fix(coding-agent): support all-argument prompt defaults closes #6695

packages/coding-agent/CHANGELOG.md

@@ -8,6 +8,7 @@
 
 ### Fixed
 
+- Fixed prompt-template defaults for all arguments (`${@:-default}` and `${ARGUMENTS:-default}`) ([#6695](https://github.com/earendil-works/pi/issues/6695)).
 - Fixed obsolete custom UI, custom tool, and custom editor examples in the extension documentation ([#6735](https://github.com/earendil-works/pi/issues/6735)).
 - Fixed Kimi Coding sessions to show API-equivalent implied costs with the subscription indicator.
 - Fixed OpenAI Responses early stream endings to trigger automatic retry instead of ending the agent run ([#6727](https://github.com/earendil-works/pi/issues/6727)).

packages/coding-agent/docs/prompt-templates.md

@@ -69,6 +69,7 @@ Templates support positional arguments, defaults, and simple slicing:
 - `$1`, `$2`, ... positional args
 - `$@` or `$ARGUMENTS` for all args joined
 - `${1:-default}` uses arg 1 when present/non-empty, otherwise `default`
+- `${@:-default}` or `${ARGUMENTS:-default}` uses all arguments when present/non-empty, otherwise `default`
 - `${@:N}` for args from the Nth position (1-indexed)
 - `${@:N:L}` for `L` args starting at N
 

packages/coding-agent/src/core/prompt-templates.ts

@@ -60,6 +60,7 @@ export function parseCommandArgs(argsString: string): string[] {
  * - $1, $2, ... for positional args
  * - $@ and $ARGUMENTS for all args
  * - ${N:-default} for positional arg N with default when missing/empty
+ * - ${@:-default} and ${ARGUMENTS:-default} for all args with a default when empty
  * - ${@:N} for args from Nth onwards (bash-style slicing)
  * - ${@:N:L} for L args starting from Nth
  *
@@ -70,11 +71,11 @@ export function substituteArgs(content: string, args: string[]): string {
 	const allArgs = args.join(" ");
 
 	return content.replace(
-		/\$\{(\d+):-([^}]*)\}|\$\{@:(\d+)(?::(\d+))?\}|\$(ARGUMENTS|@|\d+)/g,
-		(_match, defaultNum, defaultValue, sliceStart, sliceLength, simple) => {
-			if (defaultNum) {
-				const index = parseInt(defaultNum, 10) - 1;
-				const value = args[index];
+		/\$\{(\d+|ARGUMENTS|@):-([^}]*)\}|\$\{@:(\d+)(?::(\d+))?\}|\$(ARGUMENTS|@|\d+)/g,
+		(_match, defaultTarget, defaultValue, sliceStart, sliceLength, simple) => {
+			if (defaultTarget) {
+				const value =
+					defaultTarget === "@" || defaultTarget === "ARGUMENTS" ? allArgs : args[parseInt(defaultTarget, 10) - 1];
 				return value ? value : defaultValue;
 			}
 

packages/coding-agent/test/prompt-templates.test.ts

@@ -199,6 +199,15 @@ describe("substituteArgs - positional defaults", () => {
 		expect(substituteArgs(`List exactly \${1:-7} next steps`, [])).toBe("List exactly 7 next steps");
 	});
 
+	test("should support defaults for all arguments", () => {
+		const template = `\${@:-default}\n\${ARGUMENTS:-default}`;
+
+		expect(substituteArgs(template, [])).toBe("default\ndefault");
+		expect(substituteArgs(template, ["This", "would", "be", "the", "arguments"])).toBe(
+			"This would be the arguments\nThis would be the arguments",
+		);
+	});
+
 	test("should use positional arg when present", () => {
 		expect(substituteArgs(`List exactly \${1:-7} next steps`, ["3"])).toBe("List exactly 3 next steps");
 	});