chore: Upgrade to MCP SDK 2.x

pyproject.toml

@@ -38,7 +38,7 @@ dependencies = [
 
 [project.optional-dependencies]
 mcp = [
-    "mcp>=1.0,<2.0",
+    "mcp>=2.0,<3.0",
 ]
 benchmark = [
     "sentence-transformers>=3.0",

src/semble/mcp.py

@@ -10,14 +10,15 @@
 from pathlib import Path
 from typing import Annotated, Literal
 
-from mcp.server.fastmcp import FastMCP
+from mcp.server.mcpserver import MCPServer
 from pydantic import Field
 
 from semble.cache import get_validated_cache, save_index_to_cache
 from semble.index import SembleIndex
 from semble.index.dense import load_model
 from semble.types import ContentType
 from semble.utils import format_results, is_git_url, resolve_chunk
+from semble.version import __version__
 
 logger = logging.getLogger(__name__)
 
@@ -68,10 +69,11 @@ def _resolve_content_selection(
     return (ContentType(content),)
 
 
-def create_server(cache: _IndexCache, default_content: Sequence[ContentType] = (ContentType.CODE,)) -> FastMCP:
-    """Build and return a configured FastMCP server backed by the given cache."""
-    server = FastMCP(
+def create_server(cache: _IndexCache, default_content: Sequence[ContentType] = (ContentType.CODE,)) -> MCPServer:
+    """Build and return a configured MCP server backed by the given cache."""
+    server = MCPServer(
         "semble",
+        version=__version__,
         instructions=(
             "Instant code search for any local or remote git repository. "
             "Call `search` once with a focused query, it returns the file path and exact line. "

tests/test_cli.py

@@ -175,7 +175,7 @@ def test_cli_entrypoint_works_without_mcp_installed(
     monkeypatch.setattr(sys, "argv", argv)
     monkeypatch.setitem(sys.modules, "mcp", None)
     monkeypatch.setitem(sys.modules, "mcp.server", None)
-    monkeypatch.setitem(sys.modules, "mcp.server.fastmcp", None)
+    monkeypatch.setitem(sys.modules, "mcp.server.mcpserver", None)
     monkeypatch.setitem(sys.modules, "semble.mcp", None)
     with patch("semble.cli.SembleIndex.from_path", return_value=fake_index):
         if expect_system_exit:

tests/test_mcp.py

@@ -16,8 +16,8 @@
 
 
 def _tool_text(result: Any) -> str:
-    """Extract the text string from a FastMCP call_tool result."""
-    return result[0][0].text
+    """Extract the text string from an MCP call_tool result."""
+    return result.content[0].text
 
 
 async def _call_tool(
@@ -430,7 +430,7 @@ async def fake_stdio() -> None:
     )
     with (
         patch("semble.mcp.load_model", **load_kwargs),
-        patch("mcp.server.fastmcp.FastMCP.run_stdio_async", side_effect=fake_stdio) as mock_run,
+        patch("mcp.server.mcpserver.MCPServer.run_stdio_async", side_effect=fake_stdio) as mock_run,
     ):
         await serve()
 
@@ -452,7 +452,7 @@ async def fake_run_stdio() -> None:
 
     with (
         patch("semble.mcp.load_model", side_effect=blocking_load_model),
-        patch("mcp.server.fastmcp.FastMCP.run_stdio_async", side_effect=fake_run_stdio),
+        patch("mcp.server.mcpserver.MCPServer.run_stdio_async", side_effect=fake_run_stdio),
     ):
         await serve()