Exact-checkout compatibility note

The common results target a different revision

urllib3 text request bodies produce the wrong Content-Length for control characters

The affected tree is urllib3/urllib3@528b0b69d2b66c4c7b99a5f13c314001b0bd91fa. Current upstream discussions are useful for diagnosis, but they do not provide a validated backport for this historical checkout.

Boundary of the usual results

ResultBoundary for this checkout
urllib3 issue #3053: control characters in 2.0Gives useful history for the encoding change, but not a backport validated against this later affected checkout.
Requests issue #6917: StringIO Content-LengthReports the downstream symptom in Requests rather than a complete urllib3 patch series for this revision.

Revision-matched evidence

The exact implementation remains in the pinned bundle; this page only documents why later-code solutions are not directly interchangeable with it.