feat(pi-extension): autocomplete /ponytail arguments (#1080)

* feat(pi-extension): autocomplete /ponytail arguments

Wire getArgumentCompletions into the /ponytail command, mirroring Pi's
built-in /mcp pattern: first word completes the modes (lite, full,
ultra, off) plus status and default; default <mode> completes runtime
levels on the second word. Unknown or extra words return null.

* pi: complete values only, no second copy of the level descriptions

* pi: every completion is a full command, Enter submits it

---------

Co-authored-by: Dietrich Gebert <dietrichgebert@gmail.com>

Author: ruttybob

pi-extension/index.js

@@ -21,6 +21,14 @@ export const readQuietStartup = getQuietStartup;
 const RUNTIME_MODE_LIST = RUNTIME_MODES.join("|");
 const PONYTAIL_COMMAND_DESCRIPTION = `Set mode: ${RUNTIME_MODE_LIST}. Commands: status, default <mode>`;
 
+// Every item is a complete command: pi submits on Enter, so a bare "default" would run without a mode.
+// Values only: per-level descriptions would be a second copy of the Levels table in SKILL.md.
+export function completePonytailArgs(prefix) {
+  const typed = String(prefix || "").trimStart();
+  const values = [...RUNTIME_MODES, "status", ...RUNTIME_MODES.map((m) => `default ${m}`)].filter((v) => v.startsWith(typed));
+  return values.length ? values.map((value) => ({ value, label: value })) : null;
+}
+
 export function resolveSessionMode(entries, fallbackMode = DEFAULT_MODE) {
   const fallback = normalizePersistedMode(fallbackMode) || DEFAULT_MODE;
   if (!Array.isArray(entries)) return fallback;
@@ -118,6 +126,7 @@ export default function ponytailExtension(pi) {
 
   pi.registerCommand("ponytail", {
     description: PONYTAIL_COMMAND_DESCRIPTION,
+    getArgumentCompletions: (prefix) => completePonytailArgs(prefix),
     handler: async (args, ctx) => {
       const parsed = parsePonytailCommand(args, configuredDefaultMode, currentMode);
 

pi-extension/test/extension.test.js

@@ -4,7 +4,7 @@ import { tmpdir } from "node:os";
 import { join } from "node:path";
 import test from "node:test";
 
-import ponytailExtension from "../index.js";
+import ponytailExtension, { parsePonytailCommand } from "../index.js";
 
 function createPiHarness() {
   const events = new Map();
@@ -327,3 +327,22 @@ test("PONYTAIL_HIDE_STATUS=0 does not hide the indicator", async () => withTempC
 
   assert.ok(statusWrites.length > 0, "0 must be treated as 'do not hide'");
 }));
+
+test("/ponytail autocompletes modes, commands and default <mode>", () => {
+  const { commands } = createPiHarness();
+  const complete = (prefix) => commands.get("ponytail").getArgumentCompletions(prefix);
+
+  assert.deepEqual(complete("").map((item) => item.value),
+    ["off", "lite", "full", "ultra", "status", "default off", "default lite", "default full", "default ultra"]);
+  assert.deepEqual(complete("fu").map((item) => item.value), ["full"]);
+  assert.deepEqual(complete("default ").map((item) => item.value), ["default off", "default lite", "default full", "default ultra"]);
+  assert.deepEqual(complete("default l").map((item) => item.value), ["default lite"]);
+  assert.deepEqual(complete("default").map((item) => item.value),
+    ["default off", "default lite", "default full", "default ultra"], "never a bare default: Enter would submit it without a mode");
+  assert.equal(complete("status x"), null, "no command takes a second word after status");
+  assert.equal(complete("lite x"), null);
+  assert.equal(complete("bogus"), null, "nothing matches an unknown prefix");
+  for (const { value } of complete("")) {
+    assert.notEqual(parsePonytailCommand(value).type, "invalid", `Enter on "${value}" must run a valid command`);
+  }
+});