fix(tui): preserved autocomplete for no-arg slash prompts

- Propagated builtin allowArgs metadata into TUI autocomplete entries.

- Let no-arg slash-looking prompts fall through to prompt-composer completions while keeping argument-capable commands scoped.

- Added regressions for /settings @ and /settings #copy.

packages/coding-agent/src/modes/prompt-action-autocomplete.ts

@@ -95,11 +95,13 @@ function getPromptActionPrefix(textBeforeCursor: string): string | null {
 }
 
 export class PromptActionAutocompleteProvider implements AutocompleteProvider {
+	#commands: SlashCommand[];
 	#baseProvider: CombinedAutocompleteProvider;
 	#actions: PromptActionDefinition[];
 	#basePath: string;
 
 	constructor(commands: SlashCommand[], basePath: string, actions: PromptActionDefinition[]) {
+		this.#commands = commands;
 		this.#baseProvider = new CombinedAutocompleteProvider(commands, basePath);
 		this.#basePath = basePath;
 		this.#actions = actions;
@@ -118,8 +120,13 @@ export class PromptActionAutocompleteProvider implements AutocompleteProvider {
 			leadingSlashStart !== null && !hasPromptTextBeforeCursorLine
 				? textBeforeCursor.slice(leadingSlashStart)
 				: null;
-		if (commandText?.includes(" ")) {
-			return this.#baseProvider.getSuggestions(lines, cursorLine, cursorCol);
+		const spaceIndex = commandText?.indexOf(" ") ?? -1;
+		if (commandText !== null && spaceIndex !== -1) {
+			const commandName = commandText.slice(1, spaceIndex);
+			const command = this.#commands.find(cmd => cmd.name === commandName || cmd.aliases?.includes(commandName));
+			if (command && (!("allowArgs" in command) || command.allowArgs !== false)) {
+				return this.#baseProvider.getSuggestions(lines, cursorLine, cursorCol);
+			}
 		}
 
 		const promptActionPrefix = getPromptActionPrefix(textBeforeCursor);

packages/coding-agent/src/slash-commands/builtin-registry.ts

@@ -2437,6 +2437,7 @@ export const BUILTIN_SLASH_COMMAND_DEFS: ReadonlyArray<BuiltinSlashCommand> = BU
 	command => ({
 		name: command.name,
 		aliases: command.aliases,
+		allowArgs: command.allowArgs === true,
 		description: command.description,
 		subcommands: command.subcommands,
 		inlineHint: command.inlineHint,

packages/coding-agent/src/slash-commands/types.ts

@@ -16,6 +16,8 @@ export interface BuiltinSlashCommand {
 	name: string;
 	aliases?: string[];
 	description: string;
+	/** Whether the command consumes text after the command name. */
+	allowArgs?: boolean;
 	/** Subcommands for dropdown completion (e.g. /mcp add, /mcp list). */
 	subcommands?: SubcommandDef[];
 	/** Static inline hint when command takes a simple argument (no subcommands). */

packages/coding-agent/test/prompt-action-autocomplete.test.ts

@@ -113,7 +113,7 @@ describe("prompt action autocomplete", () => {
 
 	it("treats # prompt-action tokens as literal text inside slash command arguments without completions", async () => {
 		const provider = createPromptActionAutocompleteProvider({
-			commands: [{ name: "rename", description: "Rename current session" }],
+			commands: [{ name: "rename", description: "Rename current session", allowArgs: true }],
 			basePath: "/tmp",
 			keybindings: AppKeybindingsManager.inMemory(),
 			copyCurrentLine: () => {},
@@ -131,12 +131,34 @@ describe("prompt action autocomplete", () => {
 		expect(suggestions).toBeNull();
 	});
 
+	it("returns # prompt-action completions for matched slash commands that reject arguments", async () => {
+		const provider = createPromptActionAutocompleteProvider({
+			commands: [{ name: "settings", description: "Open settings", allowArgs: false }],
+			basePath: "/tmp",
+			keybindings: AppKeybindingsManager.inMemory(),
+			copyCurrentLine: () => {},
+			copyPrompt: () => {},
+			undo: () => {},
+			moveCursorToMessageEnd: () => {},
+			moveCursorToMessageStart: () => {},
+			moveCursorToLineStart: () => {},
+			moveCursorToLineEnd: () => {},
+		});
+
+		const line = "/settings #copy";
+		const suggestions = await provider.getSuggestions([line], 0, line.length);
+
+		expect(suggestions?.prefix).toBe("#copy");
+		expect(suggestions?.items.map(item => item.label)).toEqual(["Copy current line", "Copy whole prompt"]);
+	});
+
 	it("returns slash command argument completions instead of # prompt actions when the command defines them", async () => {
 		const provider = createPromptActionAutocompleteProvider({
 			commands: [
 				{
 					name: "rename",
 					description: "Rename current session",
+					allowArgs: true,
 					getArgumentCompletions: argumentPrefix =>
 						argumentPrefix === "repro #copy"
 							? [{ value: "repro #copy-title", label: "Keep #copy in the title" }]

packages/tui/src/autocomplete.ts

@@ -182,6 +182,8 @@ export interface SlashCommand {
 	aliases?: string[];
 	description?: string;
 	argumentHint?: string;
+	/** Whether the command consumes argument text after the command name. False means the full input stays normal prompt text once args are present. */
+	allowArgs?: boolean;
 	/** Dynamic display-only description for slash-command autocomplete. Must be synchronous and side-effect free. */
 	getAutocompleteDescription?: () => string | undefined;
 	// Function to get argument completions for this command
@@ -427,28 +429,30 @@ export class CombinedAutocompleteProvider implements AutocompleteProvider {
 				// A mid-prompt slash token with no matching skill may still be an
 				// absolute path (`see /tmp`); fall through to file-path completion.
 			} else if (!isMidPromptSkillLookup) {
-				// Submitted slash commands own their argument text. Prompt-composer
-				// completions like `@` file references must not leak into literal
-				// arguments such as `/rename <title>`.
+				// Submitted slash commands own their argument text only when the
+				// matched command accepts args. No-arg slash-looking prompts such
+				// as `/settings @file` still fall through to prompt-composer
+				// completions because submit treats them as normal prompt text.
 				const commandName = commandText.slice(1, spaceIndex); // Command without "/"
 				const argumentText = commandText.slice(spaceIndex + 1); // Text after space
 
 				const command = this.#commands.find(cmd => commandMatchesNameOrAlias(cmd, commandName));
-				if (!command || !("getArgumentCompletions" in command) || !command.getArgumentCompletions) {
-					return null; // No argument completion for this command
-				}
+				if (command && (!("allowArgs" in command) || command.allowArgs !== false)) {
+					if (!("getArgumentCompletions" in command) || !command.getArgumentCompletions) {
+						return null; // No argument completion for this command
+					}
 
-				const argumentSuggestions = await command.getArgumentCompletions(argumentText);
-				if (!Array.isArray(argumentSuggestions) || argumentSuggestions.length === 0) {
-					return null;
-				}
+					const argumentSuggestions = await command.getArgumentCompletions(argumentText);
+					if (!Array.isArray(argumentSuggestions) || argumentSuggestions.length === 0) {
+						return null;
+					}
 
-				return {
-					items: argumentSuggestions,
-					prefix: argumentText,
-				};
+					return {
+						items: argumentSuggestions,
+						prefix: argumentText,
+					};
+				}
 			}
-			if (!isMidPromptSkillLookup) return null;
 		}
 
 		// Check for @ file reference (fuzzy search) - must be after a delimiter or at start

packages/tui/test/autocomplete.test.ts

@@ -124,7 +124,7 @@ describe("CombinedAutocompleteProvider", () => {
 			try {
 				fs.writeFileSync(path.join(baseDir, "copy-target.ts"), "export {};\n");
 				const provider = new CombinedAutocompleteProvider(
-					[{ name: "rename", description: "Rename current session" }],
+					[{ name: "rename", description: "Rename current session", allowArgs: true }],
 					baseDir,
 				);
 				const line = "/rename repro @";
@@ -136,6 +136,24 @@ describe("CombinedAutocompleteProvider", () => {
 			}
 		});
 
+		it("returns @ file-reference completions for matched slash commands that reject arguments", async () => {
+			const baseDir = fs.mkdtempSync(path.join(os.tmpdir(), "autocomplete-settings-args-"));
+			try {
+				fs.writeFileSync(path.join(baseDir, "copy-target.ts"), "export {};\n");
+				const provider = new CombinedAutocompleteProvider(
+					[{ name: "settings", description: "Open settings", allowArgs: false }],
+					baseDir,
+				);
+				const line = "/settings @";
+				const result = await provider.getSuggestions([line], 0, line.length);
+
+				expect(result?.prefix).toBe("@");
+				expect(result?.items.map(item => item.value)).toContain("@copy-target.ts");
+			} finally {
+				fs.rmSync(baseDir, { recursive: true, force: true });
+			}
+		});
+
 		it("returns slash command argument completions instead of @ file references when the command defines them", async () => {
 			const baseDir = fs.mkdtempSync(path.join(os.tmpdir(), "autocomplete-rename-args-"));
 			try {
@@ -145,6 +163,7 @@ describe("CombinedAutocompleteProvider", () => {
 						{
 							name: "rename",
 							description: "Rename current session",
+							allowArgs: true,
 							getArgumentCompletions: argumentPrefix =>
 								argumentPrefix === "repro @"
 									? [{ value: "repro @literal", label: "Keep @ in the title" }]