cacheplane/b4run

What it solves

B4.run reduces the boilerplate and complexity involved in building AI agents and workflows with LangGraph.js. It transforms the process of creating these agents into a structured application development experience similar to building a Next.js app, removing the need for manual route wiring and repetitive setup.

How it works

B4.run acts as a meta-framework built on top of LangGraph.js. It introduces several key mechanisms:

• File-system Routing: Agents and workflows are defined as routes in the file system (src/app/**/index.ts), which the framework automatically discovers.
• Type Generation: It automatically generates TypeScript declarations for routes, parameters, state, and tools during the build process.
• Tool Management: Tools can be organized as shared (in src/tools/) or route-local, allowing for specific runtime policies per route.
• Deterministic Testing: It uses fixture-backed tests that replay committed responses, preventing unexpected provider calls and ensuring consistent test results.
• Build Pipeline: It compiles the project into runnable Node servers, Dockerfiles, and LangSmith graph artifacts.

Who it’s for

TypeScript developers and teams who want to use LangGraph.js but prefer a structured application framework with built-in routing, type safety, and a streamlined local development and testing loop.

Highlights

• Next.js-like experience: Uses file-system routing for agent discovery.
• Automated Typegen: Generates types for state and tool signatures automatically.
• Deterministic Tests: Replays fixtures to avoid silent provider calls during testing.
• Durable Threads: Provides persistence primitives and SQLite-backed state for local development.
• Build Artifacts: Emits production-ready Node servers and Dockerfiles.