fix(tui): await async slash command completions closes #2719

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

@@ -966,7 +966,7 @@ export interface RegisteredCommand {
 	name: string;
 	sourceInfo: SourceInfo;
 	description?: string;
-	getArgumentCompletions?: (argumentPrefix: string) => AutocompleteItem[] | null;
+	getArgumentCompletions?: (argumentPrefix: string) => AutocompleteItem[] | null | Promise<AutocompleteItem[] | null>;
 	handler: (args: string, ctx: ExtensionCommandContext) => Promise<void>;
 }
 

packages/tui/CHANGELOG.md

@@ -2,6 +2,10 @@
 
 ## [Unreleased]
 
+### Fixed
+
+- Fixed slash-command argument autocomplete to await async `getArgumentCompletions()` results and ignore invalid return values, preventing crashes when extension commands provide asynchronous completions ([#2719](https://github.com/badlogic/pi-mono/issues/2719))
+
 ## [0.64.0] - 2026-03-29
 
 ### Fixed

packages/tui/src/autocomplete.ts

@@ -218,12 +218,14 @@ export interface AutocompleteItem {
 	description?: string;
 }
 
+type Awaitable<T> = T | Promise<T>;
+
 export interface SlashCommand {
 	name: string;
 	description?: string;
 	// Function to get argument completions for this command
 	// Returns null if no argument completion is available
-	getArgumentCompletions?(argumentPrefix: string): AutocompleteItem[] | null;
+	getArgumentCompletions?(argumentPrefix: string): Awaitable<AutocompleteItem[] | null>;
 }
 
 export interface AutocompleteSuggestions {
@@ -332,8 +334,8 @@ export class CombinedAutocompleteProvider implements AutocompleteProvider {
 				return null;
 			}
 
-			const argumentSuggestions = command.getArgumentCompletions(argumentText);
-			if (!argumentSuggestions || argumentSuggestions.length === 0) {
+			const argumentSuggestions = await command.getArgumentCompletions(argumentText);
+			if (!Array.isArray(argumentSuggestions) || argumentSuggestions.length === 0) {
 				return null;
 			}
 

packages/tui/src/components/editor.ts

@@ -2141,7 +2141,7 @@ export class Editor implements Component, Focusable {
 
 		this.autocompleteAbort = undefined;
 
-		if (!suggestions || suggestions.items.length === 0) {
+		if (!suggestions || !Array.isArray(suggestions.items) || suggestions.items.length === 0) {
 			this.cancelAutocomplete();
 			this.tui.requestRender();
 			return;

packages/tui/test/editor.test.ts

@@ -2458,6 +2458,48 @@ describe("Editor component", () => {
 			assert.strictEqual(editor.getText(), "/model gpt-4o-mini");
 		});
 
+		it("awaits async slash command argument completions", async () => {
+			const editor = new Editor(createTestTUI(), defaultEditorTheme);
+			const provider = new CombinedAutocompleteProvider([
+				{
+					name: "load-skills",
+					description: "Load skills",
+					getArgumentCompletions: async (prefix) =>
+						prefix.startsWith("s") ? [{ value: "skill-a", label: "skill-a" }] : null,
+				},
+			]);
+			editor.setAutocompleteProvider(provider);
+			editor.setText("/load-skills ");
+
+			editor.handleInput("s");
+			await flushAutocomplete();
+			assert.strictEqual(editor.isShowingAutocomplete(), true);
+
+			editor.handleInput("\t");
+			assert.strictEqual(editor.getText(), "/load-skills skill-a");
+			assert.strictEqual(editor.isShowingAutocomplete(), false);
+		});
+
+		it("ignores invalid slash command argument completion results", async () => {
+			const editor = new Editor(createTestTUI(), defaultEditorTheme);
+			const provider = new CombinedAutocompleteProvider([
+				{
+					name: "load-skills",
+					description: "Load skills",
+					getArgumentCompletions: (() => "not-an-array") as unknown as (
+						argumentPrefix: string,
+					) => Promise<{ value: string; label: string }[] | null>,
+				},
+			]);
+			editor.setAutocompleteProvider(provider);
+			editor.setText("/load-skills ");
+
+			editor.handleInput("s");
+			await flushAutocomplete();
+			assert.strictEqual(editor.isShowingAutocomplete(), false);
+			assert.strictEqual(editor.getText(), "/load-skills s");
+		});
+
 		it("does not show argument completions when command has no argument completer", async () => {
 			const editor = new Editor(createTestTUI(), defaultEditorTheme);
 			const provider = new CombinedAutocompleteProvider([