The package std module takes the prebuilt C library's tokens, and an unset iOS floor is the located SDK's version (2026.9.14.1)

[Sunrisepeak]

Two engine gaps that mcpplibs/libcxx's CI surfaced once it measured every row the package claims (#630 follow-up).

The package std module lacked the prebuilt C library. A package that supplies the C++ layer over a prebuilt C library (llvm.libcxx over glibc, or over an Apple SDK) cannot name that library's headers, and the target-side broadcast carries only graph layers. The precompile therefore read whatever the driver found: on Linux the runner's /usr/include rather than the payload's glibc, which no report showed; on macOS nothing, and it stopped on mbstate_t. The command now takes the same tokens every translation unit gets (host_compile_tokens, with the C++ layer marked as the graph's), appended after the package's own directories so that libc++'s headers keep precedence over the C library's. e2e 663 asserts the recorded command names the glibc payload.

An unset ios_deployment_target was an unversioned triple. docs/20 promised the SDK's default; clang's default for arm64-apple-ios with no version is older than any SDK on the machine and refuses thread-local storage, which libc++abi uses. The located SDK's version (xcrun --sdk <name> --show-sdk-version) now fills the slot when the manifest states none; ci-macos-ios's plain fixture drops its floor and asserts LC_BUILD_VERSION minos equals the SDK's version. Docs in both languages restated.