Plankton Code Quality Skill

Integration reference for Plankton (credit: @alxfazio), a write-time code quality enforcement system for Claude Code. Plankton runs formatters and linters on every file edit via PostToolUse hooks, then spawns Claude subprocesses to fix violations the agent didn't catch.

When to Use

• You want automatic formatting and linting on every file edit (not just at commit time)
• You need defense against agents modifying linter configs to pass instead of fixing code
• You want tiered model routing for fixes (Haiku for simple style, Sonnet for logic, Opus for types)
• You work with multiple languages (Python, TypeScript, Shell, YAML, JSON, TOML, Markdown, Dockerfile)

How It Works

Three-Phase Architecture

Every time Claude Code edits or writes a file, Plankton's multi_linter.sh PostToolUse hook runs:

Phase 1: Auto-Format (Silent)
├─ Runs formatters (ruff format, biome, shfmt, taplo, markdownlint)
├─ Fixes 40-50% of issues silently
└─ No output to main agent

Phase 2: Collect Violations (JSON)
├─ Runs linters and collects unfixable violations
├─ Returns structured JSON: {line, column, code, message, linter}
└─ Still no output to main agent

Phase 3: Delegate + Verify
├─ Spawns claude -p subprocess with violations JSON
├─ Routes to model tier based on violation complexity:
│   ├─ Haiku: formatting, imports, style (E/W/F codes) — 120s timeout
│   ├─ Sonnet: complexity, refactoring (C901, PLR codes) — 300s timeout
│   └─ Opus: type system, deep reasoning (unresolved-attribute) — 600s timeout
├─ Re-runs Phase 1+2 to verify fixes
└─ Exit 0 if clean, Exit 2 if violations remain (reported to main agent)

What the Main Agent Sees

Scenario	Agent sees	Hook exit
No violations	Nothing	0
All fixed by subprocess	Nothing	0
Violations remain after subprocess	[hook] N violation(s) remain	2
Advisory (duplicates, old tooling)	[hook:advisory] ...	0

The main agent only sees issues the subprocess couldn't fix. Most quality problems are resolved transparently.

Config Protection (Defense Against Rule-Gaming)

LLMs will modify .ruff.toml or biome.json to disable rules rather than fix code. Plankton blocks this with three layers:

1. PreToolUse hook — protect_linter_configs.sh blocks edits to all linter configs before they happen
2. Stop hook — stop_config_guardian.sh detects config changes via git diff at session end
3. Protected files list — .ruff.toml, biome.json, .shellcheckrc, .yamllint, .hadolint.yaml, and more

Package Manager Enforcement

A PreToolUse hook on Bash blocks legacy package managers:

• pip, pip3, poetry, pipenv → Blocked (use uv)
• npm, yarn, pnpm → Blocked (use bun)
• Allowed exceptions: npm audit, npm view, npm publish

Setup

Quick Start

# Clone Plankton into your project (or a shared location)
# Note: Plankton is by @alxfazio
git clone https://github.com/alexfazio/plankton.git
cd plankton

# Install core dependencies
brew install jaq ruff uv

# Install Python linters
uv sync --all-extras

# Start Claude Code — hooks activate automatically
claude

No install command, no plugin config. The hooks in .claude/settings.json are picked up automatically when you run Claude Code in the Plankton directory.

Per-Project Integration

To use Plankton hooks in your own project:

1. Copy .claude/hooks/ directory to your project
2. Copy .claude/settings.json hook configuration
3. Copy linter config files (.ruff.toml, biome.json, etc.)
4. Install the linters for your languages

Language-Specific Dependencies

Language	Required	Optional
Python	ruff, uv	ty (types), vulture (dead code), bandit (security)
TypeScript/JS	biome	oxlint, semgrep, knip (dead exports)
Shell	shellcheck, shfmt	—
YAML	yamllint	—
Markdown	markdownlint-cli2	—
Dockerfile	hadolint (>= 2.12.0)	—
TOML	taplo	—
JSON	jaq	—

Pairing with clarc

Complementary, Not Overlapping

Concern	clarc	Plankton
Code quality enforcement	PostToolUse hooks (Prettier, tsc)	PostToolUse hooks (20+ linters + subprocess fixes)
Security scanning	AgentShield, security-reviewer agent	Bandit (Python), Semgrep (TypeScript)
Config protection	—	PreToolUse blocks + Stop hook detection
Package manager	Detection + setup	Enforcement (blocks legacy PMs)
CI integration	—	Pre-commit hooks for git
Model routing	Manual (/model opus)	Automatic (violation complexity → tier)

Recommended Combination

1. Install clarc as your plugin (agents, skills, commands, rules)
2. Add Plankton hooks for write-time quality enforcement
3. Use AgentShield for security audits
4. Use clarc's verification-loop as a final gate before PRs

Avoiding Hook Conflicts

If running both clarc and Plankton hooks:

• clarc's Prettier hook and Plankton's biome formatter may conflict on JS/TS files
• Resolution: disable clarc's Prettier PostToolUse hook when using Plankton (Plankton's biome is more comprehensive)
• Both can coexist on different file types (clarc handles what Plankton doesn't cover)

Configuration Reference

Plankton's .claude/hooks/config.json controls all behavior:

{
  "languages": {
    "python": true,
    "shell": true,
    "yaml": true,
    "json": true,
    "toml": true,
    "dockerfile": true,
    "markdown": true,
    "typescript": {
      "enabled": true,
      "js_runtime": "auto",
      "biome_nursery": "warn",
      "semgrep": true
    }
  },
  "phases": {
    "auto_format": true,
    "subprocess_delegation": true
  },
  "subprocess": {
    "tiers": {
      "haiku":  { "timeout": 120, "max_turns": 10 },
      "sonnet": { "timeout": 300, "max_turns": 10 },
      "opus":   { "timeout": 600, "max_turns": 15 }
    },
    "volume_threshold": 5
  }
}

Key settings:

• Disable languages you don't use to speed up hooks
• volume_threshold — violations > this count auto-escalate to a higher model tier
• subprocess_delegation: false — skip Phase 3 entirely (just report violations)

Environment Overrides

Variable	Purpose
HOOK_SKIP_SUBPROCESS=1	Skip Phase 3, report violations directly
HOOK_SUBPROCESS_TIMEOUT=N	Override tier timeout
HOOK_DEBUG_MODEL=1	Log model selection decisions
HOOK_SKIP_PM=1	Bypass package manager enforcement

References

• Plankton (credit: @alxfazio)
• Plankton REFERENCE.md — Full architecture documentation (credit: @alxfazio)
• Plankton SETUP.md — Detailed installation guide (credit: @alxfazio)