server, ui: only offer a working directory when a tool reads it (#26762)

The working directory chip showed up as soon as the server exposed any
builtin tool, so a server started with just get_datetime, or a user who
turned every filesystem tool off in the settings, still got a control
that nothing would read.

Tools now declare whether they resolve their paths and run against the
working directory, next to the write permission they already publish in
the /tools listing. The WebUI shows the chip and enables the /cwd
command only when at least one such tool is both served and left
enabled.

tools/ui/src/lib/components/app/chat/ChatForm/ChatForm.svelte

@@ -156,7 +156,7 @@
 		focusInput: refocusInput,
 		getShowModelSelector: () => showModelSelector,
 		hasPrompts: () => mcpStore.hasPromptsCapability(conversationsStore.getAllMcpServerOverrides()),
-		hasBuiltinTools: () => toolsStore.builtinTools.length > 0,
+		hasCwdTools: () => toolsStore.hasEnabledCwdTools,
 		getCwd: () => cwd,
 		getServerHome: () => toolsStore.serverHome ?? null,
 		openModelSelector: () => chatFormActionsRef?.openModelSelector(),
@@ -651,7 +651,7 @@
 
 	<ContextGaugePopup />
 
-	{#if toolsStore.builtinTools.length > 0}
+	{#if toolsStore.hasEnabledCwdTools}
 		<ChatFormWorkingDirectory
 			directory={cwd}
 			isOpen={pickers.isWorkingDirectoryPickerOpen}

tools/ui/src/lib/constants/chat-commands.ts

@@ -8,7 +8,7 @@ interface ChatCommandsOptions {
 	/** Gates `/prompt`. */
 	hasPrompts: () => boolean;
 	/** Gates `/cwd`. */
-	hasBuiltinTools: () => boolean;
+	hasCwdTools: () => boolean;
 }
 
 /**
@@ -32,7 +32,7 @@ export function getChatCommands(options: ChatCommandsOptions): ChatFormCommand[]
 			description: SET_WORKING_DIRECTORY_LABEL,
 			keywords: ['current working directory'],
 			action: ChatFormCommandAction.CWD,
-			disabled: !options.hasBuiltinTools()
+			disabled: !options.hasCwdTools()
 		},
 		{
 			name: 'model',

tools/ui/src/lib/hooks/use-chat-form-pickers.svelte.ts

@@ -24,7 +24,7 @@ export interface UseChatFormPickersOptions {
 	/** Gates `/prompt`. */
 	hasPrompts: () => boolean;
 	/** Gates `/cwd`. */
-	hasBuiltinTools: () => boolean;
+	hasCwdTools: () => boolean;
 	getCwd: () => string | null;
 	/** Mention search fallback scope. */
 	getServerHome: () => string | null;
@@ -63,7 +63,7 @@ export function useChatFormPickers(opts: UseChatFormPickersOptions) {
 		getChatCommands({
 			showModelSelector: opts.getShowModelSelector(),
 			hasPrompts: opts.hasPrompts,
-			hasBuiltinTools: opts.hasBuiltinTools
+			hasCwdTools: opts.hasCwdTools
 		})
 	);
 

tools/ui/src/lib/stores/tools.svelte.ts

@@ -27,6 +27,9 @@ class ToolsStore {
 	private _loading = $state(false);
 	private _error = $state<string | null>(null);
 	private _disabledTools = $state(new SvelteSet<string>());
+	// builtin tools that resolve their paths against the working directory,
+	// as declared by the server in its `/tools` listing
+	private _cwdAwareTools = $state(new SvelteSet<string>());
 	private _toolsEndpointUnreachable = $state(false);
 	private _serverHome = $state<string | null | undefined>(undefined);
 
@@ -476,6 +479,21 @@ class ToolsStore {
 		return this.getEnabledToolsForLLM().length > 0;
 	}
 
+	/**
+	 * Check if a working directory is worth setting: at least one builtin tool
+	 * that reads it is both served and left enabled by the user.
+	 */
+	get hasEnabledCwdTools(): boolean {
+		return this._builtinTools.some((def) => {
+			const name = def.function.name;
+
+			return (
+				this._cwdAwareTools.has(name) &&
+				!this._disabledTools.has(this.toolKey(ToolSource.BUILTIN, name))
+			);
+		});
+	}
+
 	async fetchBuiltinTools(): Promise<void> {
 		if (this._loading) return;
 
@@ -486,6 +504,9 @@ class ToolsStore {
 		try {
 			const toolInfos = await ToolsService.list();
 			this._builtinTools = toolInfos.map((info) => info.definition);
+			this._cwdAwareTools = new SvelteSet(
+				toolInfos.filter((info) => info.uses_cwd).map((info) => info.tool)
+			);
 		} catch (err) {
 			const errorMessage = err instanceof Error ? err.message : String(err);
 			this._error = errorMessage;

tools/ui/src/lib/types/mcp.d.ts

@@ -292,6 +292,7 @@ export interface ServerBuiltinToolInfo {
 	permissions: {
 		write: boolean;
 	};
+	uses_cwd: boolean;
 	definition: OpenAIToolDefinition;
 }