fix(ui-models): three faults the running app surfaced

**A hand-declared route must not offer a reasoning effort.** The earlier
commit read the create card's missing control as drift and added one. It
is the other way round: such a model has no reasoning capability — pi-ai's
installed catalog is what supplies one, and it ships nothing under the
route — so `resolveModel` throws UNSUPPORTED_REASONING_EFFORT for every
model on it and the whole provider drops out of the picker. Verified
against the adapter, not inferred. The create card no longer offers it and
the editor withholds it on the directory's `declared` bit, which is the
real bug: that control has always been wrong for these routes.

**A blocked composer locked the way out of the block.** Reusing the
no-workspace inert posture disabled the model seat along with everything
else, so the bar asked for a model while preventing the one control that
picks one. A block now rides its own `blocked` owner prop: the textarea,
send, commands, plan seat, and access chip all lock, and the model seat
alone stays live.

**A Provider ID could derive an illegal credential reference.** The card
accepted a digit-leading id, whose derived `123_API_KEY` then failed at
the credential seam with a raw regular expression the user cannot act on.
The id must now start with a letter, and a test pins the relation between
the two rules rather than the regex.

packages/client/ui-conversation/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-conversation/README.md
-README.md: 392f9956b33df88a5e9664a58de27d85fc0457d1
-README.zh.md: 6b0429a302475f84a7ce9b1cdc9fd47d90d6dba3
+README.md: ee8a4d240cdc326d158749ae8935ec99bb420d9f
+README.zh.md: 64ac1d15e20a8b60a39a8beb9ae7695543250026

packages/client/ui-conversation/README.md

@@ -8,7 +8,7 @@ Compaction renders as one collapsed row at the checkpoint's flow position withou
 
 The resident conversation shell survives no-session and session transitions. Without a current session it renders a disabled input bar; its root-scoped `conversation.hero.workspace` slot hosts the Workspace picker. Selecting a Workspace connects or reuses its Host-owned blank session and opens that session without replacing the shell. The root always owns the same scrollport and Hero/composer subtree; separate strict-session header and body outlets fill their regions when the first Session arrives, so the Workspace picker, scroll body, composer seat, and textarea retain their React and DOM identity. Blank sessions render the same composer body as active sessions, while the InputHub carries drafts across Workspace switches and mirrors them into the session store. In the active phase the session header shows only the current session title and view tabs as ordinary column chrome; fork lineage remains session data and is not projected into the header. Beneath it the scrollport (`data-conversation-scroll`) holds the flowing views and the sticky composer stack (stats dock + input docks + bar). That scrollport reserves its scrollbar gutter unconditionally, and a view opting into a composer overlay leaves it a scroll container, so the input card keeps one horizontal position whether or not the transcript scrolls and whichever view tab is shown ([decision](../../../.agents/notes/implemented/bug-fix/2026-08-04-composer-tab-gutter-reservation.md)). Wheel over the textarea chains: the capped draft scrolls locally until its edge, then forwards to that host.
 
-Another plugin can make one session's composer inert through `ctx.conversation.blocks`: it sets a block carrying its own localized reason, and the bar renders the same disabled textarea with that reason as the placeholder — the no-workspace posture, reused. The push direction is the constraint, not a preference: the plugins that know a session cannot send (ui-model, when no adapter serves its route) already depend on this package, so this package cannot read them. A block is an affordance only; the Host refuses a prompt it cannot route regardless of what any client disables. The no-workspace state wins when both hold, because picking a workspace is the earlier prerequisite.
+Another plugin can make one session's composer inert through `ctx.conversation.blocks`: it sets a block carrying its own localized reason, and the bar renders the same disabled textarea with that reason as the placeholder — the no-workspace posture, reused. The push direction is the constraint, not a preference: the plugins that know a session cannot send (ui-model, when no adapter serves its route) already depend on this package, so this package cannot read them. The model seat is the one control a block leaves live — every block this contract has is cleared by choosing a model, so locking it too would leave the composer asking for the only thing it prevents. A block is an affordance only; the Host refuses a prompt it cannot route regardless of what any client disables. The no-workspace state wins when both hold, because picking a workspace is the earlier prerequisite.
 
 The view ring is a slot: the strict session-body registration declares the session-scoped `'conversation.view'` list in its `children` table, that body renders the active entry through its renderSlot share (`only: <active id>`), and view tabs project from registration options (`id`/`order`/`label`). The chat view is this package's own entry; plugins such as ui-trajectory contribute tabs through `ctx.slots.register`, and each view owns its chrome.
 

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

@@ -8,7 +8,7 @@
 
 常驻会话壳会跨无会话与会话状态切换而保留。没有当前会话时，它会渲染禁用输入栏；其根作用域的 `conversation.hero.workspace` slot 承载 Workspace 选择器。选择 Workspace 会连接或复用由 Host 拥有的空白会话，并在不替换会话壳的情况下打开该会话。根组件始终拥有同一个滚动容器与 Hero／编辑器子树；首个会话到达时，彼此独立的严格会话页头和主体 outlet 只填入各自区域，因此 Workspace 选择器、滚动主体、编辑器 seat 与 textarea 都保留原有 React 和 DOM identity。空白会话与活跃会话渲染相同的输入区主体；InputHub 则在 Workspace 切换间携带草稿，并将草稿镜像到会话 store。活跃阶段，会话标题栏作为普通列 chrome，仅显示当前会话标题和视图标签；fork 谱系仍保留为会话数据，不投影到标题栏。其下滚动容器（`data-conversation-scroll`）承载流动排版的各视图与 sticky 编辑器栈（统计 dock＋输入区 dock＋输入栏）。该滚动容器无条件预留自己的滚动条槽，选用编辑器 overlay 的视图也仍把它保留为滚动容器，因此无论对话记录是否滚动、无论展示哪个视图标签，输入卡片都保持同一个横向位置（[决策](../../../.agents/notes/implemented/bug-fix/2026-08-04-composer-tab-gutter-reservation.md)）。textarea 上的滚轮会链式处理：限高草稿先在本地滚动，到达边缘后再转交给该宿主。
 
-别的插件可以经 `ctx.conversation.blocks` 让某个会话的编辑器变为惰性：它设置一个携带自己本地化理由的 block，输入栏就渲染同一个禁用的 textarea，并把该理由作为 placeholder——复用无 Workspace 时的那套姿态。推送方向是约束而非偏好：知道某会话发不出消息的插件（ui-model，在没有适配器服务其路由时）本就依赖本包，因此本包读不到它们。block 只是提示性设计；无论客户端禁用了什么，宿主都会拒绝一个它路由不了的 prompt。两者同时成立时以无 Workspace 姿态为准，因为选 Workspace 是更靠前的前提。
+别的插件可以经 `ctx.conversation.blocks` 让某个会话的编辑器变为惰性：它设置一个携带自己本地化理由的 block，输入栏就渲染同一个禁用的 textarea，并把该理由作为 placeholder——复用无 Workspace 时的那套姿态。推送方向是约束而非偏好：知道某会话发不出消息的插件（ui-model，在没有适配器服务其路由时）本就依赖本包，因此本包读不到它们。模型 seat 是 block 唯一保留可用的控件——这份契约里的每个 block 都靠选模型来解除，把它一起锁上会让编辑器索要它自己拦下的那件事。block 只是提示性设计；无论客户端禁用了什么，宿主都会拒绝一个它路由不了的 prompt。两者同时成立时以无 Workspace 姿态为准，因为选 Workspace 是更靠前的前提。
 
 视图环是一个 slot：严格会话主体注册在 `children` 表中声明 Session scope 的 `'conversation.view'` 列表，并通过自身的 renderSlot share 渲染活跃配置项（`only: <active id>`）；视图标签页则从注册选项（`id`／`order`／`label`）投影而来。聊天视图是该包自身的配置项；ui-trajectory 等插件通过 `ctx.slots.register` 贡献标签页，每个视图负责自己的 chrome。
 

packages/client/ui-conversation/src/client/contract/slots.ts

@@ -265,6 +265,14 @@ export interface ConversationSessionHeaderInjected {
 export interface ComposerBarOwnerProps {
   /** Hero = empty-state centered card; composer = resident bottom bar. */
   variant: 'hero' | 'composer'
+  /**
+   * A block another plugin raised for this session: the bar refuses input and
+   * shows the blocker's reason as the placeholder, but — unlike `disabled` —
+   * keeps the model seat live. Every block this contract has is one the user
+   * clears by choosing a model, so locking that seat too would leave the
+   * composer telling them to do the one thing it prevents.
+   */
+  blocked?: { readonly reason: string }
   /**
    * Inert no-workspace state: the bar renders its normal DOM fully disabled
    * (textarea, add, send) so the workspace pick transitions in place instead

packages/client/ui-conversation/src/client/skeleton/ConversationRoot.tsx

@@ -138,7 +138,10 @@ export function ConversationRoot({
     ...(inert
       ? { disabled: true, placeholder: t('placeholder.workspace') }
       : blocked
-        ? { disabled: true, placeholder: composerBlock.reason }
+        // `blocked`, not `disabled`: the bar refuses input either way, but a
+        // block keeps the model seat live because choosing a model is how the
+        // user clears it.
+        ? { blocked: composerBlock, placeholder: composerBlock.reason }
         : hero ? { placeholder: t('placeholder.hero') } : {}),
     overlay: renderSlot('conversation.input.overlay', {}),
     leftItems: zone === undefined ? null : renderSlot('conversation.input.left', zone),

packages/client/ui-conversation/src/client/skeleton/InputBar.tsx

@@ -37,7 +37,8 @@ export type InputBarProps = ComposerBarProps
 export function InputBar({
   useSession, useInput, inputActions, keyboard, resolveSubmitMode, toggleCommandMenu, stop, command, t,
   renderSlot, useNotices, useLexicon, useMenuLauncher,
-  useProjection, sessionId, variant, disabled: inert = false, placeholder, accessory, overlay, leftItems, rightItems, footer,
+  useProjection, sessionId, variant, disabled: inert = false, blocked, placeholder,
+  accessory, overlay, leftItems, rightItems, footer,
 }: InputBarProps) {
   const input = useInput(s => s)
   const notice = useNotices(s => s)
@@ -86,8 +87,13 @@ export function InputBar({
   // inert no-workspace state, or the machine faces absent (no session). The
   // transient machine locks (adjudicating pending / submitting) render
   // read-only — the draft stays visible and focused, keystrokes drop.
-  const disabled = removed || inert || !live
+  const disabled = removed || inert || !live || blocked !== undefined
   const locked = disabled
+  // The model seat is the ONE control a block leaves live: every block this
+  // contract has is cleared by choosing a model, so locking it too would leave
+  // the composer asking for the only thing it prevents. The other reasons to
+  // be disabled do lock it — there is no session to choose a model for.
+  const modelSeatLocked = removed || inert || !live
   const machineBusy = input?.phase === 'adjudicating' || input?.phase === 'submitting'
 
   // Scroll the draft scrollport the minimum that brings `caret` into view — the
@@ -512,7 +518,7 @@ export function InputBar({
           </div>
           <div className={css.trailing}>
             {rightItems}
-            {renderSlot('conversation.input.model', { locked })}
+            {renderSlot('conversation.input.model', { locked: modelSeatLocked })}
             <ContextMeter useProjection={useProjection} t={t} />
             {/* {machineBusy && <span className={css.pending} data-input-pending aria-label="处理中" />} */}
             <Tooltip label={primaryLabel} side="top" delayMs={500}>

packages/client/ui-conversation/tests/skeleton.spec.tsx

@@ -120,9 +120,14 @@ function mount(
   const stop = vi.fn()
   const open = vi.fn()
   const slotCalls: string[] = []
+  /** Owner share handed to the two composer tool-row seats, per render. */
+  const seatOwners: { key: string; owner: unknown }[] = []
   let pickerOwner: unknown
   const renderSlot = ((key: string, owner: object, opts?: { only?: string }) => {
     slotCalls.push(key)
+    if (key === 'conversation.input.model' || key === 'conversation.input.plan') {
+      seatOwners.push({ key, owner })
+    }
     if (key === 'conversation.hero.workspace') { pickerOwner = owner; return null }
     if (key === 'conversation.session.header') {
       return (
@@ -200,7 +205,12 @@ function mount(
           stop={stop}
           command={() => Promise.resolve(true)}
           t={t}
-          renderSlot={(() => null) as InputBarProps['renderSlot']}
+          renderSlot={((key: string, seatOwner: object) => {
+            // The bar's own seats: recorded so a case can assert what share
+            // each tool-row control received.
+            seatOwners.push({ key, owner: seatOwner })
+            return null
+          }) as InputBarProps['renderSlot']}
           {...bar}
         />
       )
@@ -236,7 +246,7 @@ function mount(
   }
   const view = render(<ConversationRoot {...props} />)
   return {
-    view, chat, sink, retargetWorkspace, session, slotCalls, open,
+    view, chat, sink, retargetWorkspace, session, slotCalls, seatOwners, open,
     pickerOwner: () => pickerOwner,
     rerender: () => { view.rerender(<ConversationRoot {...props} />) },
   }
@@ -262,6 +272,13 @@ describe('ConversationRoot resident composer', () => {
     expect(box.placeholder).toBe('select a model first')
     fireEvent.keyDown(box, { key: 'Enter' })
     expect(b.sink).not.toHaveBeenCalled()
+
+    // The model seat stays live. Locking it too would leave the composer
+    // asking for the one thing it prevents — every block this contract has is
+    // cleared by choosing a model.
+    const seat = (key: string) => b.seatOwners.filter(call => call.key === key).at(-1)?.owner
+    expect(seat('conversation.input.model')).toEqual({ locked: false })
+    expect(seat('conversation.input.plan')).toEqual({ locked: true })
   })
 
   it('lets the no-workspace posture win over a block', () => {