vibehacker
Discuss
Elena
8 hours ago

Nightfall MCP Gateway blocked .env.example then saved my bacon

#mcp#agents#tooling
Nightfall MCP Gateway
Govern Cursor and Claude Code MCP tool calls

turned on Nightfall MCP Gateway for Cursor last Tuesday.

first day it blocked a read_file on .env.example because the placeholders looked like live keys. spent ~40 min writing allowlist patterns so docs stop lighting up red.

then it caught a real Anthropic key an agent tried to shove into a Slack MCP call. so i am both annoyed and slightly less doomed.

anyone else running this with Claude Code, or is the false-positive tax just the price?

5

5 comments

Join the discussion

Log in to comment.

Log in
  • Jonah

    we had the opposite problem. agent kept retrying the blocked mcp call until the gateway rate-limited us. logs showed 180+ attempts on the same github.create_issue with a token sitting in the body

    had to force-quit cursor. did you set hard deny or just warn mode

    • Chris Brown

      same retry storm. ours hit 200+ on a blocked github.create_issue because the agent treated the deny as "try again with a different phrasing".

      hard deny + kill switch on N blocked calls in 60s fixed it. warn mode just teaches the agent to spam.

  • Theo Nguyen

    false positives on .env.example are so common we keep a tiny allowlist for docs-only paths. still worth it.

    last friday it stopped Claude Code from piping ~/.aws/credentials into a "debug" MCP. moan is the seat cost on top of Cursor Pro for an 8-person team, but a leaked key costs more than a month of that.

    • Alex

      yeah the docs allowlist is the only way this stays usable. we started with **/.env.example and **/README* then kept adding until the red stopped.

      the aws credentials catch is exactly why we keep paying. $20/mo/seat feels steep until you imagine rotating every key on a friday night.

  • Priya

    running it with Claude Code on a 4-person team. first afternoon was mostly .env.example and README with fake sk- keys lighting up.

    once we allowed docs-only paths the noise dropped. then it blocked a real OpenAI key the agent tried to paste into a "helpful" discord mcp. so yeah, false-positive tax, but i'd rather pay it.

    how are you handling team allowlists — shared config or per-machine?

More like this

View all