Try/Catch (Value Guard) 🛟

The name promises a programming construct ComfyUI can't actually deliver, and the author knows it. The Try/Catch (Value Guard) node from TensorVizion/OmniNodes doesn't intercept crashes - nothing in any custom pack can, because an uncaught Python exception halts a node and everything downstream of it regardless of what you wire after it. What it does do is check a value for the common "this quietly failed" signals and substitute a fallback, so a soft failure a few nodes upstream doesn't poison a long batch run.

That's still genuinely useful, because ComfyUI's Web API ecosystem has settled on a pattern: catch the exception inside the node, and return an error marker instead of raising. This node is the reusable "if that marker shows up, swap in something safe" step - so you don't have to bolt bespoke fallback routing onto every upstream node yourself.

How it checks

The failure test runs in a clear order:

• value is None → failed
• value is an empty string → failed, only if treat_empty_string_as_failure is on (default off, so a legitimately blank string passes)
• value is a string starting with error_prefix (default "ERROR") → failed
• value is a float/int that is NaN or ±Inf → failed

If none match, the value passes through untouched and caught is False. If one matches, fallback is returned instead and caught flips to True - which you can wire into a Conditional Gate or a notify node to learn a fallback fired, instead of silently continuing.

Inputs and outputs

Inputs: value (the thing to guard), fallback (what to substitute), error_prefix (what counts as an error string, default "ERROR"), and treat_empty_string_as_failure (boolean). Outputs: value (guarded), caught (BOOLEAN), and summary (STRING explaining what happened and why).

Install

Ships with OmniNodes:

cd ComfyUI/custom_nodes
git clone https://github.com/TensorVizion/OmniNodes

Or ComfyUI Manager → OmniNodes → restart. Pure Python standard library. Under TensorVizion/Workflow.

Troubleshooting

• A crash still kills the queue - correct, and unavoidable. This node only guards values that arrived from an upstream node's own error handling. If an upstream node raises, no guard after it can help.
• Fallback never fires - check what the failure actually looks like. If the upstream returns "Error: ..." with a different prefix than your error_prefix, the guard can't see it. Match the prefix to the node's real error format.
• Empty string passes when you expected a catch - that's the default toggle; flip treat_empty_string_as_failure on.
• Node missing - restart and check the terminal [OmniNodes] log.

Use it in long, unattended batch runs where one soft failure shouldn't invalidate everything downstream. It's a seatbelt, not airbags - know which one you're getting.