Append Line To Text File

When a ComfyUI workflow is being annoying, the first thing you want is evidence - what ran, when, with what. Append Line To Text File is the closest thing this pack has to a logger: every run adds a line to a text file, optionally stamped with a timestamp. It never overwrites, never truncates, just grows. That makes it perfect for debugging batch runs and for keeping a plain-text history of what you've been generating.

It's one of nine nodes in JasonHoku's Lite Text to File Tools pack. Think of it as the more opinionated sibling of Write To Text File: that node has an overwrite mode, this one is append-only by design.

How it works

Three inputs:

• text_input - the string to log (multiline, so you can log a chunk of text on one line).
• file_prefix - path relative to ComfyUI/output/; default text/log.txt → ComfyUI/output/text/log.txt.
• add_timestamp - the toggle that makes it a real log. Off, you get my text; on, you get [2026-08-16 14:02:31] my text.

The timestamp format is %Y-%m-%d %H:%M:%S, generated at execution time. Files and subdirectories are created on first use, and the node always opens in append mode, so a whole batch run adds one line per execution, oldest to newest. The status output tells you how big the log has grown: ✓ Appended to ... (total lines: 42).

One subtlety: because this node is an output node that returns a status, you can wire that status into the next thing you want to sequence after logging - a cheap way to force "log, then continue" ordering without extra plumbing.

What it's actually good for

• Debugging. Drop it after a KSampler or a conditioning step, feed it the seed and prompt, turn on the timestamp, and suddenly you can tell which run produced which weird result.
• Prompt history. A timestamped line per generation beats the PNG metadata when you want a flat, searchable record.
• Batch provenance. Log what each iteration did, then grep the log when something goes sideways three hours into a big run.

Installing it

Same install as the whole pack:

cd ComfyUI/custom_nodes/
git clone https://github.com/JasonHoku/comfyui-lite-text-to-file-tools
# restart ComfyUI

Or search "Lite Text to File Tools" in ComfyUI Manager. Standard library only - no dependencies, no models to fetch.

Gotchas

• The file only grows. There's no rotation and no cap. Log enough runs and it gets long - that's fine for grepping, less fine for reading top to bottom. Clear it out manually when it stops being useful.
• Errors are strings, not exceptions. A bad file_prefix gives you ✗ Error: ... in the status output and the workflow keeps running. You won't get a red node to alert you.
• Multiline input with a timestamp puts the whole block on one line with a leading timestamp. If you log multi-line strings a lot, expect lines that read like walls of text.