Mcp Env

[vyomakesh0728]

Description

New transport-backed MCPEnv for current main, adapted from the broader MCP foundation proposed in #566

• Adds verifiers/utils/mcp_utils/ with shared MCP utilities, tool wrapping, config models, and transports for stdio, remote streamable HTTP, sandboxed streamable HTTP, and synthetic/in-memory backends.

• MCPEnv is ported onto the current StatefulToolEnv / tool_defs architecture, supports shared or rollout-scoped MCP connections, preserves direct env.call_tool(...) compatibility, and keeps it stable across reconnects.

• transports are an interface for creating and using mcp servers with environments
• a base transport defines the basic methods needed by a transport, with the 2 main being stdio and http
• the sandbox transport is an extension of the http transport given it is still running streamable http mcp just with some extra steps and additional resource management
• during initialization of a transport a client session connected to the server is created and the list of tools available from the server
• streamable HTTP for the MCP server protocol
• TCP for Prime sandbox port exposure

class MCPTransport(ABC):
    """Base transport for MCP connections."""

    @abstractmethod
    async def connect(self) -> dict[str, MCPTool]:
        """Connect and return available tools."""

    @abstractmethod
    async def call_tool(self, tool_name: str, arguments: dict) -> Any:
        """Execute a tool call."""

    @abstractmethod
    async def disconnect(self) -> None:
        """Disconnect and clean up transport resources."""

    @abstractmethod
    async def is_connected(self) -> bool:
        """Check connection status."""

Validation

• focused tests, ty, and pre-commit passed
• stdio validated with a MCP server
• http validated with a streamable HTTP MCP server
• sandbox validated end-to-end with a Prime sandbox MCP server using TCP exposure

Type of Change

• 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 not work as expected)
• Documentation update
• Test improvement

Testing

• All existing tests pass when running uv run pytest locally.
• New tests have been added to cover the changes

Checklist

• My code follows the style guidelines of this project as outlined in AGENTS.md
• I have performed a self-review of my own code
• I have commented my code, particularly in hard-to-understand areas
• I have made corresponding changes to the documentation
• My changes generate no new warnings
• Any dependent changes have been merged and published

Additional Notes

This PR is the current-main port for the broader MCP foundation proposed in #566, adapted to today's StatefulToolEnv / tool_defs APIs and envs.

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