Make inbound message handling concurrent after the initialization
handshake, so a slow or peer-awaiting handler no longer blocks other
messages on the same connection
fixes#176, #572
## Motivation and Context
Inbound messages were processed serially on the transport read loop. One
slow or peer-awaiting request handler (sampling, elicitation, roots)
blocked every later message on that connection, including the responses
and `notifications/cancelled` those handlers depend on which could
deadlock request/response flows.
## How Has This Been Tested?
New and old tests
## Breaking Changes
- after the handshake, inbound handlers may run concurrently (processing
stays serial during initialization). There is no opt-out flag by design,
concurrency is bounded by `maxConcurrentHandlers` /
`maxInFlightHandlers`.
- `ProtocolOptions` / `ClientOptions` / `ServerOptions` gain new
parameters with defaults
- `RequestHandlerExtra` is now a coroutine-context element and is no
longer user-constructible
## Types of changes
- [x] Bug fix (non-breaking change which fixes an issue)
- [x] New feature (non-breaking change which adds functionality)
- [x] Breaking change (fix or feature that would cause existing
functionality to change)
- [ ] Documentation update
## Checklist
- [x] I have read the [MCP
Documentation](https://modelcontextprotocol.io)
- [x] My code follows the repository's style guidelines
- [x] New and existing tests pass locally
- [x] I have added appropriate error handling
- [x] I have added or updated documentation as needed
closes#410
## How Has This Been Tested?
integration and unit tests
## Breaking Changes
none
## Types of changes
- [ ] Bug fix (non-breaking change which fixes an issue)
- [x] New feature (non-breaking change which adds functionality)
- [ ] Breaking change (fix or feature that would cause existing
functionality to change)
- [ ] Documentation update
## Checklist
- [x] I have read the [MCP
Documentation](https://modelcontextprotocol.io)
- [x] My code follows the repository's style guidelines
- [x] New and existing tests pass locally
- [x] I have added appropriate error handling
- [x] I have added or updated documentation as needed
Bound the size of a single inline SSE event parsed from a POST response
in `StreamableHttpClientTransport`, so a non-conforming or unbounded
server response cannot grow the client's buffer without limit.
## How Has This Been Tested?
New unit tests
## Breaking Changes
none
## Types of changes
- [x] Bug fix (non-breaking change which fixes an issue)
- [ ] New feature (non-breaking change which adds functionality)
- [ ] Breaking change (fix or feature that would cause existing
functionality to change)
- [ ] Documentation update
## Checklist
- [x] I have read the [MCP
Documentation](https://modelcontextprotocol.io)
- [x] My code follows the repository's style guidelines
- [x] New and existing tests pass locally
- [x] I have added appropriate error handling
- [x] I have added or updated documentation as needed
Implements SEP-1577 sampling With tools
closes#409
## How Has This Been Tested?
unit + integration
## Breaking Changes
- binary changes
- MediaContent -> SamplingMessageContent
-
## Types of changes
- [ ] Bug fix (non-breaking change which fixes an issue)
- [x] New feature (non-breaking change which adds functionality)
- [x] Breaking change (fix or feature that would cause existing
functionality to change)
- [ ] Documentation update
## Checklist
- [x] I have read the [MCP
Documentation](https://modelcontextprotocol.io)
- [x] My code follows the repository's style guidelines
- [x] New and existing tests pass locally
- [x] I have added appropriate error handling
- [x] I have added or updated documentation as needed
Adds a comprehensive conformance test suite for the Kotlin MCP SDK,
covering core protocol operations, tool calls, elicitation, resources,
prompts, and 20 OAuth/auth scenarios
- Conformance server and client implementations
- OAuth/auth test scenarios: JWT, authorization code flow, client
credentials, PKCE, scope handling, cross-app access, client registration
- CI workflow
- Baseline file for tracking expected failures
- Shell script
fixes:
- #592
- #593
- #596
## Remaining known failures (tracked issues, will be fixed directly in
`main`)
- [x] `tools-call-with-logging`, `tools-call-with-progress`,
`tools-call-sampling`, `tools-call-elicitation`,
`elicitation-sep1034-defaults`- see #599,
- [x] `elicitation-sep1330-enums` - #587#600
- [x] `initialize` - #588
- [x] `tools_call`, `auth/scope-step-up`, `auth/scope-retry-limit` -
#589
- [ ] `elicitation-sep1034-client-defaults` - #414
- [x] `sse-retry` - #590
- [ ] `resources-templates-read` - #591
## Breaking Changes
from #596
- `StreamableHttpClientTransport` and
`mcpStreamableHttp`/`mcpStreamableHttpTransport`: old constructors
accepting `Duration` timeout are now `@Deprecated` — use the new
overloads with `ReconnectionOptions` instead
- `StreamableHttpClientTransport.close()` no longer calls
`terminateSession()` automatically
## Types of changes
- [x] Bug fix (non-breaking change which fixes an issue)
- [x] New feature (non-breaking change which adds functionality)
- [x] Breaking change (fix or feature that would cause existing
functionality to change)
- [ ] Documentation update
## Checklist
- [x] I have read the [MCP
Documentation](https://modelcontextprotocol.io)
- [x] My code follows the repository's style guidelines
- [x] New and existing tests pass locally
- [x] I have added appropriate error handling
- [x] I have added or updated documentation as needed
---------
Co-authored-by: Konstantin Pavlov <1517853+kpavlov@users.noreply.github.com>
## refactor: Introduce AbstractClientTransport and simplify client
transport lifecycle
This PR unifies state management logic across client transports, except
for the websocket transport, as it needs more refactoring first and is
not the primary transport.
- Introduce `AbstractClientTransport` as base class for other client
transports.
- Migrate to `ClientTransportState` states with state machine,
streamline state management.
- Ensure proper cleanup and error handling consistency across transport
implementations.
- Add unit tests to validate `AbstractClientTransport` behavior and
state transitions.
- Update related documentation and API contract.
- Make sure `onClose` callback is called at most once
- fix
[StreamableHttpClientTransportTest.kt](https://github.com/modelcontextprotocol/kotlin-sdk/pull/516/changes#diff-b9fe8891d08a492448a7ed2dc782151c6a915ae1403a4d70c2034c6062c84cb5)
to throw `McpException` on connect when received invalid Json
## Motivation and Context
Unify lifecycle handling and eliminate duplication in client Transport
implementations.
## How Has This Been Tested?
Unit test, regression tests
## Breaking Changes
- `onClose` callback is now called only once
- send(...) will throw McpException with message "Transport is not
ready" when `ClientTransportState != Operational`
## Types of changes
- [ ] Bug fix (non-breaking change which fixes an issue)
- [x] Refactoring
- [ ] New feature (non-breaking change which adds functionality)
- [x] Breaking change (fix or feature that would cause existing
functionality to change)
- [ ] Documentation update
## Checklist
<!-- Go over all the following points, and put an `x` in all the boxes
that apply. -->
- [x] I have read the [MCP
Documentation](https://modelcontextprotocol.io)
- [x] My code follows the repository's style guidelines
- [ ] New and existing tests pass locally
- [ ] I have added appropriate error handling
- [ ] I have added or updated documentation as needed
## Additional context
See #517
Add support for `TransportSendOptions` in `Transport.send` method
## Motivation and Context
This change extends the `Transport.send` method signature to support
advanced transport features like resumption tokens and progress
callbacks. This is needed to enable:
- Long-running request resumption after reconnection
- Request-response association tracking
- Progress token handling in transport layer
needed for #235
## How Has This Been Tested?
All transport tests passed
## Breaking Changes
Yes, it’s necessary to update the custom Transport implementations.
For users who rely on the transports provided by the sdk, there’s no
breaking change
## Types of changes
- [x] Bug fix (non-breaking change which fixes an issue)
- [x] New feature (non-breaking change which adds functionality)
- [ ] Breaking change (fix or feature that would cause existing
functionality to change)
- [ ] Documentation update
## Checklist
- [x] I have read the [MCP
Documentation](https://modelcontextprotocol.io)
- [x] My code follows the repository's style guidelines
- [x] New and existing tests pass locally
- [x] I have added appropriate error handling
- [x] I have added or updated documentation as needed
- Introduced `@ExperimentalMcpApi` annotation to mark experimental APIs.
- Added `mcpClient` function for initializing and connecting MCP
clients.
- Modified tests to utilize the new `mcpClient` function.
- Refactored variable naming in transport tests for improved
readability.
## Motivation and Context
To improve the creation of the MCP Client experience.
## How Has This Been Tested?
Integration test updated
## Breaking Changes
No
## Types of changes
<!-- What types of changes does your code introduce? Put an `x` in all
the boxes that apply: -->
- [ ] Bug fix (non-breaking change which fixes an issue)
- [x] New feature (non-breaking change which adds functionality)
- [ ] Breaking change (fix or feature that would cause existing
functionality to change)
- [ ] Documentation update
## Checklist
<!-- Go over all the following points, and put an `x` in all the boxes
that apply. -->
- [x] I have read the [MCP
Documentation](https://modelcontextprotocol.io)
- [x] My code follows the repository's style guidelines
- [x] New and existing tests pass locally
- [ ] I have added appropriate error handling
- [ ] I have added or updated documentation as needed
## Additional context
<!-- Add any other context, implementation notes, or design decisions
-->
Implement the last version of the mcp schema and complete restructuring
of the mcp schema implementation from a monolithic `types.kt` file into
separate files.
- #158
- #185
- #353
- #298
- #248
## Motivation and Context
The previous implementation of the mcp schema was outdated and contained
several issues. In addition, it stored all mcp types in a single large
file, which made maintenance and further development more difficult
## How Has This Been Tested?
All tests passed
## Breaking Changes
Yes. The new types are now located in a separate package. Additionally,
many types have new parameters and modified constructors
## Types of changes
- [x] Bug fix (non-breaking change which fixes an issue)
- [x] New feature (non-breaking change which adds functionality)
- [x] Breaking change (fix or feature that would cause existing
functionality to change)
- [ ] Documentation update
## Checklist
- [x] I have read the [MCP
Documentation](https://modelcontextprotocol.io)
- [x] My code follows the repository's style guidelines
- [x] New and existing tests pass locally
- [x] I have added appropriate error handling
- [x] I have added or updated documentation as needed
## Additional context
to adopt the new structure:
**Before:**
```kotlin
import io.modelcontextprotocol.kotlin.sdk.InitializeRequest
import io.modelcontextprotocol.kotlin.sdk.Resource
```
**After:**
```kotlin
import io.modelcontextprotocol.kotlin.sdk.types.InitializeRequest
import io.modelcontextprotocol.kotlin.sdk.types.Resource
```
According to
https://modelcontextprotocol.io/specification/2025-06-18/basic/index#meta,
the _meta parameter should be passable when calling tools. While the
CallToolRequest class (in types.kt) currently includes _meta in its
definition, SDK users cannot actually input _meta when invoking the
callTool method.
This Pull Request adds a metadata parameter to the CallTool method and
includes functionality to convert various data formats without loss.
Additionally, to encourage the use of valid Key name formats as defined
by the protocol, validation for prefixes has been implemented.
---------
Co-authored-by: MAERYO <maeryo@hanwha.com>
Co-authored-by: devcrocod <devcrocod@gmail.com>
<!-- Provide a brief summary of your changes -->
## Motivation and Context
The
[schema](cca15204f6/schema/2025-03-26/schema.ts (L192))
for the InitializeResult contains an optional 'instructions' string
## Additional context
The instructions string is included in the schema for for version
"2025-03-26"
The instructions in the Server class are given as a provider function
with the result of the provider propagated to the underlying
ServerSession. As the ServerSession change is meant to allow for a
'Singleton scoped' server class, this provides the ability to
dynamically modify the instructions at the server level but have them be
immutable per session.
This also refactors the `serverInfo` and `instructions` properties to be
protected. This `Server` class is open and meant to be overridden, there
is no harm in having these immutable properties available to subclasses.
This adds the serverInstructions to the client as returned from the
InitializeResult. This is used to verify the response in the Server
tests.
fix#272
## How Has This Been Tested?
Locally
## Breaking Changes
No
## Types of changes
- [x] Bug fix (non-breaking change which fixes an issue)
- [ ] New feature (non-breaking change which adds functionality)
- [ ] Breaking change (fix or feature that would cause existing
functionality to change)
- [ ] Documentation update
## Checklist
- [x] I have read the [MCP
Documentation](https://modelcontextprotocol.io)
- [x] My code follows the repository's style guidelines
- [x] New and existing tests pass locally
- [ ] I have added appropriate error handling
- [ ] I have added or updated documentation as needed
* Modularize SDK: migrated client and server implementations to separate modules. Removed old configuration files and reorganized the source code structure
* add support native targets and update js/wasm configurations
* Refactor sample projects: add samples as composite builds, replace hardcoded dependencies with version catalog, remove obsolete gradle wrapper files
* Update .gitignore: exclude SWE agent directories (.claude/ and .junie/)
* Refine CodeQL workflow: update Kotlin build steps to target individual modules separately instead of building all at once
