> ## Documentation Index
> Fetch the complete documentation index at: https://cts-docs.cosmos.network/llms.txt
> Use this file to discover all available pages before exploring further.

# Overview

> How the Cosmos Tokenization Suite connects to a bank's core banking platform and keeps tokenized balances synchronized.

The Cosmos Tokenization Suite (CTS) synchronizes tokenized deposits with the bank's
existing core. The core banking platform remains the record of record: a
tokenized deposit represents a balance the core already holds, not its
replacement.

## Supported cores

<CardGroup cols={2}>
  <Card title="Fiserv" icon="circle-check" href="/banking-core-integrations/fiserv">
    Production. Live on the Fiserv AppMarket, integrated by the Fiserv team.
  </Card>

  <Card title="Jack Henry" icon="circle-check" href="/banking-core-integrations/jack-henry">
    Production on SilverLake, including securities held on the general ledger.
  </Card>

  <Card title="Custom cores" icon="wrench" href="/banking-core-integrations/custom-cores">
    Batch and API based cores without a prebuilt connector, integrated through
    the deposit product model.
  </Card>
</CardGroup>

[Custom Cores](/banking-core-integrations/custom-cores) supports any other core,
including batch and API-based platforms. Banks that exchange messages instead
of exposing an API can use the
[ISO 20022 file drop path](/banking-core-integrations/iso-20022).

<Card title="Cosmos Tokenization Suite on the Fiserv AppMarket" icon="external-link" href="https://appmarket.fiservapps.com/cosmos-tokenization-suite.html">
  Banks with a Fiserv-based core can start from the AppMarket listing. The
  Fiserv team has already integrated CTS there.
</Card>

## Tokenize and writeback

The integration runs in both directions. The model requires both directions.

Tokenization is the process that reads a client's deposit balance from the core
ledger and creates a corresponding digital ledger entry. Writeback is the
process that pushes digital ledger balance changes back to the core. This
ensures that an on-ledger payment appears in the bank's reporting system.

```mermaid theme={"theme":{"light":"github-light-high-contrast","dark":"github-dark-high-contrast"}}
flowchart LR
  subgraph Existing["Existing Banking Systems"]
    Core["Core Ledger"]
  end
  subgraph Issuance["Issuance"]
    Digital[("Digital Ledger")]
  end

  Core -->|"Tokenize"| Digital
  Digital -->|"Writeback"| Core
```

Without writeback, the two ledgers drift apart, and the tokenized balance stops
being trustworthy. Reconciliation is the connector's normal operating mode,
not a periodic batch process added afterward. See
[Reconciliation](/banking-core-integrations/reconciliation).

## What this preserves

Keeping the core authoritative is a deliberate constraint:

* Accounting, regulatory reporting, and audit continue to use the same system
  they use today
* The deposit continues to be held and reported on the core
* Existing controls over the core remain unchanged
* A bank can stop issuing tokenized deposits without unwinding its books

## Before you start

[Core Requirements](/banking-core-integrations/core-requirements) lists the read
and write surface CTS needs from any core. Checking a core against these
requirements is the fastest way to establish whether an integration is viable.
The requirements apply with or without a prebuilt connector.

<Note>
  Version requirements for each core, the certification process, and the setup
  steps specific to each platform still need to be documented.
</Note>

## Integration reference

* [Core Requirements](/banking-core-integrations/core-requirements) describes
  the read and write surface that any core must expose
* [Integration Architecture](/banking-core-integrations/architecture) describes
  connection patterns and failure handling
* [Custom Cores](/banking-core-integrations/custom-cores) describes the deposit
  product model and cores without a connector
* [ISO 20022 Messaging](/banking-core-integrations/iso-20022) describes the
  message-based path
* [Reconciliation](/banking-core-integrations/reconciliation) describes
  tokenization, writeback, and divergence

## Related

* [Issuance](/cts-issuance/overview), the solution this integration supports
* [Getting Started](/what-is-cts/getting-started) for the setup flow
* [Digital Ledger Support](/digital-ledger-support/overview) for the platforms
  that run the digital ledger