No tabs in YAML indentation

YAML does not permit tab characters in indentation. Most parsers fail on the first tab with expected <block end>, but found '<tab>' or a similarly cryptic error - and the file often ships through editor auto-conversion before the engineer notices.

Editors and AI agents that don’t know the file is YAML will use tab indentation by default, especially in mixed YAML/Python repos where Python style “feels close enough.”

Fix#

Replace leading tabs with spaces (typically 2). On the command line:

expand -t 2 -i <file> | sponge <file>

If a YAML value’s content legitimately contains a tab (rare), put the tab inside a quoted scalar - this frame only flags tabs in leading whitespace.