diff --git a/pyproject.toml b/pyproject.toml
index fd748120..bac15979 100644
--- a/pyproject.toml
+++ b/pyproject.toml
@@ -21,7 +21,7 @@ dependencies = [
     "docstring_parser",
     "pyyaml>=6",  # persona manifest frontmatter (YAML)
     "pydantic>=2",
-    "mcp>=1.1,<2",  # MCP client (stdio + streamable-http); 2.0 removed streamablehttp_client
+    "mcp>=1.28.1,<2",  # MCP client (stdio + streamable-http); floor >=1.28.1 avoids PYSEC-2026-3481/3482/3483 (fixed in 1.27.2/1.28.1); <2 since 2.0.0 removed streamablehttp_client
     "httpx>=0.27",  # sync outbound senders for messaging connectors (send_message tool)
     "websockets>=13",  # managed Slack relay client transport (relay_client.py)
     "ddgs>=9",  # keyless default web-search provider (DuckDuckGo); Tavily/Brave use httpx