0.11.0

Adds URL-mode elicitation with typed schema definitions, configurable server payload size limits, and upgrades core dependencies to Kotlin 2.3.

Breaking Changes

ElicitRequestParams is now a sealed interface by @devcrocod in #660

Restructured to support both form-based and URL-based elicitation modes per the MCP specification. ElicitRequestParams changed from a data class to a sealed interface with two variants: ElicitRequestFormParams and ElicitRequestUrlParams. A deprecated factory function preserves source compatibility for existing calls.

- val params = ElicitRequestParams(message = "...", requestedSchema = schema)
+ val params = ElicitRequestFormParams(message = "...", requestedSchema = schema)

RequestedSchema.properties type changed by @devcrocod in #660

Changed from JsonObject to Map<String, PrimitiveSchemaDefinition> for type safety.

macosX64 target removed by @devcrocod in #625

The macosX64 native target was removed following its deprecation in Kotlin 2.2 and scheduled removal in Kotlin 2.3. Use macosArm64 instead.

Features

• URL-mode elicitation and typed PrimitiveSchemaDefinition hierarchy aligned with MCP specification by @devcrocod in #660
• Configurable max request payload size for StreamableHttpServerTransport via Configuration.maxRequestBodySize by @jskjw157 in #646
• Auto-install ContentNegotiation with McpJson in mcp(), mcpStreamableHttp(), and mcpStatelessStreamableHttp() — users no longer need to configure JSON serialization manually (#664) by @kpavlov in
  #665
• notifications/elicitation/complete notification from server to client for out-of-band elicitation completion by
  @devcrocod in #667

Fixed

• Elicitation schema defaults are now applied for missing fields in client responses by @devcrocod in #661
• Duplicate initialize requests are now rejected with INVALID_REQUEST error by @devcrocod in #624

Maintenance

• Updated Kotlin to 2.3.10, Ktor to 3.3.3, kotlinx-io to 0.9.0, kotlinx-serialization to 1.10.0 by @devcrocod in #611
• Enabled SseTransportTest on Wasm and refactored test structure by @devcrocod in #662
• Improved dependabot configuration by @devcrocod in #619
• Updated mcp-kotlin to 0.10.0 across sample projects by @kpavlov in #645

Dependencies

• modelcontextprotocol/conformance to 0.1.16 in #657
• atomicfu-gradle-plugin to 0.32.1 in #644
• path-to-regexp to 8.4.0 in #647
• Kotest group in #629
• Testing group in #630
• Gradle-plugins group in #633
• Infrastructure group in #632
• GitHub Actions group in #631
• JavaScript dependencies group in #627
• Cross-directory dependencies in #634, #648
• Sample project dependencies (mcp-kotlin, Ktor BOM) in #638, #651, #652, #654

Full Changelog: 0.10.0...0.11.0

0.10.0

Highlights

This release adds MCP conformance testing infrastructure, SSE reconnection support, Tasks protocol types, resource template matching, and
tool execution properties. It also completes a deprecation cycle — removing all previously deprecated (error-level) symbols from
io.modelcontextprotocol.kotlin.sdk in favor of their replacements in io.modelcontextprotocol.kotlin.sdk.types.

Breaking Changes

• Deprecation cycle completed — All symbols deprecated at ERROR level in 0.9.0 have been removed by @devcrocod (#615). This includes
  the entire io.modelcontextprotocol.kotlin.sdk.types.kt compatibility file (type aliases such as CallToolResult, CancelledNotification,
  ClientCapabilities, CompleteRequest, etc.) and the legacy McpJson in io.modelcontextprotocol.kotlin.sdk. Migrate to the equivalents
  in io.modelcontextprotocol.kotlin.sdk.types.
• SSE/Streamable HTTP transport changes — StreamableHttpClientTransport now accepts ReconnectionOptions for configurable retry
  behavior by @devcrocod (#585, #596). The previous constructor signatures remain available.

Features

• MCP conformance test infrastructure — Comprehensive conformance test suite covering core protocol operations, tool calls, elicitation,
  resources, prompts, and 20 OAuth/auth scenarios. Includes CI workflow, baseline tracking, and shell runner by @devcrocod (#585)
• SSE reconnection with retry support — Client transports now support configurable reconnection with exponential backoff via
  ReconnectionOptions (initial delay, max delay, multiplier, max retries) by @devcrocod (#596)
• Tasks protocol types — Added Task, TaskStatus, and related models per the MCP tasks specification by @devcrocod (#566)
• Resource templates with basic template matcher — Server-side support for URI template-based resource matching by @kpavlov (#502, #606)
• Tool execution properties — Tool now exposes execution properties for richer tool metadata by @devcrocod (#567)

Bug Fixes

• Notifications not delivered over Streamable HTTP — Fixed server-side notification delivery for Streamable HTTP transport sessions by
  @kpavlov (#587, #599)
• Conformance: SEP-1330 enum schemas — Corrected elicitation enum schemas in conformance tests by @kpavlov (#600)

Documentation

• New Streamable HTTP server sample by @devcrocod (#595)
• Updated client and server samples by @devcrocod (#598)
• Added Context7 config file by @devcrocod (#605)
• Updated AGENTS.md by @devcrocod (#612)
• Added missing KDoc for public API members by @kpavlov (#621)

Maintenance

• Simplified and cleaned up CI workflows by @devcrocod (#617)
• Modernized TypeScript integration tests, renamed SSE references to HTTP by @devcrocod (#618)
• Bumped Gradle wrapper from 9.3.1 to 9.4.1 by @dependabot (#614)
• Fix Kotlin language and api version to 2.1 by @kpavlov (#620)

Full Changelog: 0.9.0...0.10.0

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

0.8.4

Changes

• feat: Ktor extensions for streamable http (#504) by @devcrocod
• fix: Add $defs to ToolSchema and tests (#526) by @i1bro

Full Changelog: 0.8.3...0.8.4

0.8.3

What's Changed

Bugfixes

• breaking change!: StdioClientTransport.send(...) and StreamableHttpClientTransport.send(...) now throw McpException when not ready (#487) by @kpavlov
• #450 Properly check content type (#451) by @nerzhulart
• Fix flaky StdioClientTransportErrorHandlingTest (#457) by @kpavlov
• Fix tests for notifications (#446) by @tiginamaria
• Fix kotlin-mcp-server sample (#459) by @devcrocod
• Fix GitHub Actions build workflow (#474) by @kpavlov
• Fix confirmance tests (#483) by @Fuud and @kpavlov
• Refactor integration test infrastructure, fix and enable tests with ts-client (#478) by @kpavlov

New features

• Mark DSL functions for types as public (#472) by @kpavlov

Chores

• Update licensing to Apache 2.0 for new contributions (#481) by @domdomegg
• Add centralized TypeScript server factory for integration tests (#477) by @kpavlov
• Bump actions/setup-node from 4 to 6 (#453) by @dependabot
• Update GitHub Actions workflow (#452) by @kpavlov
• Bump io.mockk:mockk from 1.14.6 to 1.14.7 (#455) by @dependabot
• Bump io.github.oshai:kotlin-logging from 7.0.13 to 7.0.14 (#471) by @dependabot
• Bump org.jetbrains.kotlinx.kover from 0.9.3 to 0.9.4 (#466) by @dependabot
• Bump io.netty:netty-bom from 4.2.7.Final to 4.2.9.Final (#468) by @dependabot
• Bump actions/upload-artifact from 5 to 6 (#465) by @dependabot

New Contributors

• @nathaniellombardi-toast made their first contribution in #472
• @domdomegg made their first contribution in #481
• @Fuud made their first contribution in #483

Full Changelog: 0.8.1...0.8.2

0.8.1

What's Changed

• fix(stdio-client): Monitor STDERR and refactor StdioClientTransport to use flows. Fixes #107 by @kpavlov
• fix(sse-client): Skip SSE in StreamableHttpClientTransport when data is empty (#433) by @kpavlov
• Server feature list changed and resource updated notifications (#441) by @tiginamaria
• Add MCP conformance test coverage  (#435) by @skarpovdev

Chores

• Update samples to use new schema (#443) by @kpavlov
• Bump org.jetbrains.kotlinx:kotlinx-io-core from 0.8.1 to 0.8.2 (#440)
• Bump dev.mokksy:mokksy from 0.6.1 to 0.6.2 (#431)
• Bump kotest from 6.0.4 to 6.0.7 (#439)
• Bump actions/checkout from 5 to 6 (#429)

Full Changelog: 0.8.0...0.8.1

0.8.0

🚨 Breaking changes

MCP schema types refactor (#386)

The MCP schema implementation has been updated to the latest MCP spec and reorganized into dedicated packages:

• All MCP types moved to io.modelcontextprotocol.kotlin.sdk.types package
• Many schema types have new fields and updated constructor signatures
• Request/response types now use nested params objects

Migration:

// Before:
import io.modelcontextprotocol.kotlin.sdk.InitializeRequest
import io.modelcontextprotocol.kotlin.sdk.Resource

// After:
import io.modelcontextprotocol.kotlin.sdk.types.InitializeRequest
import io.modelcontextprotocol.kotlin.sdk.types.Resource

---

Minimum JVM version raised to 11 (#394)

The minimum supported JVM version is now 11. Projects running on Java 8 must upgrade their runtime and build toolchain.

---

Transport.send signature change (#408)

The Transport.send method now accepts TransportSendOptions? parameter to support resumption tokens, progress callbacks, and request–response association.

Note

Who is affected?
Only custom Transport implementations. Built-in transports require no changes.

Migration:
Update all Transport.send implementations to include the new TransportSendOptions? parameter.

---

Features

• New MCP Schema types (#386) @devcrocod
• Add server session id (#381) @tiginamaria
• Add new helper properties to request and notification types (#388) @devcrocod
• Add experimental mcpClient(...) factory method (#396) @kpavlov
• Proposal: DSL Builders for request types (#399) @devcrocod
• Add options in Transport.send method (#408) @devcrocod
• Add convenience constructors to JSONRPCRequest (#336) @kpavlov

Improvements

• Raise the version of the supported specification (#391) @devcrocod
• Increase deprecation levels (#393) @devcrocod
• Updated ServerPromptsTest, move AbstractTransport to its own file (#376) @kpavlov
• Add backwards compatibility constructors and tests (#395) @kpavlov
• Add warning message to ExperimentalMcpApi annotation and change level (#398) @devcrocod
• Handle additional error types in client initialization handling (#404) @devcrocod
• Add test with new schema types (#389) @devcrocod

Bug Fixes

• Kotlin-MCP can't be used without ktor-bom starting from 0.7.5 (#392) @IRus
• Fix providing progressToken with request (#405) @devcrocod

Documentation & Examples

• Add example Kotlin Notebook demonstrating MCP client (#397) @kpavlov

Build & Dependencies

• Bump version to 0.8.0-SNAPSHOT and update mcp-kotlin dependency in samples (#385) @kpavlov
• Update JVM target to 11 in Gradle build configuration (#394) @kpavlov
• Bump org.jlleitschuh.gradle.ktlint from 13.1.0 to 14.0.1 (#402) @dependabot[bot]
• Bump com.vanniktech:gradle-maven-publish-plugin from 0.34.0 to 0.35.0 (#403) @dependabot[bot]

New Contributors

• @IRus made their first contribution in #392

Full Changelog: 0.7.7...0.8.0

0.7.7

What's Changed

• 💥 Breaking change: Replace Instant with String for lastModified in Annotations by @kpavlov in #383

Full Changelog: 0.7.6...0.7.7

0.7.6

What's Changed

Bugfixes

• #355 Handle coroutine cancellation in Server Transports by @kpavlov in #375

Dependencies

• Bump version to 0.7.6-SNAPSHOT and update version to 0.7.5 in samples by @kpavlov in #374
• Update Gradle to version 9.2.0 across all projects by @kpavlov in #377

Full Changelog: 0.7.5...0.7.6

0.7.5

What's Changed

• Refactor WebSocket dependency by @devcrocod in #350
• Fix: Return CallToolResult with isError for tool errors to conform with MCP spec by @devcrocod in #354
• Relocate WebSocketIntegrationTest from commonTest to jvmTest by @devcrocod in #352
• Fix kotlin-mcp-server example and update samples by @devcrocod in #345
• Fix security for logging in server by @devcrocod in #360
• Refactor mcp server, rename connect to by @tiginamaria in #364
• Fix: Memory leak from unclosed sessions in Server by @devcrocod in #359
• Move features(tools, prompts, resources) management to the FeatureRegistry by @tiginamaria in #365
• Refactor ServerTest test structure by @tiginamaria in #366
• Fix: Handle logging/setLevel request for server by @devcrocod in #358
• Add Ktor BOM for dependency management across all modules, run Kotlin-MCP-Server Sample by @kpavlov in #367
• Add tests to server samples by @tiginamaria in #369
• Adds optional _meta field to Tool by @jclyne in #339
• Update Kotlin-MCP-Server with STDIO support, logging & CORS by @kpavlov in #371
• Update .gitignore to exclude kotlin-js-store directory by @devcrocod in #343
• Add AGENTS.md by @devcrocod in #349

Dependencies

• Bump org.openapi.generator from 7.16.0 to 7.17.0 by @dependabot[bot] in #362
• Bump mikepenz/action-junit-report from 5 to 6 by @dependabot[bot] in #363
• Bump actions/upload-artifact from 4 to 5 by @dependabot[bot] in #348

Full Changelog: 0.7.4...0.7.5