Merge latest master into PR 555

# Conflicts:
#	docs/architecture.i18n.yaml
#	docs/core-data-structures/core.i18n.yaml
#	examples/acp-agent/tests/snapshots/cordis-inspect-jsdoc/session.jsonl
#	packages/client/runtime/README.i18n.yaml
#	packages/client/ui-conversation/README.i18n.yaml
#	packages/client/ui-conversation/src/client/chat/MessageItem.tsx
#	packages/compact/compact-basic/README.i18n.yaml
#	packages/ui/tui/README.i18n.yaml

packages/client/ui-conversation/src/client/chat/MessageItem.module.css

@@ -200,6 +200,40 @@
   color: var(--dsw-alias-label-secondary);
 }
 
+.turnErrorRow {
+  display: grid;
+  grid-template-columns: 10px minmax(0, 1fr) auto;
+  gap: 8px;
+  align-items: start;
+  padding: 2px 0;
+  font-size: 13px;
+  line-height: 20px;
+}
+
+.turnErrorDot {
+  margin-top: 5px;
+}
+
+.turnErrorCopy {
+  min-width: 0;
+  overflow-wrap: anywhere;
+}
+
+.turnErrorTitle {
+  margin-right: 6px;
+  color: var(--dsw-alias-state-error-primary);
+  font-weight: 600;
+}
+
+.turnErrorMessage {
+  color: var(--dsw-alias-label-secondary);
+}
+
+.turnErrorCode {
+  color: var(--dsw-alias-label-tertiary);
+  font: var(--dsw-font-markdown-code-block-small);
+}
+
 @keyframes retry-shimmer {
   from {
     background-position: 100% 50%;

packages/client/ui-conversation/src/client/chat/MessageItem.tsx

@@ -6,9 +6,9 @@ import { memo, useEffect, useMemo, useState } from 'react'
 import type { ReactNode } from 'react'
 import type {
   CompactionSummaryNode, ContextMessageNode, ModelRetryNode, SteeringMessageNode,
-  UnknownSurfaceNode, UserMessageNode,
+  TurnErrorNode, UnknownSurfaceNode, UserMessageNode,
 } from '@deepseek-ai/dsh-client-runtime/client'
-import { JsonBlock, MessageText } from '@deepseek-ai/dsh-client-ui-primitives'
+import { JsonBlock, MessageText, StateDot } from '@deepseek-ai/dsh-client-ui-primitives'
 import type { ChatViewSlotProps } from '../contract/slots.ts'
 import { CompactionItem } from './CompactionItem.tsx'
 import { ContextInjectionRow } from './ContextInjectionRow.tsx'
@@ -17,7 +17,14 @@ import css from './MessageItem.module.css'
 import { ImageGallery, type ImageLoader } from './MessageImage.tsx'
 
 export interface MessageItemProps {
-  node: UserMessageNode | SteeringMessageNode | ContextMessageNode | CompactionSummaryNode | ModelRetryNode | UnknownSurfaceNode
+  node:
+    | UserMessageNode
+    | SteeringMessageNode
+    | ContextMessageNode
+    | CompactionSummaryNode
+    | ModelRetryNode
+    | TurnErrorNode
+    | UnknownSurfaceNode
   loadImage?: ImageLoader
   retryActive?: boolean
   /** Fork the session through the turn containing this message (user-bubble branch action). */
@@ -121,6 +128,24 @@ function ModelRetryItem({ node, active, t }: {
     </details>
   )
 }
+
+/** Persistent, turn-positioned feedback for a terminal failure. */
+function TurnErrorItem({ node, t }: {
+  node: TurnErrorNode
+  t: ChatViewSlotProps['t']
+}) {
+  return (
+    <div className={css.turnErrorRow} role="status">
+      <StateDot state="error" className={css.turnErrorDot} />
+      <div className={css.turnErrorCopy}>
+        <span className={css.turnErrorTitle}>{t('message.turnError')}</span>
+        <span className={css.turnErrorMessage}>{node.message}</span>
+      </div>
+      {node.code !== undefined && <code className={css.turnErrorCode}>{node.code}</code>}
+    </div>
+  )
+}
+
 /**
  * Display projection of reference forms in a user bubble (free geometry — no
  * textarea alignment constraint here); everything else stays plain text. The
@@ -214,6 +239,8 @@ export const MessageItem = memo(function MessageItem({
       return <CompactionItem node={node} t={t} />
     case 'model-retry':
       return <ModelRetryItem node={node} active={retryActive} t={t} />
+    case 'turn-error':
+      return <TurnErrorItem node={node} t={t} />
     default:
       return (
         <div className={css.contextRow}>

packages/client/ui-conversation/src/client/locales.ts

@@ -77,6 +77,7 @@ export const zh = {
   'message.retry.status': '{label}（{retry}/{maximum}） · {seconds}s',
   'message.retry.delay': '重试延迟：',
   'message.retry.failure': '失败原因：',
+  'message.turnError': '本轮运行失败',
   'command.running': '执行中…',
   'command.failed': '命令失败',
   'command.done': '已完成',
@@ -191,6 +192,7 @@ export const en = {
   'message.retry.status': '{label} ({retry}/{maximum}) · {seconds}s',
   'message.retry.delay': 'Retry delay: ',
   'message.retry.failure': 'Failure reason: ',
+  'message.turnError': 'This turn failed',
   'command.running': 'Running…',
   'command.failed': 'Command failed',
   'command.done': 'Completed',

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

@@ -22,6 +22,7 @@ export function ConversationRoot({
   const session = useSession(s => s)
   const inputState = useInput(s => s)
   const cwd = useSessions(s => sessionId === undefined ? undefined : s.byId[sessionId]?.cwd)
+  const summaryBlank = useSessions(s => sessionId === undefined ? undefined : s.byId[sessionId]?.blank)
   const workspaces = useWorkspaces(s => s)
 
   const [pickerOpen, setPickerOpen] = useState(false)
@@ -65,8 +66,16 @@ export function ConversationRoot({
   // While a session is still replaying (loading + blank) the hero/docked
   // choice is unknowable — render the composer hidden instead of flashing
   // the centered hero and snapping to the docked bar (or vice versa).
+  // Exemption: a session the list summary already proves blank can only
+  // land on the hero, so hiding would blank the column for the whole
+  // history round-trip (the startup auto-selection flash) for nothing.
+  // The exemption is deliberately open-state-wide, not loading-only: a
+  // summary-blank session is the hero before its open starts (`cold`) and
+  // after one fails (`error`) for the same reason — there is no history.
   const settling = sessionId !== undefined && composerPhase === 'blank' && openState === 'loading'
-  const hero = sessionId === undefined || (composerPhase === 'blank' && openState === 'open')
+    && summaryBlank !== true
+  const hero = sessionId === undefined
+    || (composerPhase === 'blank' && (openState === 'open' || summaryBlank === true))
   const zone: InputZone | undefined =
     session === undefined || inputState === undefined ? undefined : { session, input: inputState }