beton

BETON

A Claude Code plugin that runs lint, typecheck, and the affected tests after every Write, Edit, or MultiEdit. If anything fails, the tool call is blocked and the error is returned to Claude. The shortcut moves Claude usually reaches for (adding # noqa, @ts-ignore, pytest.mark.skip, or renaming a failing test) are blocked at the PreToolUse layer, so the skill prompt and the hook layer enforce the same rule.

That's the whole product. No notation, no DSL.

How an edit flows through BETON

flowchart TD
    A["Claude calls a tool"]:::entry

    subgraph PRE ["PreToolUse: bypass guard"]
        direction TB
        B{"Bypass pattern<br/>in the edit?"}:::decision
        R["Refuse"]:::block
        B -- "noqa, ts-ignore,<br/>skip markers,<br/>rm/mv test files" --> R
    end

    subgraph POST ["PostToolUse: verifier chain"]
        direction TB
        L["Lint"]:::stage --> T["Typecheck"]:::stage --> P["Run affected tests"]:::stage
        L -. "errors" .-> X["Block"]:::block
        T -. "errors" .-> X
        P -. "fail" .-> X
        P -- "pass" --> K["Pass"]:::ok
    end

    A --> B
    B -- "clean" --> C["Tool executes"]:::neutral
    C --> L

    R --> S["Statusline + stats counter"]:::neutral
    X --> S
    K --> S

    classDef entry fill:#dbeafe,stroke:#1e40af,color:#1e3a8a
    classDef decision fill:#fef3c7,stroke:#a16207,color:#713f12
    classDef block fill:#fee2e2,stroke:#b91c1c,color:#7f1d1d
    classDef ok fill:#dcfce7,stroke:#15803d,color:#14532d
    classDef stage fill:#ffffff,stroke:#475569,color:#0f172a
    classDef neutral fill:#f1f5f9,stroke:#475569,color:#0f172a

Two hook layers, same rule. PreToolUse refuses shortcuts before they land; PostToolUse runs the real checks after the edit. Every outcome (refusal, block, clean pass) ticks the stats counter and the statusline reflects it.

Install

claude plugin marketplace add https://github.com/NetBr3ak/beton
claude plugin install beton@beton

From a local clone:

claude plugin marketplace add /path/to/beton
claude plugin install beton@beton

Verifier matrix

Language	Lint	Typecheck	Tests
Python	ruff or flake8	mypy or pyright	pytest
TypeScript / JS	eslint	tsc	bun test or vitest
Rust	clippy	clippy	cargo test
Go	staticcheck	go vet

Missing tools are skipped. Unknown file extensions never block. If a tool you need isn't installed, BETON stays silent on those edits.

pip install ruff mypy pytest
npm install -g eslint typescript
brew install universal-ctags  # optional, makes repo-map smarter

Demo

examples/buggy-flask/ ships a tiny Flask app with one planted bug. Open it in Claude Code and ask:

There's an off-by-one in is_token_valid. Add a regression test that catches it, then fix it.

You should see the localize subagent run, a new test get written, the verifier block on the failing test, the fix land, and the statusline flip from BETON ✗1 to BETON ✓. Full walkthrough in examples/buggy-flask/README.md.

Who this is for

You'll get value from BETON if:

• You use Claude Code for real code changes, not one-off questions.
• Your codebase has ruff/mypy/eslint/etc. already configured.
• Your test suite catches things, even partially.
• You've caught yourself or an assistant suppressing errors instead of fixing them.

You probably won't get much from BETON if:

• You use Claude Code mostly for prototyping and throwaway scripts.
• The project has no lint, type checking, or tests.
• You want quick conversational help, not engineered changes.

Bypass guard

The beton-swebench skill tells Claude not to take shortcuts. The PreToolUse guard enforces it. The following patterns are refused before the edit lands:

• Suppression comments: # noqa, # type: ignore, @ts-ignore, @ts-expect-error, eslint-disable, biome-ignore, prettier-ignore, # ruff: noqa.
• Test-skip markers: @pytest.mark.skip, @pytest.mark.xfail, @unittest.skip, it.skip/test.skip/describe.skip, .only on test functions.
• Bash commands that rm or mv test files (test_*.py, *_test.go, *.test.ts, *.spec.ts).

Each refusal returns a JSON block to Claude with the exact pattern that triggered it. If you genuinely need a suppression (legacy code, false-positive lint rule), turn the guard off for that edit:

BETON_BYPASS_GUARD=off