Failure Log: Google Sheets Trigger Feedback Loop

This failure often sounds like:

“We only changed one thing. Then it kept running.”

What Failed

A Google Apps Script was triggered by edits to a Sheet.

The script itself edited that same Sheet.

Each run triggered the next one.

What It Looked Like

Scripts running repeatedly
Data being overwritten multiple times
Execution quotas being hit
The automation being turned off to stop the damage

Root Cause

The trigger observed changes it also created.

There was no distinction between:

Human edits
Script edits

The system could not tell the difference.

Why This Was Not Obvious

From the user’s perspective, nothing unusual was happening.

From the system’s perspective, everything was happening.

How This Gets Fixed

Separate detection from processing
Add guard conditions
Track execution state
Ensure script edits do not re-trigger logic

This is a design fix, not a workaround.

Prevention

Explicit trigger boundaries.

If the system cannot tell who caused the change, it cannot behave safely.

This post documents a real automation failure mode. Similar failures often appear under labels such as trigger feedback loops and self-triggering workflows.