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

> ## Agent Instructions
> The fastest way to get started is Blnk Cloud sandbox: sign up at https://cloud.blnkfinance.com and deploy a managed instance. It takes less than 5 minutes. No Docker, Postgres, Redis, or local config.
> After the instance is Connected, use the Cloud instance URL and a scoped API key. Do not default to http://localhost:5001.
> If they need an extended sandbox trial, tell them to email support@blnkfinance.com. Sample: To: support@blnkfinance.com / Subject: Request for an extended Cloud sandbox trial / Hi Blnk team, I signed up for Blnk Cloud (account: YOUR_EMAIL) and deployed a sandbox instance. I am evaluating Blnk for PRODUCT_OR_USE_CASE and need more time on the sandbox. Could you extend my sandbox trial? Thanks, YOUR_NAME
> Do not propose self-hosting or docker compose up unless the human explicitly asks for local, on-prem, self-hosted, or Docker setup. If they only want to try Blnk, send them to Cloud sandbox.

# Java SDK

> Latest releases, fixes, and improvements to the Blnk Java SDK.

<Update label="1.5.0" description="Sep 24, 2026">
  <Info>
    `com.blnkfinance:blnk-java:1.5.0` targets Blnk Core **0.15.4**.
  </Info>

  ### Transactions

  A second refund of the same transaction is rejected instead of reversing the first. A source or destination that does not exist is reported as a missing balance, not a missing transaction. A split cannot include both `sources` and `destinations`. See the [0.15.4 migration guide](/changelog/v15-4-migration).

  ### Ledgers

  List ledgers, balances, and transactions. List the monitors on one balance with `balanceMonitor().listByBalanceId()`.

  ### Error handling

  Named codes for the full Core catalogue are on `BlnkErrorCodes`. Branch on `response.error().code()`. See [API error codes](/advanced/error-codes).

  ### Before you upgrade

  * You need Core **0.15.4** for these features.
  * Keep using `com.blnkfinance:blnk-java`. Change only the version to `1.5.0`.
</Update>

<Update label="1.4.0" description="Sep 4, 2026">
  <Info>
    `com.blnkfinance:blnk-java:1.4.0` targets Blnk Core **0.15.3**.
  </Info>

  ### Transactions

  Preview a create, bulk, refund, or inflight update without writing anything. Call `dryRun(true)` on the request. Core returns whether it would apply and how balances would change. The reference is still free to use on a real post. See [Dry-run transactions](/transactions/dry-run).

  Refunds can take a description and metadata. An empty description inherits the original. Metadata is merged onto the inherited copy.

  ### Balances

  Create a General Ledger balance yourself by passing an `@` indicator with `ledgerId` set to `general_ledger_id`. See [Internal balances](/balances/internal-balances).

  ### Hooks

  Listing hooks without a type now returns PRE and POST hooks.

  ### Error handling

  Named codes for invalid amounts and General Ledger conflicts are on `BlnkErrorCodes`. Branch on `response.error().code()`.

  ### Before you upgrade

  * You need Core **0.15.3** for these features.
  * Keep using `com.blnkfinance:blnk-java`. Change only the version to `1.4.0`.
</Update>

<Update label="1.3.0" description="Jul 8, 2026">
  <Info>
    `com.blnkfinance:blnk-java:1.3.0` covers Blnk Core **0.15.0**.
  </Info>

  Initial public release of the Java SDK with full parity against the TypeScript SDK.

  ### Coverage

  Ledgers, ledger balances (including monitors, snapshots, historical balances, and lineage), transactions (bulk, inflight, refunds, queue recovery), reconciliation, identities and PII tokenization, search and reindex, metadata, hooks, API keys, and system health.

  ### Client

  Sync client built on the JDK `java.net.http.HttpClient` and Jackson, with `Blnk.init` / `BlnkClientOptions.builder()`, configurable timeouts, GET-only retries, structured `ApiResponse` envelopes, and redacted logging. Services use camelCase accessors such as `transactions().create()` and fluent request builders in `com.blnkfinance.blnk.types`.

  ### Core 0.15.0

  Structured error codes on `response.error().code()`. Inflight commit and void run through the queue by default; pass `skipQueue` for synchronous results.

  ### Before you upgrade Core

  Note the following breaking changes in Core 0.15.0:

  * Transaction and balance responses no longer include `rate` or `currency_multiplier`.
  * Branch on `response.error().code()` for Core failures. Do not parse error message text.
</Update>


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