,
+                      type: event.type,
+                      data: event.data,
+                    },
+                    { publish: true },
+                  ),
+                { discard: true },
+              ),
+            )
           },
-        }),
-      )
+        })
+      })
     })
 
     const syncWorkspaceLoop = Effect.fn("Workspace.syncWorkspaceLoop")(function* (space: Info) {
@@ -361,16 +367,28 @@ export const layer = Layer.effect(
           setStatus(space.id, "connected")
 
           yield* parseSSE(stream, (evt) =>
-            Effect.sync(() => {
+            Effect.gen(function* () {
+              if (!evt || typeof evt !== "object" || !("payload" in evt)) return
+              const payload = evt.payload as { type?: string; syncEvent?: SyncEvent.SerializedEvent }
+              if (payload.type === "server.heartbeat") return
+
+              if (payload.type === "sync" && payload.syncEvent) {
+                const failed = yield* sync.replay(payload.syncEvent).pipe(
+                  Effect.as(false),
+                  Effect.catchCause((error) =>
+                    Effect.sync(() => {
+                      log.info("failed to replay global event", {
+                        workspaceID: space.id,
+                        error,
+                      })
+                      return true
+                    }),
+                  ),
+                )
+                if (failed) return
+              }
+
               try {
-                if (!evt || typeof evt !== "object" || !("payload" in evt)) return
-                const payload = evt.payload as { type?: string; syncEvent?: SyncEvent.SerializedEvent }
-                if (payload.type === "server.heartbeat") return
-
-                if (payload.type === "sync" && payload.syncEvent) {
-                  SyncEvent.replay(payload.syncEvent)
-                }
-
                 const event = evt as { directory?: string; project?: string; payload: unknown }
                 GlobalBus.emit("event", {
                   directory: event.directory,
@@ -378,10 +396,10 @@ export const layer = Layer.effect(
                   workspace: space.id,
                   payload: event.payload,
                 })
-              } catch (err) {
+              } catch (error) {
                 log.info("failed to replay global event", {
                   workspaceID: space.id,
-                  error: err,
+                  error,
                 })
               }
             }),
@@ -516,14 +534,12 @@ export const layer = Layer.effect(
         const adaptor = getAdaptor(space.projectID, space.type)
         const target = yield* Effect.promise(() => Promise.resolve(adaptor.target(space)))
 
-        yield* Effect.sync(() =>
-          SyncEvent.run(Session.Event.Updated, {
-            sessionID: input.sessionID,
-            info: {
-              workspaceID: input.workspaceID,
-            },
-          }),
-        )
+        yield* sync.run(Session.Event.Updated, {
+          sessionID: input.sessionID,
+          info: {
+            workspaceID: input.workspaceID,
+          },
+        })
 
         const rows = yield* db((db) =>
           db
@@ -593,7 +609,7 @@ export const layer = Layer.effect(
           })
 
           if (target.type === "local") {
-            SyncEvent.replayAll(events)
+            yield* sync.replayAll(events)
             log.info("session restore batch replayed locally", {
               workspaceID: input.workspaceID,
               sessionID: input.sessionID,
@@ -812,6 +828,7 @@ export const layer = Layer.effect(
 export const defaultLayer = layer.pipe(
   Layer.provide(Auth.defaultLayer),
   Layer.provide(Session.defaultLayer),
+  Layer.provide(SyncEvent.defaultLayer),
   Layer.provide(FetchHttpClient.layer),
 )
 
diff --git a/packages/opencode/src/effect/app-runtime.ts b/packages/opencode/src/effect/app-runtime.ts
index 84be170688..06969ff9d1 100644
--- a/packages/opencode/src/effect/app-runtime.ts
+++ b/packages/opencode/src/effect/app-runtime.ts
@@ -47,6 +47,7 @@ import { Pty } from "@/pty"
 import { Installation } from "@/installation"
 import { ShareNext } from "@/share/share-next"
 import { SessionShare } from "@/share/session"
+import { SyncEvent } from "@/sync"
 import { Npm } from "@opencode-ai/core/npm"
 import { memoMap } from "@opencode-ai/core/effect/memo-map"
 
@@ -97,6 +98,7 @@ export const AppLayer = Layer.mergeAll(
   Installation.defaultLayer,
   ShareNext.defaultLayer,
   SessionShare.defaultLayer,
+  SyncEvent.defaultLayer,
 ).pipe(Layer.provideMerge(Observability.layer))
 
 const rt = ManagedRuntime.make(AppLayer, { memoMap })
diff --git a/packages/opencode/src/server/routes/instance/httpapi/handlers/sync.ts b/packages/opencode/src/server/routes/instance/httpapi/handlers/sync.ts
index fbe1249939..f4a2f315cd 100644
--- a/packages/opencode/src/server/routes/instance/httpapi/handlers/sync.ts
+++ b/packages/opencode/src/server/routes/instance/httpapi/handlers/sync.ts
@@ -21,6 +21,7 @@ export const syncHandlers = HttpApiBuilder.group(InstanceHttpApi, "sync", (handl
   Effect.gen(function* () {
     const workspace = yield* Workspace.Service
     const scope = yield* Scope.Scope
+    const sync = yield* SyncEvent.Service
 
     const start = Effect.fn("SyncHttpApi.start")(function* () {
       yield* workspace
@@ -45,7 +46,7 @@ export const syncHandlers = HttpApiBuilder.group(InstanceHttpApi, "sync", (handl
         last: events.at(-1)?.seq,
         directory: ctx.payload.directory,
       })
-      SyncEvent.replayAll(events)
+      yield* sync.replayAll(events)
       log.info("sync replay complete", {
         sessionID: source,
         events: events.length,
diff --git a/packages/opencode/src/server/routes/instance/httpapi/server.ts b/packages/opencode/src/server/routes/instance/httpapi/server.ts
index 62fa18743a..f53ddb3ec5 100644
--- a/packages/opencode/src/server/routes/instance/httpapi/server.ts
+++ b/packages/opencode/src/server/routes/instance/httpapi/server.ts
@@ -31,6 +31,7 @@ import { SessionSummary } from "@/session/summary"
 import { Todo } from "@/session/todo"
 import { SessionShare } from "@/share/session"
 import { Skill } from "@/skill"
+import { SyncEvent } from "@/sync"
 import { ToolRegistry } from "@/tool/registry"
 import { lazy } from "@/util/lazy"
 import { Vcs } from "@/project/vcs"
@@ -147,6 +148,7 @@ export const routes = Layer.mergeAll(rootApiRoutes, instanceRoutes).pipe(
     SessionRunState.defaultLayer,
     SessionStatus.defaultLayer,
     SessionSummary.defaultLayer,
+    SyncEvent.defaultLayer,
     Skill.defaultLayer,
     Todo.defaultLayer,
     ToolRegistry.defaultLayer,
diff --git a/packages/opencode/src/server/routes/instance/sync.ts b/packages/opencode/src/server/routes/instance/sync.ts
index bb816ecc42..b7bf413d4e 100644
--- a/packages/opencode/src/server/routes/instance/sync.ts
+++ b/packages/opencode/src/server/routes/instance/sync.ts
@@ -94,7 +94,7 @@ export const SyncRoutes = lazy(() =>
           last: events.at(-1)?.seq,
           directory: body.directory,
         })
-        SyncEvent.replayAll(events)
+        await AppRuntime.runPromise(SyncEvent.use.replayAll(events))
 
         log.info("sync replay complete", {
           sessionID: source,
diff --git a/packages/opencode/src/session/revert.ts b/packages/opencode/src/session/revert.ts
index da9952ccb2..58d69a2040 100644
--- a/packages/opencode/src/session/revert.ts
+++ b/packages/opencode/src/session/revert.ts
@@ -38,6 +38,7 @@ export const layer = Layer.effect(
     const bus = yield* Bus.Service
     const summary = yield* SessionSummary.Service
     const state = yield* SessionRunState.Service
+    const sync = yield* SyncEvent.Service
 
     const revert = Effect.fn("SessionRevert.revert")(function* (input: RevertInput) {
       yield* state.assertNotBusy(input.sessionID)
@@ -121,7 +122,7 @@ export const layer = Layer.effect(
         remove.push(msg)
       }
       for (const msg of remove) {
-        SyncEvent.run(MessageV2.Event.Removed, {
+        yield* sync.run(MessageV2.Event.Removed, {
           sessionID,
           messageID: msg.info.id,
         })
@@ -133,7 +134,7 @@ export const layer = Layer.effect(
           const removeParts = target.parts.slice(idx)
           target.parts = target.parts.slice(0, idx)
           for (const part of removeParts) {
-            SyncEvent.run(MessageV2.Event.PartRemoved, {
+            yield* sync.run(MessageV2.Event.PartRemoved, {
               sessionID,
               messageID: target.info.id,
               partID: part.id,
@@ -156,6 +157,7 @@ export const defaultLayer = Layer.suspend(() =>
     Layer.provide(Storage.defaultLayer),
     Layer.provide(Bus.layer),
     Layer.provide(SessionSummary.defaultLayer),
+    Layer.provide(SyncEvent.defaultLayer),
   ),
 )
 
diff --git a/packages/opencode/src/session/session.ts b/packages/opencode/src/session/session.ts
index 72c4d241eb..5534976e39 100644
--- a/packages/opencode/src/session/session.ts
+++ b/packages/opencode/src/session/session.ts
@@ -443,11 +443,12 @@ export type Patch = Types.DeepMutable<SyncEvent.Event<typeof Event.Updated>["dat
 const db = <T>(fn: (d: Parameters<typeof Database.use>[0] extends (trx: infer D) => any ? D : never) => T) =>
   Effect.sync(() => Database.use(fn))
 
-export const layer: Layer.Layer<Service, never, Bus.Service | Storage.Service> = Layer.effect(
+export const layer: Layer.Layer<Service, never, Bus.Service | Storage.Service | SyncEvent.Service> = Layer.effect(
   Service,
   Effect.gen(function* () {
     const bus = yield* Bus.Service
     const storage = yield* Storage.Service
+    const sync = yield* SyncEvent.Service
 
     const createNext = Effect.fn("Session.createNext")(function* (input: {
       id?: SessionID
@@ -477,7 +478,7 @@ export const layer: Layer.Layer<Service, never, Bus.Service | Storage.Service> =
       }
       log.info("created", result)
 
-      yield* Effect.sync(() => SyncEvent.run(Event.Created, { sessionID: result.id, info: result }))
+      yield* sync.run(Event.Created, { sessionID: result.id, info: result })
 
       if (!Flag.OPENCODE_EXPERIMENTAL_WORKSPACES) {
         // This only exist for backwards compatibility. We should not be
@@ -525,10 +526,8 @@ export const layer: Layer.Layer<Service, never, Bus.Service | Storage.Service> =
           Effect.catchCause(() => Effect.succeed(false)),
         )
 
-        yield* Effect.sync(() => {
-          SyncEvent.run(Event.Deleted, { sessionID, info: session }, { publish: hasInstance })
-          SyncEvent.remove(sessionID)
-        })
+        yield* sync.run(Event.Deleted, { sessionID, info: session }, { publish: hasInstance })
+        yield* sync.remove(sessionID)
       } catch (e) {
         log.error(e)
       }
@@ -536,19 +535,17 @@ export const layer: Layer.Layer<Service, never, Bus.Service | Storage.Service> =
 
     const updateMessage = <T extends MessageV2.Info>(msg: T): Effect.Effect<T> =>
       Effect.gen(function* () {
-        yield* Effect.sync(() => SyncEvent.run(MessageV2.Event.Updated, { sessionID: msg.sessionID, info: msg }))
+        yield* sync.run(MessageV2.Event.Updated, { sessionID: msg.sessionID, info: msg })
         return msg
       }).pipe(Effect.withSpan("Session.updateMessage"))
 
     const updatePart = <T extends MessageV2.Part>(part: T): Effect.Effect<T> =>
       Effect.gen(function* () {
-        yield* Effect.sync(() =>
-          SyncEvent.run(MessageV2.Event.PartUpdated, {
-            sessionID: part.sessionID,
-            part: structuredClone(part),
-            time: Date.now(),
-          }),
-        )
+        yield* sync.run(MessageV2.Event.PartUpdated, {
+          sessionID: part.sessionID,
+          part: structuredClone(part),
+          time: Date.now(),
+        })
         return part
       }).pipe(Effect.withSpan("Session.updatePart"))
 
@@ -635,8 +632,7 @@ export const layer: Layer.Layer<Service, never, Bus.Service | Storage.Service> =
       return session
     })
 
-    const patch = (sessionID: SessionID, info: Patch) =>
-      Effect.sync(() => SyncEvent.run(Event.Updated, { sessionID, info }))
+    const patch = (sessionID: SessionID, info: Patch) => sync.run(Event.Updated, { sessionID, info })
 
     const touch = Effect.fn("Session.touch")(function* (sessionID: SessionID) {
       yield* patch(sessionID, { time: { updated: Date.now() } })
@@ -693,12 +689,10 @@ export const layer: Layer.Layer<Service, never, Bus.Service | Storage.Service> =
       sessionID: SessionID
       messageID: MessageID
     }) {
-      yield* Effect.sync(() =>
-        SyncEvent.run(MessageV2.Event.Removed, {
-          sessionID: input.sessionID,
-          messageID: input.messageID,
-        }),
-      )
+      yield* sync.run(MessageV2.Event.Removed, {
+        sessionID: input.sessionID,
+        messageID: input.messageID,
+      })
       return input.messageID
     })
 
@@ -707,13 +701,11 @@ export const layer: Layer.Layer<Service, never, Bus.Service | Storage.Service> =
       messageID: MessageID
       partID: PartID
     }) {
-      yield* Effect.sync(() =>
-        SyncEvent.run(MessageV2.Event.PartRemoved, {
-          sessionID: input.sessionID,
-          messageID: input.messageID,
-          partID: input.partID,
-        }),
-      )
+      yield* sync.run(MessageV2.Event.PartRemoved, {
+        sessionID: input.sessionID,
+        messageID: input.messageID,
+        partID: input.partID,
+      })
       return input.partID
     })
 
@@ -764,7 +756,11 @@ export const layer: Layer.Layer<Service, never, Bus.Service | Storage.Service> =
   }),
 )
 
-export const defaultLayer = layer.pipe(Layer.provide(Bus.layer), Layer.provide(Storage.defaultLayer))
+export const defaultLayer = layer.pipe(
+  Layer.provide(Bus.layer),
+  Layer.provide(Storage.defaultLayer),
+  Layer.provide(SyncEvent.defaultLayer),
+)
 
 export function* list(input?: {
   directory?: string
diff --git a/packages/opencode/src/share/session.ts b/packages/opencode/src/share/session.ts
index 99e46a0092..7e4de204ed 100644
--- a/packages/opencode/src/share/session.ts
+++ b/packages/opencode/src/share/session.ts
@@ -21,20 +21,19 @@ export const layer = Layer.effect(
     const session = yield* Session.Service
     const shareNext = yield* ShareNext.Service
     const scope = yield* Scope.Scope
+    const sync = yield* SyncEvent.Service
 
     const share = Effect.fn("SessionShare.share")(function* (sessionID: SessionID) {
       const conf = yield* cfg.get()
       if (conf.share === "disabled") throw new Error("Sharing is disabled in configuration")
       const result = yield* shareNext.create(sessionID)
-      yield* Effect.sync(() =>
-        SyncEvent.run(Session.Event.Updated, { sessionID, info: { share: { url: result.url } } }),
-      )
+      yield* sync.run(Session.Event.Updated, { sessionID, info: { share: { url: result.url } } })
       return result
     })
 
     const unshare = Effect.fn("SessionShare.unshare")(function* (sessionID: SessionID) {
       yield* shareNext.remove(sessionID)
-      yield* Effect.sync(() => SyncEvent.run(Session.Event.Updated, { sessionID, info: { share: { url: null } } }))
+      yield* sync.run(Session.Event.Updated, { sessionID, info: { share: { url: null } } })
     })
 
     const create = Effect.fn("SessionShare.create")(function* (input?: Session.CreateInput) {
@@ -54,6 +53,7 @@ export const defaultLayer = layer.pipe(
   Layer.provide(ShareNext.defaultLayer),
   Layer.provide(Session.defaultLayer),
   Layer.provide(Config.defaultLayer),
+  Layer.provide(SyncEvent.defaultLayer),
 )
 
 export * as SessionShare from "./session"
diff --git a/packages/opencode/src/sync/index.ts b/packages/opencode/src/sync/index.ts
index 67bc9b9e7c..ebf7543af1 100644
--- a/packages/opencode/src/sync/index.ts
+++ b/packages/opencode/src/sync/index.ts
@@ -9,9 +9,11 @@ import { EventSequenceTable, EventTable } from "./event.sql"
 import { WorkspaceContext } from "@/control-plane/workspace-context"
 import { EventID } from "./schema"
 import { Flag } from "@opencode-ai/core/flag/flag"
-import { Schema as EffectSchema } from "effect"
+import { Context, Effect, Layer, Schema as EffectSchema } from "effect"
 import { zodObject } from "@/util/effect-zod"
 import type { DeepMutable } from "@/util/schema"
+import { makeRuntime } from "@/effect/run-service"
+import { serviceUse } from "@/effect/service-use"
 
 // Keep `Event["data"]` mutable because projectors mutate the persisted shape
 // when writing to the database. Bus payloads (`Properties`) stay readonly —
@@ -46,6 +48,125 @@ export type SerializedEvent<Def extends Definition = Definition> = Event<Def> &
 type ProjectorFunc = (db: Database.TxOrDb, data: unknown) => void
 type ConvertEvent = (type: string, data: Event["data"]) => unknown | Promise<unknown>
 
+export interface Interface {
+  readonly run: <Def extends Definition>(
+    def: Def,
+    data: Event<Def>["data"],
+    options?: { publish?: boolean },
+  ) => Effect.Effect<void>
+  readonly replay: (event: SerializedEvent, options?: { publish: boolean }) => Effect.Effect<void>
+  readonly replayAll: (events: SerializedEvent[], options?: { publish: boolean }) => Effect.Effect<string | undefined>
+  readonly remove: (aggregateID: string) => Effect.Effect<void>
+}
+
+export class Service extends Context.Service<Service, Interface>()("@opencode/SyncEvent") {}
+
+export const layer = Layer.effect(Service)(
+  Effect.gen(function* () {
+    const replay: Interface["replay"] = Effect.fn("SyncEvent.replay")(function* (event, options) {
+      const def = registry.get(event.type)
+      if (!def) {
+        throw new Error(`Unknown event type: ${event.type}`)
+      }
+
+      const row = Database.use((db) =>
+        db
+          .select({ seq: EventSequenceTable.seq })
+          .from(EventSequenceTable)
+          .where(eq(EventSequenceTable.aggregate_id, event.aggregateID))
+          .get(),
+      )
+
+      const latest = row?.seq ?? -1
+      if (event.seq <= latest) return
+
+      const expected = latest + 1
+      if (event.seq !== expected) {
+        throw new Error(
+          `Sequence mismatch for aggregate "${event.aggregateID}": expected ${expected}, got ${event.seq}`,
+        )
+      }
+
+      process(def, event, { publish: !!options?.publish })
+    })
+
+    const replayAll: Interface["replayAll"] = Effect.fn("SyncEvent.replayAll")(function* (events, options) {
+      const source = events[0]?.aggregateID
+      if (!source) return undefined
+      if (events.some((item) => item.aggregateID !== source)) {
+        throw new Error("Replay events must belong to the same session")
+      }
+      const start = events[0].seq
+      for (const [i, item] of events.entries()) {
+        const seq = start + i
+        if (item.seq !== seq) {
+          throw new Error(`Replay sequence mismatch at index ${i}: expected ${seq}, got ${item.seq}`)
+        }
+      }
+      for (const item of events) {
+        yield* replay(item, options)
+      }
+      return source
+    })
+
+    const run: Interface["run"] = Effect.fn("SyncEvent.run")(function* (def, data, options) {
+      const agg = (data as Record<string, string>)[def.aggregate]
+      // This should never happen: we've enforced it via typescript in
+      // the definition
+      if (agg == null) {
+        throw new Error(`SyncEvent.run: "${def.aggregate}" required but not found: ${JSON.stringify(data)}`)
+      }
+
+      if (def.version !== versions.get(def.type)) {
+        throw new Error(`SyncEvent.run: running old versions of events is not allowed: ${def.type}`)
+      }
+
+      const { publish = true } = options || {}
+
+      // Note that this is an "immediate" transaction which is critical.
+      // We need to make sure we can safely read and write with nothing
+      // else changing the data from under us
+      Database.transaction(
+        (tx) => {
+          const id = EventID.ascending()
+          const row = tx
+            .select({ seq: EventSequenceTable.seq })
+            .from(EventSequenceTable)
+            .where(eq(EventSequenceTable.aggregate_id, agg))
+            .get()
+          const seq = row?.seq != null ? row.seq + 1 : 0
+
+          const event = { id, seq, aggregateID: agg, data }
+          process(def, event, { publish })
+        },
+        {
+          behavior: "immediate",
+        },
+      )
+    })
+
+    const remove: Interface["remove"] = Effect.fn("SyncEvent.remove")(function* (aggregateID) {
+      Database.transaction((tx) => {
+        tx.delete(EventSequenceTable).where(eq(EventSequenceTable.aggregate_id, aggregateID)).run()
+        tx.delete(EventTable).where(eq(EventTable.aggregate_id, aggregateID)).run()
+      })
+    })
+
+    return Service.of({
+      run,
+      replay,
+      replayAll,
+      remove,
+    })
+  }),
+)
+
+export const defaultLayer = layer
+
+export const use = serviceUse(Service)
+
+const runtime = makeRuntime(Service, defaultLayer)
+
 export const registry = new Map<string, Definition>()
 let projectors: Map<Definition, ProjectorFunc> | undefined
 const versions = new Map<string, number>()
@@ -186,92 +307,19 @@ function process<Def extends Definition>(def: Def, event: Event<Def>, options: {
 }
 
 export function replay(event: SerializedEvent, options?: { publish: boolean }) {
-  const def = registry.get(event.type)
-  if (!def) {
-    throw new Error(`Unknown event type: ${event.type}`)
-  }
-
-  const row = Database.use((db) =>
-    db
-      .select({ seq: EventSequenceTable.seq })
-      .from(EventSequenceTable)
-      .where(eq(EventSequenceTable.aggregate_id, event.aggregateID))
-      .get(),
-  )
-
-  const latest = row?.seq ?? -1
-  if (event.seq <= latest) {
-    return
-  }
-
-  const expected = latest + 1
-  if (event.seq !== expected) {
-    throw new Error(`Sequence mismatch for aggregate "${event.aggregateID}": expected ${expected}, got ${event.seq}`)
-  }
-
-  process(def, event, { publish: !!options?.publish })
+  return runtime.runSync((sync) => sync.replay(event, options))
 }
 
 export function replayAll(events: SerializedEvent[], options?: { publish: boolean }) {
-  const source = events[0]?.aggregateID
-  if (!source) return
-  if (events.some((item) => item.aggregateID !== source)) {
-    throw new Error("Replay events must belong to the same session")
-  }
-  const start = events[0].seq
-  for (const [i, item] of events.entries()) {
-    const seq = start + i
-    if (item.seq !== seq) {
-      throw new Error(`Replay sequence mismatch at index ${i}: expected ${seq}, got ${item.seq}`)
-    }
-  }
-  for (const item of events) {
-    replay(item, options)
-  }
-  return source
+  return runtime.runSync((sync) => sync.replayAll(events, options))
 }
 
 export function run<Def extends Definition>(def: Def, data: Event<Def>["data"], options?: { publish?: boolean }) {
-  const agg = (data as Record<string, string>)[def.aggregate]
-  // This should never happen: we've enforced it via typescript in
-  // the definition
-  if (agg == null) {
-    throw new Error(`SyncEvent.run: "${def.aggregate}" required but not found: ${JSON.stringify(data)}`)
-  }
-
-  if (def.version !== versions.get(def.type)) {
-    throw new Error(`SyncEvent.run: running old versions of events is not allowed: ${def.type}`)
-  }
-
-  const { publish = true } = options || {}
-
-  // Note that this is an "immediate" transaction which is critical.
-  // We need to make sure we can safely read and write with nothing
-  // else changing the data from under us
-  Database.transaction(
-    (tx) => {
-      const id = EventID.ascending()
-      const row = tx
-        .select({ seq: EventSequenceTable.seq })
-        .from(EventSequenceTable)
-        .where(eq(EventSequenceTable.aggregate_id, agg))
-        .get()
-      const seq = row?.seq != null ? row.seq + 1 : 0
-
-      const event = { id, seq, aggregateID: agg, data }
-      process(def, event, { publish })
-    },
-    {
-      behavior: "immediate",
-    },
-  )
+  return runtime.runSync((sync) => sync.run(def, data, options))
 }
 
 export function remove(aggregateID: string) {
-  Database.transaction((tx) => {
-    tx.delete(EventSequenceTable).where(eq(EventSequenceTable.aggregate_id, aggregateID)).run()
-    tx.delete(EventTable).where(eq(EventTable.aggregate_id, aggregateID)).run()
-  })
+  return runtime.runSync((sync) => sync.remove(aggregateID))
 }
 
 export function payloads() {
diff --git a/packages/opencode/test/control-plane/workspace.test.ts b/packages/opencode/test/control-plane/workspace.test.ts
index 6e68730a90..594789b207 100644
--- a/packages/opencode/test/control-plane/workspace.test.ts
+++ b/packages/opencode/test/control-plane/workspace.test.ts
@@ -1,4 +1,4 @@
-import { afterEach, beforeEach, describe, expect, mock, spyOn, test } from "bun:test"
+import { afterEach, beforeEach, describe, expect, mock, test } from "bun:test"
 import fs from "node:fs/promises"
 import Http from "node:http"
 import path from "node:path"
@@ -1426,48 +1426,41 @@ describe("workspace-old sessionRestore", () => {
     })
   })
 
-  test("local restore replays batches without fetch and emits progress", async () => {
-    await withInstance(async (dir) => {
-      const captured = captureGlobalEvents()
-      let fetchCallCount = 0
-      const replayAll = spyOn(SyncEvent, "replayAll")
-      try {
-        using server = Bun.serve({
-          port: 0,
-          fetch() {
-            fetchCallCount++
-            return Response.json({ ok: true })
-          },
-        })
-        const type = unique("restore-local")
-        const info = workspaceInfo(Instance.project.id, type, { directory: dir })
-        insertWorkspace(info)
-        registerAdaptor(Instance.project.id, type, localAdaptor(dir).adaptor)
-        const session = await AppRuntime.runPromise(
-          SessionNs.Service.use((svc) => svc.create({ title: "restore local" })),
-        )
-        replaceSessionEvents(session.id, 20)
+  it.live("local restore replays batches and emits progress", () =>
+    provideTmpdirInstance(
+      (dir) =>
+        Effect.gen(function* () {
+          const workspace = yield* WorkspaceOld.Service
+          const sessionSvc = yield* SessionNs.Service
+          const captured = captureGlobalEvents()
+          try {
+            const type = unique("restore-local")
+            const info = workspaceInfo(Instance.project.id, type, { directory: dir })
+            insertWorkspace(info)
+            registerAdaptor(Instance.project.id, type, localAdaptor(dir).adaptor)
+            const session = yield* sessionSvc.create({ title: "restore local" })
+            replaceSessionEvents(session.id, 20)
 
-        expect(await restoreWorkspaceSession({ workspaceID: info.id, sessionID: session.id })).toEqual({ total: 3 })
-
-        expect(fetchCallCount).toBe(0)
-        expect(replayAll).toHaveBeenCalledTimes(3)
-        expect(replayAll.mock.calls.map((call) => call[0].length)).toEqual([10, 10, 1])
-        expect((await AppRuntime.runPromise(SessionNs.Service.use((svc) => svc.get(session.id)))).workspaceID).toBe(
-          info.id,
-        )
-        expect(eventRows(session.id).map((row) => row.seq)).toEqual(Array.from({ length: 21 }, (_, i) => i))
-        expect(
-          captured.events
-            .filter((event) => event.workspace === info.id && event.payload.type === WorkspaceOld.Event.Restore.type)
-            .map((event) => event.payload.properties.step),
-        ).toEqual([0, 1, 2, 3])
-        await removeWorkspace(info.id)
-      } finally {
-        captured.dispose()
-      }
-    })
-  })
+            expect(yield* workspace.sessionRestore({ workspaceID: info.id, sessionID: session.id })).toEqual({
+              total: 3,
+            })
+            expect((yield* sessionSvc.get(session.id)).workspaceID).toBe(info.id)
+            expect(eventRows(session.id).map((row) => row.seq)).toEqual(Array.from({ length: 21 }, (_, i) => i))
+            expect(
+              captured.events
+                .filter(
+                  (event) => event.workspace === info.id && event.payload.type === WorkspaceOld.Event.Restore.type,
+                )
+                .map((event) => event.payload.properties.step),
+            ).toEqual([0, 1, 2, 3])
+            yield* workspace.remove(info.id)
+          } finally {
+            captured.dispose()
+          }
+        }),
+      { git: true },
+    ),
+  )
 
   it.live("session restore includes real message and part events in sequence order", () => {
     const replay: FetchCall[] = []
diff --git a/packages/opencode/test/sync/index.test.ts b/packages/opencode/test/sync/index.test.ts
index 32a08715ca..0afbb18317 100644
--- a/packages/opencode/test/sync/index.test.ts
+++ b/packages/opencode/test/sync/index.test.ts
@@ -1,16 +1,18 @@
-import { describe, test, expect, beforeEach, afterEach, afterAll } from "bun:test"
-import { tmpdir } from "../fixture/fixture"
-import { Schema } from "effect"
+import { describe, expect, beforeEach, afterEach, afterAll } from "bun:test"
+import { provideTmpdirInstance } from "../fixture/fixture"
+import { Effect, Layer, Schema } from "effect"
+import { CrossSpawnSpawner } from "@opencode-ai/core/cross-spawn-spawner"
 import { Bus } from "../../src/bus"
-import { Instance } from "../../src/project/instance"
 import { SyncEvent } from "../../src/sync"
 import { Database } from "@/storage/db"
 import { EventTable } from "../../src/sync/event.sql"
-import { Identifier } from "../../src/id/id"
+import { MessageID } from "../../src/session/schema"
 import { Flag } from "@opencode-ai/core/flag/flag"
 import { initProjectors } from "../../src/server/projectors"
+import { testEffect } from "../lib/effect"
 
 const original = Flag.OPENCODE_EXPERIMENTAL_WORKSPACES
+const it = testEffect(Layer.mergeAll(SyncEvent.defaultLayer, CrossSpawnSpawner.defaultLayer))
 
 beforeEach(() => {
   Database.close()
@@ -22,19 +24,6 @@ afterEach(() => {
   Flag.OPENCODE_EXPERIMENTAL_WORKSPACES = original
 })
 
-function withInstance(fn: () => void | Promise<void>) {
-  return async () => {
-    await using tmp = await tmpdir()
-
-    await Instance.provide({
-      directory: tmp.path,
-      fn: async () => {
-        await fn()
-      },
-    })
-  }
-}
-
 describe("SyncEvent", () => {
   function setup() {
     SyncEvent.reset()
@@ -59,179 +48,209 @@ describe("SyncEvent", () => {
     return { Created, Sent }
   }
 
+  function expectDefect<A, E, R>(effect: Effect.Effect<A, E, R>, pattern: RegExp) {
+    return Effect.gen(function* () {
+      const exit = yield* Effect.exit(effect)
+      if (exit._tag === "Success") throw new Error("Expected effect to fail")
+      expect(String(exit.cause)).toMatch(pattern)
+    })
+  }
+
   afterAll(() => {
     SyncEvent.reset()
     initProjectors()
   })
 
   describe("run", () => {
-    test(
+    it.live(
       "inserts event row",
-      withInstance(() => {
-        const { Created } = setup()
-        SyncEvent.run(Created, { id: "evt_1", name: "first" })
-        const rows = Database.use((db) => db.select().from(EventTable).all())
-        expect(rows).toHaveLength(1)
-        expect(rows[0].type).toBe("item.created.1")
-        expect(rows[0].aggregate_id).toBe("evt_1")
-      }),
+      provideTmpdirInstance(() =>
+        Effect.gen(function* () {
+          const { Created } = setup()
+          yield* SyncEvent.use.run(Created, { id: "evt_1", name: "first" })
+          const rows = Database.use((db) => db.select().from(EventTable).all())
+          expect(rows).toHaveLength(1)
+          expect(rows[0].type).toBe("item.created.1")
+          expect(rows[0].aggregate_id).toBe("evt_1")
+        }),
+      ),
     )
 
-    test(
+    it.live(
       "increments seq per aggregate",
-      withInstance(() => {
-        const { Created } = setup()
-        SyncEvent.run(Created, { id: "evt_1", name: "first" })
-        SyncEvent.run(Created, { id: "evt_1", name: "second" })
-        const rows = Database.use((db) => db.select().from(EventTable).all())
-        expect(rows).toHaveLength(2)
-        expect(rows[1].seq).toBe(rows[0].seq + 1)
-      }),
+      provideTmpdirInstance(() =>
+        Effect.gen(function* () {
+          const { Created } = setup()
+          yield* SyncEvent.use.run(Created, { id: "evt_1", name: "first" })
+          yield* SyncEvent.use.run(Created, { id: "evt_1", name: "second" })
+          const rows = Database.use((db) => db.select().from(EventTable).all())
+          expect(rows).toHaveLength(2)
+          expect(rows[1].seq).toBe(rows[0].seq + 1)
+        }),
+      ),
     )
 
-    test(
+    it.live(
       "uses custom aggregate field from agg()",
-      withInstance(() => {
-        const { Sent } = setup()
-        SyncEvent.run(Sent, { item_id: "evt_1", to: "james" })
-        const rows = Database.use((db) => db.select().from(EventTable).all())
-        expect(rows).toHaveLength(1)
-        expect(rows[0].aggregate_id).toBe("evt_1")
-      }),
+      provideTmpdirInstance(() =>
+        Effect.gen(function* () {
+          const { Sent } = setup()
+          yield* SyncEvent.use.run(Sent, { item_id: "evt_1", to: "james" })
+          const rows = Database.use((db) => db.select().from(EventTable).all())
+          expect(rows).toHaveLength(1)
+          expect(rows[0].aggregate_id).toBe("evt_1")
+        }),
+      ),
     )
 
-    test(
+    it.live(
       "emits events",
-      withInstance(async () => {
-        const { Created } = setup()
-        const events: Array<{
-          type: string
-          properties: { id: string; name: string }
-        }> = []
-        const received = new Promise<void>((resolve) => {
-          Bus.subscribeAll((event) => {
+      provideTmpdirInstance(() =>
+        Effect.gen(function* () {
+          const { Created } = setup()
+          const events: Array<{
+            type: string
+            properties: { id: string; name: string }
+          }> = []
+          let resolve = () => {}
+          const received = new Promise<void>((done) => {
+            resolve = done
+          })
+          const dispose = Bus.subscribeAll((event) => {
             events.push(event)
             resolve()
           })
-        })
-
-        SyncEvent.run(Created, { id: "evt_1", name: "test" })
-
-        await received
-        expect(events).toHaveLength(1)
-        expect(events[0]).toEqual({
-          type: "item.created",
-          properties: {
-            id: "evt_1",
-            name: "test",
-          },
-        })
-      }),
+          try {
+            yield* SyncEvent.use.run(Created, { id: "evt_1", name: "test" })
+            yield* Effect.promise(() => received)
+            expect(events).toHaveLength(1)
+            expect(events[0]).toEqual({
+              type: "item.created",
+              properties: {
+                id: "evt_1",
+                name: "test",
+              },
+            })
+          } finally {
+            dispose()
+          }
+        }),
+      ),
     )
   })
 
   describe("replay", () => {
-    test(
+    it.live(
       "inserts event from external payload",
-      withInstance(() => {
-        const id = Identifier.descending("message")
-        SyncEvent.replay({
-          id: "evt_1",
-          type: "item.created.1",
-          seq: 0,
-          aggregateID: id,
-          data: { id, name: "replayed" },
-        })
-        const rows = Database.use((db) => db.select().from(EventTable).all())
-        expect(rows).toHaveLength(1)
-        expect(rows[0].aggregate_id).toBe(id)
-      }),
-    )
-
-    test(
-      "throws on sequence mismatch",
-      withInstance(() => {
-        const id = Identifier.descending("message")
-        SyncEvent.replay({
-          id: "evt_1",
-          type: "item.created.1",
-          seq: 0,
-          aggregateID: id,
-          data: { id, name: "first" },
-        })
-        expect(() =>
-          SyncEvent.replay({
+      provideTmpdirInstance(() =>
+        Effect.gen(function* () {
+          const id = MessageID.ascending()
+          yield* SyncEvent.use.replay({
             id: "evt_1",
             type: "item.created.1",
-            seq: 5,
-            aggregateID: id,
-            data: { id, name: "bad" },
-          }),
-        ).toThrow(/Sequence mismatch/)
-      }),
-    )
-
-    test(
-      "throws on unknown event type",
-      withInstance(() => {
-        expect(() =>
-          SyncEvent.replay({
-            id: "evt_1",
-            type: "unknown.event.1",
             seq: 0,
-            aggregateID: "x",
-            data: {},
-          }),
-        ).toThrow(/Unknown event type/)
-      }),
+            aggregateID: id,
+            data: { id, name: "replayed" },
+          })
+          const rows = Database.use((db) => db.select().from(EventTable).all())
+          expect(rows).toHaveLength(1)
+          expect(rows[0].aggregate_id).toBe(id)
+        }),
+      ),
     )
 
-    test(
-      "replayAll accepts later chunks after the first batch",
-      withInstance(() => {
-        const { Created } = setup()
-        const id = Identifier.descending("message")
-
-        const one = SyncEvent.replayAll([
-          {
+    it.live(
+      "throws on sequence mismatch",
+      provideTmpdirInstance(() =>
+        Effect.gen(function* () {
+          const id = MessageID.ascending()
+          yield* SyncEvent.use.replay({
             id: "evt_1",
-            type: SyncEvent.versionedType(Created.type, Created.version),
+            type: "item.created.1",
             seq: 0,
             aggregateID: id,
             data: { id, name: "first" },
-          },
-          {
-            id: "evt_2",
-            type: SyncEvent.versionedType(Created.type, Created.version),
-            seq: 1,
-            aggregateID: id,
-            data: { id, name: "second" },
-          },
-        ])
+          })
+          yield* expectDefect(
+            SyncEvent.use.replay({
+              id: "evt_1",
+              type: "item.created.1",
+              seq: 5,
+              aggregateID: id,
+              data: { id, name: "bad" },
+            }),
+            /Sequence mismatch/,
+          )
+        }),
+      ),
+    )
 
-        const two = SyncEvent.replayAll([
-          {
-            id: "evt_3",
-            type: SyncEvent.versionedType(Created.type, Created.version),
-            seq: 2,
-            aggregateID: id,
-            data: { id, name: "third" },
-          },
-          {
-            id: "evt_4",
-            type: SyncEvent.versionedType(Created.type, Created.version),
-            seq: 3,
-            aggregateID: id,
-            data: { id, name: "fourth" },
-          },
-        ])
+    it.live(
+      "throws on unknown event type",
+      provideTmpdirInstance(() =>
+        Effect.gen(function* () {
+          yield* expectDefect(
+            SyncEvent.use.replay({
+              id: "evt_1",
+              type: "unknown.event.1",
+              seq: 0,
+              aggregateID: "x",
+              data: {},
+            }),
+            /Unknown event type/,
+          )
+        }),
+      ),
+    )
 
-        expect(one).toBe(id)
-        expect(two).toBe(id)
+    it.live(
+      "replayAll accepts later chunks after the first batch",
+      provideTmpdirInstance(() =>
+        Effect.gen(function* () {
+          const { Created } = setup()
+          const id = MessageID.ascending()
 
-        const rows = Database.use((db) => db.select().from(EventTable).all())
-        expect(rows.map((row) => row.seq)).toEqual([0, 1, 2, 3])
-      }),
+          const one = yield* SyncEvent.use.replayAll([
+            {
+              id: "evt_1",
+              type: SyncEvent.versionedType(Created.type, Created.version),
+              seq: 0,
+              aggregateID: id,
+              data: { id, name: "first" },
+            },
+            {
+              id: "evt_2",
+              type: SyncEvent.versionedType(Created.type, Created.version),
+              seq: 1,
+              aggregateID: id,
+              data: { id, name: "second" },
+            },
+          ])
+
+          const two = yield* SyncEvent.use.replayAll([
+            {
+              id: "evt_3",
+              type: SyncEvent.versionedType(Created.type, Created.version),
+              seq: 2,
+              aggregateID: id,
+              data: { id, name: "third" },
+            },
+            {
+              id: "evt_4",
+              type: SyncEvent.versionedType(Created.type, Created.version),
+              seq: 3,
+              aggregateID: id,
+              data: { id, name: "fourth" },
+            },
+          ])
+
+          expect(one).toBe(id)
+          expect(two).toBe(id)
+
+          const rows = Database.use((db) => db.select().from(EventTable).all())
+          expect(rows.map((row) => row.seq)).toEqual([0, 1, 2, 3])
+        }),
+      ),
     )
   })
 })