fix: handle undefined result from custom() in RPC mode for ask_user_questions (#156, #165, #171) (#199)

In RPC mode, `ctx.ui.custom()` returns `undefined as never`, causing
`showInterviewRound` to return undefined and `Object.keys(result.answers)`
to throw TypeError.

When `showInterviewRound` returns undefined (RPC mode), fall back to
sequential `ctx.ui.select()` calls for each question, forwarding the
abort signal (#171) and supporting `allowMultiple` (#165).

- Add `allowMultiple` to `ExtensionUIDialogOptions`
- Widen `select()` return type to `string | string[] | undefined`
- Add `allowMultiple` to RPC select request and `values` array to response
- Update RPC `select()` to forward `allowMultiple` and parse array responses
- Guard existing `ctx.ui.select()` callers against the widened return type

Co-authored-by: Claude Opus 4.6 <noreply@anthropic.com>

packages/pi-coding-agent/src/core/extensions/types.ts

@@ -86,6 +86,8 @@ export interface ExtensionUIDialogOptions {
 	signal?: AbortSignal;
 	/** Timeout in milliseconds. Dialog auto-dismisses with live countdown display. */
 	timeout?: number;
+	/** When true, the user can select multiple options. The return type becomes `string[]`. */
+	allowMultiple?: boolean;
 }
 
 /** Placement for extension widgets. */
@@ -105,8 +107,8 @@ export type TerminalInputHandler = (data: string) => { consume?: boolean; data?:
  * Each mode (interactive, RPC, print) provides its own implementation.
  */
 export interface ExtensionUIContext {
-	/** Show a selector and return the user's choice. */
-	select(title: string, options: string[], opts?: ExtensionUIDialogOptions): Promise<string | undefined>;
+	/** Show a selector and return the user's choice. When `opts.allowMultiple` is true, returns an array. */
+	select(title: string, options: string[], opts?: ExtensionUIDialogOptions): Promise<string | string[] | undefined>;
 
 	/** Show a confirmation dialog. */
 	confirm(title: string, message: string, opts?: ExtensionUIDialogOptions): Promise<boolean>;

packages/pi-coding-agent/src/modes/rpc/rpc-mode.ts

@@ -119,8 +119,8 @@ export async function runRpcMode(session: AgentSession): Promise<never> {
 	 */
 	const createExtensionUIContext = (): ExtensionUIContext => ({
 		select: (title, options, opts) =>
-			createDialogPromise(opts, undefined, { method: "select", title, options, timeout: opts?.timeout }, (r) =>
-				"cancelled" in r && r.cancelled ? undefined : "value" in r ? r.value : undefined,
+			createDialogPromise(opts, undefined, { method: "select", title, options, timeout: opts?.timeout, allowMultiple: opts?.allowMultiple }, (r) =>
+				"cancelled" in r && r.cancelled ? undefined : "values" in r ? r.values : "value" in r ? r.value : undefined,
 			),
 
 		confirm: (title, message, opts) =>

packages/pi-coding-agent/src/modes/rpc/rpc-types.ts

@@ -210,7 +210,7 @@ export type RpcResponse =
 
 /** Emitted when an extension needs user input */
 export type RpcExtensionUIRequest =
-	| { type: "extension_ui_request"; id: string; method: "select"; title: string; options: string[]; timeout?: number }
+	| { type: "extension_ui_request"; id: string; method: "select"; title: string; options: string[]; timeout?: number; allowMultiple?: boolean }
 	| { type: "extension_ui_request"; id: string; method: "confirm"; title: string; message: string; timeout?: number }
 	| {
 			type: "extension_ui_request";
@@ -253,6 +253,7 @@ export type RpcExtensionUIRequest =
 /** Response to an extension UI request */
 export type RpcExtensionUIResponse =
 	| { type: "extension_ui_response"; id: string; value: string }
+	| { type: "extension_ui_response"; id: string; values: string[] }
 	| { type: "extension_ui_response"; id: string; confirmed: boolean }
 	| { type: "extension_ui_response"; id: string; cancelled: true };
 

src/resources/extensions/ask-user-questions.ts

@@ -144,6 +144,46 @@ export default function AskUserQuestions(pi: ExtensionAPI) {
 			// Delegate to shared interview UI
 			const result = await showInterviewRound(params.questions, {}, ctx);
 
+			// RPC mode fallback: custom() returns undefined, so showInterviewRound
+			// may return undefined. Fall back to sequential ctx.ui.select() calls.
+			if (!result) {
+				const answers: Record<string, { answers: string[] }> = {};
+				for (const q of params.questions) {
+					const options = q.options.map((o) => o.label);
+					if (!q.allowMultiple) {
+						options.push(OTHER_OPTION_LABEL);
+					}
+					const selected = await ctx.ui.select(
+						`${q.header}: ${q.question}`,
+						options,
+						{ signal, ...(q.allowMultiple ? { allowMultiple: true } : {}) },
+					);
+					if (selected === undefined) {
+						return errorResult("ask_user_questions was cancelled", params.questions);
+					}
+					answers[q.id] = {
+						answers: Array.isArray(selected) ? selected : [selected],
+					};
+				}
+				const roundResult: RoundResult = {
+					endInterview: false,
+					answers: Object.fromEntries(
+						Object.entries(answers).map(([id, a]) => [
+							id,
+							{ selected: a.answers.length === 1 ? a.answers[0] : a.answers, notes: "" },
+						]),
+					),
+				};
+				return {
+					content: [{ type: "text" as const, text: JSON.stringify({ answers }) }],
+					details: {
+						questions: params.questions,
+						response: roundResult,
+						cancelled: false,
+					} satisfies LocalResultDetails,
+				};
+			}
+
 			// Check if cancelled (empty answers = user exited)
 			const hasAnswers = Object.keys(result.answers).length > 0;
 			if (!hasAnswers) {

src/resources/extensions/search-the-web/command-search-provider.ts

@@ -81,7 +81,7 @@ export function registerSearchProviderCommand(pi: ExtensionAPI): void {
           return
         }
 
-        chosen = parseSelectChoice(result)
+        chosen = parseSelectChoice(Array.isArray(result) ? result[0] : result)
       }
 
       setSearchProviderPreference(chosen)