dsh-ponytail

Ponytail, lazy senior dev mode, as a DeepSeek Harness plugin.

Adapted from DietrichGebert/ponytail (MIT). "He says nothing. He writes one line. It works."

Capability	Extension point	Effect
Always-on ruleset	ctx.systemPrompt.section()	While a level other than off is active, the mode-filtered ponytail ruleset is part of every request.
Six skills	ctx.skills.registerProvider()	ponytail, ponytail-review, ponytail-audit, ponytail-debt, ponytail-gain, ponytail-help load through the skill tool — and so appear as /ponytail-review, /ponytail-audit, … in the composer, which is DSH's own command surface for user-invocable skills.
Level control	ctx.tools.register() + ctx.commands.register() + ctx.on('session/event')	The model calls the ponytail tool; the human types /ponytail [lite|full|ultra|review|off] or just says stop ponytail / normal mode.
Settings card	ctx.settings.installSection() + settings.plugin.item	A Ponytail card in Settings → Plugins → Plugin configuration, collapsed like the shipped cards and expanding to an Off/Lite/Full/Ultra picker.
Composer chip	conversation.input.left	A read-only level chip in the composer tool row, so the active level is visible without opening Settings. Hidden while the level is off.
Localized copy	ctx.locale.register()	The card and the chip ship en + zh dictionaries under the ponytail locale namespace.

The ladder

Seven rungs — YAGNI, reuse, stdlib, native platform, already-installed dependency, one line, then the minimum code that works. skills/ponytail/SKILL.md is the source of truth, and it is the exact text injected into every request while a level other than off is active; this README deliberately keeps no second copy of it.

Lazy, not negligent: understanding the problem, trust-boundary validation, data-loss handling, security, and accessibility are never on the chopping block.

Levels

Level	Behavior	Persisted
lite	Build what was asked, name the lazier alternative in one line.	yes
full	The ladder enforced. Default.	yes
ultra	YAGNI extremist: challenge the requirement before building it.	yes
review	Over-engineering review; points at the ponytail-review skill.	no — session only
off	No injection. Normal behavior.	yes

The four persistable levels live in the ponytail settings namespace (~/.dsh/settings.yaml), so the card, the chip, the tool, and /ponytail all agree and the choice survives a restart. review is session-only because it is a review mode, not a level a deployment should start in; the tool and /ponytail still accept it.

Switching from a message

/ponytail full is a command. Typing stop ponytail or normal mode as an ordinary message is picked up from the durable user/message event, which arrives before the turn's prompt is assembled — so the turn that carried the command already runs without the ruleset, rather than one turn later.

Only the human's own words count. Injected context (a skill body, a file reference, replayed history) rides the same event stream and can never toggle the level, and the message must be the command: "add a normal mode toggle" is left alone.

One deliberate difference from upstream, which clears only the session mode: this writes the same off that /ponytail off writes, because in DSH the level is the persisted preference and a session-only override would leave the card and the chip reporting something the prompt does not do.

Install

The plugin is two halves in one package and has no runtime dependencies beyond @deepseek-ai/schemastery (the settings service serializes the namespace schema with it):

• host half — src/index.ts, loaded by the Loader from the profile;
• browser half — lib/client.js, served by the client module system because the package declares dsh.client and exports ./client.

Install

Live-reload install: keep the package as a plain dependency (no dsh.bundle) and put the Loader row in the profile's own cordis.patch.yml. That file is what patchReload: live watches. dsh.profile.bundles is frozen at boot — do not put this package there.

dsh plugin --profile web add /path/to/dsh-ponytail
# pnpm will warn "declares no dsh.bundle — installed as a plain dependency". That is the point.

Then paste this into ~/.dsh/profiles/web/cordis.patch.yml (or merge into an existing - insert: list):

- insert:
    - id: ponytail
      name: dsh-ponytail
      config:
        defaultMode: full

Saving that file remounts the plugin. No profile restart. insert does not dedupe ids — never also list this package in dsh.profile.bundles.

Verify

After the profile patch save (and a page refresh of the Web client the first time):

• Settings → Plugins → Plugin configuration shows the Ponytail card;
• the skill tool's catalog lists the six ponytail skills;
• the composer tool row shows a Ponytail: full chip until the level is off;
• /ponytail reports the current level in the composer;
• sending exactly stop ponytail in a message turns the chip off and the next request carries no ruleset.

Configuration

Field	Default	Meaning
defaultMode	PONYTAIL_DEFAULT_MODE, then full	The composition-layer level. The user's settings namespace overrides it. Must be off, lite, full, or ultra.

Invalid configuration fails while the plugin loads rather than silently doing the wrong thing.

Layout

src/index.ts        host plugin: section, provider, tool, command, message watcher, settings namespace
src/modes.ts        levels, the mode filter, the injected ruleset, default resolution
src/skills.ts       skills provider over skills/<name>/SKILL.md
src/frontmatter.ts  minimal frontmatter reader (plain, `>`, `|`, quoted scalars)
src/host.ts         structural declaration of the host surface
lib/client.js       browser half: the settings card + the composer chip (loader factory format)
cordis.patch.yml    the Loader row to paste into the profile's live-watched patch
skills/             the six skills, verbatim from upstream
tests/              node:test unit + fake-host integration coverage

lib/client.js is plain JavaScript on purpose. The client module system serves a package's exports["./client"] artifact as a lazy-CJS factory registered on window.__ModuleLoader__; an out-of-tree plugin can author that directly instead of reproducing the repository's tsdown client preset.

Its chrome is a stylesheet, not inline style objects. The factory appends one <style> tag while it materializes, which the module system claims for this package and removes on unload. That keeps every state change (card open, pill selected, disabled) out of React's inline-style diffing — a removed style key is cleared with an empty string, which decomposes a shorthand set alongside it, and that is what silently blanked a deselected pill's border in v0.3.1.

Development

npm test          # node --test tests/*.test.ts (Node >= 22.6, no build step)
npm run typecheck # tsc --noEmit

Uninstall

dsh plugin --profile web remove dsh-ponytail

and delete the id: ponytail row from ~/.dsh/profiles/<profile>/cordis.patch.yml. Saving unmounts it.

Limits

• Host source edits remount when id: hmr is enabled with this checkout in config.root. Without that, a live patch reload re-runs apply from the ESM module already in memory.
• A browser-half edit needs a page refresh. The client module system serves exports["./client"] from the package, so the host half can stay up.
• The level is process-wide. The ruleset is a global prompt section and the level is one namespace value, so every agent in the process shares it.
• Two locales. The card and the chip ship en and zh; any other active locale falls back through the service's own chain.
• External subagents are out of reach. In-process children join the parent composition and inherit the ruleset, but subagent-claude-code and subagent-codex spawn their own CLI with its own system prompt, and no harness extension point wraps a spawn. Upstream covers this with a SubagentStart hook; DSH has the equivalent of no such hook to register.
• emit modes: a level change is not announced as a session event; a replayed session shows the ruleset each request already carried.

Attribution and license

MIT. Skill content and mode semantics: © DietrichGebert (ponytail). DSH port: see LICENSE.

The six skills/*/SKILL.md files are verbatim copies, so they carry upstream's figures and citations rather than this package's. /ponytail-gain therefore reports the original five-task single-shot benchmark — 80–94% fewer lines, 47–77% cheaper, 3–6× faster — which upstream's own README has since revised to roughly 54% fewer lines, 20% cheaper and 27% faster on its agentic benchmark; and its Source: line names benchmarks/, which this package does not ship. Both are left as written rather than forked, because a fork re-diverges at every upstream sync.