EzFlex-LoopStart

You cannot draw a loop in ComfyUI. Not "it's awkward" - the engine rejects it. A link that points backwards is a dependency cycle, and the graph walker throws on it. Which is a problem, because the interesting jobs in 2026 are loops: generate a 30-second video in six chunks and feed each chunk the last frame of the one before it, or run the same face-detailer pass three times at descending denoise. So every pack that solves this does the same thing: it doesn't draw the loop, it unrolls it. The prompt gets rewritten between rounds - the body cloned, the next round's inputs written in as literal values - and the queue runs it as a straight line.

EzFlex-LoopStart is the node that surfaces what that unrolling produces: which round you're on, and the values carried in from the last one. It does exactly one job, and the pack's own comment says so - "hand the previous LoopEnd's product back to this round."

What the panel and the ports actually do

The panel has a single field: index, the starting round, 0 by default. Read-only at runtime. You set where the loop begins; the loop increments from there, one per pass.

Outputs, in order: index (INT) first, always - that's the one you wire into the index input of EzFlex-PromptHelper, EzFlex-MediaLoader, or EzFlex-TimeLine so each round reads the right card or the right segment. Then value1 through value20, which are dynamic: a port appears once you've connected something to the matching port on the LoopEnd, and not before.

Inputs: an optional index (leave it unwired and the panel value wins; wire it if an upstream node, like Easy-Use's forLoop index, should decide the start round) plus initial value1 through initial value20 - one per value port.

The initial values are the whole subtlety. Round one has no previous round, so valueN outputs whatever you put on initial valueN; from round two onward the fed-back value overrides it. If you leave an initial unwired, round one hands the downstream node nothing - which is fine for a node with an optional input, and a hard error for torch.cat, a VAE encode, or anything else that needs a real tensor. The classic case is the long-video chunk loop: LoopEnd.value1 receives the last frame of the current segment, LoopStart.value1 hands it to the next segment's conditioning - and on the first segment there is no last frame, so you feed the initial frame (or a still you want the motion to start from) into initial value1 and the body never sees a None.

Installing it

Same pack, same two lines. ComfyUI Manager → search EzFlex (pack title Comfyui-EzFlex-Presets) → install → restart. By hand:

cd ComfyUI/custom_nodes
git clone https://github.com/blackbossokok/Comfyui-EzFlex-Presets
# then restart ComfyUI

Dependencies are almost nothing: the only extra is mutagen, for reading audio/video tags - pip install -r requirements.txt inside the folder, or pip install mutagen. llama-cpp-python, gguf and onnx are optional and deliberately kept out of requirements so Manager never kicks off a compile. The pack wants ComfyUI 0.3.13+ because it uses the official i18n endpoint. It's a personal AI-assisted project with Chinese-first docs, so treat it as a power tool you debug yourself rather than a supported product - there's essentially no English-language discussion of it to fall back on.

Wiring it without hurting yourself

Full contract, in order: LoopStart.index → the index input of whatever needs to know which round it is. LoopStart.valueK → the body node that consumes the carried data. The body's output → LoopEnd.valueK. Done. Nothing goes from LoopEnd back to LoopStart on the canvas. The feed is implicit; a real wire closes the cycle and you get Dependency cycle detected.

When it doesn't work

• Round one dies on a None. You skipped an initial value. Wire the same kind of data you expect LoopEnd to carry back.
• It runs once and stops. No paired EzFlex-LoopEnd, or the End's round counter is 0. You'll see a line about it in the terminal - the loop nodes print rather than fail, so read the console, not the canvas.
• Dependency cycle detected. You wired End → Start. Delete it.
• The loop seems to skip the body. The body is defined by reachability: everything downstream of the Start, stopping at the End. Anything fed from outside the loop keeps its original wire and is not cloned, so it's computed once and reused.
• Only the last round's values survive. That's EzFlex-LoopEnd working as designed - out1..out20 are the final round's carried values. To keep every round, carry a list: merge each round's product with EzFlex-MergeList and hand the merged list back through a valueK port.

One pleasant side effect: each round's clone gets different literal inputs, so the cache key changes and the body genuinely re-executes - no always-rerun tricks needed in the body.