## Summary
- reject empty sampling content in SamplingMessage and
CreateMessageResult constructors
- clarify sampling validation docs and emit an explicit error when
tool_use is not followed by tool_result
- return sampled text from the conformance test_sampling tool instead of
content object strings
Fixes#730
## Testing
- ./gradlew
-Dorg.gradle.java.installations.paths="/Users/ubl/Documents/New
project/oss-contributions/.jdks/jdk-21.0.11+10/Contents/Home"
:kotlin-sdk-core:jvmTest :kotlin-sdk-server:jvmTest
:conformance-test:compileKotlin
Co-authored-by: Pavel Gorgulov <devcrocod@gmail.com>
Add `DnsRebindingProtection` Ktor route-scoped plugin and enable it by
default across all http transports
## Motivation and Context
DNS rebinding protection was disabled by default
(`enableDnsRebindingProtection = false`), and sse endpoints
(`Route.mcp()`) had zero protection. Same vulnerability as typescript
sdk
[GHSA-w48q-cv73-mx4w](https://github.com/modelcontextprotocol/typescript-sdk/security/advisories/GHSA-w48q-cv73-mx4w)
## How Has This Been Tested?
all tests pass
## Breaking Changes
- `Route.mcp()`, `Application.mcp()` signatures changed (new
`enableDnsRebindingProtection`, `allowedHosts`, `allowedOrigins`
params), binary incompatible on JVM
- `enableDnsRebindingProtection` default changed from `false` to `true`
on `mcpStreamableHttp`/`mcpStatelessStreamableHttp`
- Default allowed hosts: `localhost`, `127.0.0.1`, `[::1]` — opt out
with `enableDnsRebindingProtection = false`
- Host validation is now port-agnostic (matches ts sdk)
- Origin validation now allows missing `Origin` header (non-browser
clients)
- `Configuration.enableDnsRebindingProtection`, `.allowedHosts`,
`.allowedOrigins` deprecated in favor of the plugin
## 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
Migrate detekt to a convention plugin in `buildSrc`, switch the project
to a fully explicit YAML config (`buildUponDefaultConfig = false`), fix
the real findings that this stricter setup revealed, and remove
`@Suppress` annotations that became unnecessary after the rule changes.
## Motivation and Context
- Explicit visibility into the rule set
- Lock against detekt version upgrades
## 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)
- [x] 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
Users currently must manually `install(ContentNegotiation) {
json(McpJson) }` before calling `mcp()`,
`mcpStreamableHttp()`, or `mcpStatelessStreamableHttp()`. Forgetting
this or using the default `json()`
instead of `json(McpJson)` causes silent serialization failures at
runtime (e.g., explicit null fields in JSON-RPC
responses). This PR makes the SDK install it automatically.
Fixes#664
## Changes
- **Core feature** — `mcp()`, `mcpStreamableHttp()`, and
`mcpStatelessStreamableHttp()` now auto-install `ContentNegotiation`
configured with `McpJson`. If the user already installed
`ContentNegotiation`, a warning is logged instead of crashing with
`DuplicatePluginException`.
- **`KtorServerHelpers.kt`** (new) — `installMcpContentNegotiation()`
internal helper with `pluginOrNull` guard and warning
- **`KtorServer.kt`** — calls the helper from all three entry points
- **`build.gradle.kts`** — adds `ktor-server-content-negotiation` and
`ktor-serialization` as `implementation` deps to `kotlin-sdk-server`
- **Removed manual installs** from `ConformanceServer.kt` and
`AbstractStreamableHttpIntegrationTest.kt`.
- **Test infrastructure** — replaced `slf4j-simple` with Logback and use
`ListAppender` (`LogCapture` utility) for deterministic log assertion.
Added `logback-test.xml` matching previous log levels.
- **`StreamableHttpServerConfigurationTest.kt`** (new) — verifies the
warning for all three entry points: `mcpStreamableHttp`,
`mcpStatelessStreamableHttp`, and `mcp` (SSE).
- **README.md** — removed manual `ContentNegotiation` boilerplate from
examples, documented automatic installation, added CORS configuration
snippet for browser-based clients.
- **CI** — added `ktlintCheck` to the Linux build matrix job.
## How Has This Been Tested?
Unit/integration tests. Conformance tests updated
## Breaking Changes
No
## 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)
- [x] 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
Add URL mode elicitation support and typed `PrimitiveSchemaDefinition`
hierarchy to align with MCP specification 2025-11-25
closes#540
## How Has This Been Tested?
unit/integration/conformance
## Breaking Changes
- `ElicitRequestParams` changed from `data class` to `sealed interface`.
A deprecated factory function preserves source compatibility for
`ElicitRequestParams(message, requestedSchema)`.
- `RequestedSchema.properties` changed from `JsonObject` to `Map<String,
PrimitiveSchemaDefinition>`.
- `ElicitRequest.requestedSchema` is deprecated, use `(params as
ElicitRequestFormParams).requestedSchema`.
## 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
## Correct SEP-1330 enum schemas in test_elicitation_sep1330_enums
**NB! This PR contains changes from #599 and should be rebased and
merged after #599 is merged.**
Update conformance test according to [test
requirements](https://github.com/modelcontextprotocol/conformance/blob/main/src/scenarios/server/elicitation-enums.ts#L14C1-L35C9).
- Fix legacyEnum: was using `oneOf` with const/title pairs; now
correctly uses `enum` + `enumNames` arrays per LegacyEnumSchema spec
- Fix titledMulti: items were using `oneOf` with extra `type:"string"`;
now correctly uses `anyOf` per TitledMultiSelectEnumSchema spec
- Fix return text format to match expected "Elicitation completed:
action=..., content=..."
- Remove _elicitation-sep1330-enums_ from conformance baseline (test now
passes)
## How Has This Been Tested?
```shell
./conformance-test/run-conformance.sh server
```
## 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
<!-- 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
---------
Co-authored-by: devcrocod <devcrocod@gmail.com>
## Changes
- fix(server): keep SSE connection open until explicitly cancelled
- conformance: add logging to test_tool_with_logging and update
troubleshooting documentation
- chore(conformance): remove 5 passing server tests from conformance
baselines:
- tools-call-with-logging
- tools-call-with-progress
- tools-call-sampling
- tools-call-elicitation
- elicitation-sep1034-defaults
## Motivation and Context
Two bugs in StreamableHttpServerTransport caused server-to-client
notifications (e.g. notifications/message during tool calls) to be
silently dropped.
**Bug 1 — GET SSE stream closed immediately**
`handleGetRequest` rejected GET requests with 405 when
`enableJsonResponse = true` (which `mcpStreamableHttp` always sets).
Since the Ktor `sse {}` handler commits response headers before the body
runs, the reject failed silently and the function returned, causing Ktor
to close the SSE stream. There was also no `awaitCancellation()` to keep
the connection alive.
**Bug 2 — Notifications discarded in JSON mode**
In `send()`, notifications with a relatedRequestId entered the
POST-stream path but hit `if (!isTerminated) return` without being
forwarded anywhere.
**Fix**
- Remove the enableJsonResponse guard from handleGetRequest. The GET SSE
stream is an always-required notification channel, orthogonal to how
POST responses are delivered.
- Add `awaitCancellation()` to keep the GET SSE connection open until
the client disconnects or the transport closes.
- In `send()`, route notifications with a relatedRequestId to the
standalone GET SSE stream when `enableJsonResponse = true`.
## How Has This Been Tested?
Verified against the MCP conformance test suite — the
ToolsCallWithLogging scenario now passes. ngrep confirms the `GET /mcp`
stream stays open and `notifications/message` events arrive before the
`tools/call` response.
## Breaking Changes
<!-- Will users need to update their code or configurations? -->
## Types of changes
<!-- What types of changes does your code introduce? Put an `x` in all
the boxes that apply: -->
- [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
<!-- 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
Fixes#587
Requires #585 to be merged first.
---------
Co-authored-by: devcrocod <devcrocod@gmail.com>
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>
