Ponytail V2

Ponytail for OpenCode 2.x. The upstream OpenCode plugin only supports the V1 plugin API, so OpenCode 2.x refuses to load it. This package is the same ponytail, ported to V2.

Install

opencode plugin add @filecrop/opencode-ponytail-v2

That's it. Ponytail is active in your next OpenCode session. Confirm with opencode plugin list (look for ponytail), then switch levels any time with /ponytail lite|full|ultra|off.

Prefer config files? See other ways to install.

What is ponytail?

Ponytail makes your agent think like the laziest senior dev in the room: before writing code it stops at the first rung that holds (does this need to exist → already in the codebase → stdlib → native platform feature → installed dependency → one line → the minimum that works), while never cutting input validation, error handling, security, or accessibility.

Ponytail is by Dietrich Gebert; see upstream for the ruleset itself. This package does not reimplement it: the ruleset, skills, commands, and instruction builders under vendor/upstream/ are copied verbatim from the pinned upstream release, so what the model sees is byte-identical.

Upstream's plugin fails on OpenCode 2.x with:

Plugin must export a default definition with an id and an effect or setup function

What it does

• Injects the active level's ruleset into the system prompt of every request (lite, full, ultra; off stays silent).
• Registers the six commands: /ponytail, /ponytail-review, /ponytail-audit, /ponytail-debt, /ponytail-gain, /ponytail-help.
• Registers the six bundled skills with the same ids, names, descriptions, and content as upstream.
• Persists /ponytail <level> to the same flag file upstream uses ($XDG_CONFIG_HOME/opencode/.ponytail-active, falling back to ~/.config/opencode/.ponytail-active), so levels stay shared with every other ponytail host.
• Resolves the default level exactly like upstream: PONYTAIL_DEFAULT_MODE → ~/.config/ponytail/config.json (defaultMode) → full.

Deliberately preserved upstream quirk, for parity: a bare /ponytail persists the default level (it does not merely report). A level change is written before the command's prompt is sent, so it applies from that request on.

Requirements

OpenCode 2.x (verified on 2.0.14). For OpenCode 1.x, use upstream's own plugin.

Other ways to install

Add the package to plugins in your OpenCode config. A project config (opencode.json in the repo) scopes it to that project; the global config (~/.config/opencode/opencode.jsonc) applies everywhere:

{
  "$schema": "https://opencode.ai/config.json",
  "plugins": ["@filecrop/opencode-ponytail-v2"]
}

Or from a local checkout (point at the directory, not index.js):

{
  "$schema": "https://opencode.ai/config.json",
  "plugins": ["/path/to/opencode-ponytail-v2"]
}

Update or remove with opencode plugin update / opencode plugin remove.

Why it works on V2

The upstream V1 hooks map to V2 like this:

Upstream (V1)	This package (V2)
experimental.chat.system.transform	ctx.session.hook("context", ...) appending to event.system
config.command + command.execute.before	ctx.command.transform, with execute rendering the same template and persisting /ponytail
config.skills.paths	ctx.skill.transform, registering each vendored SKILL.md

The plugin is a plain { id, setup } object, so it has no runtime dependencies: nothing to install alongside it and nothing to build.

Repo layout

index.js                 V2 plugin entry (id + setup)
src/                     paths, mode state, instructions, commands, skills
vendor/upstream/         upstream content, verbatim (hooks, skills, commands, LICENSE);
                         its package.json marks the vendored CJS builders as CommonJS
scripts/upstream.mjs     sync/check the vendored content against the pinned release
test/plugin.test.js      node --test suite

Updating from upstream

The pinned release is the @dietrichgebert/ponytail version in devDependencies; vendor/upstream/UPSTREAM_VERSION records it.

npm install
npm run check-drift      # fails if vendor/upstream differs from the pinned release
npm run sync-upstream    # after bumping the devDependency; then review the diff
npm test

Scope

OpenCode V2 only. No V1 fallback, no other hosts. This is an unofficial port; see upstream for the ruleset itself. The port aims for exact behavioral parity; if it ever diverges, that is a bug.

Credits & license

MIT. The ruleset, skills, commands, and instruction builders come from ponytail by Dietrich Gebert (MIT); see vendor/upstream/LICENSE.