Custom validation failed: read the node's own error details
A custom validator can return a rejection or raise an exception; ComfyUI records these as different errors. Read the specific node error before changing inputs or code.
Symptoms and scope
A custom validator can return a rejection or raise an exception; ComfyUI records these as different errors. Read the specific node error before changing inputs or code.
Error fragments for search; IDs, values and filenames may vary:
Custom validation failed for node
custom_validation_failed
exception_during_validation
Source-supported context
Core validation calls a node’s VALIDATE_INPUTS (or its newer validation override). A non-true result becomes custom_validation_failed, with the input name and returned detail. An exception escaping node validation becomes exception_during_validation, with its exception type and traceback; it is not the same event or necessarily the same detail set. An exception while recursively validating a linked input has the separate type exception_during_inner_validation. These are pre-execution checks, distinct from a later node or GPU execution error. Source 1 Source 2
Cases to distinguish
1. A node deliberately rejects an unavailable resource or unsupported input combination.
2. Its validation code is incompatible with the current core interface.
3. An environment/resource error inside validation is wrapped by the generic message.
Diagnostic sequence
The sequence below is an editorial procedure based on the cited context, not a diagnosis already confirmed for your environment.
Step 1. In node_errors, record the node ID/class and exact error type. For custom_validation_failed, keep input_name and the returned detail; for an exception, keep exception_type, exception_message and traceback when provided. Redact private paths or tokens before sharing.
Step 2. If the validator returned a refusal, check the named field, resource and author’s input requirements. If it raised an exception, use the first relevant traceback frame to locate the failing validator or linked node before assuming the input alone is wrong.
Step 3. Compare the node's minimal original example. Consider version/environment conflicts if even documented valid input fails.
Step 4. Report the minimal reproduction to that node's project with core and extension versions. Do not delete its validator to bypass the refusal.
Completion check
The original input passes the relevant validation path, then the node executes with the intended result. Suppressing the validator does not establish that the data is correct.
Limitations and cautions
Validation can protect file, parameter and remote-interface constraints. Bypassing it may replace a clear early error with a harder runtime failure.
Original sources
- ComfyUI execution.py validation — source rechecked 2026-09-27.
- ComfyUI custom node troubleshooting — source rechecked 2026-09-27.
Source review and separate English editorial pass: 2026-09-27. No local validation request, workflow or GPU run occurred.
Related troubleshooting and guides
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Sources & references
2026-09-27 reviewed current ComfyUI execution.py validation return, exception and linked-input branches plus official custom-node troubleshooting; independent English editorial pass. No local run.
01ComfyUI execution.py validationSource checked: 2026-09-2702ComfyUI custom node troubleshootingSource checked: 2026-09-27