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• Bambu Studio's configuration (~/Library/Application Support/BambuStudio/BambuStudio.conf): shambu reads the selected printer serial and its LAN access code from it, and never writes it. Studio's stored code is the last source of the code: a one-shot flag (--access-code-file, --access-code-stdin) comes first, then the code that shambu printer login stored for the profile's serial, then Studio's. The code stays in memory, is never logged, printed or passed on a command line, and the serial is masked in output.
• shambu's config dir ($SHAMBU_CONFIG_DIR, else $XDG_CONFIG_HOME/shambu, else ~/.config/shambu; a relative or empty value counts as unset). printers.json holds the printer profiles: names, serials, IPs and modes, never a code. credentials.json holds the access codes, mode 0600; shambu creates the dir 0700. shambu refuses a symlink or anything that is not a regular file at either path. shambu printer forget --printer NAME removes the profile and its code. The code file gets the same protection as Studio's own plain-text config against another process that runs as the same user, with a tighter file mode. It lives outside any repository.
• The printer, over LAN MQTT (TCP 8883, TLS): shambu subscribes to the printer's report topic and publishes one pushall status request. It never starts, pauses, stops or modifies a print and never uploads files. TLS is verified against the CA bundle shipped with Bambu Studio; --insecure disables that and is the user's choice.
• Bambu Studio's binary: shambu runs it as a subprocess with an argument list (no shell), a timeout and a private data directory. Project files it reads are local files the user chose.
• The network, and only from the commands that read the printer (doctor, check, build, sweep and every printer action). shambu connects to the printer's broker on TCP 8883. A read through a profile goes to the IP the profile stores and does not search. To find the printer it connects to TCP 8883 on candidate hosts: the hosts in the ARP table, as 0.4.0 does, and then, in a subnet pass, the other hosts of the IPv4 network of the interface that carries the default route, only when its mask is /24 or narrower. The subnet pass runs in printer discover (always), in login when it has no IP (--from-studio without --ip), and on a profile read only when the profile has no IP, which login never leaves. A read without a profile and without --ip uses the ARP table only. A wider mask scans nothing. A point-to-point interface (inet A --> B, for example utun) is not scanned. A candidate gets a TCP connect and, when the serial came from a flag or a profile and TLS is verified, a TLS handshake that reads its certificate, and nothing else; a serial from Studio's config gets a TCP connect only. With TLS verified, no access code goes to a host before its certificate names the serial. There are no other network calls.

First-time enrolment has a trust boundary. shambu printer login --ip IP without --serial takes the serial from the certificate that answers at that IP, so the profile binds to whatever Bambu-signed device answers there: a chain-valid certificate proves a Bambu device, not the intended one. The serial from the printer's touchscreen, given as --serial, is the stronger binding.

The latest release on main. Fixes land as new releases; there are no backports.