diff --git a/apps/web/tests/preset-migration.snapshot.ts b/apps/web/tests/preset-migration.snapshot.ts
index 1791e88639..3ca55f2f85 100644
--- a/apps/web/tests/preset-migration.snapshot.ts
+++ b/apps/web/tests/preset-migration.snapshot.ts
@@ -5,7 +5,6 @@ import { dirname } from 'node:path'
 import { fileURLToPath } from 'node:url'
 import { zstdCompressSync, zstdDecompressSync } from 'node:zlib'
 import { describe, expect, it } from 'vitest'
-import { installModelSelection } from '@deepseek-ai/dsh-agent'
 import { SESSION_FORMAT_VERSION, SessionId } from '@deepseek-ai/dsh-session'
 import { generationLogPath } from '../../../packages/session/session-persistence-jsonl/src/format.ts'
 import { scanZstdFrames } from '../../../packages/session/session-persistence-jsonl/src/zstd.ts'
@@ -18,9 +17,7 @@ const childFixturePath = fileURLToPath(new URL('../../../snapshots/web/preset-mi
 const fixturePath = fileURLToPath(new URL('../../../snapshots/web/preset-migration/session.v2.jsonl', import.meta.url))
 
 describe.skipIf(webSnapshotMode() === 'record')('historical preset restoration through the Web Host', () => {
-  it.each([
-    ['controller', false], ['controller', true], ['external', true],
-  ] as const)('resumes code as PTC through %s (selection events=%s)', async (activation, withSelections) => {
+  it.each([false, true])('resumes code as PTC (selection events=%s)', async (withSelections) => {
     const scaffold = await launchWebScaffold()
     try {
       const id = SessionId('preset-migration')
@@ -72,36 +69,7 @@ describe.skipIf(webSnapshotMode() === 'record')('historical preset restoration t
       }
       await expect(readFile(successor)).rejects.toMatchObject({ code: 'ENOENT' })
 
-      const resolved = activation === 'controller' ? await scaffold.ctx.sessionController.resolveAgent(id) : await (async () => {
-        const setupEntered = Promise.withResolvers<undefined>()
-        const releaseSetup = Promise.withResolvers<undefined>()
-        const initialization = scaffold.ctx.agents.resume({
-          resumeSessionId: id,
-          setup: async (ctx) => {
-            installModelSelection(ctx)
-            await scaffold.ctx.agentPresets.mount(ctx, 'ptc')
-            setupEntered.resolve(undefined)
-            await releaseSetup.promise
-          },
-        })
-        try {
-          await Promise.race([setupEntered.promise, initialization])
-          expect(scaffold.ctx.agents.get(id)).toBeUndefined()
-          const lookup = scaffold.ctx.sessionController.resolveAgent(id)
-          releaseSetup.resolve(undefined)
-          const original = await initialization
-          const result = await lookup
-          expect({ sameAgent: 'agent' in result && result.agent === original.agent }).toMatchInlineSnapshot(`
-            {
-              "sameAgent": true,
-            }
-          `)
-          return result
-        } finally {
-          releaseSetup.resolve(undefined)
-          await initialization
-        }
-      })()
+      const resolved = await scaffold.ctx.sessionController.resolveAgent(id)
       if ('error' in resolved) throw resolved.error
       expect(scaffold.ctx.agentPresets.composedPreset(resolved.agent.ctx)).toBe('ptc')
       expect(resolved.agent.session.header.agentPreset).toBe('ptc')
diff --git a/packages/api/session-controller/README.i18n.yaml b/packages/api/session-controller/README.i18n.yaml
index bf2da83432..6df1300fd1 100644
--- a/packages/api/session-controller/README.i18n.yaml
+++ b/packages/api/session-controller/README.i18n.yaml
@@ -15,8 +15,8 @@
   en: 1fdf707322fb6996
   zh: 0204f7e9d4aa3cce
 /session-controller/use-this-package:
-  en: 2bea5826e7c25c99
-  zh: 40fbc767c15e4cb5
+  en: aabd5be911e477f5
+  zh: 2f7fdb44bc8777bc
 /session-controller/client-references:
   en: 41bdda1ac32df558
   zh: aa5d0e325924066b
diff --git a/packages/api/session-controller/README.md b/packages/api/session-controller/README.md
index eb70ee3959..abbb52cd63 100644
--- a/packages/api/session-controller/README.md
+++ b/packages/api/session-controller/README.md
@@ -37,10 +37,6 @@ Each endpoint states its activation policy. List reads only stored headers and p
 
 Every Remote endpoint is access-controlled: a Peer whose principal is not the owner reaches an endpoint only when, on every resource the call touches, a binding of that principal kind's policy in [`dsh-api-remote-access`](../remote-access/README.md) grants a role listing the action ([Peer principals Agent Note](../../../.agents/notes/implemented/architecture/2026-10-12-peer-principal-and-remote-access.md)). The controller injects `remoteAccess` and registers the `session` resource kind with the default field `sessionId` through `typert.resources`. `session/page` and `session/follow` declare a `session` reader in `@Remote({ resources })` that reads `request.address.sessionId` for an ordinary Session address and `request.address.childSessionId` for a subagent address; whether access to the parent Session covers its children is the policy's rule. `session/projections` reads the Session resource from `request.sessionId`, so a reconnecting reader reloads only the projections of Sessions it may read. `session/list`, `session/search`, and `session/control` read no resource, so their calls touch the `global` resource and need a `global` role; for a non-owner caller, `session/list` returns only the rows, `session/search` only the hits, and `session/control` only the baseline projections and projection frames, whose Session `ctx.remoteAccess.allows()` admits for the same action, so that action also belongs to a `session` role; owner results are unfiltered. `session/prompt` builds the durable `user-rpc` message source in its Remote method and records `principal` only for a non-owner caller, read through `principalOf(this.ctx.invocation)`; a source without `principal` belongs to the owner.
 
-Session history is readable before its Agent is ready; the summary reports `agentAvailable: false` during setup. Agent operations and named blank reuse wait for a local initialization whose Session was published while this controller was active, without acquiring its disposal ownership. Unpublished initializations, bare Sessions, and external writers retain their existing writer-conflict behavior.
-
-If a joined initialization fails or is cancelled, waiters return `session/not-found` after the Session is released. Controller unload also ends its waiters with that error. These failures do not automatically restart initialization.
-
 List rows carry `formatStatus` when available, so Clients can identify migration-required Sessions without requesting their projections.
 
 Host list generation yields between complete rows only when its configured work slice is exhausted; cheap remaining work returns without a forced yield. Request cancellation is checked per row and after each yield and rejects without partial results. Each row is synchronous; the list does not promise one cross-Session snapshot. A Session already queued as cold remains a cached row if it attaches during a yield: Client in-flight mutation replay corrects its availability, and sequenced projections supersede cached hints.
diff --git a/packages/api/session-controller/README.zh.md b/packages/api/session-controller/README.zh.md
index eaae8243e5..58bdbbf48b 100644
--- a/packages/api/session-controller/README.zh.md
+++ b/packages/api/session-controller/README.zh.md
@@ -37,10 +37,6 @@ Client journal 在发布 follow 快照、live entry 或历史页之前验证当
 
 每个 Remote 端点都受访问控制：principal 不是 owner 的 Peer 只有在本次调用访问的每个资源上，该 principal kind 在 [`dsh-api-remote-access`](../remote-access/README.zh.md) 中的 policy 都有某个 binding 授予列出该 action 的 role 时，才能调用该端点（[Peer 身份属性 Agent Note](../../../.agents/notes/implemented/architecture/2026-10-12-peer-principal-and-remote-access.zh.md)）。控制器注入 `remoteAccess`，并经 `typert.resources` 以默认字段 `sessionId` 登记 `session` 资源种类。`session/page` 与 `session/follow` 在 `@Remote({ resources })` 中声明 `session` 读取函数：对普通 Session 地址读 `request.address.sessionId`，对 subagent 地址读 `request.address.childSessionId`；父会话的访问权是否覆盖其子会话由 policy 决定。`session/projections` 从 `request.sessionId` 读取会话资源，因此重连的读者只会重新读取它可读的会话的 projections。`session/list`、`session/search` 与 `session/control` 不读取资源，其调用访问 `global` 资源，需要 `global` role；对非 owner 调用方，`session/list` 只返回其 Session 被 `ctx.remoteAccess.allows()` 按同一 action 允许的行，`session/search` 只返回这类 Session 的命中，`session/control` 也只返回这类 Session 的 baseline projection 与 projection 帧，因此该 action 也要列在 `session` role 中；owner 的结果不过滤。`session/prompt` 在其 Remote 方法内构造持久的 `user-rpc` 消息 source，且只为非 owner 调用方记录经 `principalOf(this.ctx.invocation)` 读取的 `principal`；不带 `principal` 的 source 属于 owner。
 
-Session 历史在 Agent 就绪前即可读取；setup 期间，摘要中的 `agentAvailable` 为 `false`。Agent 操作和命名空白会话复用会等待本地初始化，前提是其 Session 在此控制器活动期间发布；等待者不取得初始化所属 Agent 的销毁权限。尚未发布 Session 的初始化、裸 Session 和外部写入者仍遵循现有的写入冲突行为。
-
-等待的初始化失败或被取消时，等待者在 Session 释放后收到 `session/not-found`。控制器卸载也会以同一错误结束其等待者。这些失败不会自动重启初始化。
-
 列表行在状态可用时携带 `formatStatus`，Client 无需请求其投影即可识别需要迁移的 Session。
 
 Host 仅在配置的工作时间片耗尽时，于完整条目之间让出事件循环；剩余工作较少时直接返回，不强制让出。每行及每次让出之后检查请求取消，取消时拒绝返回部分结果。每行同步计算；列表不承诺跨 Session 的统一快照。已经进入冷态队列的 Session 若在让出期间接入，仍返回缓存行：Client 对进行中请求的变更重放会纠正其可用性，带序号的投影会覆盖缓存提示。
diff --git a/packages/api/session-controller/src/agent.ts b/packages/api/session-controller/src/agent.ts
index 108ef3015b..4467fefc0f 100644
--- a/packages/api/session-controller/src/agent.ts
+++ b/packages/api/session-controller/src/agent.ts
@@ -8,7 +8,6 @@ import type {} from '@deepseek-ai/dsh-agent-default-model'
 import { installModelSelection } from '@deepseek-ai/dsh-agent'
 import type {} from '@deepseek-ai/dsh-agent-preset-registry'
 import { brandString } from '@deepseek-ai/dsh-brand'
-import { carrierKeyOf } from '@deepseek-ai/dsh-scope'
 import type { Session, SessionId } from '@deepseek-ai/dsh-session'
 import type { SessionInspection } from '@deepseek-ai/dsh-session-persistence'
 import { SessionQueryError, type SessionObservation } from '@deepseek-ai/dsh-session-query'
@@ -160,7 +159,6 @@ export async function inspectApiSession(
 
 /** Owns every operation that may create, resume, or configure a Web Agent. */
 export class ApiSessionAgentController {
-  private readonly initializing = new Map<Session, PromiseWithResolvers<Agent | undefined>>()
   private readonly resumes = new Map<SessionId, Promise<Agent>>()
   private readonly claims = new Map<SessionId, Promise<void>>()
   private readonly imageAdmissionChains = new WeakMap<Agent, Promise<void>>()
@@ -173,25 +171,6 @@ export class ApiSessionAgentController {
    */
   initialize(): void {
     const ctx = this.ctx
-    const initializing = this.initializing
-    ctx.on('session/created', function (session) {
-      // AgentLoop publishes through its own Agent scope; bare Sessions and
-      // Sessions created by another Agent do not announce their own readiness.
-      const owner = carrierKeyOf(this) as Agent | undefined
-      if (owner?.session === session) initializing.set(session, Promise.withResolvers())
-    })
-    ctx.on('agent/created', ({ agent }) => {
-      initializing.get(agent.session)?.resolve(agent)
-      initializing.delete(agent.session)
-    })
-    ctx.on('session/disposed', (session) => {
-      initializing.get(session)?.resolve(undefined)
-      initializing.delete(session)
-    })
-    ctx.effect(() => () => {
-      for (const pending of initializing.values()) pending.resolve(undefined)
-      initializing.clear()
-    }, 'session-controller: Agent readiness')
     ctx.typert.lookups.configure('agent', async (sessionId: SessionId) => {
       const found = await this.resolveAgent(sessionId)
       if ('error' in found) throw found.error
@@ -240,8 +219,7 @@ export class ApiSessionAgentController {
 
     let resume = this.resumes.get(sessionId)
     if (resume === undefined) {
-      resume = (this.pendingAgent(sessionId) ?? this.resume(sessionId, observation))
-        .finally(() => { this.resumes.delete(sessionId) })
+      resume = this.resume(sessionId, observation).finally(() => { this.resumes.delete(sessionId) })
       this.resumes.set(sessionId, resume)
     }
     try {
@@ -260,7 +238,6 @@ export class ApiSessionAgentController {
       const raced = this.liveAgent(sessionId)
       if (raced !== undefined) return raced
       const racedSession = this.ctx.sessions.get(sessionId)
-      if (racedSession !== undefined && this.initializing.has(racedSession)) return this.resolve(sessionId)
       if (racedSession !== undefined && hasApiSessionSubagentOwner(this.ctx, racedSession, undefined)) {
         return { error: apiSessionSubagentOwnershipError(sessionId) }
       }
@@ -277,16 +254,6 @@ export class ApiSessionAgentController {
     }
   }
 
-  /** Observe Web readiness without acquiring the initializing Agent's disposal capability. */
-  private pendingAgent(sessionId: SessionId): Promise<Agent> | undefined {
-    const session = this.ctx.sessions.get(sessionId)
-    const pending = session === undefined ? undefined : this.initializing.get(session)
-    return pending?.promise.then((agent) => {
-      if (agent === undefined) throw new ApiSessionNotFound(`session "${sessionId}" initialization did not complete`)
-      return agent
-    })
-  }
-
   /**
    * Create a Session for a new conversation, reusing the named blank Session
    * while it is still reusable. A reused Session runs the requested preset, or
@@ -303,7 +270,6 @@ export class ApiSessionAgentController {
    * @throws ApiSessionSubagentOwnership when subagent routing owns the named Session.
    * @throws RemoteError `agent-preset/not-found` or `agent-preset/invalid` for the requested or default preset.
    * @throws ApiSessionPresetConflict when no roster is composed and the request names a preset for a reused Session.
-   * @throws ApiSessionNotFound when a joined initialization ends without an Agent.
    */
   async createSession(request: ApiSessionCreateRequest): Promise<ApiSessionCreated> {
     const named = request.sessionId
@@ -385,8 +351,6 @@ export class ApiSessionAgentController {
       throw new ApiSessionSubagentOwnership(sessionId)
     }
     const composition = await this.composeAgent(this.presetForObservation(observation))
-    const pending = this.pendingAgent(sessionId)
-    if (pending !== undefined) return pending
     const published = this.ctx.sessions.get(sessionId)
     const live = this.ctx.agents.get(sessionId)
     if (published !== undefined && hasApiSessionSubagentOwner(this.ctx, published, live)) {
@@ -412,7 +376,6 @@ export class ApiSessionAgentController {
 
   /** @returns the reused Session, a new Session under `sessionId` when none is stored, or a new Session under a minted identity. */
   private async claim(sessionId: SessionId, request: ApiSessionCreateRequest): Promise<Agent> {
-    await this.pendingAgent(sessionId)
     const attached = this.ctx.sessions.get(sessionId)
     const live = this.ctx.agents.get(sessionId)
     if (attached !== undefined && hasApiSessionSubagentOwner(this.ctx, attached, live)) {
@@ -456,7 +419,6 @@ export class ApiSessionAgentController {
       if (error instanceof ApiSessionStartedSinceObserved) return this.createMinted(request.cwd, composition)
       if (!(error instanceof Error) || error.name !== 'SessionAlreadyOwnedError') throw error
       // Another resume in this process may hold the writer for the Agent it published.
-      await this.pendingAgent(sessionId)
       return this.ctx.agents.get(sessionId) === undefined
         ? this.createMinted(request.cwd, composition)
         : this.claim(sessionId, request)
diff --git a/packages/api/session-controller/src/commands.ts b/packages/api/session-controller/src/commands.ts
index 29871acc62..c91f6e5b02 100644
--- a/packages/api/session-controller/src/commands.ts
+++ b/packages/api/session-controller/src/commands.ts
@@ -132,7 +132,7 @@ export class SessionCommandController {
           && (workspace === undefined || workspace.sessionIds.includes(sessionId)),
       })
     } catch (error) {
-      this.rejectCreation(error, request.sessionId)
+      this.rejectCreation(error)
     }
     const sessionId = created.agent.id
     if (workspace !== undefined) {
@@ -513,11 +513,8 @@ export class SessionCommandController {
     return found.agent
   }
 
-  private rejectCreation(error: unknown, sessionId: SessionId | undefined): never {
+  private rejectCreation(error: unknown): never {
     if (remoteErrorOf(error) !== undefined) throw error
-    if (sessionId !== undefined && error instanceof ApiSessionNotFound) {
-      throw new RemoteError('session/not-found', error.message, { sessionId })
-    }
     if (error instanceof ApiSessionPresetConflict) {
       throw new RemoteError('agent-preset/conflict', error.message, {
         sessionId: error.sessionId,
diff --git a/packages/api/session-controller/tests/agent-initialization.host.spec.ts b/packages/api/session-controller/tests/agent-initialization.host.spec.ts
deleted file mode 100644
index 5ecd4fd160..0000000000
--- a/packages/api/session-controller/tests/agent-initialization.host.spec.ts
+++ /dev/null
@@ -1,362 +0,0 @@
-/** Web operations join the original Agent setup while history remains readable. */
-import { mkdtemp, rm } from 'node:fs/promises'
-import { tmpdir } from 'node:os'
-import { join } from 'node:path'
-import { Context } from '@deepseek-ai/cordis'
-import { mountAgentLoopTestDependencies, mountAgentLoopTestHarness } from '@deepseek-ai/dsh-agent-loop-testkit'
-import { SessionId, SessionSeq, type SessionEvent } from '@deepseek-ai/dsh-session'
-import * as JsonlPersistence from '@deepseek-ai/dsh-session-persistence-jsonl'
-import SessionTitle from '@deepseek-ai/dsh-session-title'
-import { SessionAlreadyOwnedError } from '@deepseek-ai/dsh-session-persistence'
-import { describe, expect, it, onTestFinished, vi } from 'vitest'
-import { ApiSessionAgentController } from '../src/agent.ts'
-import type { SessionRequestId } from '../src/types.ts'
-import { createSessionTestController, createSessionTestRemote } from './test-remote.ts'
-
-const seed: SessionEvent[] = [
-  { type: 'turn/start', seq: SessionSeq(0), time: 1, data: { turn: 1 } },
-  { type: 'turn/end', seq: SessionSeq(1), time: 2, data: { turn: 1, reason: { kind: 'completed' } } },
-]
-
-async function harness() {
-  const root = await mkdtemp(join(tmpdir(), 'dsh-web-readiness-'))
-  const ctx = new Context()
-  onTestFinished(async () => {
-    await ctx.fiber.dispose()
-    await rm(root, { recursive: true, force: true })
-  })
-  await mountAgentLoopTestDependencies(ctx)
-  await ctx.plugin(JsonlPersistence, { root })
-  await mountAgentLoopTestHarness(ctx)
-  await ctx.plugin(SessionTitle, { fallbackMaxWords: 5, fallbackMaxBytes: 40, maxTitleBytes: 80 })
-  ctx.provide('workspaceRegistry', { get: () => undefined, list: () => [], archivedSessionIds: [] } as never)
-  ctx.on('agent/pre-step', async () => ({ kind: 'reject' }))
-  const defaults = { defaultModelSelection: () => ({ provider: 'fixture', model: 'fixture' }), cwd: root }
-  const api = ctx.plugin({
-    inject: ['agents', 'sessions', 'sessionProjections', 'llm', 'workspaceRegistry', 'sessionPersistence', 'sessionTitle'],
-    apply() {},
-  })
-  await api
-  const controller = await createSessionTestController(api.ctx, defaults)
-  const remote = await createSessionTestRemote(api.ctx, defaults)
-  return { ctx, root, controller, remote, api }
-}
-
-function nextSessionRead(ctx: Context, sessionId: SessionId): Promise<undefined> {
-  const read = Promise.withResolvers<undefined>()
-  const get = ctx.sessions.get.bind(ctx.sessions)
-  const spy = vi.spyOn(ctx.sessions, 'get').mockImplementation((id) => {
-    const session = get(id)
-    if (id === sessionId) read.resolve(undefined)
-    return session
-  })
-  onTestFinished(() => { spy.mockRestore() })
-  return read.promise
-}
-
-describe('Web Agent initialization', () => {
-  it.each(['create', 'resume'] as const)('keeps %s history readable and joins setup for mutations', async (mode) => {
-    const { ctx, root, controller, remote } = await harness()
-    const sessionId = SessionId('initializing')
-    if (mode === 'resume') {
-      const previous = await ctx.agents.create({ sessionId, meta: { cwd: root }, seed })
-      await previous.dispose()
-    }
-    const entered = Promise.withResolvers<undefined>()
-    const release = Promise.withResolvers<undefined>()
-    const setup = async (): Promise<void> => { entered.resolve(undefined); await release.promise }
-    const creation = mode === 'create'
-      ? ctx.agents.create({ sessionId, meta: { cwd: root }, seed, setup })
-      : ctx.agents.resume({ resumeSessionId: sessionId, setup })
-    onTestFinished(async () => { release.resolve(undefined); await creation })
-    await entered.promise
-    const resume = vi.spyOn(ctx.agents, 'resume')
-    const abort = new AbortController()
-    const iterator = controller.follow({ address: { kind: 'session', sessionId } }, abort.signal)
-      [Symbol.asyncIterator]()
-    try {
-      expect(ctx.sessions.get(sessionId)).toBeDefined()
-      expect(ctx.agents.get(sessionId)).toBeUndefined()
-      expect((await controller.list({}, abort.signal)).items.find(item => item.sessionId === sessionId))
-        .toMatchObject({ blank: false, agentAvailable: false })
-      const snapshot = await iterator.next()
-      if (snapshot.done || snapshot.value.type !== 'snapshot') throw new Error('missing history snapshot')
-      expect(snapshot.value.records.slice(0, 2).map(record => record.event)).toEqual(seed)
-      const resolved = controller.resolveAgent(sessionId)
-      const renamed = remote.rename({ sessionId, title: 'Ready title' })
-      const prompted = remote.prompt({
-        requestId: 'ready-prompt' as SessionRequestId, sessionId, mode: 'queue',
-        content: [{ type: 'text', text: 'hello' }], clientTimeZone: 'UTC',
-      })
-      release.resolve(undefined)
-      const handle = await creation
-      const resolution = await resolved
-      expect('agent' in resolution && resolution.agent).toBe(handle.agent)
-      await expect(renamed).resolves.toMatchObject({ ok: true, value: { title: 'Ready title' } })
-      await expect(prompted).resolves.toMatchObject({ ok: true })
-      expect(resume).not.toHaveBeenCalled()
-      await ctx.sessions.flush(handle.agent.session)
-      await using stored = await ctx.sessionPersistence.open(sessionId, 'read')
-      expect((await stored.read()).events.findLast(event => event.type === 'session/title')?.data)
-        .toMatchObject({ title: 'Ready title' })
-    } finally {
-      release.resolve(undefined)
-      abort.abort()
-      await iterator.return?.()
-      resume.mockRestore()
-    }
-  })
-
-  it('reuses a named blank after its original setup completes', async () => {
-    const { ctx, root, remote } = await harness()
-    const sessionId = SessionId('blank-initializing')
-    const entered = Promise.withResolvers<undefined>()
-    const release = Promise.withResolvers<undefined>()
-    const creation = ctx.agents.create({
-      sessionId, meta: { cwd: root },
-      setup: async () => { entered.resolve(undefined); await release.promise },
-    })
-    const resume = vi.spyOn(ctx.agents, 'resume')
-    try {
-      await entered.promise
-      const reused = remote.create({ sessionId, cwd: root })
-      release.resolve(undefined)
-      await creation
-      const result = await reused
-      if (!result.ok) throw result.error
-      expect(result.value.sessionId).toBe(sessionId)
-      expect(ctx.agents.list()).toHaveLength(1)
-      expect(resume).not.toHaveBeenCalled()
-    } finally {
-      release.resolve(undefined)
-      await creation
-      resume.mockRestore()
-    }
-  })
-
-  it.each(['failure', 'cancel'] as const)('ends waiters after initialization %s releases its writer', async (outcome) => {
-    const { ctx, root, controller } = await harness()
-    const sessionId = SessionId('failed-initializing')
-    const entered = Promise.withResolvers<undefined>()
-    const release = Promise.withResolvers<undefined>()
-    const cancellation = new AbortController()
-    const creation = ctx.agents.create({
-      sessionId, meta: { cwd: root }, seed, signal: cancellation.signal,
-      setup: async () => { entered.resolve(undefined); await release.promise; throw new Error('setup failed') },
-    })
-    const failed = expect(creation).rejects.toThrow()
-    try {
-      await entered.promise
-      const resolution = controller.resolveAgent(sessionId)
-      if (outcome === 'cancel') cancellation.abort(new Error('cancelled'))
-      release.resolve(undefined)
-      await failed
-      await expect(resolution).resolves.toMatchObject({ error: { code: 'session/not-found' } })
-      expect(ctx.agents.get(sessionId)).toBeUndefined()
-      await using writer = await ctx.sessionPersistence.open(sessionId, 'write')
-      expect(writer.id).toBe(sessionId)
-    } finally {
-      release.resolve(undefined)
-      await failed
-    }
-  })
-
-  it.each(['failure', 'cancel'] as const)('reports named blank initialization %s without starting another Agent', async (outcome) => {
-    const { ctx, root, remote } = await harness()
-    const sessionId = SessionId('failed-blank')
-    const entered = Promise.withResolvers<undefined>()
-    const release = Promise.withResolvers<undefined>()
-    const cancellation = new AbortController()
-    const creation = ctx.agents.create({
-      sessionId, meta: { cwd: root }, signal: cancellation.signal,
-      setup: async () => {
-        entered.resolve(undefined)
-        await release.promise
-        if (outcome === 'failure') throw new Error('setup failed')
-      },
-    })
-    const failed = expect(creation).rejects.toThrow()
-    const create = vi.spyOn(ctx.agents, 'create')
-    try {
-      await entered.promise
-      const published = ctx.sessions.get(sessionId)
-      if (published === undefined) throw new Error('initializing Session was not published')
-      const waiting = nextSessionRead(ctx, sessionId)
-      const reused = remote.create({ sessionId, cwd: root })
-      await waiting
-      if (outcome === 'cancel') cancellation.abort(new Error('cancelled'))
-      release.resolve(undefined)
-      await failed
-      await expect(reused).resolves.toMatchObject({ ok: false, error: { code: 'session/not-found', details: { sessionId } } })
-      expect(create).not.toHaveBeenCalled()
-      expect(ctx.agents.list()).toHaveLength(0)
-      await using writer = await ctx.sessionPersistence.create(published.header)
-      expect(writer.id).toBe(sessionId)
-    } finally {
-      release.resolve(undefined)
-      await failed
-      create.mockRestore()
-    }
-  })
-
-  it.each([
-    ['resolve', 'success'], ['create', 'success'], ['create', 'failure'], ['create', 'cancel'],
-  ] as const)('joins the external writer after %s races its acquisition (%s)', async (operation, outcome) => {
-    const { ctx, root, controller, remote } = await harness()
-    const sessionId = SessionId('writer-race')
-    const previous = await ctx.agents.create({ sessionId, meta: { cwd: root }, seed: [
-      { type: 'session/title', seq: SessionSeq(0), time: 1, data: { title: 'Blank', messageSeqs: [], source: { kind: 'user' } } },
-    ] })
-    await previous.dispose()
-    const acquiring = Promise.withResolvers<undefined>()
-    const conflict = Promise.withResolvers<undefined>()
-    const resume = vi.spyOn(ctx.agents, 'resume').mockImplementationOnce(async () => {
-      acquiring.resolve(undefined)
-      await conflict.promise
-      throw new SessionAlreadyOwnedError(sessionId)
-    })
-    const request = operation === 'resolve'
-      ? controller.resolveAgent(sessionId).then(result => 'agent' in result
-        ? { sessionId: result.agent.id, agent: result.agent } : result)
-      : remote.create({ sessionId, cwd: root }).then(result => result.ok ? result.value : { error: result.error })
-    const entered = Promise.withResolvers<undefined>()
-    const release = Promise.withResolvers<undefined>()
-    const cancellation = new AbortController()
-    onTestFinished(async () => {
-      conflict.resolve(undefined)
-      release.resolve(undefined)
-      await request
-      resume.mockRestore()
-    })
-    await Promise.race([acquiring.promise, request.then((result) => {
-      if ('error' in result) throw result.error
-      throw new Error('request settled before write acquisition')
-    })])
-    const initialization = ctx.agents.resume({
-      resumeSessionId: sessionId, signal: cancellation.signal,
-      setup: async () => {
-        entered.resolve(undefined)
-        await release.promise
-        if (outcome === 'failure') throw new Error('setup failed')
-      },
-    })
-    const settled = initialization.then(handle => ({ handle }), (error: unknown) => ({ error }))
-    onTestFinished(async () => {
-      release.resolve(undefined)
-      await settled
-    })
-    await Promise.race([entered.promise, initialization])
-    const waiting = nextSessionRead(ctx, sessionId)
-    conflict.resolve(undefined)
-    await waiting
-    if (outcome === 'cancel') cancellation.abort(new Error('cancelled'))
-    release.resolve(undefined)
-    const original = await settled
-    const result = await request
-    if (outcome === 'success') {
-      if ('error' in original) throw original.error
-      expect(result).toMatchObject({ sessionId })
-      if ('agent' in result) expect(result.agent).toBe(original.handle.agent)
-      expect(ctx.agents.get(sessionId)).toBe(original.handle.agent)
-    } else {
-      expect(original).toHaveProperty('error')
-      expect(result).toMatchObject({ error: { code: 'session/not-found', details: { sessionId } } })
-      expect(ctx.agents.list()).toHaveLength(0)
-      await using writer = await ctx.sessionPersistence.open(sessionId, 'write')
-      expect(writer.id).toBe(sessionId)
-    }
-    expect(resume).toHaveBeenCalledTimes(2)
-  })
-
-  it('joins initialization that starts during preset resolution without another resume', async () => {
-    const { ctx, root, controller } = await harness()
-    const sessionId = SessionId('composition-race')
-    const previous = await ctx.agents.create({ sessionId, meta: { cwd: root }, seed })
-    await previous.dispose()
-    const composing = Promise.withResolvers<undefined>()
-    const finishComposition = Promise.withResolvers<undefined>()
-    // oxlint-disable-next-line typescript/unbound-method -- Invoked with the intercepted controller through call().
-    const compose = ApiSessionAgentController.prototype.composeAgent
-    const composition = vi.spyOn(ApiSessionAgentController.prototype, 'composeAgent')
-      .mockImplementationOnce(async function (this: ApiSessionAgentController, preset) {
-        composing.resolve(undefined)
-        await finishComposition.promise
-        return compose.call(this, preset)
-      })
-    const resolving = controller.resolveAgent(sessionId)
-    const entered = Promise.withResolvers<undefined>()
-    const release = Promise.withResolvers<undefined>()
-    onTestFinished(async () => {
-      finishComposition.resolve(undefined)
-      release.resolve(undefined)
-      await resolving
-      composition.mockRestore()
-    })
-    await composing.promise
-    const initialization = ctx.agents.resume({
-      resumeSessionId: sessionId,
-      setup: async () => { entered.resolve(undefined); await release.promise },
-    })
-    const resume = vi.spyOn(ctx.agents, 'resume')
-    try {
-      await Promise.race([entered.promise, initialization])
-      const waiting = nextSessionRead(ctx, sessionId)
-      finishComposition.resolve(undefined)
-      await waiting
-      release.resolve(undefined)
-      const original = await initialization
-      const result = await resolving
-      expect('agent' in result && result.agent).toBe(original.agent)
-      expect(resume).not.toHaveBeenCalled()
-    } finally {
-      finishComposition.resolve(undefined)
-      release.resolve(undefined)
-      await initialization
-      await resolving
-      resume.mockRestore()
-    }
-  })
-
-  it('does not wait for a bare Session whose writer belongs to another owner', async () => {
-    const { ctx, root, controller } = await harness()
-    const sessionId = SessionId('bare-session')
-    const session = ctx.sessions.create(sessionId, { meta: { cwd: root } })
-    await using writer = await ctx.sessionPersistence.create(session.header)
-    expect(writer.id).toBe(sessionId)
-    await expect(controller.resolveAgent(sessionId)).resolves.toMatchObject({ error: { code: 'session/writer-held' } })
-  })
-
-  it('releases Controller waiters without disposing the original Agent owner', async () => {
-    const { ctx, root, controller, api } = await harness()
-    const sessionId = SessionId('independently-owned')
-    const previous = await ctx.agents.create({ sessionId, meta: { cwd: root }, seed })
-    await previous.dispose()
-    const abort = new AbortController()
-    const iterator = controller.follow({ address: { kind: 'session', sessionId } }, abort.signal)[Symbol.asyncIterator]()
-    await iterator.next()
-    const entered = Promise.withResolvers<undefined>()
-    const release = Promise.withResolvers<undefined>()
-    const creation = ctx.agents.resume({
-      resumeSessionId: sessionId,
-      setup: async () => { entered.resolve(undefined); await release.promise },
-    })
-    try {
-      await entered.promise
-      // Continuing the cold follow starts its background promotion while the original resume owns setup.
-      const following = iterator.next()
-      const resolving = controller.resolveAgent(sessionId)
-      await api.dispose()
-      await following
-      await expect(resolving).resolves.toMatchObject({ error: { code: 'session/not-found' } })
-      expect(ctx.sessions.get(sessionId)).toBeDefined()
-      release.resolve(undefined)
-      const handle = await creation
-      expect(ctx.agents.get(sessionId)).toBe(handle.agent)
-    } finally {
-      release.resolve(undefined)
-      abort.abort()
-      await iterator.return?.()
-      await creation
-    }
-  })
-})