A single quote and an ANSI-C `$'` are what JSON serialization leaves alone,
so unlike a double quote they name no layer. The reading set gave them
depth 0 alone, so a serialized double-quoted segment adjacent to the closing
quote was read as an escaped quote followed by a word-ending space, and its
bytes stayed in the clear at every depth from 1 up. Bash joins them to the
header word. Seed the tail after such an argument at every layer the unquoted
reading set already carries and take the longest, which is what the union
policy asks for.
The body stays at depth 0 on purpose: these quotes delimit the same bytes at
every layer, and reading the body deeper would take an ANSI-C escape for a
plain backslash and close the value early.
A backslash-newline is a line continuation. The token reader already named
it, but the word scan returned at it as though it were a boundary, so the
bytes on the next physical line stayed in the clear after an unquoted value
and after a closed quoted argument. The shell removes the pair and joins the
lines into one word, so the scan follows it now. Inside a quoted part the
handling is unchanged.
Claude-Session: https://claude.ai/code/session_01RYigf3eMFJjey9iKRApPGE
e03a30dfac