fix(web): follow a blank session's preset switch in the slash catalog

Presets own the rows that decide what a session's `/` menu contains, but
both browser catalogs cache per session and had no invalidation edge for a
recompose: `commands/changed` is registry-wide and recomposing registers
nothing, so the menu kept serving the composition the session no longer ran.

The host stream now frames the logged `agent-preset/selected` commit as
`host/session-preset-changed`; the runtime bridges it to the typed
`session/preset-changed` event, `ui-command` soft-refreshes that session's
directory key and `ui-skill` invalidates its catalog entry.

Reaching the host on a second switch was a separate defect: the list-row
identity guard compared every summary field except `agentPreset`, and the
merge keeps the row's `updatedAt`, so a switched row looked unchanged and
served its cached instance forever. The hero chip compares the pick against
that row, so switching back to the creation-time preset sent no RPC at all.

packages/client/ui-command/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/client/ui-command/README.md
-README.md: bc7386c8fca3b5c623473328bee6322fa7295277
-README.zh.md: 54190ac9144b1bfc12ba84a47474311d5a5391ea
+README.md: db785e769cb40235a77d05b4b66d096896a35d8a
+README.zh.md: f0f23319a8919a0dee715e9da03ab064b6e3298a

packages/client/ui-command/README.md

@@ -6,7 +6,7 @@ Client command surface (`ctx.command`): the session-keyed command-directory cach
 
 `src/client/contract.ts` is the frozen business face: `CommandServiceContract.register(name, spec)` and `decorate(name, spec)` are everything a business package consumes; `CommandUiSpec{options, onSelect}` keeps popup data self-served — the shell component is this package's and business never sees it. A contribution is a client-owned command (a host-name collision fails loud); a decoration hangs a bare-invocation popup on an EXISTING host command — the host keeps its catalog row, argument claim (space / argued enter), and lifecycle logging, and a decorated name with no host row in the session's directory simply never fires. Command kinds derive per dispatch, never per registration: a host descriptor with `input` is leadingInput, a registered `CommandUiSpec` is popupSelect, everything else is execute.
 
-`CommandDirectory` (`src/client/directory.ts`) is the one wire-derived cache, keyed by session. Ordinary sessions fetch through `command.list({sessionId})`, and the source's scope-birth `warm` hook prewarms the session's entry. Catalog-addressed continuable children resolve an empty command directory locally: `command.list` is Agent-bound, so prewarming it would activate a child merely to view persisted history. Entries are soft-invalidated by the `commands/changed` typed event (old snapshot serves while the repull flies), hard-invalidated by `connection/reset`, epoch-guarded so a superseded pull can never overwrite a newer one. `matchSpace` answers synchronously from this cache only; `matchEnter` strong-waits it on the SubmitAttempt signal and rejects on warmup failure — a `/` line is never silently downgraded to a plain prompt.
+`CommandDirectory` (`src/client/directory.ts`) is the one wire-derived cache, keyed by session. Ordinary sessions fetch through `command.list({sessionId})`, and the source's scope-birth `warm` hook prewarms the session's entry. Catalog-addressed continuable children resolve an empty command directory locally: `command.list` is Agent-bound, so prewarming it would activate a child merely to view persisted history. Entries are soft-invalidated by the `commands/changed` typed event (old snapshot serves while the repull flies) and by `session/preset-changed` for that one session (recomposing an agent registers nothing, so the registry-wide signal never fires for it), hard-invalidated by `connection/reset`, epoch-guarded so a superseded pull can never overwrite a newer one. `matchSpace` answers synchronously from this cache only; `matchEnter` strong-waits it on the SubmitAttempt signal and rejects on warmup failure — a `/` line is never silently downgraded to a plain prompt.
 
 Menu queries fuzzy-match ordered, case-insensitive subsequences of command names. Prefixes rank first; separator boundaries, adjacent characters, and shorter gaps rank the remaining matches, with directory and contribution order breaking ties. This affects discovery only: space and Enter still require an exact command name. Rationale: [Web slash-command fuzzy discovery](../../../.agents/notes/implemented/feature/2026-08-04-web-slash-command-fuzzy-discovery.md).
 

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

@@ -6,7 +6,7 @@
 
 `src/client/contract.ts` 是冻结的业务表层：`CommandServiceContract.register(name, spec)` 与 `decorate(name, spec)` 是业务包消费的全部内容；`CommandUiSpec{options, onSelect}` 让 popup 数据自给自足——壳组件归本包所有，业务永远见不到它。contribution 是 client 自有命令（与 host 同名碰撞即 fail-loud）；decoration（装饰）则把裸调用 popup 挂在**已存在的** host 命令上——host 保留目录行、带参 claim（space / 带参 enter）与生命周期记账，被装饰的名字若在会话目录中无 host 行则装饰永不触发。命令三型按每次派发派生，绝不在注册时定型：带 `input` 的 host descriptor 是 leadingInput，注册了 `CommandUiSpec` 的是 popupSelect，其余全部是 execute。
 
-`CommandDirectory`（`src/client/directory.ts`）是唯一的 wire 派生缓存，以会话为 key。普通会话通过 `command.list({sessionId})` 拉取，source 的 scope 出生 `warm` 钩子会预热该会话的缓存项。由目录寻址的可继续子代理会在客户端解析为空命令目录：`command.list` 绑定 Agent，若预热它，就会仅因查看持久化历史而激活子代理。缓存项由 `commands/changed` 类型化事件软失效（重拉在途期间旧快照继续服务），由 `connection/reset` 硬失效，并以 epoch 把关，被取代的旧拉取永远无法覆盖更新的结果。`matchSpace` 只凭该缓存同步应答；`matchEnter` 在 SubmitAttempt 信号上强等缓存，预热失败即拒绝——`/` 开头的一行绝不会被静默降级为普通提示词。
+`CommandDirectory`（`src/client/directory.ts`）是唯一的 wire 派生缓存，以会话为 key。普通会话通过 `command.list({sessionId})` 拉取，source 的 scope 出生 `warm` 钩子会预热该会话的缓存项。由目录寻址的可继续子代理会在客户端解析为空命令目录：`command.list` 绑定 Agent，若预热它，就会仅因查看持久化历史而激活子代理。缓存项由 `commands/changed` 类型化事件软失效（重拉在途期间旧快照继续服务），也由 `session/preset-changed` 对该会话单独软失效（重组 agent 不产生任何注册，注册表级信号不会为它触发），由 `connection/reset` 硬失效，并以 epoch 把关，被取代的旧拉取永远无法覆盖更新的结果。`matchSpace` 只凭该缓存同步应答；`matchEnter` 在 SubmitAttempt 信号上强等缓存，预热失败即拒绝——`/` 开头的一行绝不会被静默降级为普通提示词。
 
 菜单查询会按顺序且不区分大小写地模糊匹配命令名的子序列。前缀排名最高；其余匹配项按分隔符边界优先、相邻字符优先、间隔越短越优先的规则排序，若仍同分，则以目录顺序和 contribution 顺序打破平局。此行为只影响命令发现：space 和 Enter 仍要求命令名精确匹配。原理：[Web 斜杠命令模糊发现](../../../.agents/notes/implemented/feature/2026-08-04-web-slash-command-fuzzy-discovery.md)。
 

packages/client/ui-command/src/client/service.ts

@@ -124,6 +124,11 @@ export class CommandService extends Service implements CommandServiceContract {
       warm: (session) => { this.directory.warm(session.sessionId) },
     }), 'command: slash source')
     ctx.on('commands/changed', () => { this.directory.invalidateAll() })
+    // A preset switch changes which commands ONE session's agent resolves and
+    // registers nothing globally, so the registry-wide signal above never
+    // fires for it: repull that key alone, soft, so the old snapshot serves
+    // the menu until the new one lands.
+    ctx.on('session/preset-changed', (sessionId) => { void this.directory.refresh(sessionId) })
     ctx.on('connection/reset', () => { this.directory.resetConnected() })
   }
 

packages/client/ui-command/tests/service.spec.ts

@@ -617,6 +617,30 @@ describe('directory invalidation events', () => {
     expect(source.matchSpace!(proj('s1'), '/goal')).toBeUndefined()
   })
 
+  it('session/preset-changed repulls the recomposed session and leaves the others served', async () => {
+    const rounds = new Map<SessionId, number>()
+    const { ctx, source, warm } = await bench({
+      commands: (payload) => {
+        const round = (rounds.get(payload.sessionId) ?? 0) + 1
+        rounds.set(payload.sessionId, round)
+        return Promise.resolve({
+          commands: round === 1
+            ? S1_CMDS
+            : [{ name: 'fresh', description: '', input: { hint: 'h' } }],
+        })
+      },
+    })
+    await warm(proj('s1'))
+    await warm(proj('s2'))
+    // A preset switch changes which commands one session's agent resolves;
+    // every other session keeps the catalog its own composition serves.
+    ctx.emit('session/preset-changed', sid('s1'), 'minimal')
+    await new Promise(resolve => setTimeout(resolve, 0))
+    expect(source.matchSpace!(proj('s1'), '/fresh')).not.toBeUndefined()
+    expect(source.matchSpace!(proj('s1'), '/goal')).toBeUndefined()
+    expect(source.matchSpace!(proj('s2'), '/goal')).not.toBeUndefined()
+  })
+
   it('connection/reset hard-drops every session key until its rewarm lands', async () => {
     let block = false
     let release!: (value: { commands: CommandDescriptor[] }) => void