When a workflow uses a node that is deprecated, renamed or missing on the target ComfyUI, what does the server and frontend do, and how can I pre-check?

Problem. Moving a workflow between versions can silently swap in deprecated nodes or leave red placeholder nodes. Conditions. ComfyUI 9fe7ef76 (server.py, nodes.py) and frontend 174bd880 (app.ts). Method. Server side: any node class with DEPRECATED = True is reported with 'deprecated': true in the node info (likewise 'experimental' and 'dev_only'); core examples are CheckpointLoader (display name 'Load Checkpoint With Config (DEPRECATED)') and ImageBatch ('Batch Images (DEPRECATED)'). Frontend side: while loading a graph it builds a missingNodeTypes list, skips nodes that are muted or bypassed, records the pack id (cnr_id) when present, and marks an entry replaceable when its node-replacement store has a replacement. Pre-flight (inference, built from those behaviours): fetch /object_info from the target server; for every node type in the workflow JSON, check it exists and read its deprecated flag; list types that exist only in disabled or non-registry packs using properties.cnr_id/aux_id; then load once and treat any remaining missing placeholder as a blocker. Failure modes. Muted or bypassed missing nodes are not reported but still break the graph if later un-muted; a deprecated node keeps working until it is removed, so absence of an error does not show future compatibility; renames that keep the same class name but change inputs are not detected by presence checks (inference). Limitations. Code read only; the /object_info endpoint behaviour is inferred from server.py's node-info builder and was not queried. Version and date. ComfyUI 9fe7ef76; frontend 174bd880. Curator qualifications: All cited documentation excerpts located on the live pages by curator GET; no video sources. Limitations: Pre-flight recipe is the worker's inference; nothing was run against a server. Evidence status: statements located in the cited sources by a correlated desk review (Claude); not executed; not independently reviewed.

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