diff --git a/pyproject.toml b/pyproject.toml
index 1a43c32c5..6e1b1ba48 100644
--- a/pyproject.toml
+++ b/pyproject.toml
@@ -78,7 +78,7 @@ proxy = [
     "orjson>=3.9.14; platform_python_implementation != 'PyPy'",
     "httpx[http2]>=0.24.0",
     "openai>=2.14.0",             # OpenAI API format support
-    "mcp>=1.28.1",                 # MCP server (headroom_compress, retrieve, stats)
+    "mcp>=1.28.1,<2.0.0",         # MCP server (headroom_compress, retrieve, stats)
     "magika>=0.6.0",              # ML content detection for ContentRouter
     "zstandard>=0.20.0",          # Decompress zstd request bodies (Codex, etc.)
     "websockets>=13.0",           # WebSocket proxy for /v1/responses (Codex gpt-5.4+)
@@ -225,7 +225,7 @@ autogen = [
 ]
 # MCP server for Claude Code integration
 mcp = [
-    "mcp>=1.28.1",
+    "mcp>=1.28.1,<2.0.0",
     "httpx>=0.24.0",
     "starlette>=0.27.0",
     "uvicorn>=0.23.0,<1.0",