refactor(agent-loop): drop the steering/message session event

Steer, inject, and followup now land as durable user/message events on the
session surface; the steering/message event type and its ConversationNode
kind are removed from the client projection. Update tests, docs, generated
catalogs, and agent notes to match, and align the steering e2e fixture and
prompt inventory assertions with the durable user/message landing.

packages/client/connection/src/client/fixture.ts

@@ -339,7 +339,7 @@ function fixtureUsage(turn: number, step: number): TokenUsage {
 }
 
 /** fx-alpha history script: 60 turns (~130+ messages -> 3 pages at PAGE_MESSAGES=50),
- *  mixing reasoning blocks / tool call+result / steering / context. */
+ *  mixing reasoning blocks / tool call+result / context. */
 function buildAlphaLog(): SessionEvent[] {
   const events: Record<string, unknown>[] = []
   let time = Date.now() - 3_600_000
@@ -393,9 +393,6 @@ function buildAlphaLog(): SessionEvent[] {
       push({ type: 'assistant/message', surfaceOp: 'append', data: { turn, step: 0, message: assistantMessage(blocks) } })
       push({ type: 'step/end', data: { turn, step: 0 } })
     }
-    if (turn % 13 === 6) {
-      push({ type: 'steering/message', surfaceOp: 'append', data: { turn, message: userMessage(text(`插话 ${turn}：fixture steering 消息。`)) } })
-    }
     push({ type: 'turn/end', data: { turn, reason: { kind: 'completed' } } })
   }
   // Three view-sample turns (60-62) cover the built-in card types. The real filesystem names in
@@ -957,7 +954,7 @@ function pageOf(
     const event = log[i]
     /* v8 ignore next -- dense-array guard: log seqs are array indexes, i stays within [0, end). */
     if (event === undefined) break
-    if (event.type === 'user/message' || event.type === 'assistant/message' || event.type === 'steering/message') messages++
+    if (event.type === 'user/message' || event.type === 'assistant/message') messages++
     if (event.type === 'turn/start' && messages >= maxMessages) {
       start = i
       break
@@ -986,11 +983,11 @@ function searchBlockText(block: ContentBlock): string[] {
   }
 }
 
-/** One current-surface user/assistant/steering document, if searchable. */
+/** One current-surface user/assistant document, if searchable. */
 function searchEventText(event: SessionEvent): string {
   const content = event.type === 'user/message'
     ? event.data.content
-    : event.type === 'assistant/message' || event.type === 'steering/message'
+    : event.type === 'assistant/message'
       ? event.data.message.content
       : undefined
   if (content === undefined) return ''
@@ -1833,10 +1830,8 @@ export function createFixtureApi(options: FixtureOptions = {}): ApiProxy {
         summary.blank = false
         const userText = content.map(b => (b.type === 'text' ? b.text : '')).join('')
         if (mode === 'steer' && replays.has(id)) {
-          // Steering: insert a steering message into the current turn; the replay continues.
-          /* v8 ignore next -- the ?? arm needs a missing counter, but a live replay implies a prior prompt already set it. */
-          const turn = (nextTurn.get(id) ?? 1) - 1
-          append(id, { type: 'steering/message', surfaceOp: 'append', data: { turn, message: userMessage(content) } })
+          // Steering: the durable user/message lands inside the current turn; the replay continues.
+          append(id, { type: 'user/message', surfaceOp: 'append', data: userMessage(content) })
           return ok(request, { accepted: true as const })
         }
         const turn = nextTurn.get(id) ?? 0

packages/client/connection/tests/fixture.spec.ts

@@ -301,7 +301,7 @@ describe('createFixtureApi', () => {
     expect(idleCancel.result).toMatchObject({ ok: true })
   })
 
-  it('steer during a replay inserts a steering message and the replay continues to completion', async () => {
+  it('steer during a replay lands a user/message inside the current turn and the replay continues', async () => {
     const api = createFixtureApi()
     const created = await api.sessions.create(req({}))
     if (!created.result.ok) throw new Error('create failed')
@@ -314,7 +314,7 @@ describe('createFixtureApi', () => {
     await api.sessions.prompt(req({ sessionId: id, mode: 'steer' as const, content: [{ type: 'text' as const, text: '插话' }] }))
     const frames = await framesPromise
     const types = frames.filter((f): f is Extract<MuxFrame, { type: 'session/event' }> => f.type === 'session/event').map(f => f.event.type)
-    expect(types).toContain('steering/message')
+    expect(JSON.stringify(frames)).toContain('插话')
     expect(types.at(-1)).toBe('turn/end') // steer did not restart the turn
   })
 
@@ -362,7 +362,7 @@ describe('createFixtureApi', () => {
     }))
     const frames = await framesPromise
     const types = frames.filter((f): f is Extract<MuxFrame, { type: 'session/event' }> => f.type === 'session/event').map(f => f.event.type)
-    expect(types[0]).toBe('turn/start') // idle steer degraded to a queued turn, not a steering insert
+    expect(types[0]).toBe('turn/start') // idle steer degraded to a queued turn, not an in-turn insert
   })
 
   it('gamma interval flip emits host/session-status and a running log-less session subscribes at lastSeq -1', async () => {

packages/client/runtime/src/client/index.ts

@@ -48,7 +48,7 @@ export type {
   AssistantTiming, CodeSubCall, CommandNode, CompactionSummaryNode, ComposerPhase,
   ContextMessageNode, ConversationNode, ConversationSnapshot, ModelRetryNode, QueuedMessage,
   RunningToolCall,
-  SteeringMessageNode, TodoItem, ToolResultNode, TurnErrorNode, UnknownSurfaceNode, UserMessageNode,
+  TodoItem, ToolResultNode, TurnErrorNode, UnknownSurfaceNode, UserMessageNode,
 } from './sessions/conversation.ts'
 export type {
   ConversationContext, ConversationContextOriginKind,

packages/client/runtime/src/client/session-history/history-fold.ts

@@ -144,12 +144,6 @@ function materializeNode(
         ...(requestConfig === undefined ? {} : { requestConfig }),
         ...(assistantTiming === undefined ? {} : { timing: assistantTiming }),
       }
-    case 'steering/message':
-      return {
-        kind: 'steering', messageId: event.data.message.id,
-        seq: event.seq, time: event.time, turn: event.data.turn,
-        content: event.data.message.content, source: event.data.message.source,
-      }
     case 'tool/result': {
       const result = event.data.message.content[0]
       const callId = String(event.data.message.source.callId)

packages/client/runtime/src/client/sessions/conversation.ts

@@ -102,19 +102,6 @@ export interface AssistantMessageNode {
   interrupted?: true
 }
 
-/** A steering message injected mid-turn. */
-export interface SteeringMessageNode {
-  kind: 'steering'
-  /** Stable identity shared with its pre-admission inbox occurrence. */
-  messageId: MessageId
-  seq: number
-  /** Unix epoch ms from the source session event. */
-  time: number
-  turn: number
-  content: readonly ContentBlock[]
-  source: unknown
-}
-
 /** A context/system injection surfaced in the flow. */
 export interface ContextMessageNode {
   kind: 'context'
@@ -236,7 +223,6 @@ export interface CommandNode {
 export type ConversationNode =
   | UserMessageNode
   | AssistantMessageNode
-  | SteeringMessageNode
   | ContextMessageNode
   | ModelRetryNode
   | TurnErrorNode

packages/client/runtime/src/client/sessions/session.ts

@@ -656,12 +656,8 @@ export class Session implements SessionFace {
 
   /** Retire the first matching live steering occurrence when its durable message takes over. */
   private handoffPendingSteering(event: SessionEvent): void {
-    const message = event.type === 'user/message'
-      ? event.data
-      : event.type === 'steering/message'
-        ? event.data.message
-        : undefined
-    if (message === undefined) return
+    if (event.type !== 'user/message') return
+    const message = event.data
     const index = this.queued.findIndex(item =>
       item.placement === 'steering' && item.messageId === message.id)
     if (index === -1) return

packages/client/runtime/src/client/sessions/transcript-adapter.ts

@@ -72,12 +72,6 @@ function materializeNode(
         turn: event.data.turn, step: event.data.step,
         blocks: toAssistantBlocks(event.data.message.content), usage: event.data.usage,
       }
-    case 'steering/message':
-      return {
-        kind: 'steering', messageId: event.data.message.id,
-        seq: event.seq, time: event.time, turn: event.data.turn,
-        content: event.data.message.content, source: event.data.message.source,
-      }
     case 'tool/result': {
       const result = event.data.message.content[0]
       const callId = String(event.data.message.source.callId)

packages/client/runtime/tests/queue-store.spec.ts

@@ -149,16 +149,16 @@ describe('queue snapshot intake', () => {
     const durable = {
       seq: 0,
       time: 1_700_000_000_000,
-      type: 'steering/message',
+      type: 'user/message',
       surfaceOp: 'append',
-      data: { turn: 1, message },
+      data: message,
     } as SessionEvent
 
     session.handleMuxEnvelope(rid('env-durable'), {
       type: 'session/event', sessionId: SID, event: durable,
     })
     expect(session.getSnapshot().queue.map(item => item.id)).toEqual(['s-second'])
-    expect(session.getSnapshot().nodes.filter(node => node.kind === 'steering')).toHaveLength(1)
+    expect(session.getSnapshot().nodes.filter(node => node.kind === 'user')).toHaveLength(1)
 
     session.handleMuxEnvelope(rid('env-reused-id'), queueFrame([
       { id: 's-later', body: '', placement: 'steering', message },

packages/client/runtime/tests/transcript-adapter.spec.ts

@@ -88,21 +88,14 @@ describe('TranscriptAdapter', () => {
     adapter.reset([
       ev.user(0, '用户'),
       ev.assistant(1, 0, '助手'),
-      at(2, { type: 'steering/message', surfaceOp: 'append', data: {
-        turn: 0,
-        message: createUserMessage({
-          content: [{ type: 'text', text: '插话' }],
-          source: { kind: 'user' },
-        }),
-      } }),
-      at(3, { type: 'user/message', surfaceOp: 'append', data: createUserMessage({
+      at(2, { type: 'user/message', surfaceOp: 'append', data: createUserMessage({
         content: [{ type: 'text', text: '上下文' }], source: { kind: 'plugin', plugin: 'p' },
       }) }),
-      ev.toolCall(4, 0, 'c1', 'echo', '{"x":1}'),
-      ev.toolResult(5, 0, 'c1', '结果'),
+      ev.toolCall(3, 0, 'c1', 'echo', '{"x":1}'),
+      ev.toolResult(4, 0, 'c1', '结果'),
     ])
     const nodes = adapter.nodes()
-    expect(nodes.map(n => n.kind)).toEqual(['user', 'assistant', 'steering', 'context', 'tool-result'])
+    expect(nodes.map(n => n.kind)).toEqual(['user', 'assistant', 'context', 'tool-result'])
     expect(nodes.find(n => n.kind === 'tool-result')).toMatchObject({
       callId: 'c1', call: { name: 'echo', argsRaw: '{"x":1}' }, isError: false,
     })

packages/client/ui-conversation/README.md

@@ -38,7 +38,7 @@ The todo surfaces are two registrations over that shape, both plain registrant p
 
 `QueueDock` is the terminal input-dock entry at `order: 20`. It hides while empty, renders one pending row directly, and defaults two or more rows to a collapsed `"<n> 条排队消息"` header whose button expands or collapses the complete list. The header exposes `aria-expanded` and `aria-controls`; the expanded list scrolls within a 180px height bound. An active edit or mutation keeps its rows visible, and emptying the queue restores the collapsed default for the next queue. Each visible ordinary-session row remains a single-line preview with its exact-occurrence edit, delete, and strict-steer actions; addressed subagents retain the rows as a read-only projection because their continuation transport does not expose queue mutation. If strict steer loses to a closed window, the original occurrence remains queued for normal delivery; if the driver already claimed it, normal delivery is already underway. Neither converged race displays a failure, while transport and unknown failures do.
 
-The Host's placement-aware `session/queue` snapshot also carries pending steering. QueueDock filters it out, while ChatView projects it as a user-style bubble with Copy at the conversation tail; Fork stays absent because the message has not entered a durable turn. The Host delays steering retirement until the durable `steering/message` has entered the mux stream. On that accepted live event, the client runtime retires the first matching current steering occurrence before publishing the snapshot; historical events cannot hide later occurrences that reuse the same `MessageId`. The bubble therefore hands off without a gap or duplicate, restores Copy and Fork from the durable node, and survives reconnect from the same authority.
+The Host's placement-aware `session/queue` snapshot also carries pending steering. QueueDock filters it out, while ChatView projects it as a user-style bubble with Copy at the conversation tail; Fork stays absent because the message has not entered a durable turn. The Host delays steering retirement until the durable `user/message` carrying the steering has entered the mux stream. On that accepted live event, the client runtime retires the first matching current steering occurrence before publishing the snapshot; historical events cannot hide later occurrences that reuse the same `MessageId`. The bubble therefore hands off without a gap or duplicate, restores Copy and Fork from the durable node, and survives reconnect from the same authority.
 
 Keyboard message submission resolves delivery from the addressed session's running state and steering capability. While idle, Enter and Cmd/Ctrl+Enter both perform an ordinary Queue send. While a primary session is running, the browser-persisted General Settings preference assigns plain Enter to `Queue` (the default) or `Steer`, and Cmd/Ctrl+Enter performs the other behavior; Shift+Enter remains a newline. Addressed subagents keep both gestures on their Queue-only continuation transport even while running. The preference affects only the steer-capable busy-state gesture pair, and the send button and non-keyboard submit actions remain Queue. Composer Steer uses the existing best-effort `session.prompt(mode: 'steer')` contract: if the current next-step window closes before acceptance, AgentLoop admits the message as the next waking Queue turn without surfacing a failure or losing the draft transaction.
 
@@ -69,4 +69,4 @@ None; this package neither assembles nor sends a provider request.
 - **The approval panel's "Always allow this type" is deferred** — durable grants need a grant-storage design; only allow-once/reject answer today.
 - **TodoPanel truncates long item text to one ellipsized line** — the figma strip has no wrap or expand affordance; full text is not readable inline.
 - **Queue edit is text-only** — rows containing non-text blocks still show a flattened preview, but their edit control is disabled because the inline editor cannot preserve those blocks. A text row's edit mode replaces delete and strict steer with save and cancel; Enter saves and Escape cancels.
-- **Queue strict steer preserves complete messages** — while the Agent is running, the steer action atomically transfers the addressed Queue occurrence into the current next-step window. Mixed-content rows remain eligible because the action forwards the immutable message instead of the text projection. The placement-aware Host snapshot renders pending steering at the conversation tail until the consumed `steering/message` folds into the durable transcript, so immediate display, reconnect, and replay share one linear authority.
+- **Queue strict steer preserves complete messages** — while the Agent is running, the steer action atomically transfers the addressed Queue occurrence into the current next-step window. Mixed-content rows remain eligible because the action forwards the immutable message instead of the text projection. The placement-aware Host snapshot renders pending steering at the conversation tail until the consumed `user/message` folds into the durable transcript, so immediate display, reconnect, and replay share one linear authority.

packages/client/ui-conversation/README.zh.md

@@ -38,7 +38,7 @@ todo 两个面就是在该形状上的两个注册项，都是普通注册方插
 
 `QueueDock` 是 `order: 20` 的末端 input-dock 条目。队列为空时隐藏；只有一个待处理项时直接渲染该行；存在两个或更多待处理项时，默认收起为 `"<n> 条排队消息"` 表头，其按钮可展开或收起完整列表。表头暴露 `aria-expanded` 和 `aria-controls`；展开后的列表以 180px 为高度上限，并可滚动。存在进行中的编辑或变更时，列表行会保持可见；队列清空后，下一次出现队列时会恢复默认收起状态。普通会话中的每条可见行仍是单行预览，并提供针对精确单次入队项的编辑、删除和严格 steering（中途引导）操作；已寻址 subagent 则保留只读行，因为其继续执行传输不提供 Queue 变更。如果严格 steering 输给已关闭的窗口，原单次入队项会留在 Queue 中正常投递；如果驱动器已经认领该项，正常投递就已开始。这两种已收敛的竞态都不显示失败，传输和未知错误仍会显示。
 
-Host 带 placement 的 `session/queue` 快照也会携带待处理 steering。QueueDock 会将其过滤掉，ChatView 则把它投影为会话流末尾带复制操作的用户样式气泡；消息尚未进入持久轮次，因此不显示 fork。Host 会等持久 `steering/message` 进入 mux 流之后再退役 steering。客户端运行时接纳该实时事件时，会在发布快照前退役第一个匹配的当前 steering 单次入队项；历史事件无法隐藏后来复用同一 `MessageId` 的单次入队项。气泡交接时因而不会产生空档或重复，会从持久节点恢复复制与 fork 操作，并能在重连后从同一权威恢复。
+Host 带 placement 的 `session/queue` 快照也会携带待处理 steering。QueueDock 会将其过滤掉，ChatView 则把它投影为会话流末尾带复制操作的用户样式气泡；消息尚未进入持久轮次，因此不显示 fork。Host 会等携带该 steering 的持久 `user/message` 进入 mux 流之后再退役 steering。客户端运行时接纳该实时事件时，会在发布快照前退役第一个匹配的当前 steering 单次入队项；历史事件无法隐藏后来复用同一 `MessageId` 的单次入队项。气泡交接时因而不会产生空档或重复，会从持久节点恢复复制与 fork 操作，并能在重连后从同一权威恢复。
 
 键盘消息提交会根据所寻址会话的运行状态和 steering 能力解析投递方式。空闲时，Enter 和 Cmd/Ctrl+Enter 都执行普通 Queue 发送。主会话运行期间，浏览器持久化的 General Settings 偏好会把普通 Enter 分配为 `Queue`（默认值）或 `Steer`，Cmd/Ctrl+Enter 则执行另一种行为；Shift+Enter 仍然换行。已寻址 subagent 即使正在运行，也会让这两个手势都使用其仅支持 Queue 的继续执行传输。该偏好只影响支持 steering 的繁忙态手势对，发送按钮与非键盘提交操作仍使用 Queue。Composer Steer 复用现有尽力而为的 `session.prompt(mode: 'steer')` 契约：如果当前 next-step 窗口在接纳前关闭，AgentLoop 会把消息接纳为下一条唤醒 Queue 轮次，不显示失败，也不会丢失草稿事务。
 
@@ -69,4 +69,4 @@ Host 带 placement 的 `session/queue` 快照也会携带待处理 steering。Qu
 - **审批面板的「始终允许此类」暂缓**：持久授权需要授权存储设计；今天只能回答允许一次／拒绝。
 - **TodoPanel 将过长条目截成单行省略号**：figma 条没有换行或展开入口，完整文本无法在行内读完。
 - **Queue 编辑仅支持文本**：包含非文本块的行仍显示扁平化预览，但由于内联编辑器无法保留这些块，其编辑控件会被禁用。文本行进入编辑模式后，删除和严格 steering（中途引导）操作会被保存和取消取代；Enter 保存，Escape 取消。
-- **Queue 严格 steering 会保留完整消息**：Agent 运行期间，steering 操作会以原子方式把所寻址的 Queue 单次入队项转移到当前 next-step 窗口。包含混合内容的行仍可使用此操作，因为它会转发不可变消息，而非文本投影。带 placement 的 Host 快照会在会话流末尾渲染待处理 steering，直到已消费的 `steering/message` 折叠进持久 transcript（文本记录），因此立即展示、重连和回放共享同一个线性权威。
+- **Queue 严格 steering 会保留完整消息**：Agent 运行期间，steering 操作会以原子方式把所寻址的 Queue 单次入队项转移到当前 next-step 窗口。包含混合内容的行仍可使用此操作，因为它会转发不可变消息，而非文本投影。带 placement 的 Host 快照会在会话流末尾渲染待处理 steering，直到已消费的 `user/message` 折叠进持久 transcript（文本记录），因此立即展示、重连和回放共享同一个线性权威。

packages/client/ui-conversation/src/client/chat/MessageIconActions.tsx

@@ -1,4 +1,4 @@
-// Shared IconActions chrome for user, steering, and assistant messages: copy
+// Shared IconActions chrome for user and assistant messages: copy
 // live, optional branch wiring, and an optional date-aware clock.
 
 import { useCallback } from 'react'

packages/client/ui-conversation/src/client/chat/MessageItem.tsx

@@ -1,4 +1,4 @@
-// MessageItem: simple chat nodes — user and consumed-steering bubbles
+// MessageItem: simple chat nodes — user bubbles
 // (right-aligned, with clock + copy / branch IconActions), pending steering
 // (copy only), context injection, compaction marker, retry disclosure, and
 // unknown-surface JSON rows.
@@ -6,7 +6,7 @@
 import { memo, useEffect, useMemo, useState } from 'react'
 import type { ReactNode } from 'react'
 import type {
-  CompactionSummaryNode, ContextMessageNode, ModelRetryNode, SteeringMessageNode,
+  CompactionSummaryNode, ContextMessageNode, ModelRetryNode,
   TurnErrorNode, UnknownSurfaceNode, UserMessageNode,
 } from '@deepseek-ai/dsh-client-runtime/client'
 import { JsonBlock, MessageText, StateDot } from '@deepseek-ai/dsh-client-ui-primitives'
@@ -19,7 +19,6 @@ import css from './MessageItem.module.css'
 export interface MessageItemProps {
   node:
     | UserMessageNode
-    | SteeringMessageNode
     | ContextMessageNode
     | CompactionSummaryNode
     | ModelRetryNode
@@ -225,7 +224,6 @@ export const MessageItem = memo(function MessageItem({
   const truncated = (total: number): string => t('json.truncated', { total })
   switch (node.kind) {
     case 'user':
-    case 'steering':
       return (
         <UserStyleBubble
           content={node.content}

packages/client/ui-conversation/tests/chat-branch-tails.spec.tsx

@@ -1,5 +1,5 @@
 // @vitest-environment jsdom
-// Remaining chat branch tails: MessageItem context/unknown/steering arms,
+// Remaining chat branch tails: MessageItem context/unknown arms,
 // user IconActions, StatsLine no-cache join,
 // AssistantMarkdown single-line reasoning. (Tool-row dispatch tails live
 // with the keyed-slot machinery specs since the tool ring dissolved into
@@ -102,30 +102,6 @@ describe('MessageItem arms', () => {
     fireEvent.click(screen.getByRole('button', { name: '复制' }))
   })
 
-  it('consumed steering renders copy and branch actions without a badge', () => {
-    const writeText = vi.fn().mockResolvedValue(undefined)
-    Object.defineProperty(navigator, 'clipboard', {
-      configurable: true,
-      value: { writeText },
-    })
-    const fork = vi.fn()
-    const view = render(
-      <MessageItem t={t} node={{
-        kind: 'steering', messageId: 'steer-message', seq: 2, time: 1_000, turn: 1, source: null,
-        content: [{ type: 'text', text: 'steer!' }, { type: 'image', data: 'x' }] as never,
-      } as never}
-      onFork={fork}
-      />,
-    )
-    expect(view.queryByText('插话')).toBeNull()
-    expect(view.getByText('steer!')).toBeTruthy()
-    expect(view.getByText(/附加内容块/)).toBeTruthy()
-    fireEvent.click(view.getByRole('button', { name: '复制' }))
-    expect(writeText).toHaveBeenCalledWith('steer!')
-    fireEvent.click(view.getByRole('button', { name: '在新对话中分支' }))
-    expect(fork).toHaveBeenCalledWith(2)
-  })
-
   it('context uses the Tool calls disclosure chrome and keeps its JSON collapsed by default', () => {
     const ctxView = render(
       <MessageItem t={t} node={{

packages/client/ui-conversation/tests/chat-view.spec.tsx

@@ -292,8 +292,7 @@ describe('ChatView', () => {
         nodes: [
           assistant(1, 'working'),
           {
-            kind: 'steering', messageId: pending.messageId,
-            seq: 2, time: 2_000, turn: 1,
+            kind: 'user', seq: 2, time: 2_000,
             content: [{ type: 'text', text: 'interrupt now' }], source: null,
           },
         ],
@@ -320,8 +319,7 @@ describe('ChatView', () => {
     const h = makeHarness({
       queue: [pending],
       nodes: [{
-        kind: 'steering', messageId: pending.messageId,
-        seq: 2, time: 2_000, turn: 1,
+        kind: 'user', seq: 2, time: 2_000,
         content: pending.content, source: null,
       }],
       running: true,

packages/client/ui-trajectory/src/client/layout.ts

@@ -75,7 +75,7 @@ const PREVIEW_OUTPUT_CHARACTERS = 512
 
 type InputNode = Extract<
   ConversationSnapshot['nodes'][number],
-  { kind: 'user' | 'steering' | 'context' }
+  { kind: 'user' | 'context' }
 >
 
 type OrderedLayoutEntry =
@@ -325,19 +325,17 @@ export function deriveTrajectoryLayout(input: TrajectoryLayoutInput): readonly T
       continue
     }
     const { node, nodeIndex: i } = entry
-    if (node.kind === 'user' || node.kind === 'steering') {
+    if (node.kind === 'user') {
       // user/message has no turn on the wire; enclose it in the next assistant
       // (or partial) turn, else open the turn after the last assistant.
-      const turn = node.kind === 'steering'
-        ? node.turn
-        : enclosingUserTurn(nodes, i, partial, lastAssistantTurn)
+      const turn = enclosingUserTurn(nodes, i, partial, lastAssistantTurn)
       pushMessage(turn, {
         absTime: finiteTime(node.time),
         cell: {
           index: ++index,
           kind: 'user',
           ...inputCellDetail(node),
-          opensTurn: node.kind === 'user',
+          opensTurn: true,
         },
       })
       prevAbsTime = finiteTime(node.time) ?? prevAbsTime
@@ -453,7 +451,7 @@ export function deriveTrajectoryLayout(input: TrajectoryLayoutInput): readonly T
     else for (const laid of laidList) pushMessage(call.turn, laid)
   }
 
-  // Orphan turn-0 cells (orphaned tools / steering turn 0) fold into Turn 1.
+  // Orphan turn-0 cells (orphaned tools) fold into Turn 1.
   const prologue = turns.get(0)
   if (prologue !== undefined) {
     turns.delete(0)
@@ -733,7 +731,7 @@ function stringifySourceValue(value: unknown): string {
 }
 
 /**
- * Turn that encloses a user/message: next assistant/steering turn, else the
+ * Turn that encloses a user/message: next assistant turn, else the
  * in-flight partial, else the turn after the last finalized assistant (or 1).
  */
 function enclosingUserTurn(
@@ -746,7 +744,7 @@ function enclosingUserTurn(
     const n = nodes[i]
     /* v8 ignore next -- dense-array guard: i stays within nodes.length, so the undefined arm needs a sparse array no caller builds. */
     if (n === undefined) continue
-    if (n.kind === 'assistant' || n.kind === 'steering') return n.turn
+    if (n.kind === 'assistant') return n.turn
   }
   if (partial !== null) return partial.turn
   if (lastAssistantTurn !== null) return lastAssistantTurn + 1
@@ -770,7 +768,7 @@ function firstVisibleTurn(
   partial: ConversationSnapshot['partial'],
 ): number {
   const turns = nodes.flatMap(node =>
-    (node.kind === 'assistant' || node.kind === 'steering') && node.turn > 0
+    node.kind === 'assistant' && node.turn > 0
       ? [node.turn]
       : [],
   )