Internal builds before the versioned layout wrote .credentials.yaml as a flat
mapping; refusing it outright would strand every key stored through the Models
page and fail the next model request. Boot now recognizes exactly that layout
- addressable names over non-empty string scalars, no directives - and
rewrites it under the writer lock, nesting the original lines verbatim under
refs: with the values byte for byte unchanged. Everything the recognizer
declines keeps the loud by-name refusal, a live reload still never migrates,
and the parser continues to read exactly one layout. The migration step
retires with the pre-release stance at the first tagged release.
Yichen Jiang
933d1f2ab2