CPython compatibility #

The current checkpoint runs a statically linked AArch64 musl CPython 3.12.13 in both the native host and Chromium Worker, plus a dynamically linked native acceptance fixture. Generated runtime and standard library artifacts stay under the repository's ignored .tmp/cpython-3.12.13 directory.

Verified behavior #

• Startup and version reporting from the ordinary CPython executable.
• Source-based standard-library bootstrap, including encodings.
• Multi-file programs under /project.
• Filesystem-backed package discovery and imports.
• A separately packaged pure-Python project image installed over the runtime snapshot.
• A separately packaged, checksum-pinned packaging 26.2 wheel installed as a second overlay, imported from the guest filesystem, and accompanied by its original distribution metadata.
• Unhandled exceptions with readable guest file paths, source lines, exception type, message, and exit status 1.
• Identical project image and script behavior in the native CLI and Chromium.
• Dynamic libpython3.12.so loading through the guest musl interpreter.
• CPython's normal dlopen import of the _struct native extension, including its relocations against both libpython and guest libc.

The regression project is in guest-tests/cpython/project. It imports phase5pkg.calculator and packaging, prints multi-file result: 42, verifies the installed wheel's version and METADATA file, then raises a deliberate RuntimeError. One bounded guest run therefore covers project and third-party package discovery, source loading, package data, and traceback formatting.

Packaging and execution #

binarrow image pack --guest-root /project/phase5 ... creates the project image. Browser hosts install it through the existing project-image operation. Native hosts can apply the same image over a base snapshot with the repeatable --filesystem-install <image> run option.

guest-tests/cpython/package-packaging.sh downloads the official pure-Python wheel into .tmp, verifies its pinned SHA-256 digest, retains the wheel's package and distribution metadata layout, and creates a separate installable image. It does not install anything into the host Python environment.

Use these end-to-end verifiers after guest-tests/cpython/build.sh:

guest-tests/cpython/verify.sh
guest-tests/cpython/verify-browser.sh
guest-tests/cpython/build-dynamic.sh
guest-tests/cpython/verify-dynamic.sh

Both scripts set TMPDIR and all build caches beneath the repository's .tmp directory. The browser test is opt-in because the generated artifacts are about 76 MiB and the guest run currently takes several minutes.

Current limitations #

• The dynamic checkpoint deliberately packages only _struct; broad standard library extension coverage and third-party native wheels are not claimed.
• Guest-side pip, dependency resolution, and package-index access are not implemented. Hosts can checksum-pin and package compatible pure-Python wheels as deterministic installable images; packaging 26.2 is the verified checkpoint.
• Threaded Python execution is not supported by the single-threaded guest runtime.
• Socket-backed package indexes and native wheels are outside the current browser service surface.
• Translation covers a scalar Tier-1 subset; unsupported CPython blocks fall back to the interpreter by code identity.