diff --git a/.opencode/plugins/ponytail-frontmatter.cjs b/.opencode/plugins/ponytail-frontmatter.cjs
new file mode 100644
index 0000000..1145929
--- /dev/null
+++ b/.opencode/plugins/ponytail-frontmatter.cjs
@@ -0,0 +1,23 @@
+'use strict';
+
+// ponytail command-file frontmatter parser.
+//
+// Pulled out of ponytail.mjs so the plugin module's only top-level export is
+// the plugin function itself. OpenCode's legacy plugin loader (the one that
+// runs before v1 plugins are detected) treats every function exported from a
+// plugin module as a plugin; calling the frontmatter parser as one threw
+// "path must be a string or a file descriptor" because it got the plugin
+// context object as its first argument. Keeping the parser in its own module
+// leaves exactly one plugin-shaped export on ponytail.mjs.
+
+function parseCommandFile(filePath) {
+  const fs = require('fs');
+  const content = fs.readFileSync(filePath, 'utf8');
+  // Tolerate CRLF: a Windows checkout (autocrlf) delivers \r\n, npm ships \n.
+  const match = content.match(/^---\r?\n([\s\S]*?)\r?\n---\r?\n([\s\S]*)$/);
+  if (!match) return null;
+  const description = match[1].match(/description:\s*(.+)/)?.[1]?.trim();
+  return { description, template: match[2].trim() };
+}
+
+module.exports = { parseCommandFile };
diff --git a/.opencode/plugins/ponytail.mjs b/.opencode/plugins/ponytail.mjs
index 4db6f4a..6a77468 100644
--- a/.opencode/plugins/ponytail.mjs
+++ b/.opencode/plugins/ponytail.mjs
@@ -21,6 +21,7 @@ const __dirname = path.dirname(fileURLToPath(import.meta.url));
 const require = createRequire(import.meta.url);
 const { getPonytailInstructions } = require('../../hooks/ponytail-instructions');
 const { getDefaultMode, normalizePersistedMode } = require('../../hooks/ponytail-config');
+const { parseCommandFile } = require('./ponytail-frontmatter.cjs');
 
 // OpenCode has no flag-file convention of its own; keep mode beside its config.
 const statePath = path.join(
@@ -42,15 +43,6 @@ function writeMode(mode) {
   fs.writeFileSync(statePath, mode);
 }
 
-export function parseCommandFile(filePath) {
-  const content = fs.readFileSync(filePath, 'utf8');
-  // Tolerate CRLF: a Windows checkout (autocrlf) delivers \r\n, npm ships \n.
-  const match = content.match(/^---\r?\n([\s\S]*?)\r?\n---\r?\n([\s\S]*)$/);
-  if (!match) return null;
-  const description = match[1].match(/description:\s*(.+)/)?.[1]?.trim();
-  return { description, template: match[2].trim() };
-}
-
 export default async ({ client } = {}) => {
   const log = (level, message) => {
     try { client && client.app && client.app.log({ body: { service: 'ponytail', level, message } }); } catch (e) {}
diff --git a/tests/opencode-plugin.test.js b/tests/opencode-plugin.test.js
index bb5b8ca..d598643 100644
--- a/tests/opencode-plugin.test.js
+++ b/tests/opencode-plugin.test.js
@@ -23,7 +23,11 @@ test.before(async () => {
   const url = pathToFileURL(path.join(__dirname, '..', '.opencode', 'plugins', 'ponytail.mjs'));
   const mod = await import(url);
   loadPlugin = mod.default;
-  parseCommandFile = mod.parseCommandFile;
+  // The frontmatter parser used to be exported from the plugin module itself.
+  // OpenCode's legacy loader treats every exported function as a plugin and
+  // tried to invoke it with the plugin context object, which crashed. The
+  // parser now lives in its own .cjs sibling; require it directly.
+  parseCommandFile = require(path.join(__dirname, '..', '.opencode', 'plugins', 'ponytail-frontmatter.cjs')).parseCommandFile;
 });
 
 function transform(hooks) {