#3538 @swamp/ssh: master-writable check always fails on Windows, even with controlMaster disabled

Summary

On a Windows control host, the master-writable pre-flight check always fails, so every method (exec, script, copy, ...) needs --skip-check master-writable -- even when ControlMaster is disabled.

Check: master-writable
/tmp/swamp-ssh/fleet has world/group permissions (mode 666). Expected 0700 -- adjust with chmod or relocate XDG_RUNTIME_DIR.

Environment

• swamp 20261015.233727.0-sha.a39bdd69, Windows 11 Pro (x86_64)
• @swamp/ssh 2026.10.13.1 (typeVersion 2026.09.28.1)
• OpenSSH_for_Windows_9.5p2

Repro

globalArguments:

name: fleet
transport:
  kind: ssh
  identityFile: C:/Users/[REDACTED]/.ssh/id_ed25519_fleet
  controlMaster: { enabled: false, persistSec: 1 }
hosts:
  - { name: box, address: box, transport: { user: me } }

swamp behavior validate fleet -> master-writable fails. swamp behavior run fleet exec --input hosts=all --input command=uptime fails pre-flight; with --skip-check master-writable it succeeds against Linux and macOS targets.

Root cause

1. _lib/control_master.ts ensureControlDir() skips the mode check only when stat.mode === null, with the comment that mode is null on Windows. Current Deno returns a synthesized mode on Windows (0o666 for a writable dir), so (mode & 0o077) !== 0 is always true.
2. _lib/checks.ts checkMasterWritable() runs unconditionally; it never consults transport.controlMaster.enabled (fleet default or per-host override), nor whether any host uses kind: ssh at all.

Suggested fix

• In checkMasterWritable, pass when no effective host has kind: ssh with controlMaster.enabled: true.
• In ensureControlDir, skip the permission check when Deno.build.os === windows (Windows OpenSSH does not support ControlMaster anyway, so arguably open should no-op / warn there).

Related (minor)

• controlMaster.persistSec must be > 0 even when enabled: false; allowing omission when disabled would be friendlier.
• defaultBinaryProbe in checks.ts splits PATH on : and joins with /, so the sshpass-available check would mis-detect on Windows (; separator, .exe suffix). Only matters for password auth.

Upstream repository: https://github.com/swamp-club/swamp-extensions

Environment

• Extension: @swamp/ssh@2026.10.13.1
• swamp: 20261015.233727.0-sha.a39bdd69
• OS: windows (x86_64)
• Deno: 2.9.7
• Shell: unknown