{"type":"post","id":"fastmcp-4-1-1-bounds-regex-tool-search-c332f6","slug":"fastmcp-4-1-1-bounds-regex-tool-search-c332f6","title":"FastMCP 4.1.1 bounds regex tool search to 1,000-character patterns and about one second of runtime","description":"FastMCP released v4.1.1 on October 18. The release adds bounds to its regex-based tool search patterns longer than 1 000 characters are rejected and a search stops after about one second. The feature lets clients find tools by pattern rather","retrieval_nugget":"FastMCP released v4.1.1 on October 18. The release adds bounds to its regex-based tool search patterns longer than 1 000 characters are rejected and a search stops after about one second. The feature lets clients find tools by pattern rather","published_at":"2026-10-23","updated_at":"2026-10-23","record_date":"2026-10-23","date_kind":"published_at","topics":["agent-security","sandbox"],"entities":["FastMCP","PrefectHQ","SkillsDirectoryProvider"],"related_patterns":["agent-security-moves-to-runtime-boundaries","agent-protocols-become-interoperability-layer"],"novelty_label":"new_fact","what_changed":"FastMCP 4.1.1 adds security bounds to regex tool search: patterns are capped at 1,000 characters and execution at about one second.","prior_refs":["memory:4fe2b1b2-b257-83a7-a108-b7bcc747c607"],"source_url":"https://github.com/PrefectHQ/fastmcp/releases/tag/v4.1.1","source_urls":["https://github.com/PrefectHQ/fastmcp/releases/tag/v4.1.1"],"schema_version":"newruntime-agent-readable-v0.2","stable_id":"post:fastmcp-4-1-1-bounds-regex-tool-search-c332f6","status":"published","visuals":[],"editor":{"role":"editor","name":"Andrey Reshetnikov","profile":"https://newruntime.com/owner-profile.md","profile_json":"https://newruntime.com/owner-profile.json","same_as":["https://www.linkedin.com/in/reshetnikov1/","https://t.me/lapetuse"]},"routes":{"html":"https://newruntime.com/posts/fastmcp-4-1-1-bounds-regex-tool-search-c332f6/","markdown":"https://newruntime.com/posts/fastmcp-4-1-1-bounds-regex-tool-search-c332f6.md","json":"https://newruntime.com/posts/fastmcp-4-1-1-bounds-regex-tool-search-c332f6.json"},"next_reads":[{"type":"topic","path":"/topics/agent-security/","url":"https://newruntime.com/topics/agent-security/","title":"Agent Security","reason":"Explore the agent-security topic hub.","media_type":"text/html","markdown_url":"https://newruntime.com/topics/agent-security.md","json_url":"https://newruntime.com/topics/agent-security.json"},{"type":"topic","path":"/topics/sandbox/","url":"https://newruntime.com/topics/sandbox/","title":"Sandbox","reason":"Explore the sandbox topic hub.","media_type":"text/html","markdown_url":"https://newruntime.com/topics/sandbox.md","json_url":"https://newruntime.com/topics/sandbox.json"},{"type":"collection","path":"/posts/","url":"https://newruntime.com/posts/","title":"Field Notes","reason":"Open the latest editorial analysis.","media_type":"text/html","json_url":"https://newruntime.com/posts.json"},{"type":"collection","path":"/source-ledger.json","url":"https://newruntime.com/source-ledger.json","title":"Source Ledger","reason":"Inspect the public source evidence graph.","media_type":"application/json"}]}