0.9.7 --- the package states [package] standard in place of the unread [build] cxx_standard

[Sunrisepeak]

States the language level of this package's own sources in the key the engine reads (mcpp-community/mcpp#641, item 2; mcpp-community/mcpp#644).

The defect. The manifest wrote [build] cxx_standard = "c++23". No mcpp release has read that key: at the package's own root the engine prints [build] has unsupported key 'cxx_standard' (ignored), and as a dependency it says nothing. The package therefore stated no standard, and its sources were compiled at whatever level the consuming graph used.

Changes:

• [package] standard = "c++23" replaces the unread key; version 0.9.7.
• From mcpp 2026.9.15.2 a package that provides the C++ layer compiles its implementation units at the level it states, and its std module at the consuming graph's level. An older engine reads a dependency's standard as it always has (not applied), and the package's own root is c++23 either way, so nothing changes for the engines this repository's CI pins.

Measured. This branch passed the whole workflow against the engine branch of mcpp#644 (mcpp_ref=feat/641-642, run 34895002497): the runtime job and the four host jobs, Linux, macOS and Windows.