google-cloud-compute fails to import on Python 3.14 — protobuf<5 pins incompatible protobuf 4.x (TypeError: Metaclasses with custom tp_new are not supported)

[liucy1983]

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Summary of the issue

Context
I upgraded our project to Python 3.14 (CPython 3.14.7, via mise/uv). google-cloud-compute is a direct dependency (currently ==1.15.0). Its metadata declares protobuf>=3.19.5,<5.0.0dev, so the resolver installs the newest allowed protobuf on the 4.x line.

Expected Behavior:
import google.cloud.compute works on Python 3.14, the same way it works on 3.11–3.13.

Actual Behavior:
Importing the package (or any package that pulls in protobuf, e.g. temporalio) immediately raises TypeError: Metaclasses with custom tp_new are not supported. on Python 3.14. protobuf 4.x ships a C extension whose metaclass uses a custom tp_new, which CPython 3.14 now rejects. The protobuf<5 upper bound blocks the only line (protobuf 6.x) whose C extension is fixed for 3.14.

API client name and version

google-cloud-compute==1.15.0

Reproduction steps: code

file: main.py

import google.cloud.compute # raises TypeError on Python 3.14
print("ok")

### Reproduction steps: supporting files

No extra data files are required. The only relevant constraint is the version pin resolved from the dependency:

file: requirements.txt (minimal)

google-cloud-compute==1.15.0


### Reproduction steps: actual results

$ python3 -c "import google.cloud.compute"
Traceback (most recent call last):
 File "<string>", line 1, in <module>
 File ".../site-packages/google/cloud/compute/__init__.py", line 18, in <module>
 ...
 File ".../site-packages/google/protobuf/internal/api_implementation.py", line 51, in <module>
 if _CanImport('google._upb._message'):
 File ".../site-packages/google/protobuf/internal/api_implementation.py", line 41, in _CanImport
 mod = importlib.import_module(mod_name)
 File ".../lib/python3.14/importlib/__init__.py", line 88, in import_module
 return _bootstrap._gcd_import(name, level)
TypeError: Metaclasses with custom tp_new are not supported.

Setting PROTOCOL_BUFFERS_PYTHON_IMPLEMENTATION=python does NOT help: protobuf probes
google._upb._message first and the probe itself raises TypeError (not ImportError), so the
pure-Python fallback never engages.

### Reproduction steps: expected results

$ python3 -c "import google.cloud.compute"
ok

### OS & version + platform

macOS 27 (Golden Gate), Apple Silicon (arm64) 

### Python environment

Python 3.14.7

### Python dependencies

pip list | grep -iE "protobuf|google-cloud-compute|google-api-core|proto-plus"
google-api-core 2.27.0
google-cloud-compute 1.15.0
proto-plus 1.26.1
protobuf 4.25.9 # forced by google-cloud-compute <5.0.0dev

### Additional context

Root cause
 google-cloud-compute pins `protobuf>=3.19.5,<5.0.0dev`. On Python 3.14:
 - protobuf 4.25.9 (highest allowed) -> C extension fails with
 `TypeError: Metaclasses with custom tp_new are not supported.`
 (CPython 3.14 forbids custom-tp_new metaclasses).
 - protobuf 6.x (C extension fixed for 3.14) -> blocked by the <5 upper bound.
 This is a hard deadlock for anyone running google-cloud-compute on Python 3.14.

Evidence that 6.x works at runtime
 We forced protobuf 6.33.6 (uv `override-dependencies = ["protobuf>=6.31.0,<7"]`)
 and verified on Python 3.14.7:
 - import google.cloud.compute -> OK
 - import temporalio (also protobuf-dependent) -> OK
 - protobuf message serialization round-trips -> OK
 - temporalio generated *_pb2 round-trips -> OK
 So the <5 upper bound is overly conservative; the client runs fine on protobuf 6.x.

Suggested fix
 Loosen the protobuf upper bound in google-cloud-compute, e.g. to <8.0.0
 (consistent with the other google-cloud-* clients) or at least <7.0.0, and add a
 Python 3.14 CI job so this regression is caught earlier.

Workaround (for affected users)
 - With uv: override-dependencies = ["protobuf>=6.31.0,<7"] in [tool.uv].
 - With pip: pip install --no-deps "google-cloud-compute==1.15.0" "protobuf>=6.31.0"
 then resolve the rest normally.

Related: temporalio already allows protobuf>=3.20,<8.0.0, confirming 6.x is the intended target line.

[parthea]

Hi @liucy1983,

Regrettably, as per https://www.python.org/downloads/release/python-3140/, the release date for 3.14 was Oct. 7, 2025 whereas google-cloud-compute==1.15.0 was released in December 2023. It's not possible for an older version of the package, such asgoogle-cloud-compute==1.15.0, to support a newer runtime since 3.14 wasn't available at the time of release.

google-cloud-compute==1.15.0 only supports Python 3.12 and older as per https://pypi.org/project/google-cloud-compute/1.15.0/

google-cloud-compute==1.40.0 or newer is needed for 3.14 support as per https://pypi.org/project/google-cloud-compute/1.40.0/

I'm going to close this issue but please feel free to open a new issue if you have additional questions.