Anvil

Anvil is a Git-native IDE for LangGraph agent graphs built on Prompt Driven Development (PDD) — a methodology that treats prompts, plans, evals, and decisions as versioned engineering artifacts in the repo, not throwaway chat. From one sentence (anvil init "build a support triage agent"), Anvil scaffolds a full PDD project: a pdd/ layer with project context, conventions, and a phased plan; typed LangGraph nodes; an eval-driven suite with a 7-case golden dataset (3 happy / 2 edge / 2 fail) plus pytest and an LLM-as-judge — so every node ships with the test that proves it works; Architecture Decision Records capturing the why; and a GitHub PR — all committed to a real repo. It retrofits existing LangGraph projects (anvil init --existing), extends them conversationally (anvil edit), and ships them as a hosted API with a live graph view (anvil serve --web). The inner loop fans out four Gemini 3.5 Flash sub-agents in parallel — NodeForge (node), EvalSmith (golden dataset + judge), DocScribe (ADR), MergeBot (PR) — so every phase produces code, evals, decisions, and review materials together, in the wall-time of one Flash call. Nothing merges without an eval; nothing changes without a recorded decision.