merge(local): Phase B — auto-reject questions/permissions for stuck subagents

Phase B adds RunEvents handler that subscribes to Question.Event.Asked
and Permission.Event.Asked and auto-rejects (or auto-approves in
skipPermissions mode) events targeting descendant sessions of the root
run. Prevents subagent livelock from stalling the root session.

- B.1 (45566e4): RED test + branch
- B.2a (3464886 + 64e0b68): handler module + 8 tests + defect narrowing
- B.2b (1813c42): wire into run.ts non-attach path, remove double-reply

Diamond review: general (spec) + codex-5.3 (quality), both APPROVE.
Plan: docs/superpowers/plans/2026-04-18-subagent-hang-hardening.md lines 810-1207

Author: tesdal

packages/opencode/src/cli/cmd/run-events.ts

@@ -0,0 +1,123 @@
+import { Effect, Option } from "effect"
+import { Bus } from "@/bus"
+import { Permission } from "@/permission"
+import { Question } from "@/question"
+import { Session } from "@/session"
+import { NotFoundError } from "@/storage"
+import { SessionID } from "@/session/schema"
+import { Log } from "@/util"
+
+const log = Log.create({ service: "run-events" })
+
+export const LIVELOCK_WARN_THRESHOLD = 5
+export const MAX_LINEAGE_DEPTH = 32
+
+export interface Config {
+  rootSessionID: SessionID
+  skipPermissions: boolean
+  jsonMode: boolean
+}
+
+export interface Stats {
+  autoRejectedQuestions: number
+  autoRejectedPermissions: number
+  livelockWarned: boolean
+}
+
+export interface Handle {
+  readonly stats: Stats
+  readonly unsubscribe: () => void
+}
+
+export const make = Effect.fn("RunEvents.make")(function* (config: Config) {
+  const question = yield* Question.Service
+  const permission = yield* Permission.Service
+  const bus = yield* Bus.Service
+  const session = yield* Session.Service
+
+  const stats: Stats = {
+    autoRejectedQuestions: 0,
+    autoRejectedPermissions: 0,
+    livelockWarned: false,
+  }
+
+  const descendants = new Set<SessionID>([config.rootSessionID])
+
+  const emit = (type: string, data: Record<string, unknown>) => {
+    if (!config.jsonMode) return
+    process.stdout.write(
+      JSON.stringify({ type, timestamp: Date.now(), sessionID: config.rootSessionID, ...data }) + "\n",
+    )
+  }
+
+  const isDescendant = Effect.fn("RunEvents.isDescendant")(function* (sid: SessionID) {
+    if (descendants.has(sid)) return true
+    let cur: SessionID | undefined = sid
+    const chain: SessionID[] = []
+    let depth = 0
+    while (cur !== undefined && !descendants.has(cur) && depth < MAX_LINEAGE_DEPTH) {
+      chain.push(cur)
+      depth++
+      const lookup: Option.Option<Session.Info> = yield* session.get(cur).pipe(
+        Effect.option,
+        Effect.catchDefect((defect) => {
+          if (!NotFoundError.isInstance(defect)) return Effect.die(defect)
+          return Effect.succeed(Option.none<Session.Info>())
+        }),
+      )
+      if (Option.isNone(lookup)) break
+      cur = lookup.value.parentID ?? undefined
+    }
+    if (cur === undefined || !descendants.has(cur)) return false
+    chain.forEach((item) => descendants.add(item))
+    return true
+  })
+
+  const bump = (kind: "question" | "permission", sid: SessionID) => {
+    if (kind === "question") stats.autoRejectedQuestions++
+    else stats.autoRejectedPermissions++
+    const total = stats.autoRejectedQuestions + stats.autoRejectedPermissions
+    emit("auto-reject", { kind, autoRejectSessionID: sid, totalAutoRejects: total })
+    if (!stats.livelockWarned && total > LIVELOCK_WARN_THRESHOLD) {
+      stats.livelockWarned = true
+      log.warn("possible subagent livelock: >5 auto-rejects in a single run", {
+        rootSessionID: config.rootSessionID,
+      })
+    }
+  }
+
+  const unsubQuestion = yield* bus.subscribeCallback(Question.Event.Asked, (evt) =>
+    Effect.runPromise(
+      Effect.gen(function* () {
+        const mine = yield* isDescendant(evt.properties.sessionID)
+        if (!mine) return
+        bump("question", evt.properties.sessionID)
+        yield* question.reject(evt.properties.id)
+      }),
+    ),
+  )
+
+  const unsubPermission = yield* bus.subscribeCallback(Permission.Event.Asked, (evt) =>
+    Effect.runPromise(
+      Effect.gen(function* () {
+        const mine = yield* isDescendant(evt.properties.sessionID)
+        if (!mine) return
+        if (config.skipPermissions) {
+          yield* permission.reply({ requestID: evt.properties.id, reply: "once" })
+          return
+        }
+        bump("permission", evt.properties.sessionID)
+        yield* permission.reply({ requestID: evt.properties.id, reply: "reject" })
+      }),
+    ),
+  )
+
+  const unsubscribe = () => {
+    unsubQuestion()
+    unsubPermission()
+  }
+
+  return { stats, unsubscribe } satisfies Handle
+})
+
+export * as RunEvents from "./run-events"