v1.0.0

Change Log

1.0.0 (04/2/2026)

Important

This is the first GA release of Smithy Java. All client modules are now considered stable.
Some modules, including server, CLI, and MCP, are still in developer-preview and may contain bugs.
No guarantee is made about their API stability. Unstable modules are marked with a warning in their
README.md and with the @SmithyUnstableApi annotation in their package-info.java.

Features

• Added JSpecify nullness annotation support.
• Added endpoint rules engine with BDD codegen, fused opcodes, and peephole optimizations. (#1035)
• Added support for AWS Query protocol in the client.
• Added support for request compression. (#968)
• Added checksum support in requests. (#911)
• Added event streams support to AWS JSON protocols. (#1076)
• Added event stream implementation for RPCv2. (#849)
• Added support for @eventHeader and @eventPayload for RPC protocols. (#864)
• Added event stream signing support. (#1054)
• Implemented new event streams API. (#1035)
• Added an OpenTelemetry based plugin to publish operation metrics. (#1030)
• Added support for native remote MCP servers. (#943)
• Added MCP ping request support. (#1016)
• Added MCP proxy server support for prompts.
• Added MCP metrics observer support to McpServerBuilder.
• Added support for SSE + streaming with MCP notifications.
• Added structured content to MCP tool responses when possible.
• Added output schema to MCP tools/list.
• Added protocol version to MCP initialize response.
• Added workingDirectory to StdioProxy.
• Added error response parsing for restXml. (#922)
• Added support for BigDecimal Documents in CBOR.
• Added map input for dynamic client.
• Added DataStream.writeTo() and IO utilities.
• Added isAvailable to check if DataStream has not been consumed.
• Added close to DataStream to allow closing resources.
• Added generic types to JMESPath predicates. (#1067)
• Added utility to fill shapes with random values.
• Added fuzz testing framework.
• Added document discriminator sanitizer for JSON protocols. (#932)
• Added plugin phases, auto-plugins, and hierarchy for codegen.
• Added ability to register default plugins in codegen.
• Added new code sections to support deserialization overrides.
• Added plugin test runner. (#855)
• Added compile method for EndpointRuleSet in RulesEngineBuilder.
• Added singletons for AwsCredentialsResolver implementations. (#1059)
• Added strategy for writing error types to headers.
• Added ModifiableHttpHeaders method to overwrite HTTP header values.
• Generated input shape with additionalInput member for operations with Unit input.
• Added model bundle version to decide whether to wrap input or not.
• Added additionalInfo to BundleMetadata.
• Allowed event processors to compose. (#1095)
• Allowed lists to be marked as httpPayload.
• Added KEYS synchronization.
• Added HttpTransportConfig for transport settings.

Bug Fixes

• Fixed equals for float and double values. (#1129)
• Fixed CBOR deserializer crash on empty input for no-input operations. (#1103)
• Fixed protocol initialization for AwsRestJson1Protocol. (#1023)
• Fixed incorrect codegen for HttpApiKeyAuthTrait.
• Fixed encoding/decoding of errors and exception events. (#1055)
• Fixed SchemaIndex collision for Unit inputs/outputs.
• Fixed handling of timestamps inside oneOf unions.
• Fixed handling of event payload members of blob and string type. (#1064)
• Fixed bug of adding a null element to the list when list is empty or null.
• Fixed Sigv4 multivalued query key ordering and double path encoding. (#984)
• Fixed query params with more than one value per key. (#973)
• Fixed double encoding URIs for signing. (#972)
• Fixed httpQuery related protocol tests. (#945)
• Fixed httpHeader and httpPrefixHeaders protocol tests. (#914)
• Fixed QueryCustomizedError protocol test.
• Fixed type conversion issues in MCP.
• Fixed naming conflict between class name and Schema field when structure name is all capitals.
• Fixed name conflicts resolving. (#902)
• Fixed builder setters to use the correct boxed or primitive type.
• Fixed javadoc link. (#987)
• Fixed URI concat issue with HttpClientProtocol.
• Fixed bytecode loading and creation.
• Fixed O(N!) allocations for recursive union variants.
• Fixed content-type for http-payload when already in headers.
• Fixed skipping OperationGenerator in types-only codegen mode.
• Fixed gradle to generate javadoc and sources jar for publishing. (#854)
• Fixed delay publishing the initial event until fully wired. (#865)
• Fixed null protocol version handling in MCP requests.
• Fixed proxy initialization failures no longer silently swallowed.
• Correctly handled BigInteger and BigDecimal defaults.
• Correctly adapted oneOf unions nested in oneOfUnions.
• Properly supported lists of Documents. (#869)

Improvements

• Optimized hashCode computation. (#1130)
• Cleaned up query/percent parsing and encoding utilities.
• Removed indirection and overhead from interceptors (#1127)
• Optimized header name matching using generated buckets and identity checks.
• Optimized equals and hashCode of SmithyUri.
• Optimized request/response pipeline handling.
• Replaced request/response builders with modifiable copies.
• Switched to faster and cheaper array-backed headers.
• Optimized Context implementation with chunked array storage.
• Optimized SchemaConverter and MCP Schema conversion.
• Optimized string validation.
• Optimized endpoints VM with fused opcodes, ite, negative indexing, and SPLIT opcode.
• Optimized timestamp handling with minor improvements.
• Avoided unnecessary UTF-8 decoding and byte[] allocations when flushing MCP structs.
• Avoided boxing for primitive Documents and fixed equals for various Documents.
• Used SmithyUri instead of URI for performance.
• Improved HttpHeaders to only allocate names when needed.
• Added upper bound on container pre-allocation during deserialization.
• Prevented allocating large arrays based on BigInteger lengths.
• Added stricter verifications while reading lists in Json Codec.
• Added better header and value validation.
• Improved client content-type deserialization handling.
• Converted Jackson exceptions to SerializationException.
• Used JmespathRuntime for JMESPath evaluation.
• Used proper classloader for loading services. (#958)
• Used symbols instead of hardcoded strings. (#1072)
• Used sealed interfaces for enums and records for unions.
• Oriented DataStream around InputStream.
• Made Client implement Closeable.
• Made ClientTransport extend Closeable.
• Made rules engine independent of client.
• Moved to blocking client, towards virtual threads.
• Increased default MCP HTTP proxy timeout from 60s to 5 minutes.
• Upgraded to Jackson 3.0.3.

Breaking Changes

• Removed request/response builders in favor of modifiable copies.
• Removed useExternalTypes option (unused).
• Removed unused utility methods.
• Removed tracing API. (#1068)
• Removed ExternalSymbols.
• Removed MCP CLI functionality.
• Removed MCP bundles module.
• Removed unused ExecutorService from call context.
• Removed map* methods from Hooks and replaced with cast.
• Removed default from JsonArraySchema.
• Removed unused jline dependency.
• Split codegen-plugins back into codegen-core and removed client-api. (#1091)
• Moved from plugin-based codegen to mode-based codegen for types, client, and server.
• Moved endpoints to upper level.
• Separated java and resources into different folders. (#1078)
• Surface area review of client packages. (#1086)
• Surface area review of CLI package API. ([#1085](https://github.com/smithy-lang/smit...

v0.0.3 (Developer Preview)

0.0.3 (08/21/2025)

Warning

This is a developer-preview release and may contain bugs. No guarantee is made about API stability.
This release is not recommended for production use!

Features

• Added Model Context Protocol (MCP) CLI to manage MCP Servers.
• Added Model Context Protocol (MCP) server generation from Smithy models with AWS service bundles and generic bundles.
• Added @prompts trait to provide contextual guidance for LLMs when using Smithy services.
• Added @tool_assistant and @install_tool prompts for enhanced AI integration.
• Added CORS headers support for Netty server request handler.
• Added Document support and BigDecimal/BigInteger support for RPCv2 CBOR protocol.
• Added pretty printing support for JSON serialization.
• Added client-config command to configure client configurations.
• Added request-level override capabilities and call config interceptor support.
• Added JMESPath to_number function.
• Added dynamic tool loading and search tools support.
• Added StdIo MCP proxy and process I/O proxy functionality.
• Added support for customizing smithy mcp home directory.

Bug Fixes

• Fixed empty prefix headers tests.
• Changed generated getters to have 'get' prefix.
• Fixed smithy-call issues.
• Fixed Registry selection and injection.
• Fixed missing newline in generated code.
• Fixed cross-branch pollution bug in SchemaConverter recursion detection.
• Fixed incorrect bitmask exposed by DeferredMemberSchema.
• Fixed service file merging for mcp-schemas.
• Fixed message in generated exceptions when message field has different casing.
• Fixed bounds check when non-exact bytebuffer is passed.
• Fixed ResourceGenerator to handle resources with more than 10 properties.
• Fixed JSON Documents equals implementation.
• Fixed CSV header parsing to not include quotes.
• Fixed AWS model bundle operation filtering logic.
• Fixed integration tests and flaky test issues.
• Fixed README to have correct example names for lambda example.

Improvements

• Made JAR builds reproducible.
• Updated to build with JDK21 while targeting JDK17.
• Added Graal metadata generation for native CLI builds.
• Added version provider SPI and exit code telemetry.

v0.0.2 (Developer Preview)

0.0.2 (04/07/2025)

Warning

This is a developer-preview release and may contain bugs. No guarantee is made about API stability.
This release is not recommended for production use!

Features

• Added generation of root-level service-specific exceptions for clients and servers.
• Added usage examples.
• Added custom exceptions for ClientTransport.
• Added lambda endpoint functionality with updated naming.
• Consolidated Schemas into a single class.
• Updated namespace and module naming.
• Improved document serialization of wrapped structures.
• Added support for service-schema access from client-side.
• Added support for generating MCP and MCP-proxy servers

smithy-call 0.1

smithy-call

smithy-call: a CLI that uses ahead-of-time compilation and the dynamic client to make ad-hoc calls to Smithy services using Smithy models.

Functionalities provided by this CLI include:

1. Execute operations listed in a service model
2. List operations in a service model
3. SigV4 authentication
4. Multi-protocol support

Example Calls

smithy-call [SERVICE] --list-operations -m [PATH_TO_SERVICE_MODEL]

smithy-call [SERVICE] [OPERATION] -m [PATH_TO_SERVICE_MODEL] --url [ENDPOINT_URL]

smithy-call [SERVICE] [OPERATION] -m [PATH_TO_SERVICE_MODEL] --url [ENDPOINT_URL] --input-path [PATH_TO_INPUT_JSON_FILE]

smithy-call [SERVICE] [OPERATION] -m [PATH_TO_SERVICE_MODEL] --url [ENDPOINT_URL] --input-json [JSON_STRING_INPUT] --auth aws --aws-region [AWS_REGION]

Disclaimer: The attached binary is a platform-specific Native Image for Apple Silicon. Please follow the README instructions to build Native Images for other platforms.

Link to README: https://github.com/smithy-lang/smithy-java/blob/main/cli/README.md

v0.0.1 (Developer Preview)

0.0.1 (02/06/2025)

Warning

This is a developer-preview release and may contain bugs. No guarantee is made about API stability.
This release is not recommended for production use!

Features

• Implemented Client, Server and Type codegen plugins.
• Added Client event streaming support.
• Added Client Auth support - sigv4, bearer auth, http basic auth.
• Added JSON protocol support - restJson1, awsJson.
• Added RPCV2 CBOR protocol support
• Implemented Dynamic client that can load a Smithy model to call a service.
• Added Smithy Lambda Endpoint wrapper to run generated server stubs in AWS Lambda