Merge remote-tracking branch 'origin/master' into mergebot/pr711

# Conflicts: # apps/cli/README.i18n.yaml # apps/cli/README.md # apps/cli/README.zh.md # apps/cli/cordis.yml # apps/cli/package.json # docs/config-catalog.md # packages/client/runtime/README.i18n.yaml # packages/client/runtime/src/client/contract/sessions.ts # packages/client/test-runtime/src/sessions.ts # packages/client/ui-workspace/README.i18n.yaml # packages/client/ui-workspace/README.md # packages/client/ui-workspace/README.zh.md # packages/client/ui-workspace/src/client/WorkspaceBrowser.tsx # packages/client/ui-workspace/src/client/tree.ts # packages/client/ui-workspace/tests/apply.spec.ts # packages/client/ui-workspace/tests/tree.spec.ts # packages/host/apiproxy/README.i18n.yaml # packages/host/apiproxy/src/api-proxy.ts # packages/host/apiproxy/src/api/index.ts # packages/host/apiproxy/tests/client-handler.spec.ts # packages/host/apiproxy/tests/rpc-schemas.spec.ts # pnpm-lock.yaml
2026-07-31 01:28:15 +08:00
parent c9729b501d 37b68e1c31
commit ecbd8babc1
980 changed files with 30720 additions and 7127 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: 68be950ddf0c726d9ca6da98bfb66627cca712f3
-README.zh.md: 2eab7c62f9c3a38bc064d7a7d50b52deb9a98586
+README.md: 2f777fe26be6192c3c4cc211d6631645f58fd10a
+README.zh.md: 9adb379bedf84a08756bfc4b6d02ef3dbba34742
--- a/packages/host/apiproxy/README.md
+++ b/packages/host/apiproxy/README.md
@@ -2,7 +2,7 @@

 English | [中文](README.zh.md)

-The API gateway every client shape shares: the TS contract (`src/api/`, zero Node dependencies, importable from the browser), the fetch carrier pair (`src/fetch/`: `toFetchHandler` on the host side, `AbstractApiClient` plus platform subclasses on the client side), and the host-side implementation (`src/api-proxy.ts`: `createApiProxy` plus the default-exported `ApiProxyService` gateway plugin — config `{provider, model, workspaceRoot?}`, provides `ctx.apiProxy`). Transport-agnostic by design: this package registers no routes; carriers (HTTP today, IPC later) wrap `ctx.apiProxy` themselves. The shipped core composition lives in [`apps/cli/cordis.yml`](../../../apps/cli/cordis.yml).
+The API gateway every client shape shares: the TS contract (`src/api/`, zero Node dependencies, importable from the browser), the fetch carrier pair (`src/fetch/`: `toFetchHandler` on the host side, `AbstractApiClient` plus platform subclasses on the client side), and the host-side implementation (`src/api-proxy.ts`: `createApiProxy` plus the default-exported `ApiProxyService` gateway plugin — config `{provider, model, workspaceRoot?}`, provides `ctx.apiProxy`). Transport-agnostic by design: this package registers no routes; carriers (HTTP today, IPC later) wrap `ctx.apiProxy` themselves. The shipped core composition lives in [`apps/cli/config/base.cordis.yml`](../../../apps/cli/config/base.cordis.yml).

 ## Contract layer (`/api`)

@@ -10,12 +10,18 @@ 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).

+`session.history` pages on append-origin message boundaries: `maxMessages` counts `user/message`, `assistant/message`, and `steering/message` events that entered the surface by appending, so a model-only replacement copy consumes no quota. Each page stays one contiguous raw event range, which keeps a compaction's log-only provenance on the same page as the replacement that cites it.
+
 `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.rename` accepts an explicit user title (resuming a cold session first), delegating to `ctx.sessionTitle.rename` — the accepted `session/title` event pins the title against automatic regeneration — and returns the normalized title plus its event seq so a client settles its `title` projection cell ahead of the push frame; a title that normalizes to empty returns `title-invalid`.

+`session.fork` maps an optional event anchor to the first `turn/end` at or after it, letting a message action include that message's whole turn. An omitted or past-end anchor selects the last completed turn; an in-log anchor whose turn remains open returns `fork-unavailable` rather than clipping backward. The published child inherits the source's seeded history, cwd, latest logged provider/model/reasoning target, and lineage before joining the source Workspace. If Workspace attachment fails, `workspace-attach-failed` carries the already-published child id so clients can reconcile it. The [SessionStore fork decision](../../../.agents/notes/implemented/feature/2026-06-30-session-store-fork-api.md) owns the boundary rationale.
+
 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`.

+Pending queued input is a live control-plane contract, not session history. The gateway mirrors queued `InboxItem` occurrences from `agent/inbox/*` and broadcasts authoritative `session/queue` snapshots on every queued change and reconnect; pending steering stays outside this Web projection. `session.updateQueue` addresses one `InboxItemId`: edit replaces pending content and remove discards it. A driver claim wins races by retiring the address before admission; a later operation returns `queue-item-not-found`. The operation queries only an attached Agent and never resumes a cold session because process-local inbox identities do not survive restart or disposal. The client never infers retirement from turn or status events.
+
 Workspace and Session lists are separate reconnect baselines. `workspace.create` creates a unique name or adopts an existing directory, `workspace.delete` removes only the Workspace registration, `session.create` accepts an optional preallocated Session id, and `host/workspace-changed`, `host/workspace-removed`, plus `host/session-added` carry committed increments in either arrival order. Registration deletion preserves the directory and session logs; its Sessions remain in `session.list` and become Ungrouped. `SessionSummary.blank` and the `host/session-added` frame carry the derived zero-events bit: clients hide blank sessions and reuse them per workspace, flip blank on the first `host/session-status(running:true)`, and treat `session.list` as the reconnect authority; cold summaries are never blank because lazy persistence keeps never-appended sessions out of `list()`.

 `session.search` is a bounded content-search projection over the sessions visible through `session.list`. The gateway asks the optional `ctx.sessionQuery` service for globally ranked current-surface user, assistant, and steering matches, consumes that stream until it has at most 20 visible session/snippet pairs plus one lookahead, and revalidates every hit against the list-derived authorization set before returning it. Provider pages start at 20 hits; when a first-page request rejects that limit, the gateway probes 10, 5, 2, then 1 and retains the learned size for continuation and stale-generation restarts. Returned snippets contain at most 240 Unicode code points, and the response schema independently enforces that bound at each client boundary. Keeping the authorization set in Host memory avoids SQLite's variable ceiling for large valid corpora without weakening visibility or ranking.
@@ -43,7 +49,8 @@ None; this package neither assembles nor sends a provider request.
 ## Known Limitations and Deferred Work

 - **`respond` routing is shipped, but pending-interaction state is host-side work** — the wire shape (POST `/api/respond`, `RpcReceipt`) is final; the pending table that makes late/duplicate answers meaningful lives in `src/api-proxy.ts` and is still minimal (questions only, no approvals).
- **Reserved seams stay out of `RpcMethodMap`** — `session.fork`, `prompt.mode: 'inject'`, `task.list`, `host.listModels`, and a describe `hostInstanceId` are documented reservations; an unknown method fails loud at envelope parse rather than getting a not-implemented code.
+- **Reserved seams stay out of `RpcMethodMap`** — `prompt.mode: 'inject'`, `task.list`, `host.listModels`, and a describe `hostInstanceId` are documented reservations; an unknown method fails loud at envelope parse rather than getting a not-implemented code.
 - **No protocol version field** — client and host ship together; `host.describe` gains a version negotiation field only when an independently released client exists.
 - **Search failures include provider diagnostics** — the gateway is a single-user local service. A carrier that exposes it to multiple users must replace internal search details with a public-safe diagnostic.
 - **Linux native picker requires desktop tooling** — under the `native` capability, `host.pickDirectory` reports an actionable error when neither Zenity nor KDialog is installed; the browse backend is the composition-level fallback (see the [native backend README](../directory-picker-native/README.md)).
+- **A cold session's `updatedAt` counts a mere pickup as a write (per-file backends only)** — the attached projection excludes the `session/end-seed` boundary, because picking a session up is not activity, but a cold session's `updatedAt` is its log file's mtime and every durable write refreshes that, the boundary included. `agentFor()` resumes a cold session on first touch, so merely opening one in a client writes it. This applies only where `locate()` resolves a per-session artifact, i.e. JSONL; SQLite returns `undefined`, so its cold sessions fall back to `createdAt` and are skewed the other way — too old rather than too new — independently of this boundary. A session touched without being worked in therefore sorts newer than its last real activity until it attaches. Separating the two needs a log read, which is exactly what the mtime path exists to avoid; a stored last-activity field in the index would fix it at the source, scoped in the [last-activity-index Agent Note](../../../.agents/notes/proposed/architecture/2026-07-29-durable-last-activity-index.md).
--- a/packages/host/apiproxy/README.zh.md
+++ b/packages/host/apiproxy/README.zh.md
@@ -2,7 +2,7 @@

 [English](README.md) | 中文

-所有客户端形态共用的 API 网关：TS 契约（`src/api/`，不依赖 Node，可从浏览器导入）、fetch 载体对（`src/fetch/`：宿主侧的 `toFetchHandler`，以及客户端侧的 `AbstractApiClient` 与平台子类）和宿主侧实现（`src/api-proxy.ts`：`createApiProxy` 加上默认导出的 `ApiProxyService` 网关插件，其配置为 `{provider, model, workspaceRoot?}`，提供 `ctx.apiProxy`）。该包（package）在设计上与传输方式无关，不注册任何路由；载体（目前为 HTTP，未来可以是 IPC）自行包装 `ctx.apiProxy`。已发布的核心组合位于 [`apps/cli/cordis.yml`](../../../apps/cli/cordis.yml)。
+所有客户端形态共用的 API 网关：TS 契约（`src/api/`，不依赖 Node，可从浏览器导入）、fetch 载体对（`src/fetch/`：宿主侧的 `toFetchHandler`，以及客户端侧的 `AbstractApiClient` 与平台子类）和宿主侧实现（`src/api-proxy.ts`：`createApiProxy` 加上默认导出的 `ApiProxyService` 网关插件，其配置为 `{provider, model, workspaceRoot?}`，提供 `ctx.apiProxy`）。该包（package）在设计上与传输方式无关，不注册任何路由；载体（目前为 HTTP，未来可以是 IPC）自行包装 `ctx.apiProxy`。已发布的核心组合位于 [`apps/cli/config/base.cordis.yml`](../../../apps/cli/config/base.cordis.yml)。

 ## 契约层（`/api`）

@@ -10,11 +10,17 @@

 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。

+`session.history` 按追加来源的消息边界分页：`maxMessages` 统计以追加方式进入 surface 的 `user/message`、`assistant/message` 和 `steering/message` 事件，因此仅供模型使用的替换副本不占用配额。每一页仍是一段连续的原始事件区间，从而让压缩（compaction）的仅日志溯源信息与引用它的替换留在同一页。
+
 `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。`session.rename` 接受用户显式标题（冷会话先恢复），委托给 `ctx.sessionTitle.rename`——被接受的 `session/title` 事件将标题钉住、不再被自动生成覆盖——并返回规范化后的标题及其事件 seq，让 client 在推送帧到达前就结算自己的 `title` 投影格；规范化后为空的标题返回 `title-invalid`。

-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`。
+`session.fork` 将可选事件锚点映射到该锚点处或其后的首个 `turn/end`，使消息操作可包含该消息所在的完整轮次。锚点省略或超过末尾时，选择最后一个已完成轮次；若锚点已在日志中，而其所在轮次仍开放，则返回 `fork-unavailable`，不会向较早位置裁剪。发布后的子会话会先继承源会话的种子历史、cwd、日志中最新的提供方／模型／推理（reasoning）目标及谱系，再加入源 Workspace。如果附加到 Workspace 失败，`workspace-attach-failed` 会携带已发布的子会话 id，供客户端对账。[SessionStore fork 决策](../../../.agents/notes/implemented/feature/2026-06-30-session-store-fork-api.md)给出边界设计的理由。
+
+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`。
+
+待处理的 queued 输入属于实时控制平面契约，而非会话历史。网关镜像来自 `agent/inbox/*` 的 queued `InboxItem` 入队项，并在每次 queued 变更和重连时广播权威的 `session/queue` 快照；待处理 steering（中途引导）不进入此 Web 投影。`session.updateQueue` 通过 `InboxItemId` 寻址单个项：编辑会替换待处理内容，移除会将其丢弃。驱动器在接纳前退役寻址标识，因此认领会赢得竞态；之后的操作返回 `queue-item-not-found`。该操作只查询当前已挂载的 Agent，绝不恢复冷会话，因为进程本地 inbox 标识无法在重启或资源释放后存活。客户端绝不根据轮次或状态事件推断项已退役。

 Workspace 列表与 Session 列表是相互独立的重连基线。`workspace.create` 会创建唯一名称或接纳现有目录，`workspace.delete` 只移除 Workspace 注册记录，`session.create` 接受可选的预分配 Session id，`host/workspace-changed`、`host/workspace-removed` 与 `host/session-added` 则以任意到达顺序携带已提交的增量。删除注册记录会保留目录和会话日志；相关 Session 仍留在 `session.list` 中，并进入 Ungrouped。`SessionSummary.blank` 与 `host/session-added` 帧携带派生的零事件位：客户端隐藏空白会话并按 workspace 复用它们，在首个 `host/session-status(running:true)` 时翻转 blank，并以 `session.list` 作为重连权威；冷会话摘要永远不是空白：惰性持久化让从未追加过事件的会话根本不出现在 `list()` 中。

@@ -43,7 +49,8 @@ Workspace 列表与 Session 列表是相互独立的重连基线。`workspace.cr
 ## 已知限制与延期工作

 - **`respond` 路由已经发布，但待处理交互状态仍属宿主侧工作**：协议形状（POST `/api/respond`、`RpcReceipt`）已经定型；使延迟或重复回答具有明确语义的待处理表位于 `src/api-proxy.ts`，目前仍很精简（只支持问题，不支持审批）。
- **预留 seam 不进入 `RpcMethodMap`**：`session.fork`、`prompt.mode: 'inject'`、`task.list`、`host.listModels` 和描述字段 `hostInstanceId` 都是已记录的预留项；未知方法会在信封解析时直接失败，而不会返回「尚未实现」错误码。
+- **预留 seam 不进入 `RpcMethodMap`**：`prompt.mode: 'inject'`、`task.list`、`host.listModels` 和描述字段 `hostInstanceId` 都是已记录的预留项；未知方法会在信封解析时直接失败，而不会返回「尚未实现」错误码。
 - **没有协议版本字段**：客户端与宿主一同发布；只有出现独立发布的客户端后，`host.describe` 才会增加版本协商字段。
 - **搜索失败会包含提供方诊断信息**：网关是单用户本地服务。将其暴露给多名用户的载体必须用可安全公开的诊断信息替代内部搜索细节。
 - **Linux 原生选择器依赖桌面工具**：在 `native` 能力下，Zenity 和 KDialog 均未安装时，`host.pickDirectory` 会给出包含解决建议的错误提示；组合层面的回退是 browse 后端（见 [native 后端 README](../directory-picker-native/README.md)）。
+- **冷会话的 `updatedAt` 会把一次单纯的拾起算作写入（仅逐文件后端）**：已附加投影排除了 `session/end-seed` 边界，因为接手一个会话不算活动；但冷会话的 `updatedAt` 取自其日志文件的 mtime，而每一次持久写入都会刷新它，包括这条边界。`agentFor()` 会在首次触碰时恢复一个冷会话，因此在客户端里仅仅打开一个会话就会写入它。这只适用于 `locate()` 能解析出逐会话产物的场景，即 JSONL；SQLite 返回 `undefined`，因此它的冷会话回退到 `createdAt`，偏差方向相反——偏旧而不是偏新——且与这条边界无关。于是一个被触碰过却没有在里面工作过的会话，在重新附加之前会按晚于其最后一次真实活动的时间排序。要把两者区分开需要读取日志，而这恰恰是 mtime 路径存在的目的；在索引中存储一个最后活动字段可以从源头修好它，范围见[最后活动索引 Agent Note（agent 决策记录）](../../../.agents/notes/proposed/architecture/2026-07-29-durable-last-activity-index.md)。
--- a/packages/host/apiproxy/src/api-proxy.ts
+++ b/packages/host/apiproxy/src/api-proxy.ts
@@ -9,11 +9,12 @@ import { join } from 'node:path'
 import type { Context } from 'cordis'
 import { installAgentLlmTarget } from '@deepseek-ai/dsh-agent'
 import type {
-  Agent, AgentLlmTarget, AgentLlmTargetRef, AgentStatus, InboxPlacement,
+  Agent, AgentLlmTarget, AgentLlmTargetRef, AgentStatus, InboxItem, InboxItemId,
 } from '@deepseek-ai/dsh-agent'
 import { createUserMessage, ReasoningEffortId } from '@deepseek-ai/dsh-llm'
 import { errorChain } from '@deepseek-ai/dsh-llm'
-import type { MessageId, MessageSource } from '@deepseek-ai/dsh-llm'
+import type { MessageSource } from '@deepseek-ai/dsh-llm'
+import { isAppendSurfaceEvent, lastActivityTime } from '@deepseek-ai/dsh-session'
 import type { Session, SessionEvent, SessionHeader, SessionId, UserMessage } from '@deepseek-ai/dsh-session'
 import type { SessionPersistence } from '@deepseek-ai/dsh-session-persistence'
 import { SessionQueryError, type SessionSearchCursor } from '@deepseek-ai/dsh-session-query'
@@ -71,7 +72,7 @@ const SESSION_SEARCH_PROVIDER_CALL_LIMIT = 100
 /** Bound cold-log stat fan-out and settle each started batch before cancellation returns. */
 const COLD_SUMMARY_BATCH_SIZE = 16

-/** Surface message event types (the pagination counting unit). */
+/** Conversation message event types (the pagination counting unit). */
 const MESSAGE_TYPES = new Set(['user/message', 'assistant/message', 'steering/message'])

 /** Read live abort state across awaits without treating it as synchronously immutable. */
@@ -80,10 +81,14 @@ function isAborted(signal: AbortSignal): boolean {
 }

 /**
- * Message-boundary pagination: count maxMessages surface messages backwards from
- * the window tail; the cut is the starting seq of the oldest message group
- * (chunks group via sourceEventSeqs — never cut mid-message). The tail page
- * naturally includes the in-progress partial.
+ * Message-boundary pagination: count maxMessages append-origin messages
+ * backwards from the window tail. Replacement copies never entered the
+ * conversation a reader sees — they restate a shadowed range for the model
+ * alone — so they consume no quota; the page stays one contiguous raw range,
+ * which keeps a compaction's log-only provenance on the same page as its
+ * replacement. The cut is the starting seq of the oldest message group (chunks
+ * group via sourceEventSeqs — never cut mid-message). The tail page naturally
+ * includes the in-progress partial.
 */
 function paginate(
  events: readonly SessionEvent[],
@@ -95,7 +100,7 @@ function paginate(
  let cut = 0
  for (let i = window.length - 1; i >= 0; i--) {
    const event = window[i] as SessionEvent
-    if (!MESSAGE_TYPES.has(event.type)) continue
+    if (!MESSAGE_TYPES.has(event.type) || !isAppendSurfaceEvent(event)) continue
    count++
    const sources = (event as { sourceEventSeqs?: number[] }).sourceEventSeqs
    const groupStart = sources !== undefined && sources.length > 0 ? Math.min(event.seq, ...sources) : event.seq
@@ -181,7 +186,9 @@ function sessionBlank(session: Session): boolean {
 function summarize(session: Session, running: boolean): SessionSummary {
  return {
    sessionId: session.id,
-    updatedAt: session.events.at(-1)?.time ?? session.header.createdAt,
+    // Excludes end-seed: a resumed-but-untouched session
+    // must not sort as freshly worked in.
+    updatedAt: lastActivityTime(session.events) ?? session.header.createdAt,
    running,
    blank: sessionBlank(session),
    ...session.header.parentSession === undefined ? {} : { parentSessionId: session.header.parentSession },
@@ -532,46 +539,106 @@ export function createApiProxy(ctx: Context, defaults: ApiProxyDefaults): ApiPro
  })

  /**
-   * Per-session inbox occurrence mirror serving the mux-open queue snapshot
+   * Per-session queued-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
+   * queue 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, { message: UserMessage; steering: boolean }[]>()
+  const queuedMirror = new Map<SessionId, InboxItem[]>()
+  type UnseenQueueEvent =
+    | { readonly kind: 'update'; readonly item: InboxItem }
+    | { readonly kind: 'terminal' }
+  const unseenQueueEvents = new Map<SessionId, Map<InboxItemId, UnseenQueueEvent>>()
+  const rememberUnseen = (sessionId: SessionId, itemId: InboxItemId, event: UnseenQueueEvent): void => {
+    let events = unseenQueueEvents.get(sessionId)
+    if (events === undefined) {
+      events = new Map()
+      unseenQueueEvents.set(sessionId, events)
+    }
+    events.set(itemId, event)
+    // Only synchronous re-entrancy may deliver a mutation before its outer
+    // enqueue observer. Drop unmatched protocol-invalid observations instead
+    // of retaining process-local ids indefinitely.
+    queueMicrotask(() => {
+      const current = unseenQueueEvents.get(sessionId)
+      if (current?.get(itemId) !== event) return
+      current.delete(itemId)
+      if (current.size === 0) unseenQueueEvents.delete(sessionId)
+    })
+  }
+  const takeUnseen = (sessionId: SessionId, itemId: InboxItemId): UnseenQueueEvent | undefined => {
+    const events = unseenQueueEvents.get(sessionId)
+    const event = events?.get(itemId)
+    if (event === undefined) return undefined
+    events?.delete(itemId)
+    if (events?.size === 0) unseenQueueEvents.delete(sessionId)
+    return event
+  }
+  const publishQueue = (sessionId: SessionId): void => {
+    const items = queuedMirror.get(sessionId) ?? []
+    broadcast({
+      type: 'session/queue',
+      sessionId,
+      items: items.map(item => ({
+        id: item.id,
+        message: item.message,
+      })),
+    })
+  }
  ctx.effect(() => {
-    const retire = (agent: Agent, id: MessageId, placement?: InboxPlacement): void => {
+    const retire = (agent: Agent, item: InboxItem): boolean => {
      const entries = queuedMirror.get(agent.id)
-      if (entries === undefined) return
-      const index = entries.findIndex(entry =>
-        entry.message.id === id
-        && (placement === undefined || entry.steering === (placement === 'steering')))
-      if (index !== -1) entries.splice(index, 1)
+      if (entries === undefined) {
+        rememberUnseen(agent.id, item.id, { kind: 'terminal' })
+        return false
+      }
+      const index = entries.findIndex(entry => entry.id === item.id)
+      if (index === -1) {
+        rememberUnseen(agent.id, item.id, { kind: 'terminal' })
+        return false
+      }
+      entries.splice(index, 1)
      if (entries.length === 0) queuedMirror.delete(agent.id)
+      return true
    }
    const disposers = [
-      ctx.on('agent/inbox/enqueue', (agent: Agent, message: UserMessage, placement) => {
+      ctx.on('agent/inbox/enqueue', (agent: Agent, item: InboxItem) => {
+        if (item.placement !== 'queued') return
+        const unseen = takeUnseen(agent.id, item.id)
+        if (unseen?.kind === 'terminal') return
        let entries = queuedMirror.get(agent.id)
        if (entries === undefined) {
          entries = []
          queuedMirror.set(agent.id, entries)
        }
-        const steering = placement === 'steering'
-        entries.push({ message, steering })
-        broadcast({
-          type: 'session/queued',
-          sessionId: agent.id,
-          message,
-          steering,
-        })
+        entries.push(unseen?.kind === 'update' ? unseen.item : item)
+        publishQueue(agent.id)
      }),
-      ctx.on('agent/inbox/dequeue', (agent: Agent, message: UserMessage, placement) => {
-        retire(agent, message.id, placement)
+      ctx.on('agent/inbox/update', (agent: Agent, item: InboxItem) => {
+        const entries = queuedMirror.get(agent.id)
+        if (entries === undefined) {
+          rememberUnseen(agent.id, item.id, { kind: 'update', item })
+          return
+        }
+        const index = entries.findIndex(entry => entry.id === item.id)
+        if (index === -1) {
+          rememberUnseen(agent.id, item.id, { kind: 'update', item })
+          return
+        }
+        entries.splice(index, 1, item)
+        publishQueue(agent.id)
      }),
-      ctx.on('agent/inbox/discard', (agent: Agent, messages: UserMessage[]) => {
-        for (const message of messages) retire(agent, message.id)
+      ctx.on('agent/inbox/dequeue', (agent: Agent, item: InboxItem) => {
+        if (retire(agent, item)) publishQueue(agent.id)
+      }),
+      ctx.on('agent/inbox/discard', (agent: Agent, items: InboxItem[]) => {
+        let changed = false
+        for (const item of items) changed = retire(agent, item) || changed
+        if (changed) publishQueue(agent.id)
      }),
      ctx.on('session/disposed', (session: Session) => {
        queuedMirror.delete(session.id)
+        unseenQueueEvents.delete(session.id)
      }),
    ]
    return () => { for (const dispose of disposers) dispose() }
@@ -1268,6 +1335,75 @@ export function createApiProxy(ctx: Context, defaults: ApiProxyDefaults): ApiPro
        }
      },

+      async fork(request) {
+        const { sessionId, atSeq } = request.payload
+        const found = await agentFor(sessionId)
+        if ('error' in found) return err(request, found.error)
+        const source = found.agent.session
+        const events = source.events
+        // An in-log anchor belongs to the turn containing it and must never
+        // clip backward to an earlier completed turn. Omitted and past-end
+        // anchors retain the last-completed-turn shortcut.
+        const lastSeq = events.at(-1)?.seq ?? -1
+        const anchoredBoundary = atSeq === undefined
+          ? undefined
+          : events.find(e => e.type === 'turn/end' && e.seq >= atSeq)
+        const boundary = anchoredBoundary
+          ?? (atSeq === undefined || atSeq > lastSeq
+            ? events.findLast(e => e.type === 'turn/end')
+            : undefined)
+        if (boundary === undefined) {
+          return err(request, {
+            code: 'fork-unavailable',
+            message: atSeq !== undefined && atSeq <= lastSeq
+              ? `session "${sessionId}" has not completed the turn containing event ${String(atSeq)}`
+              : `session "${sessionId}" has no completed turn to fork from`,
+            details: { sessionId },
+          })
+        }
+        // Extend the cut through trailing out-of-band appends (session/title,
+        // injections) up to the next turn/start: they are standalone events, so
+        // the seed stays balanced, and the child inherits a title generated
+        // right after the boundary turn.
+        let cut = boundary.seq + 1
+        while (cut < events.length && events[cut]?.type !== 'turn/start') cut++
+        const childId = `session-${randomUUID()}` as SessionId
+        try {
+          await ctx.agents.create({
+            sessionId: childId,
+            seed: events.slice(0, cut),
+            meta: {
+              ...source.header.cwd === undefined ? {} : { cwd: source.header.cwd },
+              parentSession: source.id,
+              seedLength: cut,
+            },
+            agentOptions,
+            setup: installTarget,
+          })
+        } catch (error: unknown) {
+          return err(request, {
+            code: 'internal',
+            message: `failed to fork session "${sessionId}": ${String(error)}`,
+            details: {},
+          })
+        }
+        // Keep the child in the source's Workspace so the list nests it under
+        // its parent; the child is already published if the attach fails.
+        const workspace = ctx.workspace.list().find(w => w.sessionIds.includes(source.id))
+        if (workspace !== undefined) {
+          try {
+            await workspace.attachSession(childId)
+          } catch (error: unknown) {
+            return err(request, {
+              code: 'workspace-attach-failed',
+              message: `session "${childId}" was forked but could not attach to workspace "${workspace.id}": ${String(error)}`,
+              details: { sessionId: childId, workspaceId: workspace.id },
+            })
+          }
+        }
+        return ok(request, { sessionId: childId })
+      },
+
      async prompt(request) {
        const { sessionId, mode, content } = request.payload
        const found = await agentFor(sessionId)
@@ -1286,6 +1422,19 @@ export function createApiProxy(ctx: Context, defaults: ApiProxyDefaults): ApiPro
        return ok(request, { accepted: true as const })
      },

+      updateQueue(request) {
+        const { sessionId, itemId, action } = request.payload
+        const agent = ctx.agents.get(sessionId)
+        if (agent === undefined || agent.updateInbox(itemId, action) === 'not-found') {
+          return Promise.resolve(err(request, {
+            code: 'queue-item-not-found',
+            message: 'queued item is no longer pending',
+            details: { itemId },
+          }))
+        }
+        return Promise.resolve(ok(request, { accepted: true as const }))
+      },
+
      cancel(request) {
        const { sessionId } = request.payload
        const agent = ctx.agents.get(sessionId)
@@ -1681,15 +1830,15 @@ export function createApiProxy(ctx: Context, defaults: ApiProxyDefaults): ApiPro
        // Queue snapshot baseline (pendingQuestions precedent): frames replayed
        // 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) {
-            queue.push(frame({
-              type: 'session/queued',
-              sessionId,
-              message: entry.message,
-              steering: entry.steering,
-            }))
-          }
+        for (const [sessionId, items] of queuedMirror) {
+          queue.push(frame({
+            type: 'session/queue',
+            sessionId,
+            items: items.map(item => ({
+              id: item.id,
+              message: item.message,
+            })),
+          }))
        }
        // Per-session open-call table for result-view pairing. Bounded by the
        // per-turn call count: entries clear on turn/end; a table miss (stream
--- a/packages/host/apiproxy/src/api/events.schema.ts
+++ b/packages/host/apiproxy/src/api/events.schema.ts
@@ -10,7 +10,9 @@ import type { HostFrame, MuxFrame } from './events.ts'
 import type { Wire } from './rpc.schema.ts'
 import { rpcErrorSchema, rpcIdSchema } from './rpc.schema.ts'
 import { approvalRequestIdSchema } from './approvals.schema.ts'
-import { contentBlockSchema, sessionEventSchema, sessionIdSchema, toolEventViewSchema } from './sessions.schema.ts'
+import {
+  contentBlockSchema, inboxItemIdSchema, sessionEventSchema, sessionIdSchema, toolEventViewSchema,
+} from './sessions.schema.ts'
 import { workspaceIdSchema, workspaceViewSchema } from './workspace.schema.ts'

 /** Question shape validated strictly against core dsh-user-interaction. */
@@ -21,6 +23,11 @@ export const askUserQuestionItemSchema = z.object({
  detail: z.string().optional(),
  options: z.array(z.object({ label: z.string(), description: z.string().optional() })).optional(),
  multiSelect: z.boolean().optional(),
+  // Presentation intent: a tagged union on the wire, so an unknown tag is a
+  // rejected frame rather than a silently generic render.
+  intent: z.discriminatedUnion('kind', [
+    z.object({ kind: z.literal('plan-review'), approve: z.string() }),
+  ]).optional(),
 }) satisfies z.ZodType<Wire<AskUserQuestionItem>>

 /** Unified message envelope carried by transient queue frames. */
@@ -42,7 +49,14 @@ 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')]) }),
-  z.object({ type: z.literal('session/queued'), sessionId: sessionIdSchema, message: messageSchema, steering: z.boolean() }),
+  z.object({
+    type: z.literal('session/queue'),
+    sessionId: sessionIdSchema,
+    items: z.array(z.object({
+      id: inboxItemIdSchema,
+      message: messageSchema,
+    })),
+  }),
  // 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() }),
--- a/packages/host/apiproxy/src/api/events.ts
+++ b/packages/host/apiproxy/src/api/events.ts
@@ -9,6 +9,7 @@
 import type { AskUserQuestionItem } from '@deepseek-ai/dsh-user-interaction/types'
 import type { ApprovalOutcome, ApprovalRequestId } from '@deepseek-ai/dsh-user-approval/types'
 import type { Message } from '@deepseek-ai/dsh-llm/types'
+import type { InboxItemId } from '@deepseek-ai/dsh-agent/brand'
 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'
@@ -31,6 +32,14 @@ export type ToolEventView =
  | { for: 'call'; view: ToolCallView }
  | { for: 'result'; view: ToolResultView }

+/** One pending queued occurrence in an authoritative queue snapshot. */
+export interface QueuedInboxItem {
+  /** Agent-owned occurrence identity used by queue mutations. */
+  id: InboxItemId
+  /** Complete pending message; it is not durable until the Agent claims it. */
+  message: Message
+}
+
 /** Streaming face of the contract: the two SSE stream openers (mux + host). */
 export interface EventsApi {
  /**
@@ -62,18 +71,13 @@ export type MuxFrame =
  | { type: 'question/requested'; sessionId: SessionId; questions: AskUserQuestionItem[] }
  | { type: 'question/resolved'; sessionId: SessionId; questionRpcId: RpcId; outcome: 'answered' | 'cancelled' }
  /**
-   * A message entered the addressed agent's inbox. A queued message is not
-   * model-visible, so there is no session event to carry it; this transient
-   * frame is the only wire signal. On stream open the
-   * host replays the current queue snapshot for every attached session (same
-   * 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. `message.source` carries the prompt's rpcId
-   * when the message came over this wire (the client's provisional-echo
-   * reconciliation key).
+   * Complete transient queue state after every enqueue, mutation, claim, or
+   * discard. Pending work is not model-visible and therefore has no durable
+   * session event; the whole snapshot makes edit, deletion, cancel, and
+   * reconnect converge through one authoritative signal. Pending steering is
+   * outside this Web queue projection.
   */
-  | { type: 'session/queued'; sessionId: SessionId; message: Message; steering: boolean }
+  | { type: 'session/queue'; sessionId: SessionId; items: QueuedInboxItem[] }
  /**
   * One projection unit's finished value changed (session-projection RFC).
   * Live push state, never logged — replay recomputes on the host (the
--- a/packages/host/apiproxy/src/api/index.ts
+++ b/packages/host/apiproxy/src/api/index.ts
@@ -29,14 +29,14 @@ export interface ApiProxy {
 // ---- Domain interfaces and payload entities ----
 export type {
  HistoryEntry, ModelCatalogFailure, ModelCatalogModel, ModelProviderGroup, ModelReasoning,
-  ModelReasoningEffort, ModelTarget, SessionModels, SessionProjectionsBlock, SessionSearchItem,
+  ModelReasoningEffort, ModelTarget, QueueAction, SessionModels, SessionProjectionsBlock, SessionSearchItem,
  SessionsApi, SessionSummary,
 } from './sessions.ts'
 export type { DirectoryEntry, DirectoryListing, HostApi } from './host.ts'
 export type { WorkspaceApi, WorkspaceId, WorkspaceView } from './workspace.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 { EventsApi, MuxFrame, HostFrame, QueuedInboxItem, ToolCallView, ToolEventView, ToolResultView } from './events.ts'
 export type { GoalsApi, GoalId, GoalRef } from './goals.ts'
 export type { ApprovalResponsePayload } from './approvals.ts'
 export type { QuestionResponsePayload } from './questions.ts'
@@ -57,6 +57,7 @@ export type {
 // ---- Errors and ids ----
 export { RpcId, transportError } from './rpc.ts'
 export type { RpcError, RpcErrorCode, RpcErrorDetailsMap, RpcResult } from './rpc.ts'
+export type { InboxItemId } from '@deepseek-ai/dsh-agent/brand'

 // ---- Fixed session-search product bounds ----
 export {
--- a/packages/host/apiproxy/src/api/rpc-map.ts
+++ b/packages/host/apiproxy/src/api/rpc-map.ts
@@ -25,7 +25,9 @@ export interface RpcMethodMap {
  'session.models': SessionsApi['models']
  'session.selectModel': SessionsApi['selectModel']
  'session.rename': SessionsApi['rename']
+  'session.fork': SessionsApi['fork']
  'session.prompt': SessionsApi['prompt']
+  'session.updateQueue': SessionsApi['updateQueue']
  'session.cancel': SessionsApi['cancel']
  'host.describe': HostApi['describe']
  'host.pickDirectory': HostApi['pickDirectory']
--- a/packages/host/apiproxy/src/api/rpc.schema.ts
+++ b/packages/host/apiproxy/src/api/rpc.schema.ts
@@ -47,9 +47,11 @@ export const rpcErrorSchema: z.ZodType<RpcError> = z.discriminatedUnion('code',
  z.object({ code: z.literal('directory-create-failed'), message: z.string(), details: z.object({ path: z.string() }) }),
  z.object({ code: z.literal('directory-picker-unavailable'), message: z.string(), details: z.object({ capability: z.string() }) }),
  z.object({ code: z.literal('agent-busy'), message: z.string(), details: z.object({ reason: z.string() }) }),
+  z.object({ code: z.literal('queue-item-not-found'), message: z.string(), details: z.object({ itemId: z.string() }) }),
  z.object({ code: z.literal('command-error'), message: z.string(), details: z.object({}) }),
  z.object({ code: z.literal('unknown-command'), message: z.string(), details: z.object({}) }),
  z.object({ code: z.literal('title-invalid'), message: z.string(), details: z.object({ sessionId: z.string() }) }),
+  z.object({ code: z.literal('fork-unavailable'), message: z.string(), details: z.object({ sessionId: z.string() }) }),
  z.object({ code: z.literal('internal'), message: z.string(), details: z.object({}) }),
 ]) as unknown as z.ZodType<RpcError>

--- a/packages/host/apiproxy/src/api/rpc.ts
+++ b/packages/host/apiproxy/src/api/rpc.ts
@@ -9,6 +9,7 @@ import type { z as zCore } from 'zod'
 type ZodIssue = zCore.core.$ZodIssue
 import type { Branded } from '@deepseek-ai/dsh-brand'
 import type { SessionId } from '@deepseek-ai/dsh-session/types'
+import type { InboxItemId } from '@deepseek-ai/dsh-agent/brand'

 /**
 * Message correlation id: the initiator mints it on a request; a response
@@ -44,11 +45,13 @@ export interface RpcErrorDetailsMap {
  'directory-create-failed': { path: string }
  'directory-picker-unavailable': { capability: string }
  'agent-busy': { reason: string }
+  'queue-item-not-found': { itemId: InboxItemId }
  /** A known slash command reported a usage/state error; the message is the command's own text. */
  'command-error': {}
  /** A leading-/ prompt named no registered command; the message names the token. */
  'unknown-command': {}
  'title-invalid': { sessionId: SessionId }
+  'fork-unavailable': { sessionId: SessionId }
  'internal': {}
 }

--- a/packages/host/apiproxy/src/api/sessions.schema.ts
+++ b/packages/host/apiproxy/src/api/sessions.schema.ts
@@ -7,6 +7,7 @@

 import { z } from 'zod'
 import type { SessionEvent, SessionId } from '@deepseek-ai/dsh-session/types'
+import type { InboxItemId } from '@deepseek-ai/dsh-agent/brand'
 import type { RequestPayload, ResponseValue } from './rpc-map.ts'
 import type { Wire } from './rpc.schema.ts'
 import type {
@@ -24,6 +25,9 @@ import {
 /** SessionId: one brand cast after shape validation (the only cast point in this domain). */
 export const sessionIdSchema = z.string().min(1) as unknown as z.ZodType<SessionId>

+/** InboxItemId: one brand cast after non-empty string validation. */
+export const inboxItemIdSchema = z.string().min(1) as unknown as z.ZodType<InboxItemId>
+
 /**
 * WorkspaceId: the workspace domain's one brand cast. Hosted here rather
 * than in workspace.schema because session.create references it while
@@ -117,6 +121,17 @@ export const sessionRenameValueSchema = z.object({
  seq: z.number().int().nonnegative(),
 }) satisfies z.ZodType<Wire<ResponseValue<'session.rename'>>>

+/** session.fork request payload (atSeq anchors the completed-turn cut). */
+export const sessionForkRequestSchema = z.object({
+  sessionId: sessionIdSchema,
+  atSeq: z.number().int().nonnegative().optional(),
+}) satisfies z.ZodType<Wire<RequestPayload<'session.fork'>>>
+
+/** session.fork response value (the child session id). */
+export const sessionForkValueSchema = z.object({
+  sessionId: sessionIdSchema,
+}) satisfies z.ZodType<Wire<ResponseValue<'session.fork'>>>
+
 /** session.history request payload (beforeSeq/maxMessages page backwards from the window tail). */
 export const sessionHistoryRequestSchema = z.object({
  sessionId: sessionIdSchema,
@@ -246,6 +261,21 @@ export const sessionPromptValueSchema = z.object({
  }).optional(),
 }) satisfies z.ZodType<Wire<ResponseValue<'session.prompt'>>>

+/** session.updateQueue request payload. */
+export const sessionUpdateQueueRequestSchema = z.object({
+  sessionId: sessionIdSchema,
+  itemId: inboxItemIdSchema,
+  action: z.discriminatedUnion('kind', [
+    z.object({ kind: z.literal('edit'), content: z.array(contentBlockSchema) }),
+    z.object({ kind: z.literal('remove') }),
+  ]),
+}) as unknown as z.ZodType<RequestPayload<'session.updateQueue'>>
+
+/** session.updateQueue response value. */
+export const sessionUpdateQueueValueSchema = z.object({
+  accepted: z.literal(true),
+}) satisfies z.ZodType<Wire<ResponseValue<'session.updateQueue'>>>
+
 /** session.cancel request payload. */
 export const sessionCancelRequestSchema = z.object({
  sessionId: sessionIdSchema,
--- a/packages/host/apiproxy/src/api/sessions.ts
+++ b/packages/host/apiproxy/src/api/sessions.ts
@@ -5,6 +5,7 @@
 */

 import type { ContentBlock } from '@deepseek-ai/dsh-llm/types'
+import type { InboxItemId } from '@deepseek-ai/dsh-agent/brand'
 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.
@@ -124,10 +125,19 @@ export interface SessionModels {
  failures: ModelCatalogFailure[]
 }

+/** A client-requested mutation of one still-pending queue item. */
+export type QueueAction =
+  | { kind: 'edit'; content: ContentBlock[] }
+  | { kind: 'remove' }
+
 /** Session list entry (v1 builds no index: list does readdir+stat). */
 export interface SessionSummary {
  sessionId: SessionId
-  /** Persisted file mtime. */
+  /**
+   * Last activity. Attached: the last non-`session/end-seed` event, since a
+   * pickup is not activity. Cold: the log's mtime, or `createdAt` for a backend
+   * with no per-session file (README Known Limitations covers the skew).
+   */
  updatedAt: number
  /** Status of the attached agent; always false for cold (unattached) sessions. */
  running: boolean
@@ -193,9 +203,11 @@ export interface SessionsApi {
  Promise<RpcResponse<{ sessionId: SessionId }>>

  /**
-   * Reads a window of history events; page boundaries align to message boundaries: one page =
-   * all raw events owned by a whole number of messages (including their chunk / tool events),
-   * never cut mid-message. The tail page (beforeSeq absent) additionally carries the in-flight
+   * Reads a window of history events; page boundaries align to append-origin message
+   * boundaries: one page = all raw events owned by a whole number of such messages (including
+   * their chunk / tool events), never cut mid-message. Model-only replacement copies consume no
+   * `maxMessages`, so a compaction's provenance stays on the page of its replacement. The tail
+   * page (beforeSeq absent) additionally carries the in-flight
   * partial — chunk events already emitted for the last unfinalized message.
   * 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
@@ -243,9 +255,30 @@ export interface SessionsApi {
   * one — carried for future rendering; the state change is the feedback). A usage/state error is an
   * RPC error with code command-error; an unrecognized name is an RPC error with code unknown-command.
   */
+  /**
+   * Forks a new session from a completed-turn prefix of the source. `atSeq`
+   * anchors the cut: the boundary is the first `turn/end` at or after it
+   * (a message's fork button passes the message seq, so the fork includes
+   * that whole turn); a boundary past the log end, or an omitted `atSeq`,
+   * falls back to the source's last completed turn. An in-log anchor whose
+   * turn is still open fails with `fork-unavailable` instead of clipping to
+   * an earlier turn. The child inherits the source cwd, latest logged model
+   * target, workspace attachment, and `parentSessionId` lineage; the seed
+   * prefix carries the source title.
+   */
+  fork(request: RpcRequest<{ sessionId: SessionId; atSeq?: number }>):
+  Promise<RpcResponse<{ sessionId: SessionId }>>
+
+  /** Sends a message. content is core's ContentBlock[] verbatim; mode maps 1:1 — queue→send, steer→steer. */
  prompt(request: RpcRequest<{ sessionId: SessionId; mode: 'queue' | 'steer'; content: ContentBlock[] }>):
  Promise<RpcResponse<{ accepted: true; command?: { kind: 'success'; text?: string } }>>

+  /**
+   * Edits or removes one pending queued occurrence.
+   */
+  updateQueue(request: RpcRequest<{ sessionId: SessionId; itemId: InboxItemId; action: QueueAction }>):
+  Promise<RpcResponse<{ accepted: true }>>
+
  /** Stops: clears both FIFOs + aborts the current step (1:1 with agent.cancel). */
  cancel(request: RpcRequest<{ sessionId: SessionId }>): Promise<RpcResponse<{ accepted: true }>>

--- a/packages/host/apiproxy/src/fetch/client.ts
+++ b/packages/host/apiproxy/src/fetch/client.ts
@@ -20,6 +20,7 @@ import {
 import {
  sessionCancelValueSchema,
  sessionCreateValueSchema,
+  sessionForkValueSchema,
  sessionHistoryValueSchema,
  sessionListValueSchema,
  sessionModelsValueSchema,
@@ -27,6 +28,7 @@ import {
  sessionRenameValueSchema,
  sessionSearchValueSchema,
  sessionSelectModelValueSchema,
+  sessionUpdateQueueValueSchema,
 } from '../api/sessions.schema.ts'
 import {
  workspaceCreateValueSchema,
@@ -70,7 +72,9 @@ export interface IApiClient {
    models(payload: RequestPayload<'session.models'>, signal?: AbortSignal): Promise<RpcResponse<ResponseValue<'session.models'>>>
    selectModel(payload: RequestPayload<'session.selectModel'>, signal?: AbortSignal): Promise<RpcResponse<ResponseValue<'session.selectModel'>>>
    rename(payload: RequestPayload<'session.rename'>, signal?: AbortSignal): Promise<RpcResponse<ResponseValue<'session.rename'>>>
+    fork(payload: RequestPayload<'session.fork'>, signal?: AbortSignal): Promise<RpcResponse<ResponseValue<'session.fork'>>>
    prompt(payload: RequestPayload<'session.prompt'>, signal?: AbortSignal): Promise<RpcResponse<ResponseValue<'session.prompt'>>>
+    updateQueue(payload: RequestPayload<'session.updateQueue'>, signal?: AbortSignal): Promise<RpcResponse<ResponseValue<'session.updateQueue'>>>
    cancel(payload: RequestPayload<'session.cancel'>, signal?: AbortSignal): Promise<RpcResponse<ResponseValue<'session.cancel'>>>
  }
  host: {
@@ -122,7 +126,9 @@ const UNARY_VALUE_SCHEMAS: { [K in keyof RpcMethodMap]: z.ZodType<Wire<ResponseV
  'session.models': sessionModelsValueSchema,
  'session.selectModel': sessionSelectModelValueSchema,
  'session.rename': sessionRenameValueSchema,
+  'session.fork': sessionForkValueSchema,
  'session.prompt': sessionPromptValueSchema,
+  'session.updateQueue': sessionUpdateQueueValueSchema,
  'session.cancel': sessionCancelValueSchema,
  'host.describe': hostDescribeValueSchema,
  'host.pickDirectory': hostPickDirectoryValueSchema,
@@ -335,7 +341,9 @@ export abstract class AbstractApiClient implements IApiClient {
    models: (payload, signal) => this.callUnary('session.models', payload, signal),
    selectModel: (payload, signal) => this.callUnary('session.selectModel', payload, signal),
    rename: (payload, signal) => this.callUnary('session.rename', payload, signal),
+    fork: (payload, signal) => this.callUnary('session.fork', payload, signal),
    prompt: (payload, signal) => this.callUnary('session.prompt', payload, signal),
+    updateQueue: (payload, signal) => this.callUnary('session.updateQueue', payload, signal),
    cancel: (payload, signal) => this.callUnary('session.cancel', payload, signal),
  }

--- a/packages/host/apiproxy/src/fetch/handler.ts
+++ b/packages/host/apiproxy/src/fetch/handler.ts
@@ -17,6 +17,7 @@ import { clientRequestSchema, clientResponseSchema } from '../api/rpc.schema.ts'
 import {
  sessionCancelRequestSchema,
  sessionCreateRequestSchema,
+  sessionForkRequestSchema,
  sessionHistoryRequestSchema,
  sessionListRequestSchema,
  sessionModelsRequestSchema,
@@ -24,6 +25,7 @@ import {
  sessionRenameRequestSchema,
  sessionSearchRequestSchema,
  sessionSelectModelRequestSchema,
+  sessionUpdateQueueRequestSchema,
 } from '../api/sessions.schema.ts'
 import {
  hostCreateDirectoryRequestSchema, hostDescribeRequestSchema,
@@ -73,7 +75,9 @@ const UNARY_ROUTES: UnaryRoutes = {
  'session.models': { schema: sessionModelsRequestSchema, invoke: (api, r) => api.sessions.models(r) },
  'session.selectModel': { schema: sessionSelectModelRequestSchema, invoke: (api, r) => api.sessions.selectModel(r) },
  'session.rename': { schema: sessionRenameRequestSchema, invoke: (api, r) => api.sessions.rename(r) },
+  'session.fork': { schema: sessionForkRequestSchema, invoke: (api, r) => api.sessions.fork(r) },
  'session.prompt': { schema: sessionPromptRequestSchema, invoke: (api, r) => api.sessions.prompt(r) },
+  'session.updateQueue': { schema: sessionUpdateQueueRequestSchema, invoke: (api, r) => api.sessions.updateQueue(r) },
  'session.cancel': { schema: sessionCancelRequestSchema, invoke: (api, r) => api.sessions.cancel(r) },
  'host.describe': { schema: hostDescribeRequestSchema, invoke: (api, r) => api.host.describe(r) },
  'host.pickDirectory': { schema: hostPickDirectoryRequestSchema, invoke: (api, r, signal) => api.host.pickDirectory(r, signal) },
--- a/packages/host/apiproxy/tests/api-proxy-cold.spec.ts
+++ b/packages/host/apiproxy/tests/api-proxy-cold.spec.ts
@@ -78,6 +78,42 @@ describe('sessions.list cold merge', () => {
  })
 })

+describe('attached updatedAt excludes end-seed', () => {
+  it('reports the last real work, not the pickup, so a resumed-untouched session does not float', async () => {
+    const ctx = new Context()
+    await ctx.plugin(SessionStore)
+    await ctx.plugin(UserInteractionService)
+    await ctx.plugin(AgentRegistry)
+    const api = createApiProxy(ctx, { provider: 'p', model: 'm', cwd: '/tmp', workspaceRoot: '/tmp' })
+
+    // Old work, resumed just now: the log tail would report the pickup.
+    const worked = 1_000_000
+    const resumed = ctx.sessions.create(sid('resumed-untouched'), {
+      seed: [
+        { type: 'turn/start', seq: 0, time: worked, data: { turn: 1, trigger: { kind: 'message', source: { kind: 'user' } } } },
+        { type: 'turn/end', seq: 1, time: worked, data: { turn: 1, reason: { kind: 'completed' } } },
+      ],
+      meta: { cwd: '/proj', createdAt: 500 },
+    })
+    ctx.agents.register({ id: resumed.id, session: resumed, status: 'idle', ctx } as Agent)
+    const boundary = resumed.events.at(-1)
+    expect(boundary?.type).toBe('session/end-seed')
+    expect(boundary?.time).toBeGreaterThan(worked)
+
+    const listed = await api.sessions.list(request({}))
+    if (!listed.result.ok) throw new Error('list failed')
+    const summary = listed.result.value.items.find(item => item.sessionId === 'resumed-untouched')
+    expect(summary?.updatedAt).toBe(worked)
+
+    // Real work appended after end-seed does move it.
+    resumed.append('turn/start', { turn: 2, trigger: { kind: 'message', source: { kind: 'user' } } })
+    const after = await api.sessions.list(request({}))
+    if (!after.result.ok) throw new Error('list failed')
+    const moved = after.result.value.items.find(item => item.sessionId === 'resumed-untouched')
+    expect(moved?.updatedAt).toBeGreaterThan(worked)
+  })
+})
+
 describe('degenerate composition (no persistence, no factory)', () => {
  it('list skips the cold merge and resume maps a non-not-found failure to internal', async () => {
    const ctx = new Context()
--- a/packages/host/apiproxy/tests/api-proxy-commands.spec.ts
+++ b/packages/host/apiproxy/tests/api-proxy-commands.spec.ts
@@ -9,10 +9,10 @@ import { MessageId, freezeMessage } from '@deepseek-ai/dsh-llm'
 * open-time queue snapshot.
 */

-import { describe, expect, it } from 'vitest'
+import { describe, expect, it, vi } from 'vitest'
 import { Context } from 'cordis'
-import AgentRegistry, {} from '@deepseek-ai/dsh-agent'
-import type { Agent } from '@deepseek-ai/dsh-agent'
+import AgentRegistry, { InboxItemId } from '@deepseek-ai/dsh-agent'
+import type { Agent, InboxItem, InboxPlacement } from '@deepseek-ai/dsh-agent'
 import SessionStore from '@deepseek-ai/dsh-session'
 import type { SessionId, UserMessage } from '@deepseek-ai/dsh-session'
 import SystemPrompt from '@deepseek-ai/dsh-system-prompt'
@@ -274,84 +274,159 @@ function inboxMessage(id: string, text: string, rpcId?: string): UserMessage {
  })
 }

-describe('session/queued frames', () => {
-  it('forwards live enqueue events and replays the snapshot on a later mux open', async () => {
+/** Build one addressable inbox occurrence around a frozen message. */
+function inboxItem(id: string, message: UserMessage, placement: InboxPlacement): InboxItem {
+  return { id: InboxItemId(id), message, placement }
+}
+
+describe('session.updateQueue', () => {
+  it('routes an addressable action and reports a lost claim race', async () => {
+    const ctx = await harness()
+    const agent = stubAgent(ctx)
+    const seen: unknown[] = []
+    agent.updateInbox = (id, action) => {
+      seen.push({ id, action })
+      return id === InboxItemId('present') ? 'applied' : 'not-found'
+    }
+    const api = createApiProxy(ctx, DEFAULTS)
+
+    const applied = await api.sessions.updateQueue({
+      rpcId: RpcId('q-apply'),
+      payload: {
+        sessionId: agent.id,
+        itemId: InboxItemId('present'),
+        action: { kind: 'edit', content: [{ type: 'text', text: 'edited' }] },
+      },
+    })
+    expect(expectOk(applied)).toEqual({ accepted: true })
+    const missing = await api.sessions.updateQueue({
+      rpcId: RpcId('q-missing'),
+      payload: {
+        sessionId: agent.id,
+        itemId: InboxItemId('claimed'),
+        action: { kind: 'remove' },
+      },
+    })
+    expect(expectErr(missing)).toMatchObject({ code: 'queue-item-not-found' })
+    expect(seen).toEqual([
+      { id: 'present', action: { kind: 'edit', content: [{ type: 'text', text: 'edited' }] } },
+      { id: 'claimed', action: { kind: 'remove' } },
+    ])
+  })
+
+  it('rejects a stale occurrence without resuming a cold agent', async () => {
+    const ctx = await harness()
+    const resume = vi.spyOn(ctx.agents, 'resume')
+    const api = createApiProxy(ctx, DEFAULTS)
+    const response = await api.sessions.updateQueue({
+      rpcId: RpcId('q-cold'),
+      payload: {
+        sessionId: 'cold-session' as SessionId,
+        itemId: InboxItemId('stale-item'),
+        action: { kind: 'remove' },
+      },
+    })
+
+    expect(expectErr(response)).toMatchObject({ code: 'queue-item-not-found' })
+    expect(resume).not.toHaveBeenCalled()
+  })
+})
+
+describe('session/queue frames', () => {
+  it('folds nested mutations observed before their outer enqueue', async () => {
+    const ctx = await harness()
+    const agent = stubAgent(ctx)
+    const original = inboxItem('i-edit', inboxMessage('m-edit', 'before'), 'queued')
+    const edited = inboxItem('i-edit', inboxMessage('m-edit', 'after'), 'queued')
+    const removed = inboxItem('i-remove', inboxMessage('m-remove', 'remove me'), 'queued')
+    ctx.on('agent/inbox/enqueue', (subject, item) => {
+      if (subject !== agent) return
+      if (item.id === original.id) ctx.emit('agent/inbox/update', agent, edited)
+      if (item.id === removed.id) ctx.emit('agent/inbox/discard', agent, [removed])
+    })
+    const api = createApiProxy(ctx, DEFAULTS)
+    const live = new AbortController()
+    const collected = collect<MuxFrame>(
+      api.events.mux({ rpcId: RpcId('t-mux-reentrant'), payload: {} }, live.signal), 2, live)
+
+    ctx.emit('agent/inbox/enqueue', agent, original)
+    ctx.emit('agent/inbox/enqueue', agent, removed)
+
+    const liveFrames = (await collected).filter(frame => frame.type === 'session/queue')
+    expect(liveFrames.map(frame => frame.items)).toEqual([
+      [{ id: edited.id, message: edited.message }],
+    ])
+    const replay = new AbortController()
+    const replayFrames = await collect<MuxFrame>(
+      api.events.mux({ rpcId: RpcId('t-mux-reentrant-replay'), payload: {} }, replay.signal), 2, replay)
+    expect(replayFrames.filter(frame => frame.type === 'session/queue')).toEqual(liveFrames)
+  })
+
+  it('publishes complete live snapshots and replays the latest snapshot on reconnect', async () => {
    const ctx = await harness()
    const api = createApiProxy(ctx, DEFAULTS)
    const agent = stubAgent(ctx)
    const live = new AbortController()
    const liveStream = api.events.mux({ rpcId: RpcId('t-mux-live'), payload: {} }, live.signal)
-    // subscribed baseline + 2 queued frames
-    const liveCollected = collect<MuxFrame>(liveStream, 3, live)
+    // subscribed baseline + one queued snapshot; pending steering stays off this wire.
+    const liveCollected = collect<MuxFrame>(liveStream, 2, live)

-    const queued = inboxMessage('m-1', 'queued prompt')
-    const steering = inboxMessage('m-2', 'queued prompt')
-    ctx.emit('agent/inbox/enqueue', agent, queued, 'queued')
-    ctx.emit('agent/inbox/enqueue', agent, steering, 'steering')
+    const queued = inboxItem('i-1', inboxMessage('m-1', 'queued prompt'), 'queued')
+    const steering = inboxItem('i-2', inboxMessage('m-2', 'steering prompt'), 'steering')
+    ctx.emit('agent/inbox/enqueue', agent, queued)
+    ctx.emit('agent/inbox/enqueue', agent, steering)

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

-    // A fresh mux connection replays the still-pending entries as its baseline.
+    // A fresh mux connection replays only the current authoritative snapshot.
    const replay = new AbortController()
    const replayFrames = await collect<MuxFrame>(
-      api.events.mux({ rpcId: RpcId('t-mux-replay'), payload: {} }, replay.signal), 3, replay)
-    expect(replayFrames.filter(f => f.type === 'session/queued')).toEqual(liveFrames)
+      api.events.mux({ rpcId: RpcId('t-mux-replay'), payload: {} }, replay.signal), 2, replay)
+    expect(replayFrames.filter(f => f.type === 'session/queue')).toEqual([liveFrames[0]])
  })

-  it('retires mirror entries on their terminal dequeue', async () => {
+  it('publishes edits in place in the authoritative order', async () => {
    const ctx = await harness()
    const api = createApiProxy(ctx, DEFAULTS)
    const agent = stubAgent(ctx)
-    const queued = inboxMessage('m-3', 'x')
-    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, 'queued')
-    ctx.emit('agent/inbox/dequeue', agent, steering, 'steering')
-
    const abort = new AbortController()
-    const frames = await collect<MuxFrame>(
-      api.events.mux({ rpcId: RpcId('t-mux-after'), payload: {} }, abort.signal), 1, abort)
-    expect(frames.filter(f => f.type === 'session/queued')).toHaveLength(0)
-  })
+    const collected = collect<MuxFrame>(
+      api.events.mux({ rpcId: RpcId('t-mux-updates'), payload: {} }, abort.signal), 5, abort)
+    const first = inboxItem('i-a', inboxMessage('m-a', 'a'), 'queued')
+    const second = inboxItem('i-b', inboxMessage('m-b', 'b'), 'queued')
+    const edited = inboxItem('i-b', inboxMessage('m-b', 'b edited'), 'queued')
+    ctx.emit('agent/inbox/enqueue', agent, first)
+    ctx.emit('agent/inbox/enqueue', agent, second)
+    ctx.emit('agent/inbox/update', agent, edited)
+    ctx.emit('agent/inbox/dequeue', agent, edited)

-  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 },
+    const frames = (await collected).filter(frame => frame.type === 'session/queue')
+    expect(frames.map(frame => frame.items)).toEqual([
+      [{ id: first.id, message: first.message }],
+      [{ id: first.id, message: first.message }, { id: second.id, message: second.message }],
+      [{ id: first.id, message: first.message }, { id: edited.id, message: edited.message }],
+      [{ id: first.id, message: first.message }],
    ])
  })

-  it('retires mirror entries on a batch discard (cancel path)', async () => {
+  it('publishes an empty snapshot after terminal discard', async () => {
    const ctx = await harness()
    const api = createApiProxy(ctx, DEFAULTS)
    const agent = stubAgent(ctx)
-    const doomed = inboxMessage('m-5', 'doomed')
-    const survivor = inboxMessage('m-6', 'survivor')
-    ctx.emit('agent/inbox/enqueue', agent, doomed, 'queued')
-    ctx.emit('agent/inbox/enqueue', agent, survivor, 'queued')
+    const doomed = inboxItem('i-doomed', inboxMessage('m-5', 'doomed'), 'queued')
+    ctx.emit('agent/inbox/enqueue', agent, doomed)
    ctx.emit('agent/inbox/discard', agent, [doomed])

    const abort = new AbortController()
    const frames = await collect<MuxFrame>(
-      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({ message: survivor })
+      api.events.mux({ rpcId: RpcId('t-mux-swept'), payload: {} }, abort.signal), 1, abort)
+    expect(frames.filter(frame => frame.type === 'session/queue')).toHaveLength(0)
  })
 })
--- a/packages/host/apiproxy/tests/api-proxy-fork.spec.ts
+++ b/packages/host/apiproxy/tests/api-proxy-fork.spec.ts
@@ -0,0 +1,163 @@
+/** Session-fork boundaries, lineage, and inherited model routing. */
+
+import { describe, expect, it } from 'vitest'
+import { Context } from 'cordis'
+import AgentRegistry, { agentEvents } from '@deepseek-ai/dsh-agent'
+import type { Agent, AgentHandle, CreateAgentOptions } from '@deepseek-ai/dsh-agent'
+import { createUserMessage, ReasoningEffortId } from '@deepseek-ai/dsh-llm'
+import type { LlmCallConfig } from '@deepseek-ai/dsh-llm'
+import SessionStore from '@deepseek-ai/dsh-session'
+import type { Session, SessionId } from '@deepseek-ai/dsh-session'
+import SystemPrompt from '@deepseek-ai/dsh-system-prompt'
+import UserInteractionService from '@deepseek-ai/dsh-user-interaction'
+import type { RpcRequest } from '@deepseek-ai/dsh-host-apiproxy/api/rpc'
+import { RpcId } from '@deepseek-ai/dsh-host-apiproxy/api/rpc'
+import { createApiProxy } from '@deepseek-ai/dsh-host-apiproxy'
+
+const sid = (id: string): SessionId => id as SessionId
+
+let nextRpc = 1
+function request<P>(payload: P): RpcRequest<P> {
+  return { rpcId: RpcId(`fork-${String(nextRpc++)}`), payload }
+}
+
+async function composed(): Promise<Context> {
+  const ctx = new Context()
+  await ctx.plugin(SessionStore)
+  await ctx.plugin(SystemPrompt, { persona: '' })
+  await ctx.plugin(AgentRegistry)
+  await ctx.plugin(UserInteractionService)
+  ctx.provide('workspace', { list: () => [] } as never)
+  ctx.agents.setFactory({
+    createAgent: async (ownerCtx: Context, options: CreateAgentOptions): Promise<AgentHandle> => {
+      const session = ctx.sessions.create(options.sessionId, {
+        ...options.seed === undefined ? {} : { seed: [...options.seed] },
+        ...options.meta === undefined ? {} : { meta: options.meta },
+      })
+      const agent = {} as Agent
+      const agentCtx = ownerCtx.extend({ agent })
+      Object.assign(agent, { id: session.id, session, status: 'idle', ctx: agentCtx })
+      await options.setup?.(agentCtx)
+      ctx.agents.register(agent)
+      return { agent, dispose: () => Promise.resolve() }
+    },
+    resume: () => Promise.reject(new Error('fork test sources are live')),
+  })
+  return ctx
+}
+
+function liveAgent(ctx: Context, id: string, turns: number, openTail = false): Session {
+  const session = ctx.sessions.create(sid(id), { meta: { cwd: '/proj' } })
+  for (let turn = 1; turn <= turns; turn++) {
+    session.append('turn/start', { turn, trigger: { kind: 'message', source: { kind: 'user' } } })
+    session.append('user/message', createUserMessage({
+      content: [{ type: 'text', text: `prompt ${String(turn)}` }],
+      source: { kind: 'user' },
+    }), { surfaceOp: 'append' })
+    session.append('turn/end', { turn, reason: { kind: 'completed' } })
+  }
+  if (openTail) {
+    session.append('turn/start', { turn: turns + 1, trigger: { kind: 'message', source: { kind: 'user' } } })
+    session.append('user/message', createUserMessage({
+      content: [{ type: 'text', text: 'open prompt' }],
+      source: { kind: 'user' },
+    }), { surfaceOp: 'append' })
+  }
+  ctx.agents.register({ id: session.id, session, status: 'idle', ctx } as Agent)
+  return session
+}
+
+const api = (ctx: Context) => createApiProxy(ctx, {
+  provider: 'default-provider',
+  model: 'default-model',
+  cwd: '/tmp',
+  workspaceRoot: '/tmp',
+})
+
+describe('sessions.fork', () => {
+  it('cuts at the anchored completed turn and records lineage and cwd', async () => {
+    const ctx = await composed()
+    const source = liveAgent(ctx, 'session-source', 2)
+    const response = await api(ctx).sessions.fork(request({ sessionId: source.id, atSeq: 1 }))
+    expect(response.result.ok).toBe(true)
+    if (!response.result.ok) return
+    const child = ctx.sessions.get(response.result.value.sessionId)
+    expect(child?.events.map(event => event.type)).toEqual([
+      'turn/start', 'user/message', 'turn/end', 'session/end-seed',
+    ])
+    expect(child?.header.parentSession).toBe(source.id)
+    expect(child?.header.cwd).toBe('/proj')
+    await ctx.fiber.dispose()
+  })
+
+  it('uses the last completed turn only for omitted and past-end anchors', async () => {
+    const ctx = await composed()
+    const source = liveAgent(ctx, 'session-tail', 2, true)
+    const proxy = api(ctx)
+    const expectedTypes = [
+      'turn/start', 'user/message', 'turn/end',
+      'turn/start', 'user/message', 'turn/end',
+      'session/end-seed',
+    ]
+    const omitted = await proxy.sessions.fork(request({ sessionId: source.id }))
+    expect(omitted.result.ok).toBe(true)
+    if (omitted.result.ok) {
+      expect(ctx.sessions.get(omitted.result.value.sessionId)?.events.map(event => event.type))
+        .toEqual(expectedTypes)
+    }
+    const pastEnd = await proxy.sessions.fork(request({ sessionId: source.id, atSeq: 999 }))
+    expect(pastEnd.result.ok).toBe(true)
+    if (pastEnd.result.ok) {
+      expect(ctx.sessions.get(pastEnd.result.value.sessionId)?.events.map(event => event.type))
+        .toEqual(expectedTypes)
+    }
+    await ctx.fiber.dispose()
+  })
+
+  it('rejects an in-log anchor whose turn is still open', async () => {
+    const ctx = await composed()
+    const source = liveAgent(ctx, 'session-open', 1, true)
+    const anchor = source.events.at(-1)?.seq ?? 0
+    const response = await api(ctx).sessions.fork(request({ sessionId: source.id, atSeq: anchor }))
+    expect(response.result).toMatchObject({
+      ok: false,
+      error: { code: 'fork-unavailable', details: { sessionId: source.id } },
+    })
+    if (!response.result.ok) expect(response.result.error.message).toMatch(/has not completed/)
+    await ctx.fiber.dispose()
+  })
+
+  it('installs the latest logged model target before the child can run', async () => {
+    const ctx = await composed()
+    const source = liveAgent(ctx, 'session-routed', 1)
+    source.append('request/header', {
+      header: {
+        config: {
+          provider: 'inherited-provider',
+          model: 'inherited-model',
+          reasoningEffort: ReasoningEffortId('high'),
+        },
+      },
+      reason: 'initial',
+    })
+    const response = await api(ctx).sessions.fork(request({ sessionId: source.id }))
+    expect(response.result.ok).toBe(true)
+    if (!response.result.ok) return
+    const child = ctx.agents.get(response.result.value.sessionId)
+    if (child === undefined) throw new Error('fork did not publish the child agent')
+    const assembly = await child.ctx.systemPrompt.assemble()
+    expect(assembly.variables).toMatchObject({
+      provider: 'inherited-provider',
+      model: 'inherited-model',
+    })
+    const fallback: LlmCallConfig = { provider: 'default-provider', model: 'default-model' }
+    await expect(agentEvents(child.ctx, child).waterfall(
+      'agent/request', 1, 0, new AbortController().signal, () => Promise.resolve(fallback),
+    )).resolves.toMatchObject({
+      provider: 'inherited-provider',
+      model: 'inherited-model',
+      reasoningEffort: 'high',
+    })
+    await ctx.fiber.dispose()
+  })
+})
--- a/packages/host/apiproxy/tests/api-proxy-view.spec.ts
+++ b/packages/host/apiproxy/tests/api-proxy-view.spec.ts
@@ -14,7 +14,7 @@ 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 { CallId, createMessage, createToolResultMessage, createUserMessage } from '@deepseek-ai/dsh-llm'
 import type { ContentBlock } from '@deepseek-ai/dsh-llm'
 import type { Session, SessionEvent, SessionId } from '@deepseek-ai/dsh-session'
 import type { ToolDefinition } from '@deepseek-ai/dsh-tools'
@@ -35,6 +35,35 @@ function tool(name: string, presenters: Pick<ToolDefinition, 'presentCall' | 'pr
  })
 }

+/** Append a production-shaped human prompt to the session surface. */
+function appendUserText(session: Session, text: string): SessionEvent {
+  return session.append('user/message', createUserMessage({
+    content: [{ type: 'text', text }], source: { kind: 'user' },
+  }), { surfaceOp: 'append' })
+}
+
+/** Append a production-shaped assistant message to the session surface. */
+function appendAssistantText(session: Session, text: string, step: number): SessionEvent {
+  return session.append('assistant/message', {
+    turn: 1,
+    step,
+    message: createMessage({
+      role: 'assistant',
+      content: [{ type: 'text', text }],
+      source: { kind: 'model', provider: 'p', model: 'm' },
+    }),
+  }, { surfaceOp: 'append' })
+}
+
+/**
+ * Append a plugin-owned log-only event. The host proxy is projection-only, so it
+ * declares no compaction vocabulary; the cast writes the real event shape without
+ * depending on the owning package.
+ */
+function appendExtension(session: Session, type: string, data: unknown): SessionEvent {
+  return (session.append as unknown as (type: string, data: unknown) => SessionEvent)(type, data)
+}
+
 async function harness(): Promise<{ ctx: Context }> {
  const ctx = new Context()
  await ctx.plugin(SessionStore)
@@ -207,6 +236,55 @@ describe('mux live view computation', () => {
    expect('view' in (byKey.get('tool/result:h-plain') ?? {})).toBe(false)
  })

+  it('counts only append-origin messages toward maxMessages and keeps compaction provenance whole', 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)
+    session.append('turn/start', { turn: 1, trigger: { kind: 'message', source: { kind: 'user' } } })
+    const first = appendUserText(session, 'first prompt')
+    appendAssistantText(session, 'first reply', 1)
+    const third = appendUserText(session, 'second prompt')
+    appendAssistantText(session, 'second reply', 2)
+    const shadowed = [...session.surface.nodes]
+    // A compaction transaction: log-only provenance immediately followed by the
+    // replacement that shadows the range.
+    const summary = appendExtension(session, 'compact/summary', {
+      summary: [{ type: 'text', text: 'summary' }],
+      shadowedRange: { start: shadowed[0], end: shadowed.at(-1) },
+      shadowedSeqs: shadowed,
+      shadowedTokenCount: 0,
+      provider: 'p',
+      model: 'm',
+    })
+    session.append('user/message', createUserMessage({
+      content: [{ type: 'text', text: '<context_checkpoint>summary</context_checkpoint>' }],
+      source: { kind: 'plugin', plugin: 'compact' },
+    }), {
+      surfaceOp: { op: 'replace', start: shadowed[0] as number, end: shadowed.at(-1) as number },
+      sourceEventSeqs: [...shadowed, summary.seq],
+    })
+
+    const response = await api.sessions.history({
+      rpcId: RpcId('t-hist-compact'),
+      payload: { sessionId: session.id, maxMessages: 2 },
+    })
+    if (!response.result.ok) throw new Error('unreachable')
+    const page = response.result.value.events.map(entry => entry.event)
+    // Two append-origin messages fill the page even though a replacement copy of
+    // the same event type sits in the window: the copy is model-only.
+    const messages = page.filter(event => event.type === 'user/message' || event.type === 'assistant/message')
+    expect(messages.map(event => event.seq)).toEqual([third.seq, third.seq + 1, third.seq + 3])
+    expect(page.some(event => event.seq === first.seq)).toBe(false)
+    expect(response.result.value.hasMore).toBe(true)
+    // The range stays contiguous, so the checkpoint's provenance is readable on
+    // the same page as the checkpoint itself.
+    const summaryIndex = page.findIndex(event => event.seq === summary.seq)
+    expect(summaryIndex).toBeGreaterThan(-1)
+    expect(page[summaryIndex + 1]?.seq).toBe(summary.seq + 1)
+    expect(page.map(event => event.seq)).toEqual(page.map((_event, index) => third.seq + index))
+  })
+
  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' })
--- a/packages/host/apiproxy/tests/api-proxy-workspace.spec.ts
+++ b/packages/host/apiproxy/tests/api-proxy-workspace.spec.ts
@@ -51,6 +51,7 @@ function stubAgent(session: Session): Agent {
    steer: () => {},
    inject: () => {},
    send: () => {},
+    updateInbox: () => 'not-found',
    cancel() {},
    whenIdle: () => Promise.resolve(),
  }
--- a/packages/host/apiproxy/tests/client-handler.spec.ts
+++ b/packages/host/apiproxy/tests/client-handler.spec.ts
@@ -48,7 +48,9 @@ function scriptedApi(overrides: {
        selected: { provider: r.payload.provider, model: r.payload.model },
      }),
      rename: r => ok(r, { title: 'renamed', seq: 0 }),
+      fork: r => ok(r, { sessionId: sid('s-fork') }),
      prompt: r => ok(r, { accepted: true as const }),
+      updateQueue: r => ok(r, { accepted: true as const }),
      cancel: r => ok(r, { accepted: true as const }),
      ...overrides.sessions,
    },
@@ -148,6 +150,21 @@ describe('unary round trip', () => {
      .rejects.toThrow(/240 Unicode code points/)
  })

+  it('routes session fork with its optional cut anchor through the wire', async () => {
+    let seen: RpcRequest<{ sessionId: SessionId; atSeq?: number }> | undefined
+    const api = scriptedApi({
+      sessions: {
+        fork: (request) => {
+          seen = request
+          return ok(request, { sessionId: sid('s-child') })
+        },
+      },
+    })
+    const response = await client(api).sessions.fork({ sessionId: sid('s-parent'), atSeq: 7 })
+    expect(seen?.payload).toEqual({ sessionId: 's-parent', atSeq: 7 })
+    expect(response.result).toEqual({ ok: true, value: { sessionId: 's-child' } })
+  })
+
  it('routes workspace rename, delete, and insertSessionBefore through the wire', async () => {
    const api = scriptedApi()
    const c = client(api)
--- a/packages/host/apiproxy/tests/fetch-carrier.spec.ts
+++ b/packages/host/apiproxy/tests/fetch-carrier.spec.ts
@@ -90,9 +90,15 @@ function fakeApi(overrides: Partial<{ muxFrames: MuxFrame[]; hostFrames: HostFra
      async rename(request) {
        return { rpcId: request.rpcId, result: { ok: true, value: { title: request.payload.title, seq: 0 } } }
      },
+      async fork(request) {
+        return { rpcId: request.rpcId, result: { ok: true, value: { sessionId: 's-fork' as never } } }
+      },
      async prompt(request) {
        return { rpcId: request.rpcId, result: { ok: true, value: { accepted: true as const } } }
      },
+      async updateQueue(request) {
+        return { rpcId: request.rpcId, result: { ok: true, value: { accepted: true as const } } }
+      },
      async cancel(request) {
        return { rpcId: request.rpcId, result: { ok: true, value: { accepted: true as const } } }
      },
@@ -227,7 +233,7 @@ describe('unary round trip (handler ⇄ client, no network)', () => {
    if (!response.result.ok) expect(response.result.error.code).toBe('session-not-found')
  })

-  it('covers create/prompt/cancel/describe passthrough', async () => {
+  it('covers create/prompt/updateQueue/cancel/describe passthrough', async () => {
    const c = client()
    expect((await c.sessions.search({ query: 'fixture' })).result).toEqual({
      ok: true,
@@ -254,6 +260,11 @@ describe('unary round trip (handler ⇄ client, no network)', () => {
    const renamed = await c.sessions.rename({ sessionId: 's' as never, title: 'named' })
    expect(renamed.result).toMatchObject({ ok: true, value: { title: 'named', seq: 0 } })
    expect((await c.sessions.prompt({ sessionId: 's' as never, mode: 'queue', content: [{ type: 'text', text: 'x' }] })).result.ok).toBe(true)
+    expect((await c.sessions.updateQueue({
+      sessionId: 's' as never,
+      itemId: 'item-1' as never,
+      action: { kind: 'remove' },
+    })).result.ok).toBe(true)
    expect((await c.sessions.cancel({ sessionId: 's' as never })).result.ok).toBe(true)
    expect((await c.host.describe({})).result.ok).toBe(true)
  })
--- a/packages/host/apiproxy/tests/rpc-schemas.spec.ts
+++ b/packages/host/apiproxy/tests/rpc-schemas.spec.ts
@@ -12,6 +12,7 @@ import {
  sessionModelsValueSchema, sessionPromptRequestSchema, sessionPromptValueSchema,
  sessionSearchRequestSchema, sessionSearchValueSchema, sessionSelectModelRequestSchema,
  sessionSelectModelValueSchema, sessionSummarySchema,
+  sessionUpdateQueueRequestSchema, sessionUpdateQueueValueSchema,
 } from '../src/api/sessions.schema.ts'
 import {
  hostCreateDirectoryRequestSchema, hostCreateDirectoryValueSchema,
@@ -69,6 +70,7 @@ describe('rpcErrorSchema', () => {
      details: { provider: 'p', model: 'm' },
    }).code).toBe('model-unavailable')
    expect(rpcErrorSchema.parse({ code: 'agent-busy', message: 'm', details: { reason: 'r' } }).code).toBe('agent-busy')
+    expect(rpcErrorSchema.parse({ code: 'queue-item-not-found', message: 'm', details: { itemId: 'i' } }).code).toBe('queue-item-not-found')
    expect(rpcErrorSchema.parse({ code: 'command-error', message: 'm', details: {} }).code).toBe('command-error')
    expect(rpcErrorSchema.parse({ code: 'unknown-command', message: 'm', details: {} }).code).toBe('unknown-command')
    expect(rpcErrorSchema.parse({ code: 'title-invalid', message: 'm', details: { sessionId: 's' } }).code).toBe('title-invalid')
@@ -252,7 +254,19 @@ describe('sessions domain schemas', () => {
    expect(sessionPromptValueSchema.parse({ accepted: true, command: { kind: 'success' } }).command).toEqual({ kind: 'success' })
    expect(() => sessionPromptValueSchema.parse({ accepted: true, command: { kind: 'failure' } })).toThrow()
    expect(sessionCancelRequestSchema.parse({ sessionId: 's1' }).sessionId).toBe('s1')
+    expect(sessionUpdateQueueRequestSchema.parse({
+      sessionId: 's1',
+      itemId: 'i1',
+      action: { kind: 'edit', content: [{ type: 'text', text: 'next' }] },
+    }).action.kind).toBe('edit')
+    expect(sessionUpdateQueueRequestSchema.parse({
+      sessionId: 's1', itemId: 'i1', action: { kind: 'remove' },
+    }).action.kind).toBe('remove')
+    expect(() => sessionUpdateQueueRequestSchema.parse({
+      sessionId: 's1', itemId: 'i1', action: { kind: 'promote' },
+    })).toThrow()
    expect(sessionCancelValueSchema.parse({ accepted: true }).accepted).toBe(true)
+    expect(sessionUpdateQueueValueSchema.parse({ accepted: true }).accepted).toBe(true)
    expect(contentBlockSchema.parse({ type: 'text', text: 'x', extra: 1 })).toMatchObject({ extra: 1 })
  })
 })
@@ -396,8 +410,9 @@ describe('events frame schemas', () => {
      { 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', 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/queue', sessionId: 's', items: [
+        { id: 'i1', message: { id: 'm1', role: 'user', content: [{ type: 'text', text: 'queued prompt' }], source: { kind: 'user', rpcId: 'r9' } } },
+      ] },
      { type: 'session/projection', sessionId: 's', key: 'todos', value: [{ content: 'x', status: 'pending' }], seq: 7 },
      { type: 'stream/error', error: { code: 'internal', message: 'm', details: {} } },
    ]
@@ -415,10 +430,21 @@ describe('events frame schemas', () => {
    expect(() => muxFrameSchema.parse({ type: 'question/requested', sessionId: 's', questions: [] })).toThrow()
  })

-  it('rejects a queued frame missing its members', () => {
-    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('carries a question presentation intent through, and rejects an unknown one', () => {
+    const intent = { kind: 'plan-review', approve: 'Approve' }
+    expect(askUserQuestionItemSchema.parse({
+      id: 'plan-review', question: 'Approve?', detail: '# Plan', options: [{ label: 'Approve' }], intent,
+    }).intent).toEqual(intent)
+    // An unrecognised tag is a rejected frame, not a silently generic render.
+    for (const invalid of [{ kind: 'plan-review' }, { kind: 'poll', approve: 'Approve' }, { approve: 'Approve' }]) {
+      expect(() => askUserQuestionItemSchema.parse({ id: 'q', question: 'Q?', intent: invalid })).toThrow()
+    }
+  })
+
+  it('rejects a queue snapshot with malformed items', () => {
+    expect(() => muxFrameSchema.parse({ type: 'session/queue', sessionId: 's', items: 'x' })).toThrow()
+    expect(() => muxFrameSchema.parse({ type: 'session/queue', sessionId: 's', items: [{ id: '', message: {} }] })).toThrow()
+    expect(() => muxFrameSchema.parse({ type: 'session/queue', sessionId: 's', items: [{ id: 'i', message: { id: 'm', role: 'user', content: [], source: {} } }] })).toThrow()
  })

  it('accepts every host frame branch', () => {