feat: add experimental background subagents (#27084)

packages/opencode/src/session/prompt.ts

@@ -214,6 +214,7 @@ export const layer = Layer.effect(
         cancel: (sessionID: SessionID) => cancel(sessionID),
         resolvePromptParts: (template: string) => resolvePromptParts(template),
         prompt: (input: PromptInput) => prompt(input).pipe(Effect.catch(Effect.die)),
+        loop: (input: LoopInput) => loop(input),
       } satisfies TaskPromptOps
     })
 

packages/opencode/src/session/run-state.ts

@@ -1,5 +1,6 @@
 import { InstanceState } from "@/effect/instance-state"
 import { Runner } from "@/effect/runner"
+import { BackgroundJob } from "@/background/job"
 import { Effect, Latch, Layer, Scope, Context } from "effect"
 import * as Session from "./session"
 import { MessageV2 } from "./message-v2"
@@ -27,6 +28,7 @@ export class Service extends Context.Service<Service, Interface>()("@opencode/Se
 export const layer = Layer.effect(
   Service,
   Effect.gen(function* () {
+    const background = yield* BackgroundJob.Service
     const status = yield* SessionStatus.Service
 
     const state = yield* InstanceState.make(
@@ -72,6 +74,7 @@ export const layer = Layer.effect(
     })
 
     const cancel = Effect.fn("SessionRunState.cancel")(function* (sessionID: SessionID) {
+      yield* cancelBackgroundJobs(background, sessionID)
       const data = yield* InstanceState.get(state)
       const existing = data.runners.get(sessionID)
       if (!existing || !existing.busy) {
@@ -104,7 +107,41 @@ export const layer = Layer.effect(
   }),
 )
 
-export const defaultLayer = layer.pipe(Layer.provide(SessionStatus.defaultLayer))
+export const defaultLayer = layer.pipe(Layer.provide(BackgroundJob.defaultLayer), Layer.provide(SessionStatus.defaultLayer))
+
+const cancelBackgroundJobs = Effect.fn("SessionRunState.cancelBackgroundJobs")(function* (
+  background: BackgroundJob.Interface,
+  sessionID: SessionID,
+) {
+  const jobs = yield* background.list()
+  const pending = new Set<string>([sessionID])
+  const cancelled = new Set<string>()
+  const matches = (job: BackgroundJob.Info) => {
+    if (job.status !== "running") return false
+    if (cancelled.has(job.id)) return false
+    if (pending.has(job.id)) return true
+    if (typeof job.metadata?.sessionId === "string" && pending.has(job.metadata.sessionId)) return true
+    return typeof job.metadata?.parentSessionId === "string" && pending.has(job.metadata.parentSessionId)
+  }
+  let batch = jobs.filter(matches)
+  while (batch.length > 0) {
+    yield* Effect.forEach(
+      batch,
+      (job) =>
+        background.cancel(job.id).pipe(
+          Effect.tap(() =>
+            Effect.sync(() => {
+              cancelled.add(job.id)
+              pending.add(job.id)
+              if (typeof job.metadata?.sessionId === "string") pending.add(job.metadata.sessionId)
+            }),
+          ),
+        ),
+      { concurrency: "unbounded", discard: true },
+    )
+    batch = jobs.filter(matches)
+  }
+})
 
 function busyError(sessionID: SessionID) {
   return new Session.BusyError({ sessionID })

packages/opencode/src/session/session.ts

@@ -1,5 +1,6 @@
 import { Slug } from "@opencode-ai/core/util/slug"
 import path from "path"
+import { BackgroundJob } from "@/background/job"
 import { BusEvent } from "@/bus/bus-event"
 import { Bus } from "@/bus"
 import { Decimal } from "decimal.js"
@@ -508,10 +509,11 @@ const db = <T>(fn: (d: Parameters<typeof Database.use>[0] extends (trx: infer D)
 export const layer: Layer.Layer<
   Service,
   never,
-  Bus.Service | Storage.Service | SyncEvent.Service | RuntimeFlags.Service
+  BackgroundJob.Service | Bus.Service | Storage.Service | SyncEvent.Service | RuntimeFlags.Service
 > = Layer.effect(
   Service,
   Effect.gen(function* () {
+    const background = yield* BackgroundJob.Service
     const bus = yield* Bus.Service
     const storage = yield* Storage.Service
     const sync = yield* SyncEvent.Service
@@ -592,20 +594,19 @@ export const layer: Layer.Layer<
     const remove: Interface["remove"] = Effect.fnUntraced(function* (sessionID: SessionID) {
       const session = yield* get(sessionID)
       try {
-        const kids = yield* children(sessionID)
-        for (const child of kids) {
-          yield* remove(child.id)
-        }
-
-        // `remove` needs to work in all cases, such as a broken
-        // sessions that run cleanup. In certain cases these will
-        // run without any instance state, so we need to turn off
-        // publishing of events in that case
+        // `remove` needs to work in all cases, such as broken sessions that
+        // run cleanup without instance state.
         const hasInstance = yield* InstanceState.directory.pipe(
           Effect.as(true),
           Effect.catchCause(() => Effect.succeed(false)),
         )
 
+        if (hasInstance) yield* cancelBackgroundJobs(background, sessionID)
+        const kids = yield* children(sessionID)
+        for (const child of kids) {
+          yield* remove(child.id)
+        }
+
         yield* sync.run(Event.Deleted, { sessionID, info: session }, { publish: hasInstance })
         yield* sync.remove(sessionID)
       } catch (e) {
@@ -862,12 +863,30 @@ export const layer: Layer.Layer<
 )
 
 export const defaultLayer = layer.pipe(
+  Layer.provide(BackgroundJob.defaultLayer),
   Layer.provide(Bus.layer),
   Layer.provide(Storage.defaultLayer),
   Layer.provide(SyncEvent.defaultLayer),
   Layer.provide(RuntimeFlags.defaultLayer),
 )
 
+const cancelBackgroundJobs = Effect.fn("Session.cancelBackgroundJobs")(function* (
+  background: BackgroundJob.Interface,
+  sessionID: SessionID,
+) {
+  const jobs = yield* background.list()
+  yield* Effect.forEach(
+    jobs.filter((job) => {
+      if (job.status !== "running") return false
+      if (job.id === sessionID) return true
+      if (job.metadata?.sessionId === sessionID) return true
+      return job.metadata?.parentSessionId === sessionID
+    }),
+    (job) => background.cancel(job.id),
+    { concurrency: "unbounded", discard: true },
+  )
+})
+
 function* listByProject(
   input: ListInput & {
     projectID: ProjectID