Switch Mask

Every workflow eventually wants the same graph to do two different things. Route one mask today, another tomorrow, flip it with a boolean instead of rewiring. LF_SwitchMask is exactly that: a classic A/B switch, but typed for masks, with one genuinely nice property - it's lazy. Only the branch you're actually selecting gets evaluated, so the expensive path you're not using doesn't burn VRAM or time. It's the mask-router from the lf-nodes logic family.

How it works

The mechanism is the interesting bit, because it's what separates this from a dumb selector. A normal switch node forces both inputs to be computed before it picks one - which is wasteful when one branch is a heavy mask generator (SAM, a mask-from-depth pass, an inpainting prep) and you're only using the other. LF_SwitchMask implements ComfyUI's lazy-input protocol: it declares a check_lazy_status that tells the engine "I only need on_true if the boolean is true, otherwise I only need on_false." The engine then skips whatever branch you didn't pick. In a big graph that can be the difference between a fast flip and re-running half your pipeline.

The boolean state also gets pushed to a small progress-bar-style widget on the node, so you can see at a glance which mask is live.

The inputs that matter

• on_true (MASK) - returned when the condition is true.
• on_false (MASK) - returned when the condition is false.
• boolean (BOOLEAN, default false) - the switch. This is the widget you convert to an input and wire to a logic node, a primitive, or a control panel.

Outputs are mask (the selected mask) and mask_list (the same as a list).

Install

Part of lf-nodes:

• ComfyUI Manager: search "LF Nodes", install, restart.
• Manual: cd ComfyUI/custom_nodes && git clone https://github.com/lucafoscili/lf-nodes.git, restart.

No models. This is pure plumbing - nothing to download beyond the pack.

Common issues

• "Why is my unselected branch still running?" If the branch upstream is a plain node (not lazy), the engine can only skip it if this node's lazy request propagates. Nodes that must run (output nodes) upstream of on_true can still force evaluation. The lazy behavior applies where the engine can honor it - it's not a promise for arbitrary graphs.
• "The boolean does nothing." Check which widget is the source. If you typed true in the boolean widget, that works; if you wired a primitive into it, the wire wins. Same footgun as every ComfyUI switch.
• Type mismatch. This is a MASK switch, not an ANY switch. Feed it images or latents and it won't connect. If you need to switch mixed types, you want an any-type switch from a pack like rgthree - this node is deliberately single-type.