Coming soon: open-source payment simulation

Stop emailing banks to test payments.

Mandas is an open-core payment simulation platform for fintech teams that need reliable SEPA, SWIFT, ISO 20022, and R-transaction testing in pre-production environments.

Star/watch mandas-core Join release waitlist

Mandas Core is in active development. The website is intentionally early: follow the repository, join the release list, and help shape the flows that get built first.

# Intended developer experience
docker pull mandasio/mandas-core
docker run -p 8080:8080 mandasio/mandas-core

# Trigger a payment return
curl -X POST localhost:8080/simulate/return \
  -d '{"paymentId":"txn_001","reasonCode":"AC04"}'

status: RETURNED
message: pacs.004 dispatched
reason: AC04 ClosedAccountNumber

The problem

Bank sandboxes cover happy paths. Real integrations break on everything else.

Returns, rejects, direct debit failures, mandate problems, and R-transactions are exactly the flows teams need before production. In most bank sandboxes, those flows still require a support ticket, a manual trigger, and a release schedule that waits.

"We need to test a return. Can someone at the bank trigger one in the sandbox?"

The sentence that turns an integration test into a multi-day process.

Failures require humans. Teams still depend on a bank support queue for failures that should be deterministic test fixtures.
Mocks miss payment behavior. Wire-level stubs cannot model payment lifecycle, reason codes, and ISO 20022 message fidelity.
Internal simulators rot. Every fintech team builds a partial simulator, then carries the maintenance burden alone.

Coming open source

Mandas Core starts with the local simulator fintech teams actually need.

The MVP is deliberately narrow: SEPA Credit Transfer simulation first, with deterministic returns and rejects around the flows that block QA today. SWIFT support is planned for a later stage once the SEPA foundation is solid.

Apache 2.0

Open engine

ISO 20022 parsing, validation, message generation, and lifecycle simulation in an auditable open-source core.

SEPA-first

Credit Transfer MVP

Start with SEPA Credit Transfer flows, then expand coverage into more R-transactions and payment schemes.

Local DX

Docker and scenarios

A Docker image, REST triggers, and community scenarios that teams can run locally or in CI.

Developer preview

The workflow should feel like infrastructure, not a vendor ticket.

The first release is designed to be pulled into local dev and CI. The commands below remain a preview until Mandas Core and the Docker image are published.

mandas-core preview

# Coming soon: start the simulator
docker run -p 8080:8080 mandasio/mandas-core

# Submit or load a payment into the lifecycle
curl -X POST localhost:8080/payments \
  -H "Content-Type: application/xml" \
  --data-binary @pacs.008.xml

# Trigger the non-happy flow on demand
curl -X POST localhost:8080/simulate/return \
  -d '{"paymentId":"txn_001","reasonCode":"AM04"}'

payment.status = RETURNED
message.type = pacs.004
reason.code = AM04

Product tiers

Start local. Move hosted. Offer it under your own brand.

Mandas is open core by design: the simulator should be useful before anyone talks to sales, while hosted and white-label tiers cover collaboration, operations, and enterprise distribution.

Tier 1

Open Source

Mandas Core, Docker image, REST triggers, SEPA Credit Transfer MVP, community scenarios, and Apache 2.0 licensing. SWIFT flows are planned for a later OSS stage after the SEPA foundation.

Tier 2

Hosted Team

Managed environments, dashboard, lifecycle and event views, scenario management, CI/CD integration, and team workflows for fintech engineering and QA teams.

Tier 3

White-label / Self-hosted

Bank or PSP-branded sandbox, self-hosted deployment, enterprise controls, custom API skins, and partner-facing simulation for larger organizations.

Roadmap

Built in public, starting with SEPA Credit Transfer.

The first milestone is not a glossy dashboard. It is a trustworthy simulator that developers can inspect, run, and challenge with real integration pain.

Phase 1

SEPA CT simulator

Publish Mandas Core, define message contracts, build the SEPA Credit Transfer lifecycle, and make the Docker quick start real.

Phase 2

Team workflow

Add hosted environments, dashboard views, scenario management, community scenarios, SDKs, and CI/CD integration once core usage is validated.

Phase 3

Platform depth

Expand into SWIFT flows, API skins, enterprise controls, self-hosted deployment, and white-label partner sandbox options.

Release updates

Get notified when Mandas Core is ready to run.

Join the list for release notes, early demos, and calls for feedback from fintech engineers who have lived the sandbox problem.