Merge remote-tracking branch 'origin/doc/host-client-group-readmes' into feat/directory-picker

# Conflicts: # packages/client/connection/src/client/fixture.ts # packages/client/connection/tests/fake-api.ts # packages/client/runtime/src/client/workspaces/service.ts # packages/client/runtime/tests/fake-api.ts # packages/client/ui-workspace/src/client/WorkspaceBrowser.tsx # packages/client/ui-workspace/src/client/WorkspacePicker.tsx # packages/client/ui-workspace/tests/workspace-picker.spec.tsx # packages/host/apiproxy/README.i18n.yaml # packages/host/apiproxy/src/api-proxy.ts # packages/host/apiproxy/src/api/host.schema.ts # packages/host/apiproxy/src/api/host.ts # packages/host/apiproxy/src/api/rpc-map.ts # packages/host/apiproxy/src/fetch/client.ts # packages/host/apiproxy/src/fetch/handler.ts # packages/host/apiproxy/tests/api-proxy-workspace.spec.ts # packages/host/apiproxy/tests/client-handler.spec.ts # packages/host/apiproxy/tests/fetch-carrier.spec.ts
2026-07-28 21:21:21 +08:00
parent 5579b13503 302dfca4d5
commit a94df18bcf
750 changed files with 15381 additions and 5577 deletions
--- a/packages/host/apiproxy/README.i18n.yaml
+++ b/packages/host/apiproxy/README.i18n.yaml
@@ -2,5 +2,5 @@
 # side as of the last confirmed-consistent state. Both languages carry equal authority;
 # after editing either side, bring the other along and re-record with:
 #   pnpm run verify-translation-pairing --write packages/host/apiproxy/README.md
-README.md: 8db8a1b77913677d88dbbbfbdbfc28a90c0d0415
-README.zh.md: 1f957223bb98afb65ab8a313c49b58c701e42be0
+README.md: 3639722ab25826af8f7a0721f22d244f78b4210b
+README.zh.md: 3ac81fb412d4e4caf192953bc7a7c846a1d29965
--- a/packages/host/apiproxy/README.md
+++ b/packages/host/apiproxy/README.md
@@ -10,7 +10,9 @@ Wire messages form a four-quadrant discriminated union — who initiates × requ

 The layering/protocol decisions are recorded in the [GUI layering and RPC protocol RFC](../../../.agents/notes/implemented/architecture/2026-07-19-gui-layering-and-rpc-protocol.md); the browser-side consumption architecture in the [web client architecture RFC](../../../.agents/notes/implemented/architecture/2026-07-19-gui-web-client-architecture.md).

-The mux stream projects the latest log-backed title as a validated `session/title` control frame after each attached-session subscription baseline and immediately after the corresponding live raw title event. This projection does not add titles to `session.list`; cold sessions remain metadata-only there until opening or resuming attaches their logs.
+`session.history`'s tail page (`beforeSeq` absent) additionally carries an optional `projections` block — the watermark snapshot of every unit registered on `ctx.sessionProjections` (`@deepseek-ai/dsh-session-projection`), with `asOfSeq` = the last event seq the values reflect (`-1` on an empty log). The gateway also subscribes to the registry's change feed and mints a `session/projection` mux frame per changed unit (`{sessionId, key, value, seq}` — live push state, never logged; clients hold one generic per-session value store under higher-seq-wins). The carrier holds zero domain knowledge (each value passed its unit's own schema inside the registry; the wire schemas keep `values`/`value` wide); loadOlder pages never carry the block, and a composition without the registry serves histories without either surface.
+
+Session titles ride the generic projection pair like every other domain — the history-tail `projections` block plus `session/projection` frames under the `title` key (the bespoke `session/title` frame is retired). Titles do not join `session.list`; cold sessions remain metadata-only there until opening or resuming attaches their logs.

 Session model routing is a session-domain contract. `session.models` returns the selected provider/model/reasoning target with provider-grouped advisory models, exact-route reasoning metadata, and provider-local lookup failures. `session.selectModel` validates the optional adapter-owned reasoning effort and replaces the complete target selected for the next prompt-assembly boundary. Catalog membership is not validation: an adapter may resolve an unlisted model, while an unavailable route or unsupported effort returns `model-unavailable`.

@@ -18,9 +20,9 @@ Workspace and Session lists are separate reconnect baselines. `workspace.create`

 Directory picking delegates to the composed `ctx.directoryPicker` backend ([the directory-picker seam](../directory-picker/README.md)); `host.describe.directoryPicker` advertises the capability kind the client renders for, and a method called outside the advertised kind fails with `directory-picker-unavailable`. Under `native`, `host.pickDirectory` opens one native chooser and returns its selected path (`null` on cancel); this user-paced method is the sole unary call exempt from the default 30-second timeout, and caller/connection aborts still propagate to the native process. Under `browse`, `host.listDirectory` returns one name-sorted directory level with breadcrumb ancestry, a `home` anchor, and host-owned `hidden` flags (absent path = home directory), and `host.createDirectory` creates one validated child segment; the backend's typed failures map 1:1 onto the `directory-unreadable`/`directory-exists`/`directory-create-failed` codes. The browser carrier's prefix-wide trust fence (dsh-client-connection) covers all of these like every other `/api` request.

-`session.history` pages on message boundaries, and its tail page (no `beforeSeq`) carries two session-level extras the page window cannot supply: the in-flight partial's chunk events, and `todos` — the latest `todo/write` whole-list projection over the full log. Older pages omit `todos` because the projection is session-level, not per-page; a tail response that omits it means the whole log holds no `todo/write`, so clients read the absent field as the empty plan rather than as unchanged state.
+`host.openPath` opens a filesystem path with the operating system's default application (`open` on macOS, `Invoke-Item` on Windows, `xdg-open` on Linux). The opener is injectable for tests. The browser carrier applies the same loopback, same-origin restriction as `host.pickDirectory`.

-The `command.*` and `skill.*` domains expose the host command registry and skill catalog to clients. Every method addresses one session's agent by `sessionId` (a served session always has an Agent; `command.*` resumes cold sessions through the same path as `session.*`, while `skill.list` resolves the project root from the session header without touching the Agent registry). `command.execute` runs a slash-command line host-side and returns a detached result; the carrier's request signal cancels the running handler. `host/commands-changed` is the catalog invalidation frame: clients refetch `command.list` instead of diffing.
+The `command.*` and `skill.*` domains expose the host command registry and skill catalog to clients. Every method addresses one session's agent by `sessionId` (a served session always has an Agent; `command.*` resumes cold sessions through the same path as `session.*`, while `skill.list` resolves the project root from the session header without touching the Agent registry). `command.execute` runs a slash-command line host-side with pure admission semantics: the response reports whether the line resolved to a handler plus the minted lifecycle `commandId` when it did (correlating the acknowledgment with the flow node), while the outcome rides the durably logged `command/run`/`command/done` lifecycle pair broadcast on the mux stream; the carrier's request signal cancels the running handler. `host/commands-changed` is the catalog invalidation frame: clients refetch `command.list` instead of diffing.

 ## Carrier layer (`/client` + root)

--- a/packages/host/apiproxy/README.zh.md
+++ b/packages/host/apiproxy/README.zh.md
@@ -10,7 +10,9 @@

 分层与协议决策记录在 [GUI 分层与 RPC 协议 RFC](../../../.agents/notes/implemented/architecture/2026-07-19-gui-layering-and-rpc-protocol.md)中；浏览器侧消费架构记录在 [Web 客户端架构 RFC](../../../.agents/notes/implemented/architecture/2026-07-19-gui-web-client-architecture.md)中。

-mux 流会在每个已附加会话的订阅基线之后，以及对应的实时原始标题事件之后，立即把基于日志的最新标题投影为经过校验的 `session/title` 控制帧。该投影不会把标题加入 `session.list`；冷会话在其中仍只有元数据，直到打开或恢复操作附加其日志。
+`session.history` 的尾页（不带 `beforeSeq`）额外携带一个可选的 `projections` 块——`ctx.sessionProjections`（`@deepseek-ai/dsh-session-projection`）上每个已注册单元的水位线快照，`asOfSeq` = 这些值共同反映到的最后一个事件 seq（空日志为 `-1`）。网关还订阅注册表的变更流，为每个状态发生变化的单元铸造一个 `session/projection` mux 帧（`{sessionId, key, value, seq}`——实时推送状态，绝不入日志；客户端按 seq 高者胜维护一个按会话的通用值仓）。载体不持有任何领域知识（每个值在注册表内部已过其单元自己的 schema；协议 schema 对 `values`/`value` 保持宽松）；loadOlder 页永不携带该块，未装注册表的组合则两个面都不提供。
+
+会话标题与其他所有领域一样搭乘这对通用投影机制——历史尾页的 `projections` 块外加 `title` 键下的 `session/projection` 帧（专设的 `session/title` 帧已下线）。标题不会加入 `session.list`；冷会话在其中仍只有元数据，直到打开或恢复操作附加其日志。

 会话模型路由属于会话领域契约。`session.models` 返回选中的提供方／模型／推理（reasoning）目标，以及按提供方分组的建议性模型、精确路由推理元数据和逐提供方查询失败记录。`session.selectModel` 校验由适配器持有的可选推理强度，并替换将在下一提示词组装边界使用的完整目标。目录成员关系不构成校验：适配器可以解析未列出的模型，而不可用路由或不受支持的推理强度会返回 `model-unavailable`。

@@ -18,9 +20,9 @@ Workspace 列表与 Session 列表是相互独立的重连基线。`workspace.cr

 目录选择委托给组合的 `ctx.directoryPicker` 后端（[目录选择 seam](../directory-picker/README.md)）；`host.describe.directoryPicker` 广播客户端应按其渲染的能力 kind，调用广播之外的方法会以 `directory-picker-unavailable` 失败。在 `native` 下，`host.pickDirectory` 打开一个原生选择器并返回选中路径（取消为 `null`）；该方法需等待用户完成操作，是唯一不受默认 30 秒超时限制的一元调用，调用方与连接的中止仍会传播至原生进程。在 `browse` 下，`host.listDirectory` 返回一个按名称排序的目录层级，携带面包屑祖先链、`home` 锚点与宿主判定的 `hidden` 标志（不带路径即家目录），`host.createDirectory` 创建一个经校验的子段；后端的类型化失败 1:1 映射为 `directory-unreadable`／`directory-exists`／`directory-create-failed` 错误码。浏览器载体的前缀级信任栅栏（dsh-client-connection）像覆盖其他所有 `/api` 请求一样覆盖上述全部方法。

-`session.history` 按消息边界分页，其尾页（不带 `beforeSeq`）额外携带两项页窗口本身无法提供的会话级数据：进行中局部消息的 chunk 事件，以及 `todos`——整份日志上最后一次 `todo/write` 的整表投影。较早的页面不带 `todos`，因为该投影是会话级而非分页级的；尾页响应缺少该字段意味着整份日志中没有任何 `todo/write`，因此客户端要把缺失字段读作空计划，而不是读作「状态未变」。
+`host.openPath` 会用操作系统的默认应用打开一个文件系统路径（macOS 为 `open`，Windows 为 `Invoke-Item`，Linux 为 `xdg-open`）。打开器可在测试中注入。浏览器载体对其施加与 `host.pickDirectory` 相同的回环、同源限制。

-`command.*` 与 `skill.*` 领域向客户端暴露宿主命令注册表和技能目录。每个方法都通过 `sessionId` 寻址一个会话的 Agent（被服务的会话必有 Agent；`command.*` 经由与 `session.*` 相同的路径恢复冷会话，而 `skill.list` 从会话头解析项目根目录，不触碰 Agent 注册表）。`command.execute` 在宿主侧运行一条斜杠命令行并返回脱耦结果；载体的请求信号可取消正在运行的处理器。`host/commands-changed` 是目录失效帧：客户端重新拉取 `command.list` 而不是做差分。
+`command.*` 与 `skill.*` 领域向客户端暴露宿主命令注册表和技能目录。每个方法都通过 `sessionId` 寻址一个会话的 Agent（被服务的会话必有 Agent；`command.*` 经由与 `session.*` 相同的路径恢复冷会话，而 `skill.list` 从会话头解析项目根目录，不触碰 Agent 注册表）。`command.execute` 在宿主侧运行一条斜杠命令行，语义为纯准入：响应报告该行是否解析到处理器，并在解析到时回带铸造的生命周期 `commandId`（将本次确认与流节点关联）；结局经由持久落账并在 mux 流广播的 `command/run`/`command/done` 生命周期事件对承载；载体的请求信号可取消正在运行的处理器。`host/commands-changed` 是目录失效帧：客户端重新拉取 `command.list` 而不是做差分。

 ## 载体层（`/client` + 根路径）

--- a/packages/host/apiproxy/package.json
+++ b/packages/host/apiproxy/package.json
@@ -47,7 +47,7 @@
    "@deepseek-ai/dsh-llm": "workspace:^",
    "@deepseek-ai/dsh-session": "workspace:^",
    "@deepseek-ai/dsh-session-persistence": "workspace:^",
-    "@deepseek-ai/dsh-session-title": "workspace:^",
+    "@deepseek-ai/dsh-session-projection": "workspace:^",
    "@deepseek-ai/dsh-skill": "workspace:^",
    "@deepseek-ai/dsh-tools": "workspace:^",
    "@deepseek-ai/dsh-user-approval": "workspace:^",
--- a/packages/host/apiproxy/src/api-proxy.ts
+++ b/packages/host/apiproxy/src/api-proxy.ts
@@ -9,14 +9,13 @@ import { join } from 'node:path'
 import type { Context } from 'cordis'
 import { installAgentLlmTarget } from '@deepseek-ai/dsh-agent'
 import type {
-  Agent, AgentLlmTarget, AgentLlmTargetRef, AgentMessage, AgentMessageId, AgentStatus,
+  Agent, AgentLlmTarget, AgentLlmTargetRef, AgentStatus, InboxPlacement,
 } from '@deepseek-ai/dsh-agent'
-import { ReasoningEffortId } from '@deepseek-ai/dsh-llm'
+import { createUserMessage, ReasoningEffortId } from '@deepseek-ai/dsh-llm'
 import { errorChain } from '@deepseek-ai/dsh-llm'
-import type { ContentBlock, MessageSource } from '@deepseek-ai/dsh-llm'
-import type { JsonValue, Session, SessionEvent, SessionHeader, SessionId, TodoItem } from '@deepseek-ai/dsh-session'
+import type { MessageId, MessageSource } from '@deepseek-ai/dsh-llm'
+import type { Session, SessionEvent, SessionHeader, SessionId, UserMessage } from '@deepseek-ai/dsh-session'
 import type { SessionPersistence } from '@deepseek-ai/dsh-session-persistence'
-import { foldSessionTitle } from '@deepseek-ai/dsh-session-title'
 import type { Workspace, WorkspaceRecord } from '@deepseek-ai/dsh-workspace'
 import {
  workspaceDomainState, workspaceRecord, WorkspaceId as brandWorkspaceId,
@@ -26,9 +25,11 @@ import {
 import type {} from '@deepseek-ai/dsh-tools'
 import type {
  ApiProxy, HistoryEntry, HostFrame, ModelCatalogFailure, ModelProviderGroup, ModelReasoning,
-  MuxFrame, QuestionResponsePayload, SessionSummary, ToolEventView,
+  MuxFrame, QuestionResponsePayload, SessionProjectionsBlock, SessionSummary, ToolEventView,
  WorkspaceId, WorkspaceView,
 } from './api/index.ts'
+// Type-only: resolves `ctx.get('sessionProjections')` to the projection registry.
+import type {} from '@deepseek-ai/dsh-session-projection'
 // Type-only edges: resolve `ctx.get('commands')`, the `commands/change` event, and `ctx.get('skills')`.
 import type {} from '@deepseek-ai/dsh-commands'
 import type {} from '@deepseek-ai/dsh-skill'
@@ -40,6 +41,7 @@ import type {
 } from '@deepseek-ai/dsh-user-interaction'
 import { UserInteractionError } from '@deepseek-ai/dsh-user-interaction'
 import { DirectoryPickerError } from '@deepseek-ai/dsh-host-directory-picker'
+import { openNativePath } from './native-path-opener.ts'

 /** Page size when history is called without maxMessages. */
 const DEFAULT_MAX_MESSAGES = 50
@@ -129,26 +131,9 @@ function frame<F>(payload: F): RpcRequest<F> {
  return { rpcId: RpcId(randomUUID()), payload }
 }

-type SessionTitleFrame = Extract<MuxFrame, { type: 'session/title' }>
-
-/** Project the latest durable title without exposing title-generation policy. */
-function titleFrame(session: Session): SessionTitleFrame | undefined {
-  const title = foldSessionTitle(session.events)
-  if (title === undefined) return undefined
-  return {
-    type: 'session/title',
-    sessionId: session.id,
-    title: title.title,
-    eventSeq: title.eventSeq,
-    updatedAt: title.updatedAt,
-  }
-}
-
-/** Queue the subscription baseline followed by its optional title snapshot. */
+/** Queue the subscription baseline frame. */
 function subscribeSession(queue: FrameQueue<RpcRequest<MuxFrame>>, session: Session): void {
  queue.push(frame({ type: 'session/subscribed', sessionId: session.id, lastSeq: session.seq - 1 }))
-  const title = titleFrame(session)
-  if (title !== undefined) queue.push(frame(title))
 }

 /** SessionSummary projection for attached (in-memory) sessions. */
@@ -209,13 +194,12 @@ export interface ApiProxyDefaults {
  cwd: string
  /** Parent directory for name-created workspaces. */
  workspaceRoot: string
+  /** Native open-with-default-application; injectable for carrier tests. */
+  openPath?: (path: string, signal: AbortSignal) => Promise<void>
 }

 /** The tool/call payload fields the presenter path reads. */
 interface ToolCallData { callId: string; name: string; arguments: string }
-/** The tool/result payload fields the presenter path reads. */
-interface ToolResultData { callId: string; content: ContentBlock[]; isError: boolean; meta?: JsonValue }
-
 /** One host-owned question wait, addressed by the stable server-request id. */
 interface PendingQuestion {
  rpcId: RpcId
@@ -262,10 +246,16 @@ function viewFor(ctx: Context, event: SessionEvent, argsFor: (callId: string) =>
      return view === undefined ? undefined : { for: 'call', view }
    }
    if (event.type === 'tool/result') {
-      const { callId, content, isError, meta } = event.data as ToolResultData
+      const { message, meta } = event.data
+      const [result] = message.content
+      const callId = message.source.callId
      const call = argsFor(callId) as { name: string; args: unknown } | undefined
      if (call === undefined) return undefined
-      const view = ctx.tools.get(call.name)?.presentResult?.(call.args, { content, isError, ...meta === undefined ? {} : { meta } })
+      const view = ctx.tools.get(call.name)?.presentResult?.(call.args, {
+        content: result.content,
+        isError: result.isError === true,
+        ...meta === undefined ? {} : { meta },
+      })
      return view === undefined ? undefined : { for: 'result', view }
    }
  } catch (error: unknown) {
@@ -298,13 +288,19 @@ function backscanArgs(events: readonly SessionEvent[], callId: string): { name:
  return undefined
 }

-/** Current todo projection: the latest `todo/write` over the full log (whole-list replace ⇒ last write wins); undefined when none. */
-function backscanTodos(events: readonly SessionEvent[]): TodoItem[] | undefined {
-  for (let i = events.length - 1; i >= 0; i--) {
-    const event = events[i]
-    if (event !== undefined && event.type === 'todo/write') return event.data.todos
-  }
-  return undefined
+/**
+ * The projection baseline for one history tail page: the registry's
+ * watermark-cache snapshot — one fully synchronous read (no await between the
+ * page slice and this), so all values and `asOfSeq` form a single consistent
+ * cut and `asOfSeq` equals the window tail event seq. The carrier holds zero
+ * domain knowledge (each value passed its unit's own schema inside the
+ * registry). An absent registry means the deployment has no projection seam:
+ * the whole block is absent and clients treat every key as capability-absent.
+ */
+function projectionsFor(ctx: Context, agent: Agent): SessionProjectionsBlock | undefined {
+  const registry = ctx.get('sessionProjections')
+  if (registry === undefined) return undefined
+  return registry.snapshot(agent.session)
 }

 /**
@@ -423,42 +419,53 @@ export function createApiProxy(ctx: Context, defaults: ApiProxyDefaults): ApiPro
    for (const queue of muxQueues) queue.push(envelope)
  }

+  // Projection change feed → session/projection push frames. The carrier
+  // mints the wire frame (the seam package holds no wire vocabulary); the
+  // child activates only when a projection registry is composed, and the
+  // subscription unwinds with this gateway's fiber.
+  ctx.inject(['sessionProjections'], (projectionCtx) => {
+    projectionCtx.sessionProjections.onChanged((session, key, value, seq) => {
+      broadcast({ type: 'session/projection', sessionId: session.id, key, value, seq })
+    })
+  })
+
  /**
-   * Per-session inbox mirror serving the mux-open queue snapshot (the same
-   * refresh-recovery baseline as pending questions). Keyed by the stable
-   * AgentMessageId: every enqueued id receives exactly one terminal
-   * `agent/inbox/dequeue` OR `agent/inbox/discard` (the inbox contract), so
-   * the mirror needs no consumption heuristics or sweeps beyond disposal.
+   * Per-session inbox occurrence mirror serving the mux-open queue snapshot
+   * (the same refresh-recovery baseline as pending questions). Each terminal
+   * inbox event retires one matching occurrence, so repeated sends of the same
+   * identified message remain visible until every occurrence is claimed.
   */
-  const queuedMirror = new Map<SessionId, Map<AgentMessageId, { message: AgentMessage; steering: boolean }>>()
+  const queuedMirror = new Map<SessionId, { message: UserMessage; steering: boolean }[]>()
  ctx.effect(() => {
-    const retire = (agent: Agent, id: AgentMessageId): void => {
+    const retire = (agent: Agent, id: MessageId, placement?: InboxPlacement): void => {
      const entries = queuedMirror.get(agent.id)
      if (entries === undefined) return
-      entries.delete(id)
-      if (entries.size === 0) queuedMirror.delete(agent.id)
+      const index = entries.findIndex(entry =>
+        entry.message.id === id
+        && (placement === undefined || entry.steering === (placement === 'steering')))
+      if (index !== -1) entries.splice(index, 1)
+      if (entries.length === 0) queuedMirror.delete(agent.id)
    }
    const disposers = [
-      ctx.on('agent/inbox/enqueue', (agent: Agent, message: AgentMessage, placement) => {
+      ctx.on('agent/inbox/enqueue', (agent: Agent, message: UserMessage, placement) => {
        let entries = queuedMirror.get(agent.id)
        if (entries === undefined) {
-          entries = new Map<AgentMessageId, { message: AgentMessage; steering: boolean }>()
+          entries = []
          queuedMirror.set(agent.id, entries)
        }
        const steering = placement === 'steering'
-        entries.set(message.id, { message, steering })
+        entries.push({ message, steering })
        broadcast({
          type: 'session/queued',
          sessionId: agent.id,
-          content: message.content,
-          source: message.source,
+          message,
          steering,
        })
      }),
-      ctx.on('agent/inbox/dequeue', (agent: Agent, message: AgentMessage) => {
-        retire(agent, message.id)
+      ctx.on('agent/inbox/dequeue', (agent: Agent, message: UserMessage, placement) => {
+        retire(agent, message.id, placement)
      }),
-      ctx.on('agent/inbox/discard', (agent: Agent, messages: AgentMessage[]) => {
+      ctx.on('agent/inbox/discard', (agent: Agent, messages: UserMessage[]) => {
        for (const message of messages) retire(agent, message.id)
      }),
      ctx.on('session/disposed', (session: Session) => {
@@ -717,6 +724,8 @@ export function createApiProxy(ctx: Context, defaults: ApiProxyDefaults): ApiPro
        const { sessionId, beforeSeq, maxMessages } = request.payload
        const found = await agentFor(sessionId)
        if ('error' in found) return err(request, found.error)
+        // Everything below the resume above is synchronous: the page slice,
+        // the seq read, and the projection walk see one un-torn session state.
        const page = paginate(found.agent.session.events, beforeSeq, maxMessages ?? DEFAULT_MAX_MESSAGES)
        // Views are computed against the registry at pagination time; result
        // pairing scans within the page only (message-boundary pagination keeps
@@ -725,11 +734,14 @@ export function createApiProxy(ctx: Context, defaults: ApiProxyDefaults): ApiPro
          const view = viewFor(ctx, event, callId => backscanArgs(page.events, callId))
          return { event, ...view === undefined ? {} : { view } }
        })
-        // Tail page carries the session-level todo projection over the FULL
-        // log (the page window may not contain the last todo/write; a paged
-        // client cannot reconstruct session-level state from it).
-        const todos = beforeSeq === undefined ? backscanTodos(found.agent.session.events) : undefined
-        return ok(request, { events: entries, hasMore: page.hasMore, ...todos === undefined ? {} : { todos } })
+        // Baseline rider: tail page only — loadOlder (beforeSeq present) is
+        // the one path that never needs a fresh projection baseline.
+        const projections = beforeSeq === undefined ? projectionsFor(ctx, found.agent) : undefined
+        return ok(request, {
+          events: entries,
+          hasMore: page.hasMore,
+          ...projections === undefined ? {} : { projections },
+        })
      },

      async models(request) {
@@ -841,8 +853,9 @@ export function createApiProxy(ctx: Context, defaults: ApiProxyDefaults): ApiPro
        // The rpcId rides MessageSource into user/message (merge declaration in api/sessions.ts; provisional correlation).
        const source: MessageSource = { kind: 'user', rpcId: request.rpcId }
        try {
-          if (mode === 'steer') agent.steer({ content, source })
-          else agent.followup({ content, source })
+          const message: UserMessage = createUserMessage({ content, source })
+          if (mode === 'steer') agent.steer(message)
+          else agent.followup(message)
        } catch (error: unknown) {
          // A synchronous throw from steer/followup means disposed or invalid input; surface as agent-busy with the reason attached.
          return err(request, { code: 'agent-busy', message: 'prompt rejected', details: { reason: String(error) } })
@@ -1059,6 +1072,28 @@ export function createApiProxy(ctx: Context, defaults: ApiProxyDefaults): ApiPro
          return err(request, directoryError(error))
        }
      },
+
+      async openPath(request, signal) {
+        try {
+          const open = defaults.openPath
+            ?? ((path: string, openSignal: AbortSignal) => openNativePath(path, openSignal))
+          await open(request.payload.path, signal)
+          return ok(request, { opened: true as const })
+        } catch (error: unknown) {
+          if (signal.aborted) {
+            return err(request, {
+              code: 'cancelled',
+              message: 'path open was aborted',
+              details: {},
+            })
+          }
+          return err(request, {
+            code: 'internal',
+            message: `path open failed: ${error instanceof Error ? error.message : String(error)}`,
+            details: {},
+          })
+        }
+      },
    },

    commands: {
@@ -1086,12 +1121,15 @@ export function createApiProxy(ctx: Context, defaults: ApiProxyDefaults): ApiPro
        const found = await agentFor(sessionId)
        if ('error' in found) return err(request, found.error)
        try {
-          const result = await commands.execute(found.agent, line, signal)
-          if (result === undefined) return ok(request, { matched: false })
-          return ok(request, {
-            matched: true,
-            result: { kind: result.kind, ...result.text === undefined ? {} : { text: result.text } },
-          })
+          // Pure admission: the executor's durable command/run + command/done
+          // pair (broadcast on the mux stream) carries the outcome; the
+          // response reports whether the line resolved to a handler, plus the
+          // minted pairing id so the issuing client can correlate its request
+          // with the flow node the lifecycle events produce.
+          const execution = await commands.execute(found.agent, line, signal)
+          return ok(request, execution === undefined
+            ? { matched: false }
+            : { matched: true, commandId: execution.commandId })
        } catch (error: unknown) {
          if (signal.aborted) return err(request, { code: 'cancelled', message: 'command execution was aborted', details: {} })
          return err(request, { code: 'internal', message: `command failed: ${String(error)}`, details: {} })
@@ -1163,12 +1201,11 @@ export function createApiProxy(ctx: Context, defaults: ApiProxyDefaults): ApiPro
        // in arrival order per session; a reconnecting client rebuilds its
        // queue view from these alone.
        for (const [sessionId, entries] of queuedMirror) {
-          for (const entry of entries.values()) {
+          for (const entry of entries) {
            queue.push(frame({
              type: 'session/queued',
              sessionId,
-              content: entry.message.content,
-              source: entry.message.source,
+              message: entry.message,
              steering: entry.steering,
            }))
          }
@@ -1194,10 +1231,6 @@ export function createApiProxy(ctx: Context, defaults: ApiProxyDefaults): ApiPro
            const view = viewFor(ctx, event, callId =>
              openCalls.get(session.id)?.get(callId) ?? backscanArgs(session.events, callId))
            queue.push(frame({ type: 'session/event', sessionId: session.id, event, ...view === undefined ? {} : { view } }))
-            if (event.type === 'session/title') {
-              // The accepted raw event is already in session.events, so the fold must find it.
-              queue.push(frame(titleFrame(session) as SessionTitleFrame))
-            }
          }),
          ctx.on('session/created', (session: Session) => {
            subscribeSession(queue, session)
--- a/packages/host/apiproxy/src/api/commands.schema.ts
+++ b/packages/host/apiproxy/src/api/commands.schema.ts
@@ -4,10 +4,11 @@
 */

 import { z } from 'zod'
+import type { CommandId } from '@deepseek-ai/dsh-commands/brand'
 import type { RequestPayload, ResponseValue } from './rpc-map.ts'
 import type { Wire } from './rpc.schema.ts'
 import { sessionIdSchema } from './sessions.schema.ts'
-import type { CommandDescriptor, CommandExecuteResult } from './commands.ts'
+import type { CommandDescriptor } from './commands.ts'

 /** CommandDescriptor row of command.list. */
 export const commandDescriptorSchema = z.object({
@@ -32,14 +33,12 @@ export const commandExecuteRequestSchema = z.object({
  line: z.string(),
 }) satisfies z.ZodType<Wire<RequestPayload<'command.execute'>>>

-/** Detached command outcome (result slot of command.execute's value). */
-export const commandExecuteResultSchema = z.object({
-  kind: z.union([z.literal('success'), z.literal('error')]),
-  text: z.string().optional(),
-}) satisfies z.ZodType<Wire<CommandExecuteResult>>
+/** CommandId: one brand cast after shape validation (the only cast point in this domain). */
+export const commandIdSchema = z.string().min(1) as unknown as z.ZodType<CommandId>

-/** command.execute response value (matched=false carries no result). */
+/** command.execute response value: pure admission — outcomes ride the logged
+ * lifecycle events; commandId (present exactly when matched) correlates with them. */
 export const commandExecuteValueSchema = z.object({
  matched: z.boolean(),
-  result: commandExecuteResultSchema.optional(),
+  commandId: commandIdSchema.optional(),
 }) satisfies z.ZodType<Wire<ResponseValue<'command.execute'>>>
--- a/packages/host/apiproxy/src/api/commands.ts
+++ b/packages/host/apiproxy/src/api/commands.ts
@@ -5,6 +5,7 @@
 * together), so there is no agent-less surface on this wire.
 */

+import type { CommandId } from '@deepseek-ai/dsh-commands/brand'
 import type { SessionId } from '@deepseek-ai/dsh-session/types'
 import type { RpcRequest, RpcResponse } from './rpc.ts'

@@ -22,12 +23,6 @@ export interface CommandDescriptor {
  readonly input?: { readonly hint: string }
 }

-/** Detached command outcome rendered directly by the requesting client. */
-export interface CommandExecuteResult {
-  readonly kind: 'success' | 'error'
-  readonly text?: string
-}
-
 /** Command-domain unary methods (the map keys command.* of RpcMethodMap). */
 export interface CommandsApi {
  /**
@@ -38,11 +33,16 @@ export interface CommandsApi {

  /**
   * Parses and executes one slash-command line against the addressed agent
-   * without sending it to the model. matched=false when syntax or name does
-   * not resolve (the client falls back to its default sink). The signal rides
-   * beside the request, never on the wire: the fetch carrier's request signal
-   * cancels the running handler.
+   * without sending it to the model — pure admission semantics. matched=false
+   * when syntax or name does not resolve (the client falls back to its
+   * default sink). The handler's outcome does NOT ride the response: the host
+   * executor durably logs the lifecycle (`command/run`/`command/done`), which
+   * broadcasts on the mux stream and renders as a persistent flow node.
+   * `commandId` is present exactly when matched — the minted lifecycle
+   * pairing id, letting the issuing client correlate this acknowledgment
+   * with that flow node. The signal rides beside the request, never on the
+   * wire: the fetch carrier's request signal cancels the running handler.
   */
  execute(request: RpcRequest<{ sessionId: SessionId; line: string }>, signal: AbortSignal):
-  Promise<RpcResponse<{ matched: boolean; result?: CommandExecuteResult }>>
+  Promise<RpcResponse<{ matched: boolean; commandId?: CommandId }>>
 }
--- a/packages/host/apiproxy/src/api/events.schema.ts
+++ b/packages/host/apiproxy/src/api/events.schema.ts
@@ -23,11 +23,18 @@ export const askUserQuestionItemSchema = z.object({
  multiSelect: z.boolean().optional(),
 }) satisfies z.ZodType<Wire<AskUserQuestionItem>>

+/** Unified message envelope carried by transient queue frames. */
+const messageSchema = z.object({
+  id: z.string().min(1),
+  role: z.union([z.literal('system'), z.literal('user'), z.literal('assistant')]),
+  content: z.array(contentBlockSchema),
+  source: z.looseObject({ kind: z.string() }),
+})
+
 /** MuxFrame union (payload slot of a mux-stream ServerRequest). */
 export const muxFrameSchema = z.discriminatedUnion('type', [
  z.object({ type: z.literal('session/event'), sessionId: sessionIdSchema, event: sessionEventSchema, view: toolEventViewSchema.optional() }),
  z.object({ type: z.literal('session/subscribed'), sessionId: sessionIdSchema, lastSeq: z.number().int() }),
-  z.object({ type: z.literal('session/title'), sessionId: sessionIdSchema, title: z.string().min(1), eventSeq: z.number().int().nonnegative(), updatedAt: z.number() }),
  z.object({ type: z.literal('approval/requested'), sessionId: sessionIdSchema, approvalId: approvalRequestIdSchema, toolName: z.string(), callId: z.string().optional(), reason: z.string().optional() }),
  z.object({ type: z.literal('approval/resolved'), sessionId: sessionIdSchema, approvalId: approvalRequestIdSchema, outcome: z.union([z.literal('allowed-once'), z.literal('rejected'), z.literal('cancelled'), z.literal('unavailable')]) }),
  // Non-empty by wire contract: the user-interaction service rejects empty
@@ -35,8 +42,10 @@ export const muxFrameSchema = z.discriminatedUnion('type', [
  // and must fail loud here, not reach the composer.
  z.object({ type: z.literal('question/requested'), sessionId: sessionIdSchema, questions: z.array(askUserQuestionItemSchema).min(1) }),
  z.object({ type: z.literal('question/resolved'), sessionId: sessionIdSchema, questionRpcId: rpcIdSchema, outcome: z.union([z.literal('answered'), z.literal('cancelled')]) }),
-  // content/source reuse the wide passthroughs (both are merge-extensible in core).
-  z.object({ type: z.literal('session/queued'), sessionId: sessionIdSchema, content: z.array(contentBlockSchema), source: z.looseObject({ kind: z.string() }), steering: z.boolean() }),
+  z.object({ type: z.literal('session/queued'), sessionId: sessionIdSchema, message: messageSchema, steering: z.boolean() }),
+  // value stays wide: it already passed its unit's own schema on the host,
+  // and deep-validating here would import every domain's schema into the carrier.
+  z.object({ type: z.literal('session/projection'), sessionId: sessionIdSchema, key: z.string().min(1), value: z.unknown(), seq: z.number().int().nonnegative() }),
  z.object({ type: z.literal('stream/error'), error: rpcErrorSchema }),
 ]) as unknown as z.ZodType<MuxFrame>

--- a/packages/host/apiproxy/src/api/events.ts
+++ b/packages/host/apiproxy/src/api/events.ts
@@ -8,7 +8,7 @@

 import type { AskUserQuestionItem } from '@deepseek-ai/dsh-user-interaction/types'
 import type { ApprovalOutcome, ApprovalRequestId } from '@deepseek-ai/dsh-user-approval/types'
-import type { ContentBlock, MessageSource } from '@deepseek-ai/dsh-llm/types'
+import type { Message } from '@deepseek-ai/dsh-llm/types'
 import type { CallId } from '@deepseek-ai/dsh-llm/brand'
 import type { SessionEvent, SessionId } from '@deepseek-ai/dsh-session/types'
 import type { ToolCallView, ToolResultView } from '@deepseek-ai/dsh-tools/presentation'
@@ -35,9 +35,9 @@ export type ToolEventView =
 export interface EventsApi {
  /**
   * All-session aggregated mux stream. On open, emits a subscribed control frame for every
-   * attached session followed by its optional latest title snapshot, then replays each
-   * session's still-pending approval/question requested frames (rpcId reused verbatim — the
-   * refresh-recovery baseline).
+   * attached session, then replays each session's still-pending approval/question requested
+   * frames (rpcId reused verbatim — the refresh-recovery baseline). Session titles ride the
+   * generic projection pair (history-tail projections block + session/projection frames).
   * since: resume seam, unimplemented in v1 (ignored if passed); reconnection = reopen the
   * stream + refetch history.
   */
@@ -57,7 +57,6 @@ export interface EventsApi {
 export type MuxFrame =
  | { type: 'session/event'; sessionId: SessionId; event: SessionEvent; view?: ToolEventView }
  | { type: 'session/subscribed'; sessionId: SessionId; lastSeq: number }
-  | { type: 'session/title'; sessionId: SessionId; title: string; eventSeq: number; updatedAt: number }
  | { type: 'approval/requested'; sessionId: SessionId; approvalId: ApprovalRequestId; toolName: string; callId?: CallId; reason?: string }
  | { type: 'approval/resolved'; sessionId: SessionId; approvalId: ApprovalRequestId; outcome: ApprovalOutcome }
  | { type: 'question/requested'; sessionId: SessionId; questions: AskUserQuestionItem[] }
@@ -70,11 +69,20 @@ export type MuxFrame =
   * refresh-recovery baseline as pending questions); queue clearing on cancel
   * has no dedicated frame — clients fold it from the status flip.
   * `steering` is the host's acceptance-time queue classification and remains
-   * authoritative in reconnect snapshots. `source` carries the prompt's rpcId
+   * authoritative in reconnect snapshots. `message.source` carries the prompt's rpcId
   * when the message came over this wire (the client's provisional-echo
   * reconciliation key).
   */
-  | { type: 'session/queued'; sessionId: SessionId; content: ContentBlock[]; source: MessageSource; steering: boolean }
+  | { type: 'session/queued'; sessionId: SessionId; message: Message; steering: boolean }
+  /**
+   * One projection unit's finished value changed (session-projection RFC).
+   * Live push state, never logged — replay recomputes on the host (the
+   * tool-view posture). `value` is the unit's schema-validated view output;
+   * `seq` is the unit's watermark at emission. Clients keep one generic
+   * per-session value store under higher-seq-wins, seeded by the history
+   * tail page's projections block.
+   */
+  | { type: 'session/projection'; sessionId: SessionId; key: string; value: unknown; seq: number }
  | { type: 'stream/error'; error: RpcError }

 /**
--- a/packages/host/apiproxy/src/api/host.schema.ts
+++ b/packages/host/apiproxy/src/api/host.schema.ts
@@ -64,3 +64,12 @@ export const hostCreateDirectoryRequestSchema = z.object({
 export const hostCreateDirectoryValueSchema = z.object({
  path: z.string(),
 }) satisfies z.ZodType<Wire<ResponseValue<'host.createDirectory'>>>
+/** host.openPath request payload. */
+export const hostOpenPathRequestSchema = z.object({
+  path: z.string().min(1),
+}) satisfies z.ZodType<Wire<RequestPayload<'host.openPath'>>>
+
+/** host.openPath response value. */
+export const hostOpenPathValueSchema = z.object({
+  opened: z.literal(true),
+}) satisfies z.ZodType<Wire<ResponseValue<'host.openPath'>>>
--- a/packages/host/apiproxy/src/api/host.ts
+++ b/packages/host/apiproxy/src/api/host.ts
@@ -89,4 +89,15 @@ export interface HostApi {
  createDirectory(
    request: RpcRequest<{ path: string; name: string }>,
  ): Promise<RpcResponse<{ path: string }>>
+
+  /**
+   * Open a filesystem path with the operating system's default application
+   * (Finder / Explorer / xdg-open hand-off). The browser carrier's
+   * prefix-wide trust fence covers this privileged method like every other
+   * `/api` request.
+   */
+  openPath(
+    request: RpcRequest<{ path: string }>,
+    signal: AbortSignal,
+  ): Promise<RpcResponse<{ opened: true }>>
 }
--- a/packages/host/apiproxy/src/api/index.ts
+++ b/packages/host/apiproxy/src/api/index.ts
@@ -27,11 +27,11 @@ export interface ApiProxy {
 // ---- Domain interfaces and payload entities ----
 export type {
  HistoryEntry, ModelCatalogFailure, ModelCatalogModel, ModelProviderGroup, ModelReasoning,
-  ModelReasoningEffort, ModelTarget, SessionModels, SessionsApi, SessionSummary,
+  ModelReasoningEffort, ModelTarget, SessionModels, SessionProjectionsBlock, SessionsApi, SessionSummary,
 } from './sessions.ts'
 export type { DirectoryEntry, DirectoryListing, DirectoryPickerKind, HostApi } from './host.ts'
 export type { WorkspaceApi, WorkspaceId, WorkspaceView } from './workspace.ts'
-export type { CommandsApi, CommandDescriptor, CommandExecuteResult } from './commands.ts'
+export type { CommandsApi, CommandDescriptor } from './commands.ts'
 export type { SkillsApi, SkillEntry } from './skills.ts'
 export type { EventsApi, MuxFrame, HostFrame, ToolCallView, ToolEventView, ToolResultView } from './events.ts'
 export type { ApprovalResponsePayload } from './approvals.ts'
--- a/packages/host/apiproxy/src/api/rpc-map.ts
+++ b/packages/host/apiproxy/src/api/rpc-map.ts
@@ -28,6 +28,7 @@ export interface RpcMethodMap {
  'host.pickDirectory': HostApi['pickDirectory']
  'host.listDirectory': HostApi['listDirectory']
  'host.createDirectory': HostApi['createDirectory']
+  'host.openPath': HostApi['openPath']
  'workspace.list': WorkspaceApi['list']
  'workspace.create': WorkspaceApi['create']
  'workspace.rename': WorkspaceApi['rename']
--- a/packages/host/apiproxy/src/api/sessions.schema.ts
+++ b/packages/host/apiproxy/src/api/sessions.schema.ts
@@ -11,7 +11,7 @@ import type { RequestPayload, ResponseValue } from './rpc-map.ts'
 import type { Wire } from './rpc.schema.ts'
 import type {
  HistoryEntry, ModelCatalogFailure, ModelCatalogModel, ModelProviderGroup, ModelReasoning,
-  ModelReasoningEffort, ModelTarget, SessionSummary,
+  ModelReasoningEffort, ModelTarget, SessionProjectionsBlock, SessionSummary,
 } from './sessions.ts'
 import type { ToolEventView } from './events.ts'
 import type { WorkspaceId } from './workspace.ts'
@@ -139,17 +139,22 @@ export const historyEntrySchema = z.object({
  view: toolEventViewSchema.optional(),
 }) satisfies z.ZodType<Wire<HistoryEntry>>

-/** One todo item of the tail page's session-level projection (the todo/write payload shape). */
-export const todoItemSchema = z.object({
-  content: z.string(),
-  status: z.union([z.literal('pending'), z.literal('in_progress'), z.literal('completed')]),
-})
+/**
+ * Projection baseline passthrough: `values` stays a wide record — each value
+ * was already parsed by its provider's own schema on the host side, and
+ * deep-validating here would import every domain's schema into the carrier.
+ */
+export const sessionProjectionsBlockSchema = z.object({
+  // -1 = empty log (the lastSeq convention of session/subscribed).
+  asOfSeq: z.number().int().min(-1),
+  values: z.record(z.string(), z.unknown()),
+}) as unknown as z.ZodType<SessionProjectionsBlock>

-/** session.history response value. */
+/** session.history response value (projections rides the tail page only). */
 export const sessionHistoryValueSchema = z.object({
  events: z.array(historyEntrySchema),
  hasMore: z.boolean(),
-  todos: z.array(todoItemSchema).optional(),
+  projections: sessionProjectionsBlockSchema.optional(),
 }) satisfies z.ZodType<Wire<ResponseValue<'session.history'>>>

 /** session.models request payload. */
--- a/packages/host/apiproxy/src/api/sessions.ts
+++ b/packages/host/apiproxy/src/api/sessions.ts
@@ -5,7 +5,10 @@
 */

 import type { ContentBlock } from '@deepseek-ai/dsh-llm/types'
-import type { SessionEvent, SessionId, TodoItem } from '@deepseek-ai/dsh-session/types'
+import type { SessionEvent, SessionId } from '@deepseek-ai/dsh-session/types'
+// The pure-type outlet: api/ is browser-importable, and the package root's
+// cordis Context merge (via dsh-agent) must not enter client aggregates.
+import type { SessionProjectionMap } from '@deepseek-ai/dsh-session-projection/types'
 import type { RpcId, RpcRequest, RpcResponse } from './rpc.ts'
 import type { ToolEventView } from './events.ts'
 import type { WorkspaceId } from './workspace.ts'
@@ -32,6 +35,23 @@ export interface HistoryEntry {
  view?: ToolEventView
 }

+/**
+ * The projection baseline riding the history tail page: one synchronous cut
+ * over every registered projection unit, read from the registry's watermark
+ * cache. `asOfSeq` is the seq of the last committed event every value
+ * reflects — the window tail event seq (`-1` for an empty log, mirroring
+ * `session/subscribed.lastSeq`), directly comparable with
+ * `session/projection` frame seqs under the client's higher-seq-wins rule. A
+ * key absent from `values` means the capability is absent (its domain plugin
+ * is unmounted).
+ */
+export interface SessionProjectionsBlock {
+  /** Seq of the last event the values reflect; -1 for an empty log. */
+  asOfSeq: number
+  /** Whole current value per registered projection key. */
+  values: Partial<SessionProjectionMap>
+}
+
 /** Complete model target selected for one session. */
 export interface ModelTarget {
  /** Registered provider route. */
@@ -149,13 +169,14 @@ export interface SessionsApi {
   * Each entry pairs the raw SessionEvent with the host-computed view (tool events whose
   * presenter produced one, evaluated against the registry at pagination time); the client
   * rebuilds the surface from the events with the shared fold.
-   * The tail page (beforeSeq absent) also carries `todos` — the session's current todo
-   * projection (latest `todo/write` over the FULL log, independent of the page window) —
-   * so a paged client restores the plan without walking history; absent when the session
-   * never wrote one. Older pages omit it (the projection is session-level, not per-page).
+   * The tail page — and only the tail page — additionally carries `projections`
+   * when the deployment mounts the session-projection registry: every moment
+   * the client needs a fresh baseline already pulls the tail page, and
+   * loadOlder (the only beforeSeq path) is the only path that never needs one.
+   * A deployment without the registry serves histories without the block.
   */
  history(request: RpcRequest<{ sessionId: SessionId; beforeSeq?: number; maxMessages?: number }>):
-  Promise<RpcResponse<{ events: HistoryEntry[]; hasMore: boolean; todos?: TodoItem[] }>>
+  Promise<RpcResponse<{ events: HistoryEntry[]; hasMore: boolean; projections?: SessionProjectionsBlock }>>

  /** Reads a fresh advisory model directory for this session. Provider lookups run independently. */
  models(request: RpcRequest<{ sessionId: SessionId }>): Promise<RpcResponse<SessionModels>>
--- a/packages/host/apiproxy/src/fetch/client.ts
+++ b/packages/host/apiproxy/src/fetch/client.ts
@@ -15,7 +15,7 @@ import { rpcReceiptSchema, serverRequestSchema, serverResponseSchema } from '../
 import { hostFrameSchema, muxFrameSchema } from '../api/events.schema.ts'
 import {
  hostCreateDirectoryValueSchema, hostDescribeValueSchema,
-  hostListDirectoryValueSchema, hostPickDirectoryValueSchema,
+  hostListDirectoryValueSchema, hostOpenPathValueSchema, hostPickDirectoryValueSchema,
 } from '../api/host.schema.ts'
 import {
  sessionCancelValueSchema,
@@ -66,6 +66,7 @@ export interface IApiClient {
    pickDirectory(payload: RequestPayload<'host.pickDirectory'>, signal?: AbortSignal): Promise<RpcResponse<ResponseValue<'host.pickDirectory'>>>
    listDirectory(payload: RequestPayload<'host.listDirectory'>, signal?: AbortSignal): Promise<RpcResponse<ResponseValue<'host.listDirectory'>>>
    createDirectory(payload: RequestPayload<'host.createDirectory'>, signal?: AbortSignal): Promise<RpcResponse<ResponseValue<'host.createDirectory'>>>
+    openPath(payload: RequestPayload<'host.openPath'>, signal?: AbortSignal): Promise<RpcResponse<ResponseValue<'host.openPath'>>>
  }
  workspace: {
    list(payload: RequestPayload<'workspace.list'>, signal?: AbortSignal): Promise<RpcResponse<ResponseValue<'workspace.list'>>>
@@ -105,6 +106,7 @@ const UNARY_VALUE_SCHEMAS: { [K in keyof RpcMethodMap]: z.ZodType<Wire<ResponseV
  'host.pickDirectory': hostPickDirectoryValueSchema,
  'host.listDirectory': hostListDirectoryValueSchema,
  'host.createDirectory': hostCreateDirectoryValueSchema,
+  'host.openPath': hostOpenPathValueSchema,
  'workspace.list': workspaceListValueSchema,
  'workspace.create': workspaceCreateValueSchema,
  'workspace.rename': workspaceRenameValueSchema,
@@ -314,6 +316,7 @@ export abstract class AbstractApiClient implements IApiClient {
    pickDirectory: (payload, signal) => this.callUnary('host.pickDirectory', payload, signal, false),
    listDirectory: (payload, signal) => this.callUnary('host.listDirectory', payload, signal),
    createDirectory: (payload, signal) => this.callUnary('host.createDirectory', payload, signal),
+    openPath: (payload, signal) => this.callUnary('host.openPath', payload, signal),
  }

  readonly workspace: IApiClient['workspace'] = {
--- a/packages/host/apiproxy/src/fetch/handler.ts
+++ b/packages/host/apiproxy/src/fetch/handler.ts
@@ -25,7 +25,8 @@ import {
 } from '../api/sessions.schema.ts'
 import {
  hostCreateDirectoryRequestSchema, hostDescribeRequestSchema,
-  hostListDirectoryRequestSchema, hostPickDirectoryRequestSchema,
+  hostListDirectoryRequestSchema, hostOpenPathRequestSchema,
+  hostPickDirectoryRequestSchema,
 } from '../api/host.schema.ts'
 import {
  workspaceCreateRequestSchema,
@@ -65,6 +66,7 @@ const UNARY_ROUTES: UnaryRoutes = {
  'host.pickDirectory': { schema: hostPickDirectoryRequestSchema, invoke: (api, r, signal) => api.host.pickDirectory(r, signal) },
  'host.listDirectory': { schema: hostListDirectoryRequestSchema, invoke: (api, r) => api.host.listDirectory(r) },
  'host.createDirectory': { schema: hostCreateDirectoryRequestSchema, invoke: (api, r) => api.host.createDirectory(r) },
+  'host.openPath': { schema: hostOpenPathRequestSchema, invoke: (api, r, signal) => api.host.openPath(r, signal) },
  'workspace.list': { schema: workspaceListRequestSchema, invoke: (api, r) => api.workspace.list(r) },
  'workspace.create': { schema: workspaceCreateRequestSchema, invoke: (api, r) => api.workspace.create(r) },
  'workspace.rename': { schema: workspaceRenameRequestSchema, invoke: (api, r) => api.workspace.rename(r) },
--- a/packages/host/apiproxy/src/native-command.ts
+++ b/packages/host/apiproxy/src/native-command.ts
@@ -0,0 +1,38 @@
+/** Shared no-shell `execFile` runner for native host dialogs and openers. */
+
+import { execFile } from 'node:child_process'
+
+/** Testable command boundary; native implementations never invoke a shell. */
+export type NativeCommandRunner = (
+  command: string,
+  args: readonly string[],
+  signal: AbortSignal,
+) => Promise<{ stdout: string; stderr: string }>
+
+/**
+ * Run a host command with utf8 stdio, abort propagation, and Windows hide.
+ * @param command - executable path or PATH name.
+ * @param args - argv (never a shell string).
+ * @param signal - caller/connection lifetime; abort terminates the child.
+ * @returns captured stdout/stderr on exit 0.
+ */
+export const runNativeCommand: NativeCommandRunner = (command, args, signal) =>
+  new Promise((resolve, reject) => {
+    execFile(
+      command,
+      [...args],
+      { encoding: 'utf8', signal, windowsHide: true },
+      (error, stdout, stderr) => {
+        if (error !== null) {
+          const failure = Object.assign(new Error(error.message, { cause: error }), {
+            code: error.code,
+            stdout,
+            stderr,
+          })
+          reject(failure)
+          return
+        }
+        resolve({ stdout, stderr })
+      },
+    )
+  })
--- a/packages/host/apiproxy/src/native-path-opener.ts
+++ b/packages/host/apiproxy/src/native-path-opener.ts
@@ -0,0 +1,53 @@
+/** Cross-platform open-with-default-application used by the local GUI carrier. */
+
+import { runNativeCommand, type NativeCommandRunner } from './native-command.ts'
+
+/** Testable command boundary; native implementations never invoke a shell. */
+export type PathOpenerRunner = NativeCommandRunner
+
+/** Injectable platform facts for deterministic adapter tests. */
+export interface PathOpenerInternals {
+  platform?: NodeJS.Platform
+  run?: PathOpenerRunner
+}
+
+/** PowerShell single-quoted literal (doubles embedded quotes). */
+function powershellLiteral(path: string): string {
+  return `'${path.replace(/'/g, "''")}'`
+}
+
+/**
+ * Open a filesystem path with the operating system's default application.
+ * @param path - absolute or host-resolvable path (caller owns resolution).
+ * @param signal - caller/connection lifetime; abort terminates the native command.
+ * @param internals - platform and runner seam for deterministic tests.
+ */
+export async function openNativePath(
+  path: string,
+  signal: AbortSignal,
+  internals: PathOpenerInternals = {},
+): Promise<void> {
+  const platform = internals.platform ?? process.platform
+  const run = internals.run ?? runNativeCommand
+
+  if (platform === 'darwin') {
+    await run('open', [path], signal)
+    return
+  }
+
+  if (platform === 'win32') {
+    await run('powershell.exe', [
+      '-NoProfile',
+      '-Command',
+      `Invoke-Item -LiteralPath ${powershellLiteral(path)}`,
+    ], signal)
+    return
+  }
+
+  if (platform === 'linux') {
+    await run('xdg-open', [path], signal)
+    return
+  }
+
+  throw new Error(`native path opener is unsupported on ${platform}`)
+}
--- a/packages/host/apiproxy/tests/api-proxy-commands.spec.ts
+++ b/packages/host/apiproxy/tests/api-proxy-commands.spec.ts
@@ -1,3 +1,4 @@
+import { MessageId, freezeMessage } from '@deepseek-ai/dsh-llm'
 /**
 * Command/skill RPC handlers and the two new frames over createApiProxy:
 * command.list serves the addressed agent's effective catalog (missing
@@ -10,10 +11,10 @@

 import { describe, expect, it } from 'vitest'
 import { Context } from 'cordis'
-import AgentRegistry, { AgentMessageId } from '@deepseek-ai/dsh-agent'
-import type { Agent, AgentMessage } from '@deepseek-ai/dsh-agent'
+import AgentRegistry, {} from '@deepseek-ai/dsh-agent'
+import type { Agent } from '@deepseek-ai/dsh-agent'
 import SessionStore from '@deepseek-ai/dsh-session'
-import type { SessionId } from '@deepseek-ai/dsh-session'
+import type { SessionId, UserMessage } from '@deepseek-ai/dsh-session'
 import SystemPrompt from '@deepseek-ai/dsh-system-prompt'
 import ToolRegistry from '@deepseek-ai/dsh-tools'
 import UserInteractionService from '@deepseek-ai/dsh-user-interaction'
@@ -115,8 +116,16 @@ describe('command.execute', () => {
    const api = createApiProxy(ctx, DEFAULTS)
    const agent = stubAgent(ctx)
    const value = expectOk(await api.commands.execute(request({ sessionId: agent.id, line: '/goal ship it' }), new AbortController().signal))
-    expect(value).toEqual({ matched: true, result: { kind: 'success', text: `goal:${agent.id}` } })
+    expect(value).toMatchObject({ matched: true })
+    expect(value.commandId).toBeTruthy()
    expect(received).toBe(' ship it')
+    // Pure admission on the wire: the outcome rides the durably logged
+    // lifecycle pair instead of the response.
+    const lifecycle = agent.session.events.filter(e => e.type === 'command/run' || e.type === 'command/done')
+    expect(lifecycle).toMatchObject([
+      { type: 'command/run', data: { commandId: value.commandId, name: 'goal', args: ' ship it' } },
+      { type: 'command/done', data: { commandId: value.commandId, kind: 'success', text: `goal:${agent.id}` } },
+    ])
  })

  it('returns matched:false when syntax or name does not resolve', async () => {
@@ -238,9 +247,10 @@ describe('host/commands-changed frame', () => {
 })

 /** Build one frozen inbox message for the live `agent/inbox/*` events. */
-function inboxMessage(id: string, text: string, rpcId?: string): AgentMessage {
-  return Object.freeze({
-    id: AgentMessageId(id),
+function inboxMessage(id: string, text: string, rpcId?: string): UserMessage {
+  return freezeMessage({
+    id: MessageId(id),
+    role: 'user',
    content: [{ type: 'text' as const, text }],
    source: rpcId === undefined ? { kind: 'user' as const } : { kind: 'user' as const, rpcId: RpcId(rpcId) },
  })
@@ -263,8 +273,8 @@ describe('session/queued frames', () => {

    const liveFrames = (await liveCollected).filter(f => f.type === 'session/queued')
    expect(liveFrames).toEqual([
-      { type: 'session/queued', sessionId: agent.id, content: queued.content, source: { kind: 'user' }, steering: false },
-      { type: 'session/queued', sessionId: agent.id, content: steering.content, source: { kind: 'user' }, steering: true },
+      { type: 'session/queued', sessionId: agent.id, message: queued, steering: false },
+      { type: 'session/queued', sessionId: agent.id, message: steering, steering: true },
    ])

    // A fresh mux connection replays the still-pending entries as its baseline.
@@ -282,8 +292,8 @@ describe('session/queued frames', () => {
    const steering = inboxMessage('m-4', 'x', 'r-1')
    ctx.emit('agent/inbox/enqueue', agent, queued, 'queued')
    ctx.emit('agent/inbox/enqueue', agent, steering, 'steering')
-    ctx.emit('agent/inbox/dequeue', agent, queued)
-    ctx.emit('agent/inbox/dequeue', agent, steering)
+    ctx.emit('agent/inbox/dequeue', agent, queued, 'queued')
+    ctx.emit('agent/inbox/dequeue', agent, steering, 'steering')

    const abort = new AbortController()
    const frames = await collect<MuxFrame>(
@@ -291,6 +301,24 @@ describe('session/queued frames', () => {
    expect(frames.filter(f => f.type === 'session/queued')).toHaveLength(0)
  })

+  it('retires the matching placement when one message identity is queued and steering', async () => {
+    const ctx = await harness()
+    const api = createApiProxy(ctx, DEFAULTS)
+    const agent = stubAgent(ctx)
+    const repeated = inboxMessage('m-repeat', 'same prompt')
+    ctx.emit('agent/inbox/enqueue', agent, repeated, 'queued')
+    ctx.emit('agent/inbox/enqueue', agent, repeated, 'steering')
+    ctx.emit('agent/inbox/dequeue', agent, inboxMessage('unknown', 'not queued'), 'queued')
+    ctx.emit('agent/inbox/dequeue', agent, repeated, 'steering')
+
+    const abort = new AbortController()
+    const frames = await collect<MuxFrame>(
+      api.events.mux({ rpcId: RpcId('t-mux-repeat'), payload: {} }, abort.signal), 2, abort)
+    expect(frames.filter(f => f.type === 'session/queued')).toEqual([
+      { type: 'session/queued', sessionId: agent.id, message: repeated, steering: false },
+    ])
+  })
+
  it('retires mirror entries on a batch discard (cancel path)', async () => {
    const ctx = await harness()
    const api = createApiProxy(ctx, DEFAULTS)
@@ -306,6 +334,6 @@ describe('session/queued frames', () => {
      api.events.mux({ rpcId: RpcId('t-mux-swept'), payload: {} }, abort.signal), 2, abort)
    const remaining = frames.filter(f => f.type === 'session/queued')
    expect(remaining).toHaveLength(1)
-    expect(remaining[0]).toMatchObject({ content: survivor.content })
+    expect(remaining[0]).toMatchObject({ message: survivor })
  })
 })
--- a/packages/host/apiproxy/tests/api-proxy-projections.spec.ts
+++ b/packages/host/apiproxy/tests/api-proxy-projections.spec.ts
@@ -0,0 +1,185 @@
+/**
+ * Projection carrier paths of the host ApiProxy: the history tail page's
+ * projections block reads the registry's watermark snapshot (asOfSeq = last
+ * event seq, one consistent cut); loadOlder pages never carry the block; a
+ * composition without the registry serves histories without it; a disposed
+ * registration's key leaves subsequent responses; and every unit change is
+ * pushed to mux consumers as a session/projection frame minted here.
+ */
+
+import { describe, expect, it } from 'vitest'
+import { Context } from 'cordis'
+import { z } from 'zod'
+import AgentRegistry from '@deepseek-ai/dsh-agent'
+import type { Agent } from '@deepseek-ai/dsh-agent'
+import { createUserMessage } from '@deepseek-ai/dsh-llm'
+import SessionStore from '@deepseek-ai/dsh-session'
+import type { Session } from '@deepseek-ai/dsh-session'
+import SessionProjectionRegistry from '@deepseek-ai/dsh-session-projection'
+import type { ProjectionDefinition } from '@deepseek-ai/dsh-session-projection'
+import UserInteractionService from '@deepseek-ai/dsh-user-interaction'
+import type { MuxFrame, RpcRequest } from '@deepseek-ai/dsh-host-apiproxy/api'
+import { RpcId } from '@deepseek-ai/dsh-host-apiproxy/api/rpc'
+import { createApiProxy } from '@deepseek-ai/dsh-host-apiproxy'
+
+declare module '@deepseek-ai/dsh-session-projection/types' {
+  interface SessionProjectionMap {
+    'test/last-user': { text: string } | null
+  }
+}
+
+let nextRpc = 1
+function request<P>(payload: P): RpcRequest<P> {
+  return { rpcId: RpcId(`proj-${String(nextRpc++)}`), payload }
+}
+
+/** Whole-value unit folding the latest user/message text; null before the first. */
+type LastUserState = { text: string } | null
+const lastUserUnit = (): ProjectionDefinition<'test/last-user', LastUserState> => ({
+  key: 'test/last-user',
+  schema: z.union([z.object({ text: z.string() }), z.null()]),
+  init: () => null,
+  apply: (state, event) => (event.type === 'user/message'
+    ? { text: (event.data.content[0] as { text?: string }).text ?? '' }
+    : state),
+  view: state => state,
+  stateVersion: 1,
+})
+
+async function harness(withRegistry: boolean): Promise<{ ctx: Context; session: Session }> {
+  const ctx = new Context()
+  await ctx.plugin(SessionStore)
+  await ctx.plugin(UserInteractionService)
+  await ctx.plugin(AgentRegistry)
+  if (withRegistry) await ctx.plugin(SessionProjectionRegistry)
+  const session = ctx.sessions.create()
+  // history resolves the agent first; a live structural stub is enough (only
+  // .session is read on this path).
+  ctx.agents.register({ id: session.id, session, status: 'idle', ctx } as Agent)
+  return { ctx, session }
+}
+
+/** Append `count` user messages so the log has paginable message boundaries. */
+function seedMessages(session: Session, count: number): void {
+  for (let i = 0; i < count; i++) {
+    session.append('user/message', createUserMessage({
+      content: [{ type: 'text', text: `m${i}` }],
+      source: { kind: 'user' },
+    }), { surfaceOp: 'append' })
+  }
+}
+
+const api = (ctx: Context) => createApiProxy(ctx, { provider: 'p', model: 'm', cwd: '/tmp', workspaceRoot: '/tmp' })
+
+describe('session.history projections block', () => {
+  it('serves the unit value on the tail page with asOfSeq = last event seq', async () => {
+    const { ctx, session } = await harness(true)
+    ctx.sessionProjections.register(lastUserUnit())
+    seedMessages(session, 3)
+    const response = await api(ctx).sessions.history(request({ sessionId: session.id }))
+    expect(response.result.ok).toBe(true)
+    if (!response.result.ok) throw new Error('unreachable')
+    const { events, projections } = response.result.value
+    expect(projections).toBeDefined()
+    expect(projections?.asOfSeq).toBe(session.seq - 1)
+    expect(projections?.values['test/last-user']).toEqual({ text: 'm2' })
+    // asOfSeq IS the window tail: the last served event carries it.
+    expect(events.at(-1)?.event.seq).toBe(projections?.asOfSeq)
+  })
+
+  it('never carries the block on loadOlder pages (beforeSeq present)', async () => {
+    const { ctx, session } = await harness(true)
+    ctx.sessionProjections.register(lastUserUnit())
+    seedMessages(session, 5)
+    const older = await api(ctx).sessions.history(request({ sessionId: session.id, beforeSeq: 3, maxMessages: 2 }))
+    expect(older.result.ok).toBe(true)
+    if (!older.result.ok) throw new Error('unreachable')
+    expect('projections' in older.result.value).toBe(false)
+  })
+
+  it('serves no block when the composition has no projection registry', async () => {
+    const { ctx, session } = await harness(false)
+    seedMessages(session, 2)
+    const response = await api(ctx).sessions.history(request({ sessionId: session.id }))
+    expect(response.result.ok).toBe(true)
+    if (!response.result.ok) throw new Error('unreachable')
+    expect('projections' in response.result.value).toBe(false)
+  })
+
+  it('drops a disposed registration from subsequent tail pages (empty block, key absent)', async () => {
+    const { ctx, session } = await harness(true)
+    const dispose = ctx.sessionProjections.register(lastUserUnit())
+    seedMessages(session, 1)
+    const proxy = api(ctx)
+    const before = await proxy.sessions.history(request({ sessionId: session.id }))
+    if (!before.result.ok) throw new Error('unreachable')
+    expect(before.result.value.projections?.values['test/last-user']).toEqual({ text: 'm0' })
+
+    dispose()
+    const after = await proxy.sessions.history(request({ sessionId: session.id }))
+    if (!after.result.ok) throw new Error('unreachable')
+    // The registry is still mounted, so the block itself stays (asOfSeq cut
+    // with zero keys); the disposed key reads as capability absence.
+    expect(after.result.value.projections?.asOfSeq).toBe(session.seq - 1)
+    expect(after.result.value.projections?.values).toEqual({})
+  })
+})
+
+describe('session/projection push frame', () => {
+  /** Drain frames until `count` session/projection frames arrived. */
+  async function collect(iterable: AsyncIterable<RpcRequest<MuxFrame>>, count: number, abort: AbortController): Promise<MuxFrame[]> {
+    const frames: MuxFrame[] = []
+    for await (const envelope of iterable) {
+      frames.push(envelope.payload)
+      if (frames.filter(f => f.type === 'session/projection').length >= count) abort.abort()
+    }
+    return frames
+  }
+
+  it('broadcasts a frame per changed unit with the causing seq, and none for same-reference applies', async () => {
+    const { ctx, session } = await harness(true)
+    ctx.sessionProjections.register(lastUserUnit())
+    const proxy = api(ctx)
+    // The gateway's onChanged subscription lives in an inject child whose
+    // fiber activates asynchronously; yield until it lands before appending.
+    await new Promise(resolve => setTimeout(resolve, 0))
+    const abort = new AbortController()
+    const stream = proxy.events.mux({ rpcId: RpcId('t-proj-mux'), payload: {} }, abort.signal)
+    const collected = collect(stream, 2, abort)
+
+    seedMessages(session, 1)
+    // Same-reference apply: turn/start does not concern the unit — no frame.
+    session.append('turn/start', { turn: 1, trigger: { kind: 'message', source: { kind: 'user' } } })
+    seedMessages(session, 1)
+
+    const frames = await collected
+    const pushes = frames.filter(
+      (f): f is Extract<MuxFrame, { type: 'session/projection' }> => f.type === 'session/projection',
+    )
+    expect(pushes).toEqual([
+      { type: 'session/projection', sessionId: session.id, key: 'test/last-user', value: { text: 'm0' }, seq: 0 },
+      { type: 'session/projection', sessionId: session.id, key: 'test/last-user', value: { text: 'm0' }, seq: 2 },
+    ])
+    // Frame seq aligns with the tail block's asOfSeq vocabulary (higher-seq-wins compatible).
+    const tail = await proxy.sessions.history(request({ sessionId: session.id }))
+    if (!tail.result.ok) throw new Error('unreachable')
+    expect(tail.result.value.projections?.asOfSeq).toBe(pushes.at(-1)?.seq)
+  })
+
+  it('emits no projection frames when the composition has no registry', async () => {
+    const { ctx, session } = await harness(false)
+    const proxy = api(ctx)
+    const abort = new AbortController()
+    const stream = proxy.events.mux({ rpcId: RpcId('t-noproj-mux'), payload: {} }, abort.signal)
+    const frames: MuxFrame[] = []
+    const drained = (async () => {
+      for await (const envelope of stream) {
+        frames.push(envelope.payload)
+        if (frames.filter(f => f.type === 'session/event').length >= 2) abort.abort()
+      }
+    })()
+    seedMessages(session, 2)
+    await drained
+    expect(frames.some(f => f.type === 'session/projection')).toBe(false)
+  })
+})
--- a/packages/host/apiproxy/tests/api-proxy-view.spec.ts
+++ b/packages/host/apiproxy/tests/api-proxy-view.spec.ts
@@ -14,9 +14,9 @@ import type { Agent } from '@deepseek-ai/dsh-agent'
 import SessionStore from '@deepseek-ai/dsh-session'
 import SystemPrompt from '@deepseek-ai/dsh-system-prompt'
 import ToolRegistry, { defineContentToolFixture } from '@deepseek-ai/dsh-tools'
+import { CallId, createToolResultMessage } from '@deepseek-ai/dsh-llm'
 import type { ContentBlock } from '@deepseek-ai/dsh-llm'
-import { CallId } from '@deepseek-ai/dsh-llm'
-import type { Session, SessionId } from '@deepseek-ai/dsh-session'
+import type { Session, SessionEvent, SessionId } from '@deepseek-ai/dsh-session'
 import type { ToolDefinition } from '@deepseek-ai/dsh-tools'
 import UserInteractionService from '@deepseek-ai/dsh-user-interaction'
 import type { MuxFrame, RpcRequest } from '@deepseek-ai/dsh-host-apiproxy/api'
@@ -88,16 +88,35 @@ describe('mux live view computation', () => {
    session.append('tool/call', { turn: 1, step: 1, callId: CallId('c-term'), name: 'term', arguments: '{"cmd":"echo hi"}' })
    session.append('tool/call', { turn: 1, step: 1, callId: CallId('c-diff'), name: 'diffy', arguments: '{}' })
    session.append('tool/call', { turn: 1, step: 1, callId: CallId('c-call-only'), name: 'call-only', arguments: '{}' })
-    session.append('tool/result', { turn: 1, step: 1, callId: CallId('c-call-only'), content: [{ type: 'text', text: rawResult }], isError: false }, { surfaceOp: 'append' })
+    session.append('tool/result', {
+      turn: 1, step: 1,
+      message: createToolResultMessage({
+        callId: CallId('c-call-only'),
+        content: [{ type: 'text', text: rawResult }],
+        isError: false,
+      }),
+    }, { surfaceOp: 'append' })
    session.append('tool/call', { turn: 1, step: 1, callId: CallId('c-plain'), name: 'plain', arguments: '{}' })
    session.append('tool/call', { turn: 1, step: 1, callId: CallId('c-boom'), name: 'boom', arguments: '{}' })
-    session.append('tool/result', { turn: 1, step: 1, callId: CallId('c-gen'), content: [{ type: 'text', text: 'ok' }], isError: false }, { surfaceOp: 'append' })
+    session.append('tool/result', {
+      turn: 1, step: 1,
+      message: createToolResultMessage({
+        callId: CallId('c-gen'),
+        content: [{ type: 'text', text: 'ok' }],
+        isError: false,
+      }),
+    }, { surfaceOp: 'append' })

    const frames = await collected
    const events = frames.filter(f => f.type === 'session/event')
    const byCall = new Map(events
      .filter(f => f.event.type === 'tool/call' || f.event.type === 'tool/result')
-      .map(f => [`${f.event.type}:${(f.event.data as { callId: string }).callId}`, f]))
+      .map(f => [
+        `${f.event.type}:${f.event.type === 'tool/call'
+          ? f.event.data.callId
+          : (f.event.data as SessionEvent<'tool/result'>['data']).message.source.callId}`,
+        f,
+      ]))

    expect(byCall.get('tool/call:c-gen')?.view).toEqual({ for: 'call', view: { card: 'generic', title: 'gen call' } })
    expect(byCall.get('tool/call:c-term')?.view).toEqual({ for: 'call', view: { card: 'terminal', title: 'echo hi' } })
@@ -130,15 +149,44 @@ describe('mux live view computation', () => {
    session.append('turn/start', { turn: 1, trigger: { kind: 'message', source: { kind: 'user' } } })
    session.append('tool/call', { turn: 1, step: 1, callId: CallId('h-term'), name: 'term', arguments: '{"cmd":"ls"}' })
    // meta rides through to presentResult's ToolResult (the spread arm).
-    session.append('tool/result', { turn: 1, step: 1, callId: CallId('h-term'), content: [{ type: 'text', text: 'ok' }], isError: false, meta: { n: 1 } }, { surfaceOp: 'append' })
+    session.append('tool/result', {
+      turn: 1, step: 1,
+      message: createToolResultMessage({
+        callId: CallId('h-term'),
+        content: [{ type: 'text', text: 'ok' }],
+        isError: false,
+      }),
+      meta: { n: 1 },
+    }, { surfaceOp: 'append' })
    // Unpaired result: no tool/call with this id anywhere in the page.
-    session.append('tool/result', { turn: 1, step: 1, callId: CallId('h-orphan'), content: [{ type: 'text', text: 'x' }], isError: false }, { surfaceOp: 'append' })
+    session.append('tool/result', {
+      turn: 1, step: 1,
+      message: createToolResultMessage({
+        callId: CallId('h-orphan'),
+        content: [{ type: 'text', text: 'x' }],
+        isError: false,
+      }),
+    }, { surfaceOp: 'append' })
    // Paired, but the call's stored arguments do not parse: backscan soft-falls.
    session.append('tool/call', { turn: 1, step: 1, callId: CallId('h-bad'), name: 'term', arguments: '{broken' })
-    session.append('tool/result', { turn: 1, step: 1, callId: CallId('h-bad'), content: [{ type: 'text', text: 'y' }], isError: false }, { surfaceOp: 'append' })
+    session.append('tool/result', {
+      turn: 1, step: 1,
+      message: createToolResultMessage({
+        callId: CallId('h-bad'),
+        content: [{ type: 'text', text: 'y' }],
+        isError: false,
+      }),
+    }, { surfaceOp: 'append' })
    // Presenterless tool: pairing succeeds but presentResult is absent.
    session.append('tool/call', { turn: 1, step: 1, callId: CallId('h-plain'), name: 'plain', arguments: '{}' })
-    session.append('tool/result', { turn: 1, step: 1, callId: CallId('h-plain'), content: [{ type: 'text', text: 'z' }], isError: false }, { surfaceOp: 'append' })
+    session.append('tool/result', {
+      turn: 1, step: 1,
+      message: createToolResultMessage({
+        callId: CallId('h-plain'),
+        content: [{ type: 'text', text: 'z' }],
+        isError: false,
+      }),
+    }, { surfaceOp: 'append' })

    const response = await api.sessions.history({ rpcId: RpcId('t-hist'), payload: { sessionId: session.id } })
    expect(response.result.ok).toBe(true)
@@ -146,7 +194,12 @@ describe('mux live view computation', () => {
    const entries = response.result.value.events
    const byKey = new Map(entries
      .filter(entry => entry.event.type === 'tool/call' || entry.event.type === 'tool/result')
-      .map(entry => [`${entry.event.type}:${(entry.event.data as { callId: string }).callId}`, entry]))
+      .map(entry => [
+        `${entry.event.type}:${entry.event.type === 'tool/call'
+          ? entry.event.data.callId
+          : (entry.event.data as SessionEvent<'tool/result'>['data']).message.source.callId}`,
+        entry,
+      ]))
    expect(byKey.get('tool/call:h-term')?.view).toEqual({ for: 'call', view: { card: 'terminal', title: 'ls' } })
    expect(byKey.get('tool/result:h-term')?.view).toEqual({ for: 'result', view: { card: 'terminal', output: 'done' } })
    expect('view' in (byKey.get('tool/result:h-orphan') ?? {})).toBe(false)
@@ -154,39 +207,6 @@ describe('mux live view computation', () => {
    expect('view' in (byKey.get('tool/result:h-plain') ?? {})).toBe(false)
  })

-  it('tail page carries the full-log todo projection; older pages and todo-less sessions omit it', async () => {
-    const { ctx } = await harness()
-    const api = createApiProxy(ctx, { provider: 'p', model: 'm', cwd: '/tmp', workspaceRoot: '/tmp' })
-    const session = ctx.sessions.create()
-    ctx.agents.register({ id: session.id, session, status: 'idle', ctx } as Agent)
-    // Superseded write early in the log, latest write later; enough messages to page.
-    session.append('todo/write', { todos: [{ content: 'old', status: 'pending' }] })
-    for (let turn = 0; turn < 6; turn++) {
-      session.append('turn/start', { turn, trigger: { kind: 'message', source: { kind: 'user' } } })
-      session.append('user/message', { content: [{ type: 'text', text: `q${turn}` }], source: { kind: 'user' } }, { surfaceOp: 'append' })
-      session.append('assistant/message', { turn, step: 0, content: [{ type: 'text', text: `a${turn}` }], provenance: { provider: 'p', model: 'm' } }, { surfaceOp: 'append' })
-      session.append('turn/end', { turn, reason: { kind: 'completed' } })
-    }
-    session.append('todo/write', { todos: [{ content: 'current', status: 'in_progress' }] })
-
-    // Tail page limited to 2 messages: the latest todo/write may or may not sit
-    // in the window — the projection must come from the FULL log either way.
-    const tail = await api.sessions.history({ rpcId: RpcId('t-todos'), payload: { sessionId: session.id, maxMessages: 2 } })
-    if (!tail.result.ok) throw new Error('history failed')
-    expect(tail.result.value.todos).toEqual([{ content: 'current', status: 'in_progress' }])
-    // An older page omits the projection (session-level, tail-page-only).
-    const boundary = tail.result.value.events[0]?.event.seq ?? 0
-    const older = await api.sessions.history({ rpcId: RpcId('t-todos-2'), payload: { sessionId: session.id, beforeSeq: boundary, maxMessages: 2 } })
-    if (!older.result.ok) throw new Error('older failed')
-    expect('todos' in older.result.value).toBe(false)
-    // A session with no todo/write anywhere omits the field.
-    const bare = ctx.sessions.create()
-    ctx.agents.register({ id: bare.id, session: bare, status: 'idle', ctx } as Agent)
-    const bareTail = await api.sessions.history({ rpcId: RpcId('t-todos-3'), payload: { sessionId: bare.id } })
-    if (!bareTail.result.ok) throw new Error('bare failed')
-    expect('todos' in bareTail.result.value).toBe(false)
-  })
-
  it('drops a disposed session from the live open-call table (result after dispose gets no view)', async () => {
    const { ctx } = await harness()
    const api = createApiProxy(ctx, { provider: 'p', model: 'm', cwd: '/tmp', workspaceRoot: '/tmp' })
@@ -221,7 +241,14 @@ describe('mux live view computation', () => {
    session.append('turn/end', { turn: 1, reason: { kind: 'completed' } })
    // The turn/end above cleared the live table; pairing must fall back to
    // scanning the session's in-memory events.
-    session.append('tool/result', { turn: 1, step: 1, callId: CallId('c-late'), content: [{ type: 'text', text: 'ok' }], isError: false }, { surfaceOp: 'append' })
+    session.append('tool/result', {
+      turn: 1, step: 1,
+      message: createToolResultMessage({
+        callId: CallId('c-late'),
+        content: [{ type: 'text', text: 'ok' }],
+        isError: false,
+      }),
+    }, { surfaceOp: 'append' })

    const frames = await collected
    const result = frames.find(f => f.type === 'session/event' && f.event.type === 'tool/result')
--- a/packages/host/apiproxy/tests/api-proxy-workspace.spec.ts
+++ b/packages/host/apiproxy/tests/api-proxy-workspace.spec.ts
@@ -3,7 +3,7 @@ import { tmpdir } from 'node:os'
 import { join } from 'node:path'
 import { describe, expect, it, vi } from 'vitest'
 import { Context } from 'cordis'
-import AgentRegistry, { AgentMessageId } from '@deepseek-ai/dsh-agent'
+import AgentRegistry from '@deepseek-ai/dsh-agent'
 import type { Agent, AgentFactory } from '@deepseek-ai/dsh-agent'
 import SessionStore, { SessionId } from '@deepseek-ai/dsh-session'
 import type { Session } from '@deepseek-ai/dsh-session'
@@ -47,10 +47,10 @@ function stubAgent(session: Session): Agent {
    status: 'idle',
    acceptsNextStep: false,
    ctx: new Context(),
-    followup: () => AgentMessageId('stub'),
-    steer: () => AgentMessageId('stub'),
-    inject: () => AgentMessageId('stub'),
-    send: () => AgentMessageId('stub'),
+    followup: () => {},
+    steer: () => {},
+    inject: () => {},
+    send: () => {},
    cancel() {},
    whenIdle: () => Promise.resolve(),
  }
@@ -60,6 +60,7 @@ function stubAgent(session: Session): Agent {
 async function harness(
  workspaceRoot = realpathSync(mkdtempSync(join(tmpdir(), 'dsh-apiproxy-workspace-'))),
  picker: DirectoryPickerCapability = { kind: 'native', pick: async () => null },
+  extras: { openPath?: (path: string, signal: AbortSignal) => Promise<void> } = {},
 ) {
  const ctx = new Context()
  await ctx.plugin(SessionStore)
@@ -102,6 +103,7 @@ async function harness(
    model: 'test-model',
    cwd: workspaceRoot,
    workspaceRoot,
+    ...extras.openPath === undefined ? {} : { openPath: extras.openPath },
  })
  return { api, ctx, storageDomain, workspaceRoot }
 }
@@ -204,6 +206,30 @@ describe('host.listDirectory / host.createDirectory', () => {
  })
 })

+describe('host.openPath', () => {
+  it('opens through the injected native boundary', async () => {
+    const opened: string[] = []
+    const { api } = await harness(undefined, undefined, {
+      openPath: async (path) => { opened.push(path) },
+    })
+    expect((await api.host.openPath(request({ path: '/tmp/a.txt' }), new AbortController().signal)).result)
+      .toEqual({ ok: true, value: { opened: true } })
+    expect(opened).toEqual(['/tmp/a.txt'])
+  })
+
+  it('propagates abort into the native boundary as a cancelled RPC error', async () => {
+    const { api } = await harness(undefined, undefined, {
+      openPath: (_path, signal) => new Promise((_resolve, reject) => {
+        signal.addEventListener('abort', () => { reject(new Error('aborted')) }, { once: true })
+      }),
+    })
+    const abort = new AbortController()
+    const pending = api.host.openPath(request({ path: '/tmp/a.txt' }), abort.signal)
+    abort.abort()
+    expect((await pending).result).toMatchObject({ ok: false, error: { code: 'cancelled' } })
+  })
+})
+
 describe('workspace.create', () => {
  it('serializes concurrent names and rejects the duplicate', async () => {
    const { api, workspaceRoot } = await harness()
--- a/packages/host/apiproxy/tests/client-handler.spec.ts
+++ b/packages/host/apiproxy/tests/client-handler.spec.ts
@@ -52,6 +52,7 @@ function scriptedApi(overrides: {
      pickDirectory: r => ok(r, { path: null }),
      listDirectory: r => ok(r, { path: '/t', home: '/t', crumbs: [], entries: [] }),
      createDirectory: r => ok(r, { path: '/t/new' }),
+      openPath: r => ok(r, { opened: true as const }),
      ...overrides.host,
    },
    workspace: {
--- a/packages/host/apiproxy/tests/fetch-carrier.spec.ts
+++ b/packages/host/apiproxy/tests/fetch-carrier.spec.ts
@@ -1,3 +1,4 @@
+import { CommandId } from '@deepseek-ai/dsh-commands/brand'
 import { describe, expect, it, vi } from 'vitest'
 import type { ApiProxy, HostFrame, MuxFrame } from '../src/api/index.ts'
 import type { ClientResponse, RpcMessage, RpcReceipt, RpcRequest } from '../src/api/rpc.ts'
@@ -25,10 +26,10 @@ function fakeApi(overrides: Partial<{ muxFrames: MuxFrame[]; hostFrames: HostFra
        return { rpcId: request.rpcId, result: { ok: true, value: { sessionId: 's-new' as never } } }
      },
      async history(request) {
-        if (request.payload.sessionId === ('with-todos' as never)) {
+        if (request.payload.sessionId === ('with-projections' as never)) {
          return {
            rpcId: request.rpcId,
-            result: { ok: true, value: { events: [], hasMore: false, todos: [{ content: 'current', status: 'in_progress' as const }] } },
+            result: { ok: true, value: { events: [], hasMore: false, projections: { asOfSeq: 9, values: { todos: [{ content: 'current', status: 'in_progress' as const }] } } } },
          }
        }
        return {
@@ -86,6 +87,9 @@ function fakeApi(overrides: Partial<{ muxFrames: MuxFrame[]; hostFrames: HostFra
      async createDirectory(request) {
        return { rpcId: request.rpcId, result: { ok: true, value: { path: '/w/new' } } }
      },
+      async openPath(request) {
+        return { rpcId: request.rpcId, result: { ok: true, value: { opened: true as const } } }
+      },
    },
    workspace: {
      async list(request) {
@@ -127,7 +131,7 @@ function fakeApi(overrides: Partial<{ muxFrames: MuxFrame[]; hostFrames: HostFra
          return { rpcId: request.rpcId, result: { ok: false, error: { code: 'cancelled', message: 'aborted', details: {} } } }
        }
        if (request.payload.line.startsWith('/plan')) {
-          return { rpcId: request.rpcId, result: { ok: true, value: { matched: true, result: { kind: 'success' as const, text: 'plan set' } } } }
+          return { rpcId: request.rpcId, result: { ok: true, value: { matched: true, commandId: CommandId('cmd-x') } } }
        }
        return { rpcId: request.rpcId, result: { ok: true, value: { matched: false } } }
      },
@@ -164,10 +168,14 @@ describe('unary round trip (handler ⇄ client, no network)', () => {
    expect(response.rpcId).toMatch(/[0-9a-f-]{36}/)
  })

-  it('carries the tail-page todos projection through the wire schema (Zod must not strip it)', async () => {
-    const response = await client().sessions.history({ sessionId: 'with-todos' as never })
+  it('carries the tail-page projections block through the wire schema (Zod must not strip it)', async () => {
+    const response = await client().sessions.history({ sessionId: 'with-projections' as never })
    expect(response.result.ok).toBe(true)
-    if (response.result.ok) expect(response.result.value.todos).toEqual([{ content: 'current', status: 'in_progress' }])
+    if (response.result.ok) {
+      expect(response.result.value.projections).toEqual(
+        { asOfSeq: 9, values: { todos: [{ content: 'current', status: 'in_progress' }] } },
+      )
+    }
  })

  it('carries a business error as 200 + error result', async () => {
@@ -224,12 +232,24 @@ describe('unary round trip (handler ⇄ client, no network)', () => {
    expect(created.result).toEqual({ ok: true, value: { path: '/w/new' } })
  })

+  it('round-trips host.openPath through the wire form', async () => {
+    const api = fakeApi()
+    let opened: string | undefined
+    api.host.openPath = async (request) => {
+      opened = request.payload.path
+      return { rpcId: request.rpcId, result: { ok: true, value: { opened: true as const } } }
+    }
+    const response = await client(api).host.openPath({ path: '/tmp/a.txt' })
+    expect(opened).toBe('/tmp/a.txt')
+    expect(response.result).toEqual({ ok: true, value: { opened: true } })
+  })
+
  it('round-trips command.list / command.execute / skill.list through the wire form', async () => {
    const c = client()
    const list = await c.commands.list({ sessionId: 's' as never })
    expect(list.result).toEqual({ ok: true, value: { commands: [{ name: 'plan', description: 'Toggle plan mode', input: { hint: 'on|off' } }] } })
    const hit = await c.commands.execute({ sessionId: 's' as never, line: '/plan off' })
-    expect(hit.result).toEqual({ ok: true, value: { matched: true, result: { kind: 'success', text: 'plan set' } } })
+    expect(hit.result).toEqual({ ok: true, value: { matched: true, commandId: 'cmd-x' } })
    const miss = await c.commands.execute({ sessionId: 's' as never, line: '/nope' })
    expect(miss.result).toEqual({ ok: true, value: { matched: false } })
    const skills = await c.skills.list({ sessionId: 's' as never })
--- a/packages/host/apiproxy/tests/native-path-opener.spec.ts
+++ b/packages/host/apiproxy/tests/native-path-opener.spec.ts
@@ -0,0 +1,82 @@
+type ExecFileCallback = (
+  error: (Error & { code?: string | number }) | null,
+  stdout: string,
+  stderr: string,
+) => void
+type ExecFileMock = (
+  command: string,
+  args: readonly string[],
+  options: { encoding: string; signal: AbortSignal; windowsHide: boolean },
+  callback: ExecFileCallback,
+) => void
+
+const { execFileMock } = vi.hoisted(() => ({ execFileMock: vi.fn<ExecFileMock>() }))
+
+vi.mock('node:child_process', () => ({ execFile: execFileMock }))
+
+import { describe, expect, it, vi } from 'vitest'
+import { openNativePath, type PathOpenerRunner } from '../src/native-path-opener.ts'
+
+const signal = () => new AbortController().signal
+
+describe('native path opener', () => {
+  it('opens with macOS open(1)', async () => {
+    const run = vi.fn<PathOpenerRunner>(async () => ({ stdout: '', stderr: '' }))
+    await openNativePath('/Users/test/file.txt', signal(), { platform: 'darwin', run })
+    expect(run).toHaveBeenCalledWith('open', ['/Users/test/file.txt'], expect.any(AbortSignal))
+  })
+
+  it('opens with Windows Invoke-Item and escapes single quotes', async () => {
+    const run = vi.fn<PathOpenerRunner>(async () => ({ stdout: '', stderr: '' }))
+    await openNativePath("C:\\work\\o'reilly.txt", signal(), { platform: 'win32', run })
+    expect(run).toHaveBeenCalledWith(
+      'powershell.exe',
+      ['-NoProfile', '-Command', "Invoke-Item -LiteralPath 'C:\\work\\o''reilly.txt'"],
+      expect.any(AbortSignal),
+    )
+  })
+
+  it('opens with Linux xdg-open', async () => {
+    const run = vi.fn<PathOpenerRunner>(async () => ({ stdout: '', stderr: '' }))
+    await openNativePath('/tmp/a.txt', signal(), { platform: 'linux', run })
+    expect(run).toHaveBeenCalledWith('xdg-open', ['/tmp/a.txt'], expect.any(AbortSignal))
+  })
+
+  it('rejects unsupported platforms', async () => {
+    await expect(openNativePath('/x', signal(), { platform: 'freebsd' as NodeJS.Platform }))
+      .rejects.toThrow('unsupported on freebsd')
+  })
+
+  it('uses the current process platform when no platform override is supplied', async () => {
+    const run = vi.fn<PathOpenerRunner>(async () => ({ stdout: '', stderr: '' }))
+    await openNativePath('/tmp/platform-default.txt', signal(), { run })
+    const expected = process.platform === 'win32'
+      ? 'powershell.exe'
+      : process.platform === 'linux'
+        ? 'xdg-open'
+        : 'open'
+    expect(run.mock.calls[0]?.[0]).toBe(expected)
+  })
+
+  it('runs the default command adapter without a shell and preserves command failures', async () => {
+    execFileMock.mockImplementationOnce((_command, _args, _options, callback) => {
+      callback(null, '', '')
+    })
+    await openNativePath('/tmp/default.txt', signal(), { platform: 'darwin' })
+    const [command, args, options] = execFileMock.mock.calls[0]!
+    expect(command).toBe('open')
+    expect(args).toEqual(['/tmp/default.txt'])
+    expect(options.encoding).toBe('utf8')
+    expect(options.windowsHide).toBe(true)
+    expect(options.signal).toBeInstanceOf(AbortSignal)
+
+    const commandError = Object.assign(new Error('open failed'), { code: 1 })
+    execFileMock.mockImplementationOnce((_command, _args, _options, callback) => {
+      callback(commandError, 'partial output', 'failure details')
+    })
+    await expect(openNativePath('/tmp/missing.txt', signal(), { platform: 'darwin' })).rejects.toMatchObject({
+      message: 'open failed', cause: commandError, code: 1,
+      stdout: 'partial output', stderr: 'failure details',
+    })
+  })
+})
--- a/packages/host/apiproxy/tests/rpc-schemas.spec.ts
+++ b/packages/host/apiproxy/tests/rpc-schemas.spec.ts
@@ -123,9 +123,19 @@ describe('sessions domain schemas', () => {
    expect(sessionSummarySchema.parse({ sessionId: 's1', updatedAt: 1, running: true, blank: false, parentSessionId: 'p', cwd: '/x' }).cwd).toBe('/x')
    // blank is mandatory: a summary without it fails the parse.
    expect(() => sessionSummarySchema.parse({ sessionId: 's1', updatedAt: 1, running: false })).toThrow()
-    const event = sessionEventSchema.parse({ type: 'user/message', seq: 0, time: 1, data: { any: true } })
+    const event = sessionEventSchema.parse({
+      type: 'user/message',
+      seq: 0,
+      time: 1,
+      data: { any: true },
+    })
    expect(event).toMatchObject({ type: 'user/message' })
-    expect(() => sessionEventSchema.parse({ type: 'user/message', seq: -1, time: 1, data: {} })).toThrow()
+    expect(() => sessionEventSchema.parse({
+      type: 'user/message',
+      seq: -1,
+      time: 1,
+      data: {},
+    })).toThrow()
  })

  it('validates the per-method request/value pairs', () => {
@@ -300,10 +310,13 @@ describe('commands domain schemas', () => {
    expect(() => commandExecuteRequestSchema.parse({ line: '/compact' })).toThrow()
    expect(() => commandExecuteRequestSchema.parse({ sessionId: 's1' })).toThrow()
    expect(commandExecuteValueSchema.parse({ matched: false })).toEqual({ matched: false })
-    const matched = commandExecuteValueSchema.parse({ matched: true, result: { kind: 'success', text: 'done' } })
-    expect(matched.result?.kind).toBe('success')
-    expect(commandExecuteValueSchema.parse({ matched: true, result: { kind: 'error', text: 'bad' } }).result?.kind).toBe('error')
-    expect(() => commandExecuteValueSchema.parse({ matched: true, result: { kind: 'other' } })).toThrow()
+    // Pure admission: matched plus the optional lifecycle pairing id
+    // (outcomes ride the logged lifecycle events, never this response).
+    expect(commandExecuteValueSchema.parse({ matched: true, commandId: 'cmd-1' }))
+      .toEqual({ matched: true, commandId: 'cmd-1' })
+    expect(commandExecuteValueSchema.parse({ matched: true })).toEqual({ matched: true })
+    expect(() => commandExecuteValueSchema.parse({ matched: true, commandId: '' })).toThrow()
+    expect(() => commandExecuteValueSchema.parse({})).toThrow()
  })
 })

@@ -328,23 +341,21 @@ describe('events frame schemas', () => {
    const frames = [
      { type: 'session/event', sessionId: 's', event: { type: 't', seq: 0, time: 1, data: null } },
      { type: 'session/subscribed', sessionId: 's', lastSeq: -1 },
-      { type: 'session/title', sessionId: 's', title: 'Durable title', eventSeq: 2, updatedAt: 3 },
      { type: 'approval/requested', sessionId: 's', approvalId: 'a', toolName: 'bash', callId: 'c', reason: 'r' },
      { type: 'approval/resolved', sessionId: 's', approvalId: 'a', outcome: 'allowed-once' },
      { type: 'question/requested', sessionId: 's', questions: [{ id: 'q', question: 'Q?', options: [{ label: 'L' }], multiSelect: true }] },
      { type: 'question/resolved', sessionId: 's', questionRpcId: 'r', outcome: 'answered' },
-      { type: 'session/queued', sessionId: 's', content: [{ type: 'text', text: 'queued prompt' }], source: { kind: 'user', rpcId: 'r9' }, steering: false },
-      { type: 'session/queued', sessionId: 's', content: [{ type: 'text', text: 'steer' }], source: { kind: 'user' }, steering: true },
+      { type: 'session/queued', sessionId: 's', message: { id: 'm1', role: 'user', content: [{ type: 'text', text: 'queued prompt' }], source: { kind: 'user', rpcId: 'r9' } }, steering: false },
+      { type: 'session/queued', sessionId: 's', message: { id: 'm2', role: 'user', content: [{ type: 'text', text: 'steer' }], source: { kind: 'user' } }, steering: true },
+      { type: 'session/projection', sessionId: 's', key: 'todos', value: [{ content: 'x', status: 'pending' }], seq: 7 },
      { type: 'stream/error', error: { code: 'internal', message: 'm', details: {} } },
    ]
    for (const frame of frames) expect(muxFrameSchema.parse(frame)).toMatchObject({ type: frame.type })
    expect(() => muxFrameSchema.parse({ type: 'unknown/frame' })).toThrow()
    for (const invalid of [
-      { type: 'session/title', sessionId: 's', title: '', eventSeq: 0, updatedAt: 1 },
-      { type: 'session/title', sessionId: 's', title: 'x', eventSeq: -1, updatedAt: 1 },
-      { type: 'session/title', sessionId: 's', title: 'x', eventSeq: 0.5, updatedAt: 1 },
-      { type: 'session/title', sessionId: 's', title: 'x', eventSeq: 0, updatedAt: 'now' },
-      { type: 'session/title', sessionId: 's', title: 'x', eventSeq: 0, updatedAt: Number.NaN },
+      { type: 'session/projection', sessionId: 's', key: '', value: null, seq: 0 },
+      { type: 'session/projection', sessionId: 's', key: 'todos', value: null, seq: -1 },
+      { type: 'session/projection', sessionId: 's', key: 'todos', value: null, seq: 0.5 },
    ]) expect(() => muxFrameSchema.parse(invalid)).toThrow()
    expect(askUserQuestionItemSchema.parse({ id: 'q', question: 'Q?' }).id).toBe('q')
  })
@@ -354,9 +365,9 @@ describe('events frame schemas', () => {
  })

  it('rejects a queued frame missing its members', () => {
-    expect(() => muxFrameSchema.parse({ type: 'session/queued', sessionId: 's', content: 'x', source: { kind: 'user' } })).toThrow()
-    expect(() => muxFrameSchema.parse({ type: 'session/queued', sessionId: 's', content: [], source: { kind: 'user' } })).toThrow()
-    expect(() => muxFrameSchema.parse({ type: 'session/queued', sessionId: 's', content: [], source: {}, steering: false })).toThrow()
+    expect(() => muxFrameSchema.parse({ type: 'session/queued', sessionId: 's', message: 'x', steering: false })).toThrow()
+    expect(() => muxFrameSchema.parse({ type: 'session/queued', sessionId: 's', message: { id: 'm', role: 'user', content: [], source: { kind: 'user' } } })).toThrow()
+    expect(() => muxFrameSchema.parse({ type: 'session/queued', sessionId: 's', message: { id: 'm', role: 'user', content: [], source: {} }, steering: false })).toThrow()
  })

  it('accepts every host frame branch', () => {
--- a/packages/host/apiproxy/tsconfig.json
+++ b/packages/host/apiproxy/tsconfig.json
@@ -33,7 +33,7 @@
      "path": "../../session-persistence/session-persistence"
    },
    {
-      "path": "../../session-title/session-title"
+      "path": "../../session-projection/session-projection"
    },
    {
      "path": "../../skill/skill"
--- a/packages/host/directory-picker-native/src/native-command.ts
+++ b/packages/host/directory-picker-native/src/native-command.ts
@@ -0,0 +1,38 @@
+/** Shared no-shell `execFile` runner for native host dialogs and openers. */
+
+import { execFile } from 'node:child_process'
+
+/** Testable command boundary; native implementations never invoke a shell. */
+export type NativeCommandRunner = (
+  command: string,
+  args: readonly string[],
+  signal: AbortSignal,
+) => Promise<{ stdout: string; stderr: string }>
+
+/**
+ * Run a host command with utf8 stdio, abort propagation, and Windows hide.
+ * @param command - executable path or PATH name.
+ * @param args - argv (never a shell string).
+ * @param signal - caller/connection lifetime; abort terminates the child.
+ * @returns captured stdout/stderr on exit 0.
+ */
+export const runNativeCommand: NativeCommandRunner = (command, args, signal) =>
+  new Promise((resolve, reject) => {
+    execFile(
+      command,
+      [...args],
+      { encoding: 'utf8', signal, windowsHide: true },
+      (error, stdout, stderr) => {
+        if (error !== null) {
+          const failure = Object.assign(new Error(error.message, { cause: error }), {
+            code: error.code,
+            stdout,
+            stderr,
+          })
+          reject(failure)
+          return
+        }
+        resolve({ stdout, stderr })
+      },
+    )
+  })
--- a/packages/host/directory-picker-native/src/native-picker.ts
+++ b/packages/host/directory-picker-native/src/native-picker.ts
@@ -1,13 +1,9 @@
 /** Cross-platform native single-directory chooser behind the dialog backend's capability. */

-import { execFile } from 'node:child_process'
+import { runNativeCommand, type NativeCommandRunner } from './native-command.ts'

 /** Testable command boundary; native implementations never invoke a shell. */
-export type DirectoryPickerRunner = (
-  command: string,
-  args: readonly string[],
-  signal: AbortSignal,
-) => Promise<{ stdout: string; stderr: string }>
+export type DirectoryPickerRunner = NativeCommandRunner

 /** Injectable platform facts for deterministic adapter tests. */
 export interface DirectoryPickerInternals {
@@ -15,27 +11,6 @@ export interface DirectoryPickerInternals {
  run?: DirectoryPickerRunner
 }

-const runCommand: DirectoryPickerRunner = (command, args, signal) =>
-  new Promise((resolve, reject) => {
-    execFile(
-      command,
-      [...args],
-      { encoding: 'utf8', signal, windowsHide: true },
-      (error, stdout, stderr) => {
-        if (error !== null) {
-          const failure = Object.assign(new Error(error.message, { cause: error }), {
-            code: error.code,
-            stdout,
-            stderr,
-          })
-          reject(failure)
-          return
-        }
-        resolve({ stdout, stderr })
-      },
-    )
-  })
-
 function outputPath(stdout: string): string | null {
  const path = stdout.replace(/[\r\n]+$/, '')
  return path === '' ? null : path
@@ -72,7 +47,7 @@ export async function pickNativeDirectory(
  internals: DirectoryPickerInternals = {},
 ): Promise<string | null> {
  const platform = internals.platform ?? process.platform
-  const run = internals.run ?? runCommand
+  const run = internals.run ?? runNativeCommand

  if (platform === 'darwin') {
    try {