The control plane for coding agents

Let your agent build.Keep it on track.

Oversized prompts. Broken boundaries. Endless retries. Give your coding agent five guardrails that work inside the editor you already love.

Find your first guardrail Get your MCP key
Works with your existing editor Your code is not stored
example · mcp.hexum.dev sample flow

YOUR EDITOR › HEXUM

› hexum_shrink(repo, task)
✓
Shrink the contextOne workflow. Five ways to stay in control.
TOOLS12
PRODUCTS5
KEYS01
ZDR modeinput is never retained
⌘One connection.
Your tools stay yours.
BUILT FOR THE WAY YOU ALREADY SHIP CursorClaude CodeCodexAny MCP client See all integrations

Every failure has a guardrail

Where does your agent get stuck?

Pick a problem. See what changes. Each product handles a different moment in your workflow.

01 / 05 · Efficient

Give the model room to think.

WITHOUT THE GUARDRAIL

Entire modules, repeated helpers, irrelevant context.

WITH EFFICIENT

Task-shaped context. Expand only when the agent needs more.

Explore Efficient 
hexum_shrink → relevant context
hexum_expand → inspect a detail
hexum_splice → edit the real source
3 MCP tools · your existing editor
1/5 products explored
THE 24-TASK BENCHMARK87.6% fewer tokens.24/24 tasks passed. See the full results

Try it on your own files

See what moves forward.

Try the sample repo or choose source files from your project. See how much context Hexum trims before connecting your agent.

01 Choose relevant files02 Inspect the result03 Keep editing locally
Drop files from your project No account. Nothing is stored.

Drop source from a real folder. Hexum folds what the model does not need this turn.

Up to 8 files, 96KiB. Nothing is stored. This playground is not the MCP.

A familiar workflow

Paste one key. Keep building.

Connect Hexum once in your editor’s MCP settings. Start on the free starter window, then choose a plan if you need more.

Set up your connection

New to MCP? Follow the setup guide

mcp.jsonYOUR EDITOR CONFIG
Hexum MCP connection
{
  "mcpServers": {
    "hexum": {
      "serverUrl": "https://hexum.dev/mcp",
      "headers": { "Authorization": "Bearer hexum_live_…" }
    }
  }
}
12 tools discoveredView setup guide ↗
◌

Code stays yours
No payload tables. No stored diffs.

⌁

Built around MCP
Use it with the editor you already have.

↗

Start without a card
Personal keys include a monthly starter window.

Last updated 12 September 2026

Keep exploring

What is HexumEfficientArch ReviewControlLoop DocsPricing

FAQ

What is Hexum?

Hexum is a developer ecosystem for coding agents in Cursor, Claude Code, and the rest. One API key. Five products and twelve tools today: spend less on each prompt, block bad imports, review pull requests, stop the agent looping, and only keep building when checks pass. We do not keep your code.

Does Hexum replace Cursor or Claude Code?

No. You keep Cursor, Claude Code, Antigravity, Codex, or Grok. Hexum is not an editor and not a model. You paste a key into the agent you already use.

How does Hexum cut what I pay the model?

Your agent stops dumping the whole repo into the prompt. Hexum sends this task, not every file. On the published card, MBPP context dropped 85.2% and the combined 24-task cut is 87.6%, with 24/24 tests still passing. Tokens are ceil(utf8_bytes/4), not a provider invoice. See /benchmarks.

Does the architecture check use an AI?

No. It reads a rules file in your repo and reports forbidden imports. It does not call a model, so it does not guess.

How is Hexum billed?

You pay for what your agent sent Hexum. Usage €0.30 per million tokens. Teams €0.35 per million. No per-person fee. No monthly cap. See /pricing.

What does the dashboard mean by tokens saved?

How much smaller the reply was than what the agent sent, when that is a cut. Your invoice is still based on what the agent sent Hexum, not on the savings.

Does Hexum store my repo?

No. We do not keep the code your agent sends. We do not train on it. Policy: /zdr.

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.

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.

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 are the five Hexum products?

Hexum is an ecosystem: five products and twelve tools on one key. Efficient: don’t paste the whole repo. Arch: block a bad import. Review: architecture review on GitHub PRs. Control: when the agent loops, write the rule. Loop: only keep building if checks and tests pass.

Your tools. Your editor. More control.

Let the agent focus on the work.

Connect Hexum to the workflow your team already knows.

Get a key