webui: add OAI-Compat Harmony tool-call live streaming visualization and persistence in chat UI

- Purely visual and diagnostic change, no effect on model context, prompt
  construction, or inference behavior

- Captured assistant tool call payloads during streaming and non-streaming
  completions, and persisted them in chat state and storage for downstream use

- Exposed parsed tool call labels beneath the assistant's model info line
  with graceful fallback when parsing fails

- Added tool call badges beneath assistant responses that expose JSON tooltips
  and copy their payloads when clicked, matching the existing model badge styling

- Added a user-facing setting to toggle tool call visibility to the Developer
  settings section directly under the model selector option

Author: ServeurpersoCom

tools/server/webui/src/lib/components/app/chat/ChatMessages/ChatMessage.svelte

@@ -2,6 +2,7 @@
 	import { getDeletionInfo } from '$lib/stores/chat.svelte';
 	import { copyToClipboard } from '$lib/utils/copy';
 	import { isIMEComposing } from '$lib/utils/is-ime-composing';
+	import type { ApiChatCompletionToolCall } from '$lib/types/api';
 	import ChatMessageAssistant from './ChatMessageAssistant.svelte';
 	import ChatMessageUser from './ChatMessageUser.svelte';
 
@@ -54,6 +55,29 @@
 		return null;
 	});
 
+	let toolCallContent = $derived.by((): ApiChatCompletionToolCall[] | string | null => {
+		if (message.role === 'assistant') {
+			const trimmedToolCalls = message.toolCalls?.trim();
+
+			if (!trimmedToolCalls) {
+				return null;
+			}
+
+			try {
+				const parsed = JSON.parse(trimmedToolCalls);
+
+				if (Array.isArray(parsed)) {
+					return parsed as ApiChatCompletionToolCall[];
+				}
+			} catch {
+				// Harmony-only path: fall back to the raw string so issues surface visibly.
+			}
+
+			return trimmedToolCalls;
+		}
+		return null;
+	});
+
 	function handleCancelEdit() {
 		isEditing = false;
 		editedContent = message.content;
@@ -171,5 +195,6 @@
 		{showDeleteDialog}
 		{siblingInfo}
 		{thinkingContent}
+		{toolCallContent}
 	/>
 {/if}

tools/server/webui/src/lib/components/app/chat/ChatMessages/ChatMessageAssistant.svelte

@@ -11,7 +11,8 @@
 		Gauge,
 		Clock,
 		WholeWord,
-		ChartNoAxesColumn
+		ChartNoAxesColumn,
+		Wrench
 	} from '@lucide/svelte';
 	import { Button } from '$lib/components/ui/button';
 	import { Checkbox } from '$lib/components/ui/checkbox';
@@ -21,6 +22,7 @@
 	import { config } from '$lib/stores/settings.svelte';
 	import { modelName as serverModelName } from '$lib/stores/server.svelte';
 	import { copyToClipboard } from '$lib/utils/copy';
+	import type { ApiChatCompletionToolCall } from '$lib/types/api';
 
 	interface Props {
 		class?: string;
@@ -51,6 +53,7 @@
 		siblingInfo?: ChatMessageSiblingInfo | null;
 		textareaElement?: HTMLTextAreaElement;
 		thinkingContent: string | null;
+		toolCallContent: ApiChatCompletionToolCall[] | string | null;
 	}
 
 	let {
@@ -76,9 +79,17 @@
 		shouldBranchAfterEdit = false,
 		siblingInfo = null,
 		textareaElement = $bindable(),
-		thinkingContent
+		thinkingContent,
+		toolCallContent = null
 	}: Props = $props();
 
+	const parsedToolCalls = $derived(() =>
+		Array.isArray(toolCallContent) ? (toolCallContent as ApiChatCompletionToolCall[]) : null
+	);
+	const fallbackToolCallContent = $derived(() =>
+		typeof toolCallContent === 'string' ? toolCallContent : null
+	);
+
 	const processingState = useProcessingState();
 	let currentConfig = $derived(config());
 	let serverModel = $derived(serverModelName());
@@ -97,6 +108,58 @@
 
 		void copyToClipboard(model ?? '');
 	}
+
+	function formatToolCallBadge(toolCall: ApiChatCompletionToolCall, index: number) {
+		const callNumber = index + 1;
+		const functionName = toolCall.function?.name?.trim();
+		const label = functionName || `Call #${callNumber}`;
+
+		const payload: Record<string, unknown> = {};
+
+		const id = toolCall.id?.trim();
+		if (id) {
+			payload.id = id;
+		}
+
+		const type = toolCall.type?.trim();
+		if (type) {
+			payload.type = type;
+		}
+
+		if (toolCall.function) {
+			const fnPayload: Record<string, unknown> = {};
+
+			const name = toolCall.function.name?.trim();
+			if (name) {
+				fnPayload.name = name;
+			}
+
+			const rawArguments = toolCall.function.arguments?.trim();
+			if (rawArguments) {
+				try {
+					fnPayload.arguments = JSON.parse(rawArguments);
+				} catch {
+					fnPayload.arguments = rawArguments;
+				}
+			}
+
+			if (Object.keys(fnPayload).length > 0) {
+				payload.function = fnPayload;
+			}
+		}
+
+		const formattedPayload = JSON.stringify(payload, null, 2);
+
+		return {
+			label,
+			tooltip: formattedPayload,
+			copyValue: formattedPayload
+		};
+	}
+
+	function handleCopyToolCall(payload: string) {
+		void copyToClipboard(payload, 'Tool call copied to clipboard');
+	}
 </script>
 
 <div
@@ -189,6 +252,49 @@
 			</span>
 		{/if}
 
+		{#if config().showToolCalls}
+			{@const toolCalls = parsedToolCalls()}
+			{@const fallbackToolCalls = fallbackToolCallContent()}
+			{#if (toolCalls && toolCalls.length > 0) || fallbackToolCalls}
+				<span class="inline-flex flex-wrap items-center gap-2 text-xs text-muted-foreground">
+					<span class="inline-flex items-center gap-1">
+						<Wrench class="h-3.5 w-3.5" />
+
+						<span>Tool calls:</span>
+					</span>
+
+					{#if toolCalls && toolCalls.length > 0}
+						{#each toolCalls as toolCall, index (toolCall.id ?? `${index}`)}
+							{@const badge = formatToolCallBadge(toolCall, index)}
+							<button
+								type="button"
+								class="tool-call-badge inline-flex cursor-pointer items-center gap-1 rounded-sm bg-muted-foreground/15 px-1.5 py-0.75"
+								title={badge.tooltip}
+								aria-label={`Copy tool call ${badge.label}`}
+								onclick={() => handleCopyToolCall(badge.copyValue)}
+							>
+								{badge.label}
+
+								<Copy class="ml-1 h-3 w-3" />
+							</button>
+						{/each}
+					{:else if fallbackToolCalls}
+						<button
+							type="button"
+							class="tool-call-badge tool-call-badge--fallback inline-flex cursor-pointer items-center gap-1 rounded-sm bg-muted-foreground/15 px-1.5 py-0.75"
+							title={fallbackToolCalls}
+							aria-label="Copy tool call payload"
+							onclick={() => handleCopyToolCall(fallbackToolCalls)}
+						>
+							{fallbackToolCalls}
+
+							<Copy class="ml-1 h-3 w-3" />
+						</button>
+					{/if}
+				</span>
+			{/if}
+		{/if}
+
 		{#if currentConfig.showMessageStats && message.timings && message.timings.predicted_n && message.timings.predicted_ms}
 			{@const tokensPerSecond = (message.timings.predicted_n / message.timings.predicted_ms) * 1000}
 			<span class="inline-flex items-center gap-2 text-xs text-muted-foreground">
@@ -287,4 +393,17 @@
 		white-space: pre-wrap;
 		word-break: break-word;
 	}
+
+	.tool-call-badge {
+		max-width: 12rem;
+		white-space: nowrap;
+		overflow: hidden;
+		text-overflow: ellipsis;
+	}
+
+	.tool-call-badge--fallback {
+		max-width: 20rem;
+		white-space: normal;
+		word-break: break-word;
+	}
 </style>

tools/server/webui/src/lib/components/app/chat/ChatSettings/ChatSettingsDialog.svelte

@@ -226,6 +226,11 @@
 					label: 'Enable model selector',
 					type: 'checkbox'
 				},
+				{
+					key: 'showToolCalls',
+					label: 'Show tool call labels',
+					type: 'checkbox'
+				},
 				{
 					key: 'disableReasoningFormat',
 					label: 'Show raw LLM output',

tools/server/webui/src/lib/constants/settings-config.ts

@@ -6,6 +6,7 @@ export const SETTING_CONFIG_DEFAULT: Record<string, string | number | boolean> =
 	theme: 'system',
 	showTokensPerSecond: false,
 	showThoughtInProgress: false,
+	showToolCalls: false,
 	disableReasoningFormat: false,
 	keepStatsVisible: false,
 	showMessageStats: true,
@@ -80,6 +81,8 @@ export const SETTING_CONFIG_INFO: Record<string, string> = {
 	custom: 'Custom JSON parameters to send to the API. Must be valid JSON format.',
 	showTokensPerSecond: 'Display generation speed in tokens per second during streaming.',
 	showThoughtInProgress: 'Expand thought process by default when generating messages.',
+	showToolCalls:
+		'Display tool call labels and payloads from Harmony-compatible delta.tool_calls data below assistant messages.',
 	disableReasoningFormat:
 		'Show raw LLM output without backend parsing and frontend Markdown rendering to inspect streaming across different models.',
 	keepStatsVisible: 'Keep processing statistics visible after generation finishes.',