For badcontinue errors, the API currently returns a code of either
"??badcontinue" or "??_badcontinue" (where ?? is the module's
prefix),
depending on the module. The human-readable error message text may
also vary depending on the module.
In 1.21wmf8,[1] these will be standardized as "??badcontinue", with a
human-readable message of "Invalid continue param. You should pass the
original value returned by the previous query".
Since well-behaved API clients should never see this error message,
this change should not require any client updates.
[1]: Gerrit change
https://gerrit.wikimedia.org/r/#/c/42398
--
Brad Jorsch
Software Engineer
Wikimedia Foundation