feat(flow chat): add cancel button (#6869)

* feat(flow chat): add cancel button

Add cancel button to flow chat interface that appears when a flow is executing.
- Replace send button with red stop button when processing
- Wire up cancel functionality to stop flow execution
- Support both polling and streaming modes
- Fixes #6868

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: windmill-internal-app[bot] <windmill-internal-app[bot]@users.noreply.github.com>

* fix

---------

Co-authored-by: claude[bot] <41898282+claude[bot]@users.noreply.github.com>
Co-authored-by: windmill-internal-app[bot] <windmill-internal-app[bot]@users.noreply.github.com>

frontend/src/lib/components/flows/conversations/FlowChatInterface.svelte

@@ -1,6 +1,6 @@
 <script lang="ts">
 	import { Button, Alert } from '$lib/components/common'
-	import { MessageCircle, Loader2, ArrowUp } from 'lucide-svelte'
+	import { MessageCircle, Loader2, ArrowUp, Square } from 'lucide-svelte'
 	import { workspaceStore } from '$lib/stores'
 	import autosize from '$lib/autosize'
 	import FlowChatMessage from './FlowChatMessage.svelte'
@@ -123,16 +123,28 @@
 				rows={3}
 			></textarea>
 			<div class="flex-shrink-0 pr-2">
-				<Button
-					color="blue"
-					size="xs2"
-					btnClasses="!rounded-full !p-1.5"
-					startIcon={{ icon: ArrowUp }}
-					disabled={!manager.inputMessage?.trim() || manager.isLoading || deploymentInProgress}
-					on:click={() => manager.sendMessage()}
-					iconOnly
-					title={deploymentInProgress ? 'Deployment in progress' : 'Send message (Enter)'}
-				/>
+				{#if manager.isWaitingForResponse || manager.isLoading}
+					<Button
+						color="red"
+						size="xs2"
+						btnClasses="!rounded-full !p-1.5"
+						startIcon={{ icon: Square }}
+						on:click={() => manager.cancelCurrentJob()}
+						iconOnly
+						title="Cancel execution"
+					/>
+				{:else}
+					<Button
+						color="blue"
+						size="xs2"
+						btnClasses="!rounded-full !p-1.5"
+						startIcon={{ icon: ArrowUp }}
+						disabled={!manager.inputMessage?.trim() || manager.isLoading || deploymentInProgress}
+						on:click={() => manager.sendMessage()}
+						iconOnly
+						title={deploymentInProgress ? 'Deployment in progress' : 'Send message (Enter)'}
+					/>
+				{/if}
 			</div>
 		</div>
 	</div>

frontend/src/lib/components/flows/conversations/FlowChatManager.svelte.ts

@@ -1,5 +1,5 @@
 import type { FlowConversationMessage } from '$lib/gen/types.gen'
-import { FlowConversationService } from '$lib/gen'
+import { FlowConversationService, JobService } from '$lib/gen'
 import { sendUserToast } from '$lib/toast'
 import { waitJob } from '$lib/components/waitJob'
 import { tick } from 'svelte'
@@ -32,6 +32,7 @@ class FlowChatManager {
 	loadingMoreMessages = $state(false)
 	currentEventSource = $state<EventSource | undefined>(undefined)
 	pollingInterval = $state<ReturnType<typeof setInterval> | undefined>(undefined)
+	currentJobId = $state<string | undefined>(undefined)
 
 	// Private state
 	#conversationsCache = $state<Record<string, ChatMessage[]>>({})
@@ -69,6 +70,7 @@ class FlowChatManager {
 		this.stopPolling()
 		this.isLoading = false
 		this.isWaitingForResponse = false
+		this.currentJobId = undefined
 	}
 
 	// Public methods for component to call
@@ -86,6 +88,28 @@ class FlowChatManager {
 		this.page = 1
 	}
 
+	async cancelCurrentJob() {
+		if (!this.#workspace) {
+			return
+		}
+
+		try {
+			if (this.currentJobId) {
+				await JobService.cancelQueuedJob({
+					workspace: this.#workspace,
+					id: this.currentJobId,
+					requestBody: {}
+				})
+				sendUserToast(`Job ${this.currentJobId} cancelled`)
+			}
+		} catch (error) {
+			console.error('Error cancelling job:', error)
+			sendUserToast('Could not cancel job', true)
+		} finally {
+			this.cleanup()
+		}
+	}
+
 	async loadConversationMessages(conversationId?: string) {
 		this.page = 1
 		await this.loadMessages(true, conversationId)
@@ -370,6 +394,9 @@ class FlowChatManager {
 					const data = JSON.parse(event.data)
 
 					if (data.type === 'update') {
+						if (data.flow_stream_job_id) {
+							this.currentJobId = data.flow_stream_job_id
+						}
 						// Process new stream content
 						if (data.new_result_stream) {
 							// Stop polling since we are receiving last step streaming
@@ -476,6 +503,9 @@ class FlowChatManager {
 			return
 		}
 
+		// Store the current job ID so it can be cancelled
+		this.currentJobId = jobId
+
 		if (isNewConversation) {
 			await this.#refreshConversations?.()
 		}