diff --git a/frontend/src/run/AssistantPanel.tsx b/frontend/src/run/AssistantPanel.tsx
index c61a377e..da5b94a7 100644
--- a/frontend/src/run/AssistantPanel.tsx
+++ b/frontend/src/run/AssistantPanel.tsx
@@ -16,7 +16,7 @@ import { formatCost, formatLapse, formatOffset, formatSpan, formatTokens, shortI
 import { statusLabel } from '../lib/status'
 import { CHAT_BLUEPRINT_TEXT, runClassLabel, SQL_CHECK_TEXT } from '../lib/terms'
 import { sortSqlChecks } from '../lib/sqlcheck'
-import type { RunUsage, ToolChange } from '../types'
+import type { ConversationTurn, RunUsage, ToolChange } from '../types'
 import { AssistantStream, type StreamTurn } from './AssistantStream'
 import { Composer } from './Composer'
 import { SqlCheckBody } from './SqlChecks'
@@ -220,6 +220,21 @@ function copilotTurn(
   }
 }
 
+/**
+ * 之前那几轮的报错：落库时记了原因（meta.cause，助手本轮未完成的那种）就连「怎么办」和诊断一起摊开，
+ * 和这一轮当场看到的一样；老轮次只有一句话
+ */
+const pastError = (t: ConversationTurn): StreamTurn['error'] => {
+  const cause = t.meta?.cause
+  if (!t.error) return undefined
+  if (!cause || typeof cause !== 'object' || cause.kind !== 'copilot') return t.error
+  return {
+    error: t.error,
+    ...(typeof cause.hint === 'string' && cause.hint ? { hint: cause.hint } : {}),
+    ...(typeof cause.detail === 'string' && cause.detail ? { detail: cause.detail } : {}),
+  }
+}
+
 /** 这一轮变少了的工具，分「没让删」和「按要求」两组：和改图回执（toast）同一条规则 */
 const toolLossOf = (out: CopilotOutcome) =>
   splitShrunk(out.toolChanges, out.dropped.map((w) => ({ node_id: w.nodeId, field: w.field })))
@@ -254,7 +269,7 @@ function ChatView({ hasRun, onOpenRun }: { hasRun: boolean; onOpenRun: () => voi
     status: t.status === 'error' ? '本轮未能完成' : t.graph ? '已修改画布' : '已回答',
     steps: [],
     output: t.answer ? { 回答: t.answer } : t.explanation ? { 说明: t.explanation } : null,
-    error: t.status === 'error' ? t.error || undefined : undefined,
+    error: t.status === 'error' ? pastError(t) : undefined,
   })), [earlier])
   const shown = showPast ? [...pastTurns, ...turns] : turns
   const streamRef = useRef<HTMLDivElement>(null)
diff --git a/frontend/src/store/studio.ts b/frontend/src/store/studio.ts
index 78350ec4..ec90d9d3 100644
--- a/frontend/src/store/studio.ts
+++ b/frontend/src/store/studio.ts
@@ -484,13 +484,20 @@ const memoryOf = (past: ConversationTurn[]): StudioState['copilotMemory'] => ({
   past, total: past.length, turns: Math.min(past.length, COPILOT_HISTORY_TURNS),
 })
 
+/**
+ * 画布这一轮没完成时记下的原因：同问数据一轮的 meta.cause（backend/app/chat/record.py 的 kind=copilot）。
+ * 以前只记 error 那一句，诊断（模型交回了什么）没落库，事后查不了为什么失败
+ */
+type CanvasCause = { kind: 'copilot'; message: string; hint?: string; detail?: string; code?: string
+  diagnostics?: Record<string, unknown> }
+
 /** 把画布上这一轮记进会话，下一条指令才接得上 */
 function recordCanvasTurn(
   conversationId: string | null,
   instruction: string,
   patch: { graph?: any; explanation?: string; answer?: string; status?: 'done' | 'error'; error?: string
-    /** 这一轮的查看记录（look §2.5.8）：服务端下一轮据此写「上一轮查看过」 */
-    meta?: { looks: LookEvent[] } },
+    /** 这一轮的查看记录（look §2.5.8）：服务端下一轮据此写「上一轮查看过」；没完成的另记原因 */
+    meta?: { looks?: LookEvent[]; cause?: CanvasCause } },
   set?: (fn: (s: StudioState) => Partial<StudioState>) => void,
 ): void {
   if (!conversationId) return
@@ -2148,7 +2155,15 @@ export const useStudio = create<StudioState>((set, get) => ({
             finish({ explanation: '', error: message,
                      errorHint: typeof op.hint === 'string' ? op.hint : '',
                      errorDetail: typeof op.detail === 'string' ? op.detail : '' })
-            recordCanvasTurn(get().copilotConversationId, instruction, { status: 'error', error: message, ...looksMeta() }, set)
+            const cause: CanvasCause = {
+              kind: 'copilot', message,
+              ...(typeof op.hint === 'string' && op.hint ? { hint: op.hint } : {}),
+              ...(typeof op.detail === 'string' && op.detail ? { detail: op.detail } : {}),
+              ...(typeof op.code === 'string' && op.code ? { code: op.code } : {}),
+              ...(op.diagnostics && typeof op.diagnostics === 'object' ? { diagnostics: op.diagnostics } : {}),
+            }
+            recordCanvasTurn(get().copilotConversationId, instruction,
+              { status: 'error', error: message, meta: { ...looksMeta().meta, cause } }, set)
             break
           }
         }