Comfy Flow Control

ComfyUI flow control

Routing, switching, broadcast, bundling, looping, gating. Where does the signal go once the decision is made.

Six packs on this install contribute flow-control primitives. Each has overlapping options and pack-specific quirks — the goal of this skill is to pick the right one in one decision, not browse a dropdown.

When to Use This Skill

Sources of truth

• custom_nodes/rgthree-comfy/__init__.py — context bundles, Any Switch, Power Lora Loader, fast groups muter (frontend-only)
• custom_nodes/cg-use-everywhere/__init__.py — broadcast "Anything Everywhere" sentinels
• custom_nodes/ComfyUI-Crystools/crystools/nodes_switch.py — type-typed CSwitchBoolean* family
• custom_nodes/comfyui-impact-pack/modules/impact/special_samplers.py and core.py — ImpactSwitch (GeneralSwitch/GeneralInversedSwitch), ImpactConditionalBranch, ExecutionOrderController
• custom_nodes/comfyui-easy-use/py/nodes/logic.py and flow.py — easy switches, pipes, forLoop, whileLoop, blocker
• ComfyUI core — built-in ComfySwitchNode (boolean toggle between two same-type inputs)

Pick-a-switch decision

Input-side vs output-side mux

• Input-side mux (the standard pattern): N inputs → 1 output. The switch decides which input to forward. The bool/index selector reads before the upstream graph evaluates, so unselected branches can often be skipped (see lazy-vs-eager below).
• Output-side mux (Crystools CSwitchFromAny only): 1 input → 2 outputs. The bool picks which output port receives the value; the other port emits None / a default. Use this when one upstream feeds two divergent downstream paths and you want to send it to only one at a time.

Lazy vs eager evaluation

Lazy switches mark unselected branches as "do not evaluate", so the upstream chain feeding the discarded branch is skipped entirely. Saves GPU and time. Eager switches force every upstream branch to compute even if its output gets thrown away.

When the unselected branch is cheap (a constant or a small VAEDecode), the difference is invisible. When it's a sampler chain, lazy switches save tens of seconds per queue.

Broadcast routing — cg-use-everywhere

The Anything Everywhere family doesn't have output ports. You wire a value (model / clip / vae / seed / conditioning / anything) into the node, and it acts as an invisible producer: any unconnected input slot of the matching type elsewhere in the graph receives the value automatically.

Silent-failure mode: if two broadcasters carry compatible types and both could match an empty socket, one of them wins (depends on node id ordering) and the other is silently ignored. Color the broadcasters in the UI so the routing is visible — they're invisible by design and hard to debug otherwise. When debugging, replace with explicit reroutes to see exactly where each value lands.

Use broadcast for scalars and constants (seed, model, vae, a shared prompt). Avoid for transient intermediate values whose meaning shifts as the graph runs — explicit wires there make the workflow more legible.

Context vs pipe bundles

Both rgthree's Context and easy-use's pipeIn/pipeOut carry a multi-typed bundle on a single wire. They are not interchangeable.

Mixing the two in one workflow is allowed but every cross-bridge is a manual repack. Pick one bundle convention per workflow.

Loops

Easy-use ships the only general-purpose loop primitives in this install. Use sparingly — ComfyUI's execution model wasn't designed for iteration, and loops expand at prompt-queue time to a sequence of copied subgraph nodes (so an N=50 loop is N=50 sampler instances in the graph, not one node looping).

Best practice:

• Keep loop bodies short. Each iteration replicates the entire subgraph in the queue, so 30 iterations × 50 nodes ≈ 1500-node queue.
• Always have an exit predicate. whileLoopEnd with no terminating condition will hang the queue forever.
• The state-carry slots (values_*) are how you accumulate — write to them at the end, read at the start.
• For per-image batch iteration, prefer ComfyUI's native batch semantics (let the sampler process a batch) over a loop. Loops are for iteration where each round depends on the previous round's output.

Execution gating

ExecutionBlocker is the canonical "kill this path" primitive in ComfyUI — see comfy-conditionals for predicate formation and detailed semantics (Preview Bridge consumes the sentinel silently; SaveImage downstream is the abort target).

Recipes

Toggleable LoRA stack with bypass

You have 3–8 LoRAs stacked into a chain. You want each one individually toggleable, with a master "all off" too.

UNETLoader ─┐
            │
            ▼
rgthree Power Lora Loader  ← per-row: enabled (bool), name, strength
            │
            ▼
ModelSamplingAuraFlow (or whatever)

• One node holds the stack. UI per-row toggle + strength.
• Group the loader + downstream sampler nodes; right-click → Mute Group to bypass the whole branch when prototyping.
• To make a single LoRA toggleable as a separate node, wrap with Crystools CSwitchBooleanAny: bool=on → goes through LoraLoaderModelOnly, bool=off → bypasses straight to the next stage.

Optional upscale pass with lazy switch

User sometimes wants a 2× upscale, sometimes doesn't. Without lazy evaluation, the upscale chain (model loader + KSampler + VAEDecode) runs even when discarded.

                              ┌── on_true: UpscaleModelLoader → Sampler → VAEDecode ──┐
SaveImage upstream ────────── ┤                                                       ├── SaveImage
                              └── on_false: passthrough ─────────────────────────────┘
                                 ▲
                                 │
                              Crystools CSwitchBooleanImage (lazy)

• The Crystools switch is lazy → when bool=False, the entire upscale chain is skipped, not just discarded.
• Bool can come from a PrimitiveBoolean, a RgthreeContext field, or an easy compare predicate.

Migrating a workflow off broadcast wires for review

When sharing a workflow that uses Anything Everywhere, the rest of the graph has unconnected input sockets that "look" wrong but work fine because of the broadcaster. For readability when sending the workflow to someone:

1. Right-click Anything Everywhere → "Show connections" (frontend flag in the rgthree side panel) — renders dashed lines.
2. Manually wire what the broadcaster was implicitly doing.
3. Delete the broadcaster node.

Reverse the process when receiving a wired workflow you want to clean up.

Gotchas

• ComfySwitchNode (core) is widget-overridden by an input. When you wire a BOOLEAN into the switch slot of ComfySwitchNode, the node's own widget value is ignored — the connected input wins. This bites you when the widget shows False but a connected PrimitiveBoolean(True) is in effect.
• Any Switch (rgthree) is eager — it evaluates all upstream inputs before picking the first non-None. Don't use it as a performance optimizer; use a typed CSwitchBoolean* for laziness.
• Preview Bridge swallows ExecutionBlocker: if you tee a path through Preview Bridge to inspect it, and the path is blocked, the Preview shows nothing and the downstream abort doesn't propagate through the bridge. Use FastPreview (comfyui-kjnodes) downstream of a Preview Bridge when blockers may appear, or wire previews off branches that can't be blocked.
• ImpactConditionalBranch.cond is BOOLEAN, not INT/FLOAT. SimpleMathCondition (essentials) returns FLOAT — convert with a comparator before feeding the branch.
• Context Big silently drops mismatched slots. If you wire an IMAGE to a Context Big.latent slot the wire is ignored at evaluation. Hover the Context outputs to check what's actually populated.
• Easy-use loops expand at queue-time, not runtime. A loop of 50 iterations becomes 50 copies of the body inside the queue's prompt graph. Very large loops can OOM the frontend (browser) before even reaching the backend.

Cross-refs

• comfy-conditionals — forming the boolean / index that feeds these switches. Predicates, comparisons, null checks, ExecutionBlocker patterns.
• comfy-prompting — Power Lora Loader plays nicely with LoRA trigger-word autoload nodes; see the cross-ref there for the full recipe.
• comfy-debug-preview — Preview Bridge details, FastPreview as the blocker-aware alternative.
• comfy-math-strings — primitive sources (PrimitiveBoolean, INT/FLOAT constants, sliders) that drive these switches.

Things this skill does NOT cover

• Predicate formation — how to build the boolean that feeds a switch. → comfy-conditionals.
• Reroute nodes for visual cleanup — those are frontend-only and don't affect execution; covered by comfy-workflow-layout and rgthree's UI affordances.
• Sampler / model routing (KSampler vs DPMPP vs Euler, model loader switching) — that's model-family work; see wan, z-image, hidream-o1 skills.
• Subgraph composition — packaging part of a workflow into a reusable subgraph. That's a project CLAUDE.md topic under "Editing workflow JSON".