NoSuchMethodError in DefaultMcpTransportBuilder when using Spring AI 2.0 (MCP 1.x classpath collision)

[akbarkanso]

🔴 Required Information

Describe the Bug:
The google-adk-spring-ai library is binary-incompatible with Spring AI 2.0.0 (GA) and the MCP 1.x SDK. This is due to a classpath collision in the io.modelcontextprotocol.json.McpJsonMapper class. ADK calls a static method (.getDefault()) that existed in the legacy MCP 0.17.x SDK but has been removed in the 1.x line used by Spring AI 2.0.

Steps to Reproduce:

1. Create a Spring Boot project and include the Spring AI 2.0.0 BOM and dependencies.
2. Add the com.google.adk:google-adk-spring-ai:1.2.0 dependency.
3. Attempt to initialize an McpToolset or any code path that triggers the DefaultMcpTransportBuilder.
4. Observe the runtime crash during class loading/initialization.

Expected Behavior:
The ADK McpToolset should be compatible with the modern mcp-core:1.x architecture, allowing users to leverage the stable release of Spring AI 2.0 alongside Google ADK.

Observed Behavior:
The application fails with the following stack trace:

java.lang.NoSuchMethodError: 'io.modelcontextprotocol.json.McpJsonMapper io.modelcontextprotocol.json.McpJsonMapper.getDefault()'
    at com.google.adk.tools.mcp.DefaultMcpTransportBuilder.<clinit>(DefaultMcpTransportBuilder.java:...)

Environment Details:

• ADK Library Version: 1.2.0
• OS: macOS / Linux
• TS Version: N/A (Java Environment)

Model Information:

• Which model is being used: N/A (This is a protocol/library level initialization error)

---

🟡 Optional Information

Regression:
No. This is an incompatibility introduced by the architectural shift between MCP 0.17.x (which ADK pins) and MCP 1.x (which Spring AI 2.0 pins).

Additional Context:
Both google-adk and spring-ai now share a dependency on the same Fully Qualified Class Name (FQCN): io.modelcontextprotocol.json.McpJsonMapper.

• ADK's DefaultMcpTransportBuilder expects a static getDefault() method.
• Spring AI 2.0 pulls in mcp-core:1.x, where this method was removed/renamed to createDefault().
  Since Gradle/Maven resolves the conflict to version 1.x to satisfy Spring AI, the ADK code attempts to call a non-existent method on the 1.x class.

Minimal Reproduction Code:
In a standard Spring AI 2.0 project, simply attempting to use the default MCP transport via ADK will fail:

// This triggers the static initializer of DefaultMcpTransportBuilder
McpToolset toolset = McpToolset.builder()
    .parameters(StreamableHttpServerParameters.builder()
        .uri("https://mcp-server/mcp")
        .build())
    .build();

How often has this issue occurred?:

• Always (100%) when Spring AI 2.0 and Google ADK 1.2.0 are present on the same classpath.

[hemasekhar-p]

Hi @akbarkanso, thank you for reporting this issue. I have been able to reproduce the NoSuchMethodError as described. The reason you are getting this error because Spring transitive dependency version conflict. The ADK currently expects mcp-core:0.17.0, while Spring AI 2.0 transitively pulls in mcp-core:1.1.0. To resolve this, could you please pin the io.modelcontextprotocol.sdk:mcp-core version to <version>0.17.0</version> like below and let us know if your issue is resolved?

<dependencyManagement>
		<dependencies>
			<dependency>
				<groupId>io.modelcontextprotocol.sdk</groupId>
				<artifactId>mcp-core</artifactId>
				<version>0.17.0</version>
			</dependency>
		</dependencies>
	</dependencyManagement>