0.9.0

What's Changed

Breaking Changes

• Server call handlers now receive a RequestContext — handler lambdas for tools, prompts, and resources have a new context parameter providing access to request metadata (#515) by @rnett
• Ktor extension functions moved from Routing to Route — update call sites: routing { mcpSse() } → route("/mcp") { mcpSse() } or use directly in any Route block (#531) by @kpavlov
• StdioServerTransport rethrows CancellationException — cancellation is no longer silently swallowed; ReadBuffer parsing was also fixed (#571) by @kpavlov

New Features

• kotlin-sdk-testing module — new artifact providing an in-process, channel-based TestClientTransport / TestServerTransport for unit testing MCP servers and clients without network I/O (#505) by @kpavlov
• StreamableHttpServerTransport.Configuration — configurable builder for the Streamable HTTP server transport (timeouts, session handling, etc.) (#560) by @kpavlov
• Ktor extensions for Streamable HTTP — mcpStreamableHttp() Ktor plugin and routing DSL for mounting a Streamable HTTP MCP server (#504 by @devcrocod, #568 by @kpavlov)
• $defs support in ToolSchema — JSON Schema $defs / definitions can now be expressed in tool input schemas (#526) by @i1bro

Bug Fixes

• Fixed SSE transport endpoint resolution for non-root mount paths (#565) by @Amaneusz
• Fixed StdioClientTransport hanging indefinitely by adding proper read timeouts (#528) by @kpavlov

Improvements

• Introduced AbstractClientTransport base class, simplifying client transport lifecycle management (#516) by @kpavlov
• Deprecation cycle started — annotated APIs scheduled for removal in a future release (#498) by @devcrocod
• Detekt static analysis integrated into CI (#493, #507) by @kpavlov
• Code coverage reporting added via Codecov (#579, #580) by @kpavlov
• Flaky StdioClientTransport tests replaced with real stdin pipe–based tests (#508) by @kpavlov

Dependency Updates

• Kotest 6.1.2, MockK 1.14.9, AtomicFU 0.31.0, Gradle 9.3.1, Kover 0.9.7

New Contributors

• @jskjw157 made their first contribution in #486
• @i1bro made their first contribution in #526
• @localden made their first contribution in #536
• @aozherelyeva made their first contribution in #551
• @rnett made their first contribution in #515
• @Amaneusz made their first contribution in #565

Full Changelog: 0.8.4...0.9.0