diff --git a/.agents/notes/implemented/feature/2026-07-31-session-archive-global-set.i18n.yaml b/.agents/notes/implemented/feature/2026-07-31-session-archive-global-set.i18n.yaml
new file mode 100644
index 0000000000..6ed5f6ed3b
--- /dev/null
+++ b/.agents/notes/implemented/feature/2026-07-31-session-archive-global-set.i18n.yaml
@@ -0,0 +1,6 @@
+# Bilingual-pair consistency record (docs/i18n/README.md): the git blob hash of each
+# 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 .agents/notes/implemented/feature/2026-07-31-session-archive-global-set.md
+2026-07-31-session-archive-global-set.md: 0fe354ef0ed50ee60a69b0633522323124c80da7
+2026-07-31-session-archive-global-set.zh.md: 2b13f0eddc9aa62600a95ac5f412c51f3a38af7b
diff --git a/.agents/notes/implemented/feature/2026-07-31-session-archive-global-set.md b/.agents/notes/implemented/feature/2026-07-31-session-archive-global-set.md
new file mode 100644
index 0000000000..0fe354ef0e
--- /dev/null
+++ b/.agents/notes/implemented/feature/2026-07-31-session-archive-global-set.md
@@ -0,0 +1,33 @@
+# Agent Note: Session archive (registry-global set)
+
+Status: implemented
+
+English | [中文](2026-07-31-session-archive-global-set.zh.md)
+
+## Problem
+
+The session row menu in the sidebar workspace browser carried a purely visual "Delete session" placeholder (no handler). The product decision is **archive**, not delete: the session log and its workspace accounting stay untouched; the session merely disappears from every grouping surface (workspace groups, Ungrouped, search, the flat list). The archive record needs a home: an Ungrouped session belongs to no workspace entity, so a per-workspace field cannot carry it.
+
+## Decision
+
+**The archive set is a new field on the workspace domain's global singleton (`workspaceDomainState.archivedSessionIds`), layered over workspace accounting; display filtering converges entirely in the client's `tree.ts` derivation layer; the wire surface uses the full-snapshot posture.**
+
+- Storage: `archivedSessionIds: z.array(sessionId).default([])`, domain version stays 2 — a purely additive field; pre-field media parse to an empty set through the schema default, no migration code. An archived session keeps its `sessionIds` slot (a future unarchive restores its position), so the set never touches the one-owner accounting invariant.
+- Registry: `ctx.workspace.archiveSession(id)` rides `enqueueOperation`, serialized with create/delete; a session neither live nor persisted throws `WorkspaceUnknownSessionError`; an already archived id neither writes nor emits. The `archivedSessionIds` getter exposes the read-only set.
+- RPC: `workspace.archiveSession({sessionId}) → {archivedSessionIds}` (answers the full updated set); the `workspace.list` response carries the set as the reconnect baseline; a new host frame `host/archived-sessions-changed` pushes the full snapshot after every durable change (same posture as `host/workspace-changed`, emitted from the `domain/changed` global-put branch by set comparison). Unknown sessions reuse the `session-not-found` error code.
+- Client runtime: `WorkspaceListState.archivedSessionIds` (a `ReadonlySet`, reference replaced only on membership change); the list baseline, the unary echo, and the changed frame each install the complete set. `WorkspacesService.archiveSession` calls `sessions.clear()` when the archived session is the current selection, returning to the New Session view (user decision: archiving the open session sends the main view back to the hero).
+- UI: the `delete` menu row (visual-only) becomes `archive` (label "Archive session", non-danger styling, no confirmation dialog — a non-destructive action whose worst misfire is list hiding); filtering is one extra arm in `tree.ts`'s `sessionVisible` predicate, with `deriveGroups`/`deriveFlat` taking an `archived` set parameter so all four surfaces (group loop, stray bucket, search, flat) share one source.
+
+## Alternatives considered
+
+**Per-workspace archivedSessionIds (the original phrasing).** Rejected: Ungrouped sessions have no home; the user switched to global.
+
+**An archived flag on SessionSummary (session.list layer).** Rejected: it joins a workspace-domain fact into the sessions-domain projection, summaries have no incremental frame so a separate notification would still be needed — cross-domain coupling outweighs the saving.
+
+**Host-side filtering in `workspaceView`/the `sessionIds` getter.** Rejected: archiving ≠ changing accounting, and filtering the projection muddles the two concepts; a future restore surface also needs the client to see full accounting.
+
+**Incremental frames (single archived/removed rows).** Rejected: the set is tiny and changes rarely; full snapshots spare the client merge logic and dedup state and match the existing workspace-changed posture.
+
+## Consequences
+
+Archived sessions have no viewing or unarchive surface yet (this iteration's scope; recorded as a README Known Limitation); data and accounting slots stay intact, so a future restore is one UI surface plus one inverse RPC. The `workspace.list` response shape change is a pre-release direct edit (no compatibility layer). The workspace-management e2e pins the full chain (archive → row disappears → still hidden after reload, log still present); domain tests pin idempotence, unknown-id rejection, restart recovery, and the pre-field media default upgrade.
diff --git a/.agents/notes/implemented/feature/2026-07-31-session-archive-global-set.zh.md b/.agents/notes/implemented/feature/2026-07-31-session-archive-global-set.zh.md
new file mode 100644
index 0000000000..2b13f0eddc
--- /dev/null
+++ b/.agents/notes/implemented/feature/2026-07-31-session-archive-global-set.zh.md
@@ -0,0 +1,33 @@
+# Agent Note: Session 归档（注册表级全局集合）
+
+状态：implemented
+
+[English](2026-07-31-session-archive-global-set.md) | 中文
+
+## 问题
+
+Sidebar workspace 浏览区的 session 行菜单里，「Delete session」一直是纯视觉占位（无 handler）。产品口径定为**归档**而非删除：session 日志与 workspace 记账都不动，只把该 session 从所有分组视图（workspace 分组、Ungrouped、搜索、平铺列表）里隐藏。归档记录需要一个落点：Ungrouped 的 session 不属于任何 workspace 实体，per-workspace 字段放不下它。
+
+## 决策
+
+**归档集合是 workspace domain 全局单例（`workspaceDomainState.archivedSessionIds`）上的一个新字段，覆盖在 workspace 记账之上；显示过滤全部收敛在 client 的 `tree.ts` 派生层；wire 面走全快照姿态。**
+
+- 存储：`archivedSessionIds: z.array(sessionId).default([])`，domain version 保持 2——纯增量字段，旧介质经 schema default 解析为空集合，无迁移代码。被归档的 session 保留其 `sessionIds` 席位（未来取消归档恢复原位置），因此与「一个 session 只被一个 workspace 记账」不变式零纠缠。
+- Registry：`ctx.workspace.archiveSession(id)` 走 `enqueueOperation` 与 create/delete 串行；未知 session（实时与持久化都查不到）抛 `WorkspaceUnknownSessionError`；已归档 id 不写盘不发事件。`archivedSessionIds` getter 暴露只读集合。
+- RPC：`workspace.archiveSession({sessionId}) → {archivedSessionIds}`（应答完整更新后集合）；`workspace.list` 响应携带集合作为重连基线；新 host 帧 `host/archived-sessions-changed` 在每次持久变更后推完整快照（与 `host/workspace-changed` 同姿态，从 `domain/changed` 的 global put 分支比对推帧）。未知 session 复用错误码 `session-not-found`。
+- client runtime：`WorkspaceListState.archivedSessionIds`（`ReadonlySet`，成员不变不换引用）；list 基线、unary 回声、changed 帧三路都整体替换安装。`WorkspacesService.archiveSession` 在归档对象恰为当前 selection 时调 `sessions.clear()` 回 New Session 视图（用户拍板：归档当前打开的 session 主视图回 hero）。
+- UI：菜单项 `delete`（visual-only）改为 `archive`（label「Archive session」，非 danger 样式，无确认对话框——非破坏性操作，误触后果只是列表隐藏）；过滤实现为 `tree.ts` 的 `sessionVisible` 判据加一档，`deriveGroups`/`deriveFlat` 增加 `archived` 集合入参，四个视图（分组循环、stray 兜底、搜索、平铺）同源生效。
+
+## 已考虑的替代方案
+
+**per-workspace archivedSessionIds（最初表述）。** 否决：Ungrouped session 无落点；用户改口全局。
+
+**SessionSummary 打 archived 标（session.list 层）。** 否决：要把 workspace domain 事实 join 进 sessions domain 投影，summary 无增量帧还得另发通知，跨域耦合大于收益。
+
+**host 侧在 `workspaceView`/`sessionIds` getter 过滤。** 否决：归档 ≠ 改记账，投影过滤会把两个概念搅浑；未来恢复入口也需要 client 拿到全量记账。
+
+**增量帧（archived/removed 单条）。** 否决：集合极小、变更频率低，全快照免去 client 侧合并逻辑与去重状态，与 workspace-changed 现有姿态一致。
+
+## 后果
+
+归档后 UI 无查看/取消归档入口（本期口径，README Known Limitation 记账）；数据与席位完好，后续加恢复面只是 UI + 一个逆向 RPC。`workspace.list` 响应形状变化是 pre-release 直改（无兼容层）。e2e（workspace-management）钉住了「归档→行消失→reload 后仍隐藏、日志仍在」的全链路；domain 层测试钉住幂等、未知 id 拒绝、跨重启恢复与旧介质默认升级。
diff --git a/docs/cordis-catalog/services.md b/docs/cordis-catalog/services.md
index 0adc848ea5..958dcc10cd 100644
--- a/docs/cordis-catalog/services.md
+++ b/docs/cordis-catalog/services.md
@@ -2544,6 +2544,15 @@ list(): Workspace[]
  */
 delete(id: WorkspaceId): Promise<boolean>
 
+/**
+ * Archive one session durably. The session must exist (live or in session
+ * persistence); its workspace accounting — or lack of one — is irrelevant.
+ * An already archived id resolves without writing.
+ * @param sessionId - The session to archive.
+ * @returns resolution after durability.
+ */
+archiveSession(sessionId: SessionId): Promise<void>
+
 /**
  * Resolve by canonical directory path without creating or mutating a
  * workspace. A missing path rejects during `realpath`; an existing unowned
@@ -2554,7 +2563,9 @@ delete(id: WorkspaceId): Promise<boolean>
 async resolveByPath(path: string): Promise<Workspace | undefined>
 ```
 
-Source: [`packages/workspace/workspace/src/index.ts:78`](../../packages/workspace/workspace/src/index.ts)
+Types: [SessionId](../core-data-structures/core.md)
+
+Source: [`packages/workspace/workspace/src/index.ts:90`](../../packages/workspace/workspace/src/index.ts)
 
 ## Inherited `ctx` members (cordis core + loader/hmr/timer)
 
diff --git a/packages/cordis/tool-cordis/src/api-catalog.ts b/packages/cordis/tool-cordis/src/api-catalog.ts
index 4d986582d4..66ac086b49 100644
--- a/packages/cordis/tool-cordis/src/api-catalog.ts
+++ b/packages/cordis/tool-cordis/src/api-catalog.ts
@@ -1162,6 +1162,10 @@ export const SERVICE_API: readonly ServiceApiEntry[] = [
         signature: 'delete(id: WorkspaceId): Promise<boolean>',
         jsDoc: '/**\n * Delete one workspace registration while retaining its directory and every\n * session log. The durable order is updated before the table deletion; a\n * failed table write restores the prior order and keeps the entity\n * published. Unknown ids are an idempotent no-op for domain callers.\n * @param id - Workspace registration to remove.\n * @returns `true` when a record was deleted, `false` when it was unknown.\n */',
       },
+      {
+        signature: 'archiveSession(sessionId: SessionId): Promise<void>',
+        jsDoc: '/**\n * Archive one session durably. The session must exist (live or in session\n * persistence); its workspace accounting — or lack of one — is irrelevant.\n * An already archived id resolves without writing.\n * @param sessionId - The session to archive.\n * @returns resolution after durability.\n */',
+      },
       {
         signature: 'async resolveByPath(path: string): Promise<Workspace | undefined>',
         jsDoc: '/**\n * Resolve by canonical directory path without creating or mutating a\n * workspace. A missing path rejects during `realpath`; an existing unowned\n * directory returns `undefined`.\n * @param path - Existing directory path in any spelling.\n * @returns the workspace owning the canonical path, when one exists.\n */',