java-stellar-sdk

The Java Stellar SDK provides APIs to build transactions, query Horizon, and interact with Soroban RPC, with Android support and implementations of several Stellar Ecosystem Proposals.


Category	SDKs
Website	https://github.com/lightsail-network/java-stellar-sdk
java-stellar-sdk	https://github.com/lightsail-network/java-stellar-sdk
stellar-contract-bindings	https://github.com/lightsail-network/stellar-contract-bindings
First Released	November 2015
Intake	soft-launch
Budget Requested	$15,000
Maintenance Reserve	$15,000
Other	$0

Project Description

The Java Stellar SDK is a Java library for building Stellar applications on server-side JVM runtimes and Android. It provides transaction building, Horizon API access, Soroban RPC support, high-level Soroban smart contract support, and implements several Stellar Ecosystem Proposals. The SDK is listed on the official Stellar developer documentation and is used by projects including Lobstr Vault, Stellar Anchor Platform, and others.

This project also maintains the Java generator in stellar-contract-bindings, a CLI tool that generates typed Java client code for Soroban smart contracts from their SEP-48 interface specifications, so developers can call a contract without writing the encoding by hand.

Team & Experience

overcat (GitHub: overcat, Discord: @overcat.me) has been active in the Stellar community since 2018 and has rich experience in Stellar-related development, maintaining a series of Stellar infrastructure software. Currently maintained Stellar-related projects are listed at https://lightsail.network.

Retroactive Impact

In Q3 2026, both planned deliverables were completed, and two higher-priority items were added mid-quarter: Protocol 28 support in the SDK and SEP-48-based Java binding generation in stellar-contract-bindings. These took most of the quarter, so the planned maintenance work was smaller than expected. The SDK shipped three stable releases: 4.0.0 brought Protocol 27 support to a stable release as planned, 4.0.1 fixed a parsing bug, and 5.0.0 added Protocol 28 support, including CAP-85 external executable references. In stellar-contract-bindings, the Java generator was rewritten and now generates typed bindings for contract events as well as functions.

Maintenance still delivered results. In the SDK, a community-reported parsing bug was fixed and released the next day, the SDK no longer polls the RPC server continuously while waiting for a transaction, and text is now always encoded as UTF-8. In stellar-contract-bindings, the Java generator was simplified.

Past Deliverables

2026 Q3

D1. Release java-stellar-sdk 4.0.0 with Full Protocol 27 Support

Description from last quarter:

Finalize the 4.0.0 beta into a stable release with complete Protocol 27 support, including CAP-71 Soroban authorization (ADDRESS_V2 and delegated ADDRESS_WITH_DELEGATES credentials) and the redesigned Auth.Signer that natively supports custom account contracts (BLS, WebAuthn, threshold, policy). The implementation is already done in beta; the remaining work — validating against a live Protocol 27 network, auth examples and a migration guide for the breaking auth changes, and the stable release to Maven Central — is paced by Protocol 27 test-network availability.

Proof of completion:

Release 4.0.0: https://github.com/lightsail-network/java-stellar-sdk/releases/tag/4.0.0

4.0.0 brought Protocol 27 support to a stable release. It supports the new CAP-71 authorization credentials (ADDRESS_V2 and ADDRESS_WITH_DELEGATES), and the redesigned signing interface (Auth.Signer) supports custom account contracts such as BLS, WebAuthn, threshold, and policy contracts. The release notes include a migration guide for the breaking Auth.Signer change.

D2. Continuous Maintenance and Improvement

Description from last quarter:

Beyond routine upkeep — responding to community issues and pull requests, tracking Horizon and Soroban RPC changes, keeping Android compatibility current, and keeping CI/CD and dependencies up to date — we want to be candid about our intent for Q3: rather than adding new features, we plan to slow down and look inward. We will audit the codebase for accumulated technical debt, refactor rough edges, and optimize code that has grown organically across many releases, so the SDK stays maintainable and dependable for the long term.

This is a deliberate decision to consolidate, not to coast. For this SDK, “maintenance” has consistently produced meaningful improvements well beyond what we formally plan — Q2 is the clearest example, where full Protocol 27 support, the Auth.Signer redesign, and a JDK 21 toolchain upgrade all shipped under this same deliverable. We expect Q3 to be no different: as we dig into the code, concrete fixes and refinements will follow.

Proof of completion:

Release 4.0.1: https://github.com/lightsail-network/java-stellar-sdk/releases/tag/4.0.1
https://github.com/lightsail-network/java-stellar-sdk/pull/811
https://github.com/lightsail-network/java-stellar-sdk/pull/819
https://github.com/lightsail-network/java-stellar-sdk/pull/820
View all merged PRs (Q3 2026): https://github.com/lightsail-network/java-stellar-sdk/pulls?q=is%3Apr+is%3Amerged+merged%3A2026-07-01..2026-09-30
https://github.com/lightsail-network/stellar-contract-bindings/pull/29
https://github.com/lightsail-network/stellar-contract-bindings/pull/33

Maintenance was smaller than planned, because Protocol 28 support and SEP-48 binding generation (D3 and D4) were added mid-quarter and took up much of the time planned for it.

In the SDK, a community user reported that a valid testnet transaction could not be parsed (an ExtendFootprintTTLOperation with extendTo set to 0). The fix shipped in 4.0.1 the next day. After submitting a contract transaction, the SDK now waits between status checks instead of polling the RPC server continuously. Text is now always encoded as UTF-8, so non-ASCII text produces the same bytes on every JVM. These two fixes are in the pending release.

In stellar-contract-bindings, type mapping and templates in the Java generator were simplified, and generated Java no longer depends on the javatuples library.

D3. Protocol 28 Support

Description from last quarter:

This work was not explicitly planned but was completed as additional contribution during the quarter.

Proof of completion:

Release 5.0.0: https://github.com/lightsail-network/java-stellar-sdk/releases/tag/5.0.0
https://github.com/lightsail-network/java-stellar-sdk/pull/817
https://github.com/lightsail-network/java-stellar-sdk/pull/815

Protocol 28 support was added mid-quarter and shipped in 5.0.0, so Java and Android developers can build against the new protocol as soon as it is available. CAP-85 lets a contract follow Wasm code that an owner contract publishes under a tag, so updating the tag upgrades every contract that follows it. The SDK can now create such contracts, look up the code they point to, and read their interface specs.

D4. SEP-48 Contract Bindings in stellar-contract-bindings

Description from last quarter:

This work was not explicitly planned but was completed as additional contribution during the quarter.

Proof of completion:

Release 0.6.0b: https://github.com/lightsail-network/stellar-contract-bindings/releases/tag/0.6.0b
https://github.com/lightsail-network/stellar-contract-bindings/pull/40
https://github.com/lightsail-network/stellar-contract-bindings/pull/31
https://github.com/lightsail-network/stellar-contract-bindings/pull/32
https://github.com/lightsail-network/stellar-contract-bindings/pull/27

This work was added mid-quarter and builds on the SEP-48 support added to the SDK in Q2. 0.6.0b fixed the Java generator so that its output compiles, and CI now checks this on every change. The generator was then rewritten and merged for the next release: it generates typed bindings for contract events, structs, unions, and contract errors, with a simpler API for callers.

2026 Q2

1. Continuous Maintenance and Improvement

Description from last quarter:

Regular SDK updates addressing Horizon, Soroban RPC, and protocol changes (including Protocol 26), bug fixes, feature requests, and documentation updates. Keep CI/CD pipelines and dependency updates current.

Proof of completion:

Release 3.0.0: https://github.com/lightsail-network/java-stellar-sdk/releases/tag/3.0.0
Release 3.1.0: https://github.com/lightsail-network/java-stellar-sdk/releases/tag/3.1.0
Pre-release 4.0.0-beta0: https://github.com/lightsail-network/java-stellar-sdk/releases/tag/4.0.0-beta0

Some notable PR, not exhaustive:

PR #804: https://github.com/lightsail-network/java-stellar-sdk/pull/804 — feat: add CAP-71 (Protocol 27) Soroban authorization support
PR #807: https://github.com/lightsail-network/java-stellar-sdk/pull/807 — feat: add simulateTransaction useUpgradedAuth flag
PR #806: https://github.com/lightsail-network/java-stellar-sdk/pull/806 — refactor!: return signature SCVal from Auth.Signer for custom account contracts
PR #800: https://github.com/lightsail-network/java-stellar-sdk/pull/800 — chore: upgrade generated XDR definitions to Protocol 27
PR #784: https://github.com/lightsail-network/java-stellar-sdk/pull/784 — docs: improve xdr generator javadocs
PR #783: https://github.com/lightsail-network/java-stellar-sdk/pull/783 — docs: add missing Javadoc comments for various classes and methods
View all 23 merged PRs (Q2 2026): https://github.com/lightsail-network/java-stellar-sdk/pulls?q=is%3Apr+is%3Amerged+merged%3A2026-04-01..2026-06-30

Two stable releases shipped. The generated XDR was upgraded to Protocol 26 and then to Protocol 27, exceeding the planned Protocol 26 target. CAP-71 Protocol 27 Soroban authorization, including the new address-bound and delegated credential types, was implemented across the high-level API and shipped in the 4.0.0-beta0 pre-release, and Auth.Signer was further redesigned to natively support custom account contracts (BLS, WebAuthn, threshold, policy) in the pending release. This Protocol 27 work currently ships in the 4.0.0-beta0 pre-release rather than a stable release: Protocol 27 is not yet broadly available in real-world test environments, so the stable 4.0.0 is intentionally held until the implementation can be validated against a live Protocol 27 network. The toolchain was also modernized with a JDK 21 build toolchain and updated Gradle/Kotlin/dependencies, and Horizon request handling was hardened, alongside various bug fixes.

2. SEP-46, SEP-47, and SEP-48 Support

Description from last quarter:

Add support for SEP-46 (Contract Meta), SEP-47 (Contract Interface Discovery), and SEP-48 (Contract Interface Specification). These three SEPs form the foundation for smart contract self-description: SEP-46 defines how contracts embed metadata in Wasm custom sections, SEP-47 lets contracts declare which SEPs they implement, and SEP-48 provides a rich interface specification including Soroban host types, user-defined types, and event schemas. Together they enable the SDK to parse and expose contract metadata, which is essential for tooling, auto-generated contract clients, and off-chain systems that need to understand contract interfaces.

Proof of completion:

PR #796: https://github.com/lightsail-network/java-stellar-sdk/pull/796 — add SEP-46/47/48 contract introspection support
Release 3.1.0: https://github.com/lightsail-network/java-stellar-sdk/releases/tag/3.1.0

Introspection APIs for SEP-46 (contract metadata), SEP-47 (contract interface discovery), and SEP-48 (contract interface specification) were added and shipped in 3.1.0, including ContractMeta, ContractSpec, and ContractInfo wrappers under org.stellar.sdk.contract and SorobanServer helpers (getContractWasm, getContractMeta, getContractSpec, getContractInfo) that parse a Soroban contract’s Wasm and expose its self-described metadata. This gives tooling and off-chain systems a standard way to understand contract interfaces.

3. AI Coding Agent Skill

Description from last quarter:

Publish an AI coding agent skill for the java-stellar-sdk following the agentskills.io open standard, compatible with Claude Code, Codex CLI, Cursor, Gemini CLI, and others. The skill provides token-efficient documentation and best practices for AI-assisted development with the SDK, lowering the barrier for developers using AI tools to build on Stellar.

Proof of completion:

PR #797: https://github.com/lightsail-network/java-stellar-sdk/pull/797 — add agent skill for java-stellar-sdk
Release 3.1.0: https://github.com/lightsail-network/java-stellar-sdk/releases/tag/3.1.0

An Agent Skills-compatible skill was published under skills/, with Claude Code plugin manifests in .claude-plugin/ and Stellar-specific guidance covering transactions, operations, Horizon, Soroban, XDR/SCVal, and SEP protocols. It gives AI coding assistants token-efficient, accurate guidance for building on Stellar with the SDK, lowering the barrier for developers using AI tools.

Proposed Impact

In Q3, Protocol 28 support and SEP-48 binding generation came up mid-quarter and took much of the time we had planned for refactoring. In Q4 2026, we want to get back to that plan: refactor the SDK and pay down technical debt, so it stays easy to maintain and reliable for JVM and Android developers as the protocol keeps growing. We will keep up routine maintenance of the SDK and the Java generator in stellar-contract-bindings in parallel.

Proposed Deliverables

P1. Refactoring and Technical Debt Reduction

We will pick up the refactoring we planned for Q3: go through the codebase and test suite, pay down technical debt, and simplify code that has grown over many releases. We will decide on specific changes as we work through the code, and any breaking change will be noted in the release notes.

Proof: Commits or PRs, or release notes.

P2. Continuous Maintenance and Improvement

The usual upkeep: respond to community issues and pull requests, follow Soroban RPC changes, keep Android compatibility current, and keep CI/CD and dependencies up to date. This also covers the Java generator in stellar-contract-bindings.

Proof: Commits or PRs, or release notes.

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Legal Acknowledgements

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