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
Repository https://github.com/lightsail-network/java-stellar-sdk
First Released November 2015
Intake soft-launch
Budget Requested 15000

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.

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 Q2 2026, all three planned deliverables were completed, and protocol work went beyond the plan. The SDK shipped two stable releases (3.0.0 and 3.1.0). Support for the smart-contract self-description SEPs (SEP-46, SEP-47, SEP-48) and an AI coding agent skill both landed in 3.1.0. The generated XDR was advanced from the planned Protocol 26 to Protocol 27, with CAP-71 Soroban authorization support implemented in the 4.0.0-beta0 pre-release. Alongside features, the toolchain was modernized, a JDK 21 build toolchain, updated Gradle/Kotlin, and dependency refreshes, and Horizon request handling was hardened.

Past Deliverables

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

The primary goal for Q3 2026 is to ship java-stellar-sdk 4.0.0 as a stable release with full Protocol 27 support, giving the ecosystem’s JVM and Android developer base a supported path to the new protocol. CAP-71 Soroban authorization is already implemented in the 4.0.0 beta; the stable release is held until Protocol 27 is available on live test networks for end-to-end validation. Ongoing maintenance continues in parallel.

Proposed Deliverables

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

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: Stable 4.0.0 release on GitHub and Maven Central, auth examples and migration notes, passing CI on master.

2. Continuous Maintenance and Improvement

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: Release notes on GitHub, updated CHANGELOG, refactoring and optimization PRs, passing CI on master.

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