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Kai
9 hours ago

Nightfall blocked a legit Linear MCP call for 40 minutes

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

Tried Nightfall MCP Gateway this week so Cursor stops freelancing into prod secrets.

Setup was fine until Linear create_issue started getting Denied with path_not_allowlisted — we were writing to /tmp/agent-scratch, which is not a secret, it's where the agent dumps draft bodies before posting.

Took 40 minutes to find the allowlist rule that only permitted ~/linear-drafts. Docs never mention the cwd the agent actually uses.

Paying $20/mo for a seat that redacts the wrong thing is a weird feeling. Anyone else running Nightfall in front of Linear/GitHub MCP without living in false positives?

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  • Alex

    same class of pain. we allowlisted ~/Projects/** and the agent still wrote drafts under /var/folders/... on Mac because Cursor's temp path isn't home.

    ended up adding an explicit /var/folders/**/T/cursor-* rule. ugly. but the false positive rate dropped from ~1 in 3 Linear calls to almost nothing.

    the $20/mo only feels worth it after that rule exists. before that it's just a red light you ignore.

    • Nina Voss

      the /var/folders trick is real. we had the same Mac temp path issue.

      our allowlist ended up with three globs and a comment that says "do not delete, Cursor temp". ugly but the Linear create_issue false positives stopped.

      still feels like the gateway should resolve the live cwd instead of making us guess Apple's temp layout.

  • Nina Ortiz

    we hit this on GitHub MCP too. Nightfall said Connected, tools listed, then every create_pull_request died on a path check against the workspace root the agent never uses.

    i keep a screenshot folder of "green gateway / red call". if the deny reason doesn't name the actual cwd, the allowlist is fiction.

    did you log the denied path somewhere readable, or only in their dashboard?

    • Quiet Meadow

      only in their dashboard for us, and the deny reason was truncated to path_not_allowlisted with no absolute path.

      i started echoing pwd into the draft body before every Linear call just so we have a breadcrumb. ridiculous, but at least the next false positive has a string we can grep.

      if green Connected and red call is the default UX, the allowlist is marketing.

  • Grove Cascade

    we tried Nightfall for two weeks then killed the seat.

    false positives on /tmp drafts ate more time than the one secret it actually caught. if the allowlist can't see the agent's real cwd, you're paying $20/mo to babysit a red badge.

    went back to a dumb shell wrapper that only exports keys the MCP needs. less theater.

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