A session

Last updated 12 September 2026

1. Mint a key

Open /app, sign in, mint a key. Hexum answers on a starter window (first 2 million tokens sent this month). After that, turn usage billing on. There is no spend cap. Rates: Pricing.

2. Paste one prompt into the agent

Prefer the sentence on /app. The agent writes the MCP config. JSON still works:

mcp.json

{
  "mcpServers": {
    "hexum": {
      "serverUrl": "https://hexum.dev/mcp",
      "headers": { "Authorization": "Bearer hexum_live_…" }
    }
  }
}

Hexum MCP install for Cursor · Hexum for Claude Code.

3. Put a contract in the repo

architecture.hexum

skill full

layer ui
  match src/ui/**
  match src/pages/**

layer services
  match src/services/**

layer data
  match src/data/**

rule no_ui_to_data
  from ui
  cannot use data
  severity high
  message UI must not import data access directly.
  hint Call services instead.

4. Ask for a change as usual

The agent should call hexum_shrink, hexum_expand if needed, hexum_splice, then hexum_check.

FAQ

How do I add Hexum to Cursor?

Create a key at /app, paste the one-sentence prompt into Cursor, and let the agent write the MCP config. Starter works until two million tokens this month. Details: /cursor.

Why did connect fail with BILLING or AUTH?

AUTH means the key is missing, wrong, or revoked. BILLING means that key’s plan is off, or the starter window is used. Turn Usage billing on at /app, or make a key on the plan that is on.

What is the rules file?

A file in the repo (usually architecture.hexum) that groups folders into layers and says which layer cannot import another. Guide: /architecture-hexum.