Forall Review 2026: The Coding Agent That Proves Its Code Is Correct

Most coding agents will happily hand you code that looks right. Forall asks a harder question: can you prove it’s correct? It’s a coding agent from Astrio that generates spec-driven code alongside machine-checkable proofs — so the output isn’t just plausible, it’s verifiable.

What is Forall?

Forall is a coding agent that helps developers build correct software by generating code together with formal, machine-checkable proofs. You can run it two ways:

1. Full CLI agent — specs, proofs, and the whole workflow live in your terminal.
2. MCP verify-only — stay in Cursor, Claude Code, or GitHub Copilot and add Forall’s hosted verification as an MCP server. No CLI install required.

On first launch you sign in with a Forall account (API key) or bring your own model key (OpenAI / OpenRouter). Then forall init in a git repo and you’re working.

Key features

• Spec-driven code with proofs — the agent generates code and a machine-checkable argument that it meets the spec.
• Two deployment modes — full CLI, or MCP verify-only inside your existing agent.
• Language support — TypeScript, Java, and Rust today, with more on the way.
• Bring-your-own-model — OpenAI / OpenRouter, or a Forall account API key.
• Apache-2.0 and fully open source.

Who should use it?

Forall is built for developers and teams who can’t afford “plausible but wrong” — safety-critical code, financial systems, or anything where a silent bug is expensive. The proof layer is the point: instead of reviewing generated code by eye, you get a checkable claim that it satisfies the spec.

It’s less compelling if you just want the fastest possible codegen for a throwaway script — the proof step adds overhead you may not need there.

Pros and cons

Pros: verifiable correctness, flexible deployment (CLI or MCP), open source, BYO-model.

Cons: only three languages supported so far; proofs add workflow overhead; needs a Forall account or model key to start.

Pricing

Free and open source (Apache-2.0).

FAQ

Does Forall replace my current coding agent? Not necessarily. The MCP verify-only mode is designed to sit alongside Claude Code or Cursor and add proof-checking without moving your workflow.

Which languages are supported? TypeScript, Java, and Rust, with more planned based on demand.

Is it really free? Yes — the agent is Apache-2.0 open source. Running it still consumes tokens from whatever model you connect.