Maya 2022 / Python 3.7 Long-Term Support

Policy: Python 3.7 is an LTS compatibility profile. It has no automatic calendar expiry. See ADR 011.

Commitment

Maya 2022 embeds CPython 3.7, as do other DCC releases that studios still use in production. dcc-mcp-core therefore keeps an installable, tested Python 3.7 path until a major release completes the formal deprecation process in ADR 011.

The machine-readable source of truth is compatibility/python.json.

Supported wheel profiles

Native Python 3.7

Linux and Windows releases include native cp37-cp37m wheels built with the contracted PyO3 0.28 series. These wheels contain dcc_mcp_core._core and provide the normal Rust-backed package surface.

This is the authoritative Python 3.7 compatibility profile.

py37-lite fallback

The release also includes a py3-none-any wheel without _core. It provides pure-Python host, skill, configuration, and sidecar fallbacks for platforms where a native cp37 wheel is unavailable.

py37-lite is supported, but it is not evidence that native compatibility is healthy. Merge and release gates require both profiles.

Python 3.8+

Maintained Python versions use the cp38-abi3 wheel. One stable-ABI build per platform serves Python 3.8 through the maximum version declared in the compatibility contract.

Runtime architecture

Maya 2022 / CPython 3.7
        |
        +-- native cp37 wheel available
        |      `-- Python facade + Rust _core extension
        |
        `-- no native wheel for the platform
               `-- py37-lite facade + external dcc-mcp-server sidecar

The companion dcc-mcp-server wheel contains platform binaries rather than a Python extension ABI. It remains installable from Python 3.7 and lets lite adapters delegate gateway execution to the sidecar.

CI enforcement

Check	Frequency	Contract
Python 3.7 contract	Every PR	Package metadata, PyO3 series, CI/release jobs, docs, and test pins match compatibility/python.json
Python 3.7 native (linux-x86_64)	Every PR	Build/install native cp37 wheel, validate contents, run runtime smoke and full test suite
Python 3.7 native (windows-x86_64)	Every PR	Build/install native cp37 wheel and run runtime smoke
Test (py37-lite)	Every PR	Install lite wheel and prove fallback behavior without _core
py37 syntax check	Every PR	Compile shipped Python and test sources with a real CPython 3.7 parser
Python 3.7 compatibility	Every PR	Stable aggregate; fails on failed, skipped, or cancelled constituents

Repository rulesets should require the exact aggregate job name Python 3.7 compatibility.

Authoring rules

• Keep modules importable on Python 3.7. Use postponed annotations where modern annotation expressions are present.
• Do not use Python 3.8+ grammar such as assignment expressions, positional-only parameters, debug f-strings, or match statements in shipped Python modules.
• Do not evaluate modern annotations on Python 3.7 without a compatibility adapter. compile() alone is not a runtime proof.
• Use dcc_mcp_core._typing, which preserves standard-library identity on Python 3.8+ and provides Core's bounded fail-closed Protocol, Literal, and runtime_checkable subset on Python 3.7 without importing a backport.
• Do not import _core unconditionally on code paths that must support the lite profile.
• New public Python APIs need tests in both the native and lite profiles when they cross the Rust/Python boundary.

Local validation

The vx-managed Python 3.7 is sufficient for the syntax gate but may not include pip or the native import library. Building and installing a native wheel requires a full CPython 3.7 installation with pip and development/import libraries. On Windows, the standard python.org installation provides these.

PowerShell:

$py37 = py -3.7 -c "import sys; print(sys.executable)"
vx just check-python-support
vx just check-py37-syntax
vx just build-py37 -i $py37
$wheel = Get-ChildItem dist/dcc_mcp_core-*-cp37-cp37m-*.whl | Select-Object -First 1
& $py37 scripts/ci/check_python_wheel.py --profile native_py37 --platform windows-x86_64 $wheel.FullName
& $py37 -m pip install --force-reinstall --no-deps $wheel.FullName
& $py37 scripts/ci/smoke_python37_runtime.py --profile native_py37

Bash:

PYTHON37="${PYTHON37:-python3.7}"
vx just check-python-support
vx just check-py37-syntax
vx just build-py37 -i "$PYTHON37"
"$PYTHON37" scripts/ci/check_python_wheel.py --profile native_py37 --platform linux-x86_64 \
  'dist/dcc_mcp_core-*-cp37-cp37m-*.whl'
wheel=$(ls dist/dcc_mcp_core-*-cp37-cp37m-*.whl | head -1)
"$PYTHON37" -m pip install --force-reinstall --no-deps "$wheel"
"$PYTHON37" scripts/ci/smoke_python37_runtime.py --profile native_py37

For the lite profile, use the same full interpreter. PowerShell:

& $py37 scripts/build_py37_pure_wheel.py
$wheel = Get-ChildItem dist/dcc_mcp_core-*-py3-none-any.whl | Select-Object -First 1
& $py37 scripts/ci/check_python_wheel.py --profile lite_py37 --platform any $wheel.FullName
& $py37 -m pip install --force-reinstall --no-deps $wheel.FullName
& $py37 scripts/ci/smoke_python37_runtime.py --profile lite_py37

Bash:

"$PYTHON37" scripts/build_py37_pure_wheel.py
"$PYTHON37" scripts/ci/check_python_wheel.py --profile lite_py37 --platform any \
  'dist/dcc_mcp_core-*-py3-none-any.whl'
wheel=$(ls dist/dcc_mcp_core-*-py3-none-any.whl | head -1)
"$PYTHON37" -m pip install --force-reinstall --no-deps "$wheel"
"$PYTHON37" scripts/ci/smoke_python37_runtime.py --profile lite_py37

Deprecation process

Python 3.7 support can be removed only after an accepted superseding ADR, a major release, at least 180 days of notice, and a documented adapter migration path. A dependency upgrade or hosted-runner change is not, by itself, a reason to silently weaken the contract.

References

• ADR 011: Python 3.7 LTS Compatibility Contract
• py37-lite Architecture
• Adapter Compatibility Matrix