diff --git a/packages/app/src/context/server-sync.tsx b/packages/app/src/context/server-sync.tsx
index fc79fdaa8478..3946a10ef2d1 100644
--- a/packages/app/src/context/server-sync.tsx
+++ b/packages/app/src/context/server-sync.tsx
@@ -38,6 +38,50 @@ import type { ServerScope } from "@/utils/server-scope"
 import { persisted } from "@/utils/persist"
 import { toggleMcp } from "./global-sync/mcp"
 
+// Map a directory-scoped event to the session/message it concerns, so the listener can route it to
+// the store that actually holds that session even when the event's own instance directory has no
+// registered store. This is the cross-instance subagent case: a child anchored in a monorepo
+// subproject (directory=<subproject>) the UI never opened as its own project — the child is loaded
+// into and displayed from its PARENT project's store (via childSessions). Directory-level events
+// (server.instance.disposed / vcs / lsp) return no ids and must NOT use the fallback.
+function eventRoutingIdentity(event: { type: string; properties?: unknown }): {
+  sessionID?: string
+  messageID?: string
+} {
+  const p = (event.properties ?? {}) as {
+    info?: { id?: string; sessionID?: string }
+    part?: { sessionID?: string; messageID?: string }
+    sessionID?: string
+    messageID?: string
+  }
+  switch (event.type) {
+    case "session.created":
+    case "session.updated":
+    case "session.deleted":
+      return { sessionID: p.info?.id }
+    case "message.updated":
+      return { sessionID: p.info?.sessionID, messageID: p.info?.id }
+    case "message.part.updated":
+      return { sessionID: p.part?.sessionID, messageID: p.part?.messageID }
+    case "message.removed":
+      return { sessionID: p.sessionID, messageID: p.messageID }
+    case "message.part.removed":
+    case "message.part.delta":
+      return { messageID: p.messageID }
+    case "session.diff":
+    case "todo.updated":
+    case "session.status":
+    case "permission.asked":
+    case "permission.replied":
+    case "question.asked":
+    case "question.replied":
+    case "question.rejected":
+      return { sessionID: p.sessionID }
+    default:
+      return {}
+  }
+}
+
 type GlobalStore = {
   ready: boolean
   error?: InitError
@@ -394,22 +438,58 @@ export function createServerSyncContextInner(serverSDK: ServerSDK) {
     }
 
     const existing = children.children[key]
-    if (!existing) return
-    children.mark(key)
-    const [store, setStore] = existing
-    applyDirectoryEvent({
-      event,
-      directory,
-      store,
-      setStore,
-      push: queue.push,
-      setSessionTodo,
-      retainedLimit: sessionMeta.get(key)?.limit,
-      vcsCache: children.vcsCache.get(key),
-      loadLsp: () => {
-        void queryClient.fetchQuery(queryOptionsApi.lsp(key))
-      },
-    })
+    if (existing) {
+      children.mark(key)
+      const [store, setStore] = existing
+      applyDirectoryEvent({
+        event,
+        directory,
+        store,
+        setStore,
+        push: queue.push,
+        setSessionTodo,
+        retainedLimit: sessionMeta.get(key)?.limit,
+        vcsCache: children.vcsCache.get(key),
+        loadLsp: () => {
+          void queryClient.fetchQuery(queryOptionsApi.lsp(key))
+        },
+      })
+      return
+    }
+
+    // Fallback: the event's own instance directory has no registered store. Happens for a subagent
+    // child anchored in a subproject (directory=<subproject>) that the UI never opened as its own
+    // project — the child session is loaded into and displayed from its PARENT project's store.
+    // Without this, the child's live events (message/part deltas, status, questions) are dropped and
+    // the child view stays frozen until it is re-entered (which re-fetches a snapshot). Route such
+    // session-scoped events to every registered store that already holds that session/message.
+    const identity = eventRoutingIdentity(event)
+    if (identity.sessionID === undefined && identity.messageID === undefined) return
+    for (const targetKey of Object.keys(children.children)) {
+      const target = children.children[targetKey]
+      if (!target) continue
+      const [store, setStore] = target
+      const holdsSession =
+        identity.sessionID !== undefined &&
+        (store.message[identity.sessionID] !== undefined || store.session.some((s) => s.id === identity.sessionID))
+      const holdsMessage = identity.messageID !== undefined && store.part[identity.messageID] !== undefined
+      if (!holdsSession && !holdsMessage) continue
+      const targetDirKey = directoryKey(targetKey)
+      children.mark(targetKey)
+      applyDirectoryEvent({
+        event,
+        directory: targetKey,
+        store,
+        setStore,
+        push: queue.push,
+        setSessionTodo,
+        retainedLimit: sessionMeta.get(targetDirKey)?.limit,
+        vcsCache: children.vcsCache.get(targetDirKey),
+        loadLsp: () => {
+          void queryClient.fetchQuery(queryOptionsApi.lsp(targetDirKey))
+        },
+      })
+    }
   })
 
   onCleanup(unsub)
diff --git a/packages/opencode/src/server/routes/instance/httpapi/handlers/event.ts b/packages/opencode/src/server/routes/instance/httpapi/handlers/event.ts
index 4f24fbb4b694..b0990af27446 100644
--- a/packages/opencode/src/server/routes/instance/httpapi/handlers/event.ts
+++ b/packages/opencode/src/server/routes/instance/httpapi/handlers/event.ts
@@ -2,6 +2,8 @@ import { EventV2Bridge } from "@/event-v2-bridge"
 import { InstanceState } from "@/effect/instance-state"
 import { GlobalBus } from "@/bus/global"
 import { EventV2 } from "@opencode-ai/core/event"
+import { Session } from "@/session/session"
+import { SessionID } from "@/session/schema"
 import { Effect, Queue } from "effect"
 import * as Stream from "effect/Stream"
 import { HttpServerResponse } from "effect/unstable/http"
@@ -31,13 +33,73 @@ function eventResponse(events: EventV2.Interface) {
     const queue = yield* Queue.unbounded<EventV2.Payload>()
     const unsubscribe = yield* events.listen((event) => Effect.sync(() => Queue.offerUnsafe(queue, event)))
     yield* Effect.addFinalizer(() => unsubscribe)
+    const sessions = yield* Session.Service
+
+    // OPENCODE_EVENT_SUBTREE (default on): a subscription on directory D receives events from every
+    // session whose tree is ROOTED in D — the open session plus all of its (possibly cross-directory)
+    // descendant subagents. This is what lets a monorepo-root TUI observe a subagent launched in a
+    // subproject (live progress, child-session navigation, live questions). Matching is by session
+    // lineage (parentID), NOT by the child's own directory, so it is robust to subagents anchored
+    // anywhere — including worktrees outside the subscription directory. Events without an owning
+    // session (global/instance events) stay scoped to the exact instance directory. Set
+    // OPENCODE_EVENT_SUBTREE=0 to restore strict matching (events only for sessions whose own
+    // directory equals the subscription directory).
+    // TODO(PR anomalyco/opencode#29271): revisit this env gate before upstreaming (opt-in or drop it).
+    const subtreeEvents = !["0", "false", "off", "no"].includes(
+      (process.env["OPENCODE_EVENT_SUBTREE"] ?? "").toLowerCase(),
+    )
+
+    // Memoized lineage resolver: maps a session id to the directory of its root ancestor (the
+    // subscription anchor for the whole tree). Cached per connection; each session is walked at most
+    // once, so subsequent events for it are an O(1) map lookup.
+    const rootDirectoryCache = new Map<string, string>()
+    const rootDirectoryOf = (sessionID: string): Effect.Effect<string | undefined> =>
+      Effect.gen(function* () {
+        const chain: string[] = []
+        let current: string | undefined = sessionID
+        let root: string | undefined = undefined
+        while (current) {
+          const cached = rootDirectoryCache.get(current)
+          if (cached) {
+            root = cached
+            break
+          }
+          if (chain.includes(current)) break // cycle guard (should not happen)
+          chain.push(current)
+          const info: Session.Info | undefined = yield* sessions
+            .get(SessionID.make(current))
+            .pipe(Effect.catchCause(() => Effect.succeed(undefined)))
+          if (!info) break
+          if (!info.parentID) {
+            root = info.directory
+            break
+          }
+          current = info.parentID
+        }
+        if (root) for (const id of chain) rootDirectoryCache.set(id, root)
+        return root
+      })
+
+    const sessionIDOf = (event: EventV2.Payload): string | undefined => {
+      const sid = (event.data as { sessionID?: unknown } | undefined)?.sessionID
+      return typeof sid === "string" ? sid : undefined
+    }
+
+    const matches = (event: EventV2.Payload): Effect.Effect<boolean> =>
+      Effect.gen(function* () {
+        if (event.location?.workspaceID !== undefined && event.location.workspaceID !== workspaceID) return false
+        const sessionID = sessionIDOf(event)
+        // Global/instance events (no owning session) keep the historical exact-directory behaviour.
+        if (sessionID === undefined) return event.location?.directory === instance.directory
+        if (!subtreeEvents) return event.location?.directory === instance.directory
+        const root = yield* rootDirectoryOf(sessionID)
+        return root === instance.directory
+      })
+
     const stream = Stream.fromQueue(queue).pipe(
-      Stream.filter(
-        (event) =>
-          event.location?.directory === instance.directory &&
-          (event.location.workspaceID === undefined || event.location.workspaceID === workspaceID),
-      ),
-      Stream.map((event) => ({ id: event.id, type: event.type, properties: event.data })),
+      Stream.mapEffect((event) => matches(event).pipe(Effect.map((keep) => ({ event, keep })))),
+      Stream.filter(({ keep }) => keep),
+      Stream.map(({ event }) => ({ id: event.id, type: event.type, properties: event.data })),
     )
     const disposed = Stream.callback<{ id: string; type: string; properties: unknown }>((queue) => {
       const listener = (event: {
diff --git a/packages/opencode/src/tool/registry.ts b/packages/opencode/src/tool/registry.ts
index 541d1f4bbbd0..df69c2e317f9 100644
--- a/packages/opencode/src/tool/registry.ts
+++ b/packages/opencode/src/tool/registry.ts
@@ -49,6 +49,8 @@ import { Agent } from "../agent/agent"
 import { Skill } from "../skill"
 import { Permission } from "@/permission"
 import { BackgroundJob } from "@/background/job"
+import { InstanceStore } from "@/project/instance-store"
+import { InstanceLayer } from "@/project/instance-layer"
 import { RuntimeFlags } from "@/effect/runtime-flags"
 import { ProviderV2 } from "@opencode-ai/core/provider"
 import { ModelV2 } from "@opencode-ai/core/model"
@@ -335,6 +337,7 @@ export const defaultLayer = Layer.suspend(() =>
       Layer.provide(Format.defaultLayer),
       Layer.provide(CrossSpawnSpawner.defaultLayer),
       Layer.provide(Truncate.defaultLayer),
+      Layer.provide(InstanceLayer.layer),
     )
     .pipe(Layer.provide(Database.defaultLayer), Layer.provide(RuntimeFlags.defaultLayer)),
 )
@@ -435,6 +438,7 @@ export const node = LayerNode.make(layer.pipe(Layer.provide(Ripgrep.defaultLayer
   Truncate.node,
   RuntimeFlags.node,
   Database.node,
+  InstanceStore.node,
 ])
 
 export * as ToolRegistry from "./registry"
diff --git a/packages/opencode/src/tool/task.ts b/packages/opencode/src/tool/task.ts
index b0a866c90e23..2b5980d0bb5c 100644
--- a/packages/opencode/src/tool/task.ts
+++ b/packages/opencode/src/tool/task.ts
@@ -14,6 +14,7 @@ import { Effect, Exit, Schema, Scope } from "effect"
 import { EffectBridge } from "@/effect/bridge"
 import { RuntimeFlags } from "@/effect/runtime-flags"
 import { Database } from "@opencode-ai/core/database/database"
+import { InstanceStore } from "@/project/instance-store"
 
 export interface TaskPromptOps {
   cancel(sessionID: SessionID): Effect.Effect<void>
@@ -44,6 +45,10 @@ const BaseParameterFields = {
   description: Schema.String.annotate({ description: "A short (3-5 words) description of the task" }),
   prompt: Schema.String.annotate({ description: "The task for the agent to perform" }),
   subagent_type: Schema.String.annotate({ description: "The type of specialized agent to use for this task" }),
+  directory: Schema.optional(Schema.String).annotate({
+    description:
+      "Optional absolute path to the working directory for the subagent. When set, the subagent runs rooted at this path: its tools, agent registry, AGENTS.md chain and skill walk-up start from there instead of inheriting the parent session's directory. Omit to inherit the parent session's directory.",
+  }),
   task_id: Schema.optional(Schema.String).annotate({
     description:
       "This should only be set if you mean to resume a previous task (you can pass a prior task_id and the task will continue the same subagent session as before instead of creating a fresh one)",
@@ -88,6 +93,7 @@ export const TaskTool = Tool.define(
     const scope = yield* Scope.Scope
     const flags = yield* RuntimeFlags.Service
     const database = yield* Database.Service
+    const instanceStore = yield* InstanceStore.Service
 
     const run = Effect.fn("TaskTool.execute")(function* (
       params: Schema.Schema.Type<typeof Parameters>,
@@ -113,14 +119,23 @@ export const TaskTool = Tool.define(
         })
       }
 
-      const next = yield* agent.get(params.subagent_type)
+      const session = params.task_id
+        ? yield* sessions.get(SessionID.make(params.task_id)).pipe(Effect.catchCause(() => Effect.succeed(undefined)))
+        : undefined
+
+      // Directory anchoring: an explicit `directory` wins; on resume we fall back to the child
+      // session's stored directory. When set, the agent is resolved, the child session is created
+      // and its prompt loop runs inside that directory's instance (so project-local agents, skills
+      // and AGENTS.md resolve via walk-up from there). Omitted → inherit the parent's instance.
+      const directory = params.directory ?? session?.directory
+      const provideInstance = <A, E, R>(effect: Effect.Effect<A, E, R>): Effect.Effect<A, E, R> =>
+        directory ? instanceStore.provide({ directory }, effect) : effect
+
+      const next = yield* provideInstance(agent.get(params.subagent_type))
       if (!next) {
         return yield* Effect.fail(new Error(`Unknown agent type: ${params.subagent_type} is not a valid agent type`))
       }
 
-      const session = params.task_id
-        ? yield* sessions.get(SessionID.make(params.task_id)).pipe(Effect.catchCause(() => Effect.succeed(undefined)))
-        : undefined
       const parent = yield* sessions.get(ctx.sessionID)
       const childPermission = deriveSubagentSessionPermission({
         parentSessionPermission: parent.permission ?? [],
@@ -141,21 +156,25 @@ export const TaskTool = Tool.define(
       ]
       const nextSession =
         session ??
-        (yield* sessions.create({
-          parentID: ctx.sessionID,
-          title: params.description + ` (@${next.name} subagent)`,
-          agent: next.name,
-          permission: [
-            ...childPermission,
-            ...childToolDenies.filter(
-              (deny) =>
-                !childPermission.some(
-                  (rule) =>
-                    rule.permission === deny.permission && rule.pattern === deny.pattern && rule.action === deny.action,
-                ),
-            ),
-          ],
-        }))
+        (yield* provideInstance(
+          sessions.create({
+            parentID: ctx.sessionID,
+            title: params.description + ` (@${next.name} subagent)`,
+            agent: next.name,
+            permission: [
+              ...childPermission,
+              ...childToolDenies.filter(
+                (deny) =>
+                  !childPermission.some(
+                    (rule) =>
+                      rule.permission === deny.permission &&
+                      rule.pattern === deny.pattern &&
+                      rule.action === deny.action,
+                  ),
+              ),
+            ],
+          }),
+        ))
 
       const msg = yield* MessageV2.get({ sessionID: ctx.sessionID, messageID: ctx.messageID }).pipe(
         Effect.provideService(Database.Service, database),
@@ -239,7 +258,7 @@ export const TaskTool = Tool.define(
         )
       })
 
-      if (yield* background.extend({ id: nextSession.id, run: runTask() })) {
+      if (yield* background.extend({ id: nextSession.id, run: provideInstance(runTask()) })) {
         return {
           title: params.description,
           metadata: {
@@ -268,7 +287,7 @@ export const TaskTool = Tool.define(
           }),
           notify(nextSession.id),
         ]),
-        run: runTask().pipe(Effect.onInterrupt(() => ops.cancel(nextSession.id))),
+        run: provideInstance(runTask()).pipe(Effect.onInterrupt(() => ops.cancel(nextSession.id))),
       })
 
       function backgroundResult() {
diff --git a/packages/opencode/test/session/prompt.test.ts b/packages/opencode/test/session/prompt.test.ts
index 08828018a4a3..119d894aef13 100644
--- a/packages/opencode/test/session/prompt.test.ts
+++ b/packages/opencode/test/session/prompt.test.ts
@@ -46,6 +46,7 @@ import { SystemPrompt } from "../../src/session/system"
 import { Shell } from "@opencode-ai/core/shell"
 import { Snapshot } from "../../src/snapshot"
 import { ToolRegistry } from "@/tool/registry"
+import { InstanceLayer } from "@/project/instance-layer"
 import { Truncate } from "@/tool/truncate"
 import { CrossSpawnSpawner } from "@opencode-ai/core/cross-spawn-spawner"
 import { Ripgrep } from "@opencode-ai/core/ripgrep"
@@ -193,6 +194,7 @@ function makePrompt(input?: { processor?: "blocking" }) {
     Layer.provide(Ripgrep.defaultLayer),
     Layer.provide(Format.defaultLayer),
     Layer.provide(RuntimeFlags.layer({ experimentalEventSystem: true })),
+    Layer.provide(InstanceLayer.layer),
     Layer.provideMerge(todo),
     Layer.provideMerge(question),
     Layer.provideMerge(deps),