n8n-decanter: An MCP Guard That Turns Code Nodes Into TypeScript Files

n8n's built-in MCP server lets coding agents edit workflows structurally, but Code node source is stored as a raw string inside workflow JSON, making those edits undiffable, untyped, and impossible to share as reusable modules.

n8n-decanter sits as an MCP proxy between agent and n8n, forwarding every structural write — adding nodes, wiring connections, publishing — while blocking only the direct write to a Code node's jsCode field. Instead, each Code node's source is extracted into its own file in a git repo, with workflow.json kept as a read-only structural mirror.

On push, files compile through esbuild, inlining shared modules and opted-in npm dependencies into the single function body n8n requires. Typechecking wraps each file in a synthetic async function via a custom TypeScript compiler host to validate the node's real runtime context ($input, top-level return/await). Pushes land on the workflow's draft, publishing is a separate gated step, and compliance and drift checks run independently — a --force flag can override drift concerns, but never a structural correctness failure.

The result: engineers keep the agent's speed for structural edits while putting business logic under git, TypeScript, and code review. The tool ships as an MIT-licensed CLI on npm.