coder · DanielleMaywood · Aug 18, 2026 · Aug 17, 2026 · Aug 17, 2026 · Aug 17, 2026
@@ -1644,16 +1644,31 @@ export const AgentChatInput: FC<AgentChatInputProps> = ({
 							/>
 						)}
 						{isStreaming && onInterrupt && (
-							<Button
-								size="icon"
-								variant="default"
-								className="size-7 rounded-full transition-colors [&>svg]:!size-3 [&>svg]:p-0"
-								onClick={onInterrupt}
-								disabled={isInterruptPending}
-							>
-								<SquareIcon className="fill-current" />
-								<span className="sr-only">Stop</span>
-							</Button>
+							<Tooltip>
+								<TooltipTrigger asChild>
+									<Button
+										size="icon"
+										variant="default"
+										className="size-7 rounded-full transition-colors [&>svg]:!size-3 [&>svg]:p-0"
+										onClick={onInterrupt}
+										disabled={isInterruptPending}
+									>
+										<SquareIcon className="fill-current" />
+										<span className="sr-only">Stop</span>
+									</Button>
+								</TooltipTrigger>
+								<TooltipContent side="top">
+									{isInterruptPending ? "Interrupting…" : "Stop"}
+								</TooltipContent>
+							</Tooltip>
+						)}
+						{isInterruptPending && isStreaming && (
+							// The disabled Stop button is skipped by Tab order, so the
+							// pending interruption is also announced through a live
+							// region and a tooltip.
+							<span role="status" className="sr-only">
+								Interrupting. Waiting for the agent to stop.
+							</span>
 						)}
 						{!(isStreaming && editingQueuedMessageID === null) && (
 							<Tooltip>

@@ -1,3 +1,4 @@
+import { PauseIcon } from "lucide-react";
 import type { FC } from "react";
 import { Shimmer } from "../ChatElements";
 import { ToolIcon } from "../ChatElements/tools/ToolIcon";
@@ -6,14 +7,20 @@ import type { LiveStatusModel } from "./liveStatusModel";
 import { BlockList, type BlockListProps } from "./MessageBlocks";
 import { shouldShowGenericThinking } from "./streamingActivity";
 
-const LiveActivitySlot: FC = () => (
+const LiveActivitySlot: FC<{ interrupting?: boolean }> = ({
+	interrupting = false,
+}) => (
 	<div
 		data-testid="live-activity-slot"
 		className="flex h-6 items-center gap-2 text-content-secondary"
 	>
-		<ToolIcon name="thinking" />
+		{interrupting ? (
+			<PauseIcon className="size-4 shrink-0 stroke-[1.5]" />
+		) : (
+			<ToolIcon name="thinking" />
+		)}
 		<Shimmer as="span" className="text-[13px] leading-6">
-			Thinking
+			{interrupting ? "Interrupting" : "Thinking"}
 		</Shimmer>
 	</div>
 );
@@ -43,8 +50,11 @@ export const AssistantOutput: FC<AssistantOutputProps> = ({
 			<BlockList {...blockProps} />
 			{callout && <ChatStatusCallout status={callout} />}
 			{liveStatus &&
-				shouldShowGenericThinking({ liveStatus, blocks, tools }) && (
-					<LiveActivitySlot />
+				(liveStatus.phase === "interrupting" ||
+					shouldShowGenericThinking({ liveStatus, blocks, tools })) && (
+					<LiveActivitySlot
+						interrupting={liveStatus.phase === "interrupting"}
+					/>
 				)}
 		</div>
 	);

@@ -1,6 +1,6 @@
 import { describe, expect, it } from "vitest";
 import type { ChatDetailError } from "./chatError";
-import { deriveLiveStatus } from "./liveStatusModel";
+import { deriveLiveStatus, type LiveStatusModel } from "./liveStatusModel";
 import { buildReconnectState, buildRetryState } from "./storyFixtures";
 import type { StreamState } from "./types";
 
@@ -35,6 +35,7 @@ const derive = (
 		streamError: null,
 		persistedError: null,
 		isAwaitingFirstStreamChunk: false,
+		chatStatus: null,
 		...overrides,
 	});
 
@@ -48,7 +49,7 @@ describe("deriveLiveStatus", () => {
 		attempt: 2,
 		provider: "anthropic",
 		retryingAt: "2026-03-10T00:00:02.000Z",
-	};
+	} satisfies LiveStatusModel;
 	const reconnectingStatus = {
 		phase: "reconnecting",
 		hasAccumulatedOutput: false,
@@ -57,7 +58,7 @@ describe("deriveLiveStatus", () => {
 		attempt: 1,
 		delayMs: 1000,
 		retryingAt: "2026-03-10T00:00:01.000Z",
-	};
+	} satisfies LiveStatusModel;
 	const failedStatus = {
 		phase: "failed",
 		hasAccumulatedOutput: false,
@@ -66,9 +67,13 @@ describe("deriveLiveStatus", () => {
 		message: "Chat processing failed.",
 		provider: "anthropic",
 		statusCode: 500,
-	};
+	} satisfies LiveStatusModel;
 
-	it.each([
+	const cases: [
+		string,
+		Partial<Parameters<typeof deriveLiveStatus>[0]> | undefined,
+		LiveStatusModel,
+	][] = [
 		["idle", undefined, { phase: "idle", hasAccumulatedOutput: false }],
 		[
 			"starting",
@@ -91,10 +96,27 @@ describe("deriveLiveStatus", () => {
 			{ streamState: buildStreamState() },
 			{ phase: "streaming", hasAccumulatedOutput: false },
 		],
-	])("returns %s", (_phase, overrides, expected) => {
+		[
+			"interrupting",
+			{ chatStatus: "interrupting" },
+			{ phase: "interrupting", hasAccumulatedOutput: false },
+		],
+	];
+	it.each(cases)("returns %s", (_phase, overrides, expected) => {
 		expect(derive(overrides)).toEqual(expected);
 	});
 
+	it("treats interrupting as outranking stream leftovers", () => {
+		expect(
+			derive({
+				chatStatus: "interrupting",
+				streamState: buildStreamState({
+					blocks: [{ type: "response", text: "Partial response" }],
+				}),
+			}),
+		).toEqual({ phase: "interrupting", hasAccumulatedOutput: true });
+	});
+
 	it("uses the persisted error as the idle fallback", () => {
 		expect(derive({ persistedError: buildStreamError() })).toEqual(
 			failedStatus,

@@ -14,6 +14,7 @@ export type LiveStatusModel =
 	| ({ phase: "idle" } & LiveStatusBase)
 	| ({ phase: "starting" } & LiveStatusBase)
 	| ({ phase: "streaming" } & LiveStatusBase)
+	| ({ phase: "interrupting" } & LiveStatusBase)
 	| ({
 			phase: "retrying";
 			title: string;
@@ -46,6 +47,7 @@ export const shouldRenderLiveAssistant = (
 ): boolean =>
 	liveStatus.phase === "streaming" ||
 	liveStatus.phase === "starting" ||
+	liveStatus.phase === "interrupting" ||
 	liveStatus.phase === "retrying" ||
 	liveStatus.phase === "reconnecting" ||
 	liveStatus.hasAccumulatedOutput;
@@ -57,6 +59,7 @@ export type DeriveLiveStatusParams = {
 	streamError: ChatDetailError | null;
 	persistedError: ChatDetailError | null;
 	isAwaitingFirstStreamChunk: boolean;
+	chatStatus: TypesGen.ChatStatus | null;
 };
 
 const getHasAccumulatedOutput = (streamState: StreamState | null): boolean =>
@@ -108,6 +111,7 @@ export const deriveLiveStatus = ({
 	streamError,
 	persistedError,
 	isAwaitingFirstStreamChunk,
+	chatStatus,
 }: DeriveLiveStatusParams): LiveStatusModel => {
 	const hasAccumulatedOutput = getHasAccumulatedOutput(streamState);
 
@@ -123,6 +127,13 @@ export const deriveLiveStatus = ({
 		return toReconnectingLiveStatus(reconnectState, { hasAccumulatedOutput });
 	}
 
+	// The interrupt outranks stream leftovers: while the worker drains and
+	// finalizes an interruption, the transcript must not claim the agent is
+	// still producing output.
+	if (chatStatus === "interrupting") {
+		return { phase: "interrupting", hasAccumulatedOutput };
+	}
+
 	if (isAwaitingFirstStreamChunk) {
 		return { phase: "starting", hasAccumulatedOutput };
 	}

@@ -25,6 +25,7 @@ const DEFAULT_LIVE_STATUS_PARAMS: DeriveLiveStatusParams = {
 	streamError: null,
 	persistedError: null,
 	isAwaitingFirstStreamChunk: false,
+	chatStatus: null,
 };
 
 export const buildLiveStatus = (

@@ -38,6 +38,8 @@ const liveStatus = (phase: LiveStatusModel["phase"]): LiveStatusModel => {
 				title: "Failed",
 				message: "Failed",
 			};
+		case "interrupting":
+			return { phase: "interrupting", hasAccumulatedOutput: false };
 	}
 };
 

@@ -1,12 +1,13 @@
 import { MessageScroller } from "@shadcn/react/message-scroller";
 import type { Meta, StoryObj } from "@storybook/react-vite";
 import type { FC } from "react";
-import { expect, within } from "storybook/test";
+import { expect, fn, userEvent, within } from "storybook/test";
 import type * as TypesGen from "#/api/typesGenerated";
+import { MockChatQueuedMessage } from "#/testHelpers/chatEntities";
 import { ChatWorkspaceContext } from "../context/ChatWorkspaceContext";
 import { createChatStore } from "./ChatConversation/chatStore";
 import { FIXTURE_NOW } from "./ChatConversation/storyFixtures";
-import { ChatPageTimeline } from "./ChatPageContent";
+import { ChatPageInput, ChatPageTimeline } from "./ChatPageContent";
 
 // These stories cover transcript rendering, so history paging stays idle.
 const StoryChatPageTimeline: FC<{
@@ -34,6 +35,52 @@ type Story = StoryObj<typeof meta>;
 
 const CHAT_ID = "chat-page-content-stories";
 
+// Renders only the composer half of the chat page. chatId and
+// organizationId stay undefined so the prompt-history and draft
+// attachment queries stay disabled.
+const StoryChatPageInput: FC<{
+	store: ReturnType<typeof createChatStore>;
+	onInterrupt?: () => void;
+}> = ({ store, onInterrupt }) => (
+	<div className="mx-auto w-full max-w-3xl p-4">
+		<ChatPageInput
+			organizationId={undefined}
+			store={store}
+			compressionThreshold={undefined}
+			onSend={fn()}
+			sendShortcut="enter"
+			onDeleteQueuedMessage={fn()}
+			onPromoteQueuedMessage={fn()}
+			onInterrupt={onInterrupt ?? fn()}
+			isInputDisabled={false}
+			isSendPending={false}
+			isInterruptPending={false}
+			hasModelOptions
+			selectedModel="model-config-1"
+			onModelChange={fn()}
+			modelOptions={[
+				{
+					id: "model-config-1",
+					provider: "openai",
+					model: "gpt-4o",
+					displayName: "GPT-4o",
+				},
+			]}
+			modelSelectorPlaceholder="Select model"
+			canConfigureAgentSetup={false}
+			isEditing={false}
+			editingQueuedMessageID={null}
+			onStartQueueEdit={fn()}
+			onCancelQueueEdit={fn()}
+			isEditingHistoryMessage={false}
+			onCancelHistoryEdit={fn()}
+			workspaceOptions={[]}
+			selectedWorkspaceId={null}
+			isWorkspaceLoading={false}
+		/>
+	</div>
+);
+
 const buildMessage = (
 	id: number,
 	role: TypesGen.ChatMessageRole,
@@ -46,6 +93,27 @@ const buildMessage = (
 	content,
 });
 
+// Matches the backend I1 state: an interruption has been requested
+// and the stream has already been torn down, so the store holds no
+// stream state while the chat status is still "interrupting".
+const buildInterruptingStore = () => {
+	const store = createChatStore();
+	store.replaceMessages([
+		buildMessage(1, "user", [{ type: "text", text: "Refactor the module" }]),
+	]);
+	store.setQueuedMessages([
+		{
+			...MockChatQueuedMessage,
+			id: 2,
+			chat_id: CHAT_ID,
+			content: [{ type: "text", text: "Also rename the helpers" }],
+			created_at: new Date(FIXTURE_NOW).toISOString(),
+		},
+	]);
+	store.setChatStatus("interrupting");
+	return store;
+};
+
 const buildThinkingSpacerStore = () => {
 	const store = createChatStore();
 
@@ -165,3 +233,62 @@ export const MergedMessagesRenderInIDOrder: Story = {
 		);
 	},
 };
+
+// Interrupting is busy without stream state; interrupt retries are
+// rejected by the backend, so Stop stays present but disabled.
+const interruptingOnInterrupt = fn();
+export const InterruptingShowsBusyComposer: Story = {
+	render: () => {
+		const store = buildInterruptingStore();
+		return (
+			<MessageScroller.Provider autoScroll defaultScrollPosition="end">
+				<div className="flex h-full flex-col">
+					<ChatPageTimeline
+						store={store}
+						persistedError={undefined}
+						hasMoreMessages={false}
+						isFetchingMoreMessages={false}
+						isHydratingMessages={false}
+						hasFetchMoreError={false}
+						onFetchMoreMessages={async () => {}}
+					/>
+					<StoryChatPageInput
+						store={store}
+						onInterrupt={interruptingOnInterrupt}
+					/>
+				</div>
+			</MessageScroller.Provider>
+		);
+	},
+	play: async ({ canvasElement }) => {
+		const canvas = within(canvasElement);
+		expect(canvas.getByText("Also rename the helpers")).toBeInTheDocument();
+		expect(canvas.getByRole("button", { name: "Stop" })).toBeDisabled();
+		expect(canvas.getByRole("status")).toHaveTextContent(
+			"Interrupting. Waiting for the agent to stop.",
+		);
+		expect(canvas.queryByRole("button", { name: "Send" })).toBeNull();
+		expect(canvas.getByText("Interrupting")).toBeInTheDocument();
+		expect(canvas.queryByText("Thinking")).toBeNull();
+
+		await userEvent.click(
+			canvas.getByRole("textbox", { name: "Chat message" }),
+		);
+		await userEvent.keyboard("{Escape}");
+		expect(interruptingOnInterrupt).not.toHaveBeenCalled();
+	},
+};
+
+export const RunningShowsBusyComposer: Story = {
+	render: () => {
+		const store = buildInterruptingStore();
+		store.setChatStatus("running");
+		return <StoryChatPageInput store={store} />;
+	},
+	play: async ({ canvasElement }) => {
+		const canvas = within(canvasElement);
+		expect(canvas.getByText("Also rename the helpers")).toBeInTheDocument();
+		expect(canvas.getByRole("button", { name: "Stop" })).toBeEnabled();
+		expect(canvas.queryByRole("button", { name: "Send" })).toBeNull();
+	},
+};