OpenCode plugin fails to load in 4.8.4: "path must be a string or a file descriptor" (fixed at HEAD, needs release)

[UnoSee]

Problem

Installing @dietrichgebert/ponytail as an OpenCode plugin per the README:

{ "plugin": ["@dietrichgebert/ponytail"] }

fails at startup with:

ERROR failed to load plugin path=@dietrichgebert/ponytail error="path must be a string or a file descriptor"

Reproduced on opencode 1.18.11, ponytail 4.8.4 (npm latest), Linux x64, node 26 / bundled bun.

Root cause

.opencode/plugins/ponytail.mjs in 4.8.4 exports parseCommandFile as a named export alongside the default export:

export function parseCommandFile(filePath) { ... }   // line 45
export default async ({ client } = {}) => { ... }

OpenCode's legacy plugin loader (packages/opencode/src/plugin/index.ts, getLegacyPlugins) treats every exported function as a plugin instance and invokes each with the plugin input object:

for (const entry of Object.values(mod)) {
  ...
  const plugin = getServerPlugin(entry)
  if (!plugin) throw new TypeError("Plugin export is not a function")
  result.push(plugin)
}

So opencode calls parseCommandFile(pluginInput) → fs.readFileSync(undefined, 'utf8') → TypeError [ERR_INVALID_ARG_TYPE]: path must be a string or a file descriptor.

Already fixed at HEAD

The fix is on main — the parser was moved to .opencode/plugins/ponytail-frontmatter.cjs and the test comment in tests/opencode-plugin.test.js documents exactly this crash. It just isn't on npm yet (4.8.4 published 2026-06-29 predates it).

Request

Publish 4.8.5 (or 4.9.0) so { "plugin": ["@dietrichgebert/ponytail"] } works from npm.

Workaround (for anyone hitting this now)

Vendor the fixed files locally and point opencode at the file path:

mkdir -p ~/.config/opencode/plugins/ponytail/.opencode/plugins
cd ~/.config/opencode/plugins/ponytail
curl -sL https://raw.githubusercontent.com/DietrichGebert/ponytail/main/.opencode/plugins/ponytail.mjs -o .opencode/plugins/ponytail.mjs
curl -sL https://raw.githubusercontent.com/DietrichGebert/ponytail/main/.opencode/plugins/ponytail-frontmatter.cjs -o .opencode/plugins/ponytail-frontmatter.cjs
cp -r $(npm root -g 2>/dev/null || echo ~/.config/opencode/node_modules)/@dietrichgebert/ponytail/hooks .
cp -r ~/.config/opencode/node_modules/@dietrichgebert/ponytail/skills .
cp -r ~/.config/opencode/node_modules/@dietrichgebert/ponytail/.opencode/command .opencode/command

The directory layout must mirror the npm package (../../hooks resolves from .opencode/plugins/ up to the package root — symlinks do not work through createRequire, copy the dirs).

{ "plugin": ["./plugins/ponytail/.opencode/plugins/ponytail.mjs"] }

Verified: plugin loads, /ponytail ultra registers and persists mode, system prompt injection works.