`Content.disappearing` emitted `"ctl":true` where §6.10 specifies
`"ctl":1`. That was not a cosmetic disagreement between engines.
iOS decodes the field as a number through a synthesised `Codable`, so a
boolean did not merely fail to set the flag — it threw out of the
initialiser and failed the WHOLE envelope's decode, dropping the message
onto the plain-text path. An Android user turning on disappearing
messages sent an iPhone a bubble containing raw JSON, and the timer was
never applied at that end.
Nothing caught it because each engine parsed what it had written itself.
The piece-level tests passed on both sides, the vectors do not cover
this envelope, and the two halves only meet on two real phones.
Both spellings are accepted on the way in. `org.json`'s `optBoolean`
does not coerce a number, so reading only that missed every `"ctl":1`
the other two engines send — and reading only the number would miss the
`true` this engine wrote until today, which is on phones now and cannot
be recalled.
Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
