feat(ai-chat): close the error and abort edge-case gaps

src/features/workspaces/ai/ai-thread.ts

@@ -248,9 +248,23 @@ export function createAIThreadClass(getUserAIStore: () => typeof UserAIStore) {
 				thread,
 				tools: activeTools,
 			});
+			// A regeneration must not see the answer it replaces: Think assembles
+			// the prompt from the stored path, whose stale assistant tail would
+			// turn the turn into a "continue" (cloudflare/agents#2028 — remove
+			// once #2038 ships). Continuations keep their in-flight assistant.
+			let turnMessages = ctx.messages;
+			if (!ctx.continuation && ctx.body?.regenerate === true) {
+				let end = turnMessages.length;
+				while (end > 0 && turnMessages[end - 1]?.role !== "user") {
+					end -= 1;
+				}
+				if (end > 0) {
+					turnMessages = turnMessages.slice(0, end);
+				}
+			}
 			const messages = await resolveChatAttachmentModelMessages({
 				bucket: this.env.WORKSPACE_FILES,
-				messages: ctx.messages,
+				messages: turnMessages,
 				threadId: thread.id,
 				userId: thread.userId,
 				workspaceId: thread.workspaceId,

src/features/workspaces/components/AiChatPanel.tsx

@@ -29,6 +29,7 @@ function AiChatPanelLayout({ context }: AiChatPanelProps) {
 	const [activeThreadIsRecovering, setActiveThreadIsRecovering] = useState(false);
 	const {
 		activeThreadId,
+		threadViewKey,
 		isCreatingThread,
 		isLoading,
 		isMaximized,
@@ -64,12 +65,13 @@ function AiChatPanelLayout({ context }: AiChatPanelProps) {
 				threads={threads}
 			/>
 
-			<Suspense key={activeThreadId} fallback={<AiChatPanelLoading />}>
+			<Suspense key={threadViewKey} fallback={<AiChatPanelLoading />}>
 				<AiChatThreadView
 					context={context}
 					modelId={modelId}
 					onModelChange={onModelChange}
 					onRecoveringChange={setActiveThreadIsRecovering}
+					onStartNewChat={onNewChat}
 					threadSummary={threads.find((thread) => thread.id === activeThreadId)}
 					threadId={activeThreadId}
 				/>

src/features/workspaces/components/ai-chat/AiChatMessageList.tsx

@@ -1,5 +1,5 @@
 import type { ChatErrorClassification, ChatErrorContext } from "@cloudflare/think";
-import { AlertCircle, RotateCcw } from "lucide-react";
+import { AlertCircle, Plus, RefreshCw, RotateCcw } from "lucide-react";
 import { LazyMotion, domAnimation, m, useReducedMotion } from "motion/react";
 import type { HTMLMotionProps } from "motion/react";
 import type { ReactNode } from "react";
@@ -65,8 +65,12 @@ export type AiChatAssistantErrorState =
 	| {
 			classification?: ChatErrorClassification | null;
 			kind: "assistant";
+			message?: string | null;
 			stage?: ChatErrorContext["stage"] | null;
 	  }
+	| {
+			kind: "aborted";
+	  }
 	| {
 			kind: "connection";
 	  };
@@ -93,6 +97,7 @@ interface AiChatMessageListProps {
 	assistantError?: AiChatAssistantErrorState | null;
 	messages: AiChatMessage[];
 	onRegenerateLastResponse?: () => void;
+	onStartNewChat?: () => void;
 	presentation: AiChatPresentation;
 	sentMessageAnimationId?: string | null;
 	workspaceId: string;
@@ -102,6 +107,7 @@ export default function AiChatMessageList({
 	assistantError,
 	messages,
 	onRegenerateLastResponse,
+	onStartNewChat,
 	presentation,
 	sentMessageAnimationId,
 	workspaceId,
@@ -164,6 +170,7 @@ export default function AiChatMessageList({
 											row={row}
 											status={status}
 											onRegenerateLastResponse={onRegenerateLastResponse}
+											onStartNewChat={onStartNewChat}
 										/>
 									</AiChatMessageScrollerItem>
 								))}
@@ -233,13 +240,15 @@ function AiChatListRowView({
 	hasAssistantContent,
 	lastAssistantMessageId,
 	onRegenerateLastResponse,
+	onStartNewChat,
 	row,
 	status,
 }: {
 	canRetry: boolean;
 	hasAssistantContent: boolean;
 	lastAssistantMessageId: string | undefined;
 	onRegenerateLastResponse?: () => void;
+	onStartNewChat?: () => void;
 	row: AiChatListRow;
 	status: AiChatPresentation["status"];
 }) {
@@ -259,6 +268,7 @@ function AiChatListRowView({
 					errorState={row.errorState}
 					hasAssistantContent={hasAssistantContent}
 					onRetry={onRegenerateLastResponse}
+					onStartNewChat={onStartNewChat}
 				/>
 			</AiChatTranscriptRail>
 		);
@@ -284,12 +294,25 @@ function AiChatAssistantError({
 	errorState,
 	hasAssistantContent,
 	onRetry,
+	onStartNewChat,
 }: {
 	canRetry: boolean;
 	errorState: AiChatAssistantErrorState;
 	hasAssistantContent: boolean;
 	onRetry?: () => void;
+	onStartNewChat?: () => void;
 }) {
+	// An overflowed chat can rarely be retried into success, so the escape
+	// hatch the copy suggests gets its own action.
+	const canStartNewChat =
+		errorState.kind === "assistant" &&
+		errorState.classification === "context_overflow" &&
+		Boolean(onStartNewChat);
+	// Classified errors get curated copy; for the rest the stored server
+	// message (usage limits, recovery reasons) beats an unexplained failure.
+	const errorDetail =
+		errorState.kind === "assistant" && !errorState.classification ? errorState.message : null;
+
 	return (
 		<Message>
 			<MessageContent>
@@ -300,25 +323,60 @@ function AiChatAssistantError({
 								className="mt-0.5 size-4 shrink-0 text-muted-foreground"
 								aria-hidden="true"
 							/>
-							<p className="text-sm">
-								{getChatErrorMessage({
-									errorState,
-									hasAssistantContent,
-								})}
-							</p>
+							<div className="flex flex-col gap-1">
+								<p className="text-sm">
+									{getChatErrorMessage({
+										errorState,
+										hasAssistantContent,
+									})}
+								</p>
+								{errorDetail ? (
+									<p className="text-muted-foreground text-xs">{errorDetail}</p>
+								) : null}
+							</div>
 						</div>
-						{canRetry ? (
+						{errorState.kind === "connection" ? (
 							<Button
 								type="button"
 								variant="outline"
 								size="xs"
 								className="gap-1.5"
-								onClick={onRetry}
+								onClick={() => {
+									window.location.reload();
+								}}
 							>
-								<RotateCcw className="size-3" />
-								Try again
+								<RefreshCw className="size-3" />
+								Refresh page
 							</Button>
 						) : null}
+						{canRetry || canStartNewChat ? (
+							<div className="flex items-center gap-2">
+								{canRetry ? (
+									<Button
+										type="button"
+										variant="outline"
+										size="xs"
+										className="gap-1.5"
+										onClick={onRetry}
+									>
+										<RotateCcw className="size-3" />
+										Try again
+									</Button>
+								) : null}
+								{canStartNewChat ? (
+									<Button
+										type="button"
+										variant="outline"
+										size="xs"
+										className="gap-1.5"
+										onClick={onStartNewChat}
+									>
+										<Plus className="size-3" />
+										Start new chat
+									</Button>
+								) : null}
+							</div>
+						) : null}
 					</BubbleContent>
 				</Bubble>
 			</MessageContent>
@@ -434,7 +492,11 @@ function getChatErrorMessage({
 	hasAssistantContent: boolean;
 }) {
 	if (errorState.kind === "connection") {
-		return "The chat connection closed before the response could finish. Refresh the page to reconnect.";
+		return "The chat connection closed before the response could finish.";
+	}
+
+	if (errorState.kind === "aborted") {
+		return "The response was stopped before it started.";
 	}
 
 	if (errorState.classification === "context_overflow") {

src/features/workspaces/components/ai-chat/AiChatThreadView.tsx

@@ -25,13 +25,15 @@ export default function AiChatThreadView({
 	modelId,
 	onModelChange,
 	onRecoveringChange,
+	onStartNewChat,
 	threadSummary,
 	threadId,
 }: {
 	context: WorkspaceAiContextScope;
 	modelId: AiChatModelId;
 	onModelChange: (modelId: AiChatModelId) => void;
 	onRecoveringChange?: (isRecovering: boolean) => void;
+	onStartNewChat?: () => void;
 	threadSummary?: AIThreadSummary;
 	threadId: string;
 }) {
@@ -69,6 +71,7 @@ export default function AiChatThreadView({
 	const assistantError = deriveAiChatAssistantErrorState({
 		chatStatus: presentation.status,
 		hasConnectionError: Boolean(connectionError),
+		lastMessageRole: messages.at(-1)?.role,
 		threadSummary,
 	});
 	const sendMessage = (message: PromptInputMessage, clearDraft = true) => {
@@ -124,6 +127,7 @@ export default function AiChatThreadView({
 				sentMessageAnimationId={sentMessageAnimationId}
 				workspaceId={context.workspaceId}
 				onRegenerateLastResponse={regenerate}
+				onStartNewChat={onStartNewChat}
 			/>
 
 			<div className="px-3 pb-3">

src/features/workspaces/components/ai-chat/ai-chat-display-state.ts

@@ -1,6 +1,5 @@
 import { isToolUIPart } from "ai";
 
-import { WORKSPACE_REFERENCES_DATA_PART_TYPE } from "#/features/workspaces/ai/workspace-references";
 import type {
 	AiChatMessage,
 	AiChatMessagePart,
@@ -203,10 +202,6 @@ export function getDisplayableParts(message: AiChatMessage): AiChatRenderablePar
 }
 
 export function isDisplayableMessagePart(part: AiChatMessagePart): boolean {
-	if (part.type === WORKSPACE_REFERENCES_DATA_PART_TYPE) {
-		return false;
-	}
-
 	if (part.type === "text") {
 		return part.text.length > 0 || part.state === "streaming";
 	}
@@ -219,16 +214,10 @@ export function isDisplayableMessagePart(part: AiChatMessagePart): boolean {
 		return isVisibleToolPart(part);
 	}
 
-	if (
-		part.type === "file" ||
-		part.type === "source-url" ||
-		part.type === "source-document" ||
-		part.type.startsWith("data-")
-	) {
-		return true;
-	}
-
-	return false;
+	// Deliberately excludes `data-*` parts: old transcripts can carry data parts
+	// from retired features, and counting one as displayable makes a message
+	// render as a blank bubble instead of falling through to "no response".
+	return part.type === "file" || part.type === "source-url" || part.type === "source-document";
 }
 
 export function getToolActivityForPart(

src/features/workspaces/components/ai-chat/ai-chat-error-state.test.ts

@@ -19,17 +19,51 @@ describe("AI chat error state", () => {
 				hasConnectionError: false,
 				threadSummary: {
 					lastErrorClassification: "context_overflow",
+					lastErrorMessage: "Context window exceeded",
 					lastErrorStage: "recovery",
 					lastRunResult: "error",
 				},
 			}),
 		).toEqual({
 			classification: "context_overflow",
 			kind: "assistant",
+			message: "Context window exceeded",
 			stage: "recovery",
 		});
 	});
 
+	it("flags a run stopped before the first token so the send visibly ended", () => {
+		expect(
+			deriveAiChatAssistantErrorState({
+				chatStatus: "ready",
+				hasConnectionError: false,
+				lastMessageRole: "user",
+				threadSummary: {
+					lastErrorClassification: null,
+					lastErrorMessage: null,
+					lastErrorStage: null,
+					lastRunResult: "aborted",
+				},
+			}),
+		).toEqual({ kind: "aborted" });
+	});
+
+	it("stays quiet for a mid-stream stop that kept its partial reply", () => {
+		expect(
+			deriveAiChatAssistantErrorState({
+				chatStatus: "ready",
+				hasConnectionError: false,
+				lastMessageRole: "assistant",
+				threadSummary: {
+					lastErrorClassification: null,
+					lastErrorMessage: null,
+					lastErrorStage: null,
+					lastRunResult: "aborted",
+				},
+			}),
+		).toBeNull();
+	});
+
 	it("keeps a terminal connection error distinct", () => {
 		expect(
 			deriveAiChatAssistantErrorState({

src/features/workspaces/components/ai-chat/ai-chat-error-state.ts

@@ -1,15 +1,16 @@
 import type { AIThreadSummary } from "#/features/workspaces/ai/user-ai-agents";
 import type { AiChatAssistantErrorState } from "#/features/workspaces/components/ai-chat/AiChatMessageList";
-import type { AiChatStatus } from "#/features/workspaces/components/ai-chat/types";
+import type { AiChatMessage, AiChatStatus } from "#/features/workspaces/components/ai-chat/types";
 
 type AIThreadErrorSummary = Pick<
 	AIThreadSummary,
-	"lastErrorClassification" | "lastErrorStage" | "lastRunResult"
+	"lastErrorClassification" | "lastErrorMessage" | "lastErrorStage" | "lastRunResult"
 >;
 
 export function deriveAiChatAssistantErrorState(input: {
 	chatStatus: AiChatStatus;
 	hasConnectionError: boolean;
+	lastMessageRole?: AiChatMessage["role"];
 	threadSummary?: AIThreadErrorSummary;
 }): AiChatAssistantErrorState | null {
 	if (input.hasConnectionError) {
@@ -30,12 +31,22 @@ export function deriveAiChatAssistantErrorState(input: {
 			...(threadError
 				? {
 						classification: threadError.lastErrorClassification,
+						message: threadError.lastErrorMessage,
 						stage: threadError.lastErrorStage,
 					}
 				: {}),
 			kind: "assistant",
 		};
 	}
 
+	// A run stopped before the first token leaves the user message as the tail
+	// with nothing after it — without this row there is no sign the send ended.
+	// A mid-stream stop keeps its partial assistant tail, so no row is needed.
+	if (input.threadSummary?.lastRunResult === "aborted" && input.lastMessageRole === "user") {
+		return {
+			kind: "aborted",
+		};
+	}
+
 	return null;
 }