Open sourceThe verifier and the wire spec are public

Every agent. Accounted for.

Hard spend limits for AI agents, checked before any payment moves. And a record of every decision your auditor can verify on their own.

Try the gate Talk to Fabio

DecisionsSimulation

Sealed recordNo. 0005

A shape drawn from this record’s SHA-256 hash.

research_agentOpenAI

$420.00

Per-request limit $500.00Approved

Agent is active
OpenAI is on the allowlist
Within the per-request limit

Hash: acd69e5e…9f950a14
Prev: d077c9f2…e7e821d6

Simulated agents. Real SHA-256, computed in your browser. No money moves.

Your agents can already spend money. Before they’re allowed to, your security review will ask two questions.

“What stops it from overspending?”

Cap

A hard limit, checked before the request reaches your payment rail. A persuasive prompt can’t change it.

“Can you prove what it did?”

Seal

Every decision, approved or blocked, sealed into a chain your auditor can re-verify offline.

Three things happen to every request.

Before your agent spends a cent, and long after the money has moved.

policyresearch_agent

per_call_cap: $500.00
daily_cap: $2,000.00
vendors: openai, anthropic
frozen: false

$420.00 openai✓ Approved

$640.00 openai× Over the limit

$500

No. 0044Approved
research_agent → OpenAI$420.00
hash 140e654e7c…731f74 · prev 03269e…c0a9
No. 0043Blocked
travel_agent → Unlisted vendor$219.00
hash 03269ee39d…f0c0a9 · prev 239d07…892f
No. 0042Approved
support_agent → Twilio$38.50
hash 239d075f8c…82892f · prev 218fc7…a3dc

~/audit

$ python comptra_verify.py comptra-sample-certificate.jsonOK chain intact  9 records  root 3d12f90dae3b..  re-derived independently in PythonOK checkpoint  tree_size 9  Ed25519 root d45f95d8e734.. verifiedOK witness quorum  3/2 independent cosignaturesVERIFIED: no trust in Comptra required

Actual output of the open-source Python verifier on the signed sample report.

Cap. Give every agent a budget it can’t talk its way around.
Per-request, daily and monthly limits, vendor allowlists and an instant freeze, evaluated before the request reaches your payment rail. A clever prompt doesn’t change the policy.
- Integer cents, no float drift
- Fails closed
- Freeze any agent instantly
Seal. Every decision becomes a record. Including every no.
Approved and blocked requests are appended to a hash chain. Each record carries the hash of the one before it, so a later edit, deletion or reordering breaks the chain at an exact, locatable record.
- SHA-256 over RFC 8785 canonical JSON
- Append-only
- Blocks are recorded too
Verify. Your auditor checks the math, not our word.
Export a signed Agent Spend Audit Report. Ed25519 checkpoints and RFC 9162 Merkle proofs let anyone re-verify it offline, with independent verifiers in TypeScript and Python.
Read the wire spec

Set the limit. Then try to get past it.

A working policy engine and SHA-256 chain, running in your browser. Nothing is sent anywhere and no money moves.

Try

Decision ledger 4 records

Simulated spending requests with recorded decisions and integrity status
Record	Vendor	Amount	Decision	Integrity
0001	OpenAI	$420.00	Approved	Recorded
0002	Anthropic	$88.00	Approved	Recorded
0003	OpenAI	$640.00	Blocked	Recorded
0004	Anthropic	$120.00	Approved	Recorded

Every decision leaves a record.

Run an integrity check, then alter a record and check again.

This sandbox uses a local SHA-256 chain. The console runs the full engine with signed checkpoints.

Open the console

Agent Spend Audit Reportv1

agent_42 · signed sample

Nine decisions.
One root hash.

9Decisions

7Sealed

2Blocked

Record chain: SHA-256
Signed checkpoint: Ed25519
Merkle proofs: RFC 9162
Verifiers: TypeScript, Python

Rootd45f95d8e7340ca4…f8e21954

From the downloadable signed sample. Example data.

The audit report

Proof that leaves with you.

One file holds the decisions, the chain, the signed checkpoint and the witness cosignatures. Your auditor doesn’t need an account, our servers or our word.

Download the signed sample Open the console

What a verified report shows

No recorded decision changed since its checkpoint
Blocked requests were recorded too
Checkpoints carry the witness quorum’s cosignatures

What it doesn’t claim

That a payment settled
That an approved purchase was a good idea
Any certification or compliance status

Split-view protection assumes at least one honest, reachable witness. Keep your own copies of trusted checkpoints.

A few lines between your agent and the payment.

Your payment provider still moves the money. Comptra decides first and records the outcome. A block is a normal response, not an exception.

Your agentComptraYour rail

Simulated rail: Default, no credentials
Stripe Issuing: Test-mode adapter
x402: Preview adapter
Your rail: One interface to implement

Explore the engine

import { Comptra } from 'comptra';

const comptra = new Comptra({
  apiKey: process.env.COMPTRA_KEY,
  baseUrl: 'http://localhost:8787'
});

const decision = await comptra.gate({
  agentId: 'research_agent',
  vendor: { name: 'openai' },
  amountMinor: 42000, // $420.00
  currency: 'USD'
});

if (!decision.allowed) {
  throw new Error(decision.reason);
}

// Only then, call your payment adapter.

curl http://localhost:8787/v1/gate \
  -H "Authorization: Bearer $COMPTRA_KEY" \
  -H "Content-Type: application/json" \
  -d '{"agent_id":"research_agent",
       "vendor":{"name":"openai"},
       "amount_minor":64000}'

# HTTP 200. A block is a normal outcome.
{
  "decision": "BLOCK",
  "reason_code": "PER_CALL_CAP",
  "limit": 50000,
  "observed": 64000,
  "ledger_seq": 12,
  ...
}

Policy first. Payment second.SDK source

Questions before you build.

Does Comptra move or hold money?

No. Comptra evaluates spending policies and records decisions. Your payment provider handles execution and settlement. Comptra is not a bank and not a payment rail.

Which payment rails does it work with?

Comptra sits above the rail. The engine ships a simulated rail, a Stripe Issuing test-mode adapter and an x402 preview. A new rail is one adapter interface. Tell us which one you use.

Can I try it with my agent workflow?

Yes. Start with the playground above or run the open-source engine locally. Get in touch to scope your workflow, spending policies and deployment.

Where does it run?

The engine runs on Node today and includes a Cloudflare Workers entry point. Production key custody, such as a KMS or HSM, is scoped with each design partner.

Design partners, Vienna

What is your agent buying?

API credits, research data, a few hours of compute. Tell me what you’re building and where the spending needs a boundary.

Fabio JuranekFounder, Comptra

Used only to reply to your enquiry. Privacy policy