Sample
protobuf 6.33.6: Know which protobuf backend actually loaded: upb ships inside the binary wheel, so a musl/Alpine image with no prebuilt wheel silently gets the pure-Python fallback with different descriptor types and no warning
Verified sample for pypi protobuf 6.33.6: Know which protobuf backend actually loaded: upb ships inside the binary wheel, so a musl/Alpine image with no…
sha256:d7bea0b572b3364fc334f71559dbe438cfebc689607a583f66c1d6e1e9e2cc91
This network offers one thing: a sample that builds. It ran the sample in a sandbox and kept the signed receipt. It grades nothing and warrants nothing — whether the same code builds where you are is not something it measured.
How many distinct signing keys filed a passing contract receipt. One is the author alone; more than one means somebody else built it too. A key is self-generated with nothing registered behind it, so it counts keys, not people.
MIT-0
Execution evidence
The declared environment and the signed runs are kept apart, so you can see exactly what this sample ran and where.
- Evidence basis
- Signed contract pass
- Verification receipts
- 2
- Signing keys that built it
- 2
Declared environment
python linux x64 python python pip
Verification-run environments
| Environment | Contract | Stages | Run |
|---|---|---|---|
| python 3.12 · linux alpine/x64 · docker ed25519:d91480838ac982c9 | PASS | compile:SKIPPED · contract:PASS · load:PASS · resolve:PASS CONTAINER_RUN · python@1 |
2026-08-15 |
| python 3.12 · linux alpine/x64 · docker ed25519:2175b912ea1c23b1 | PASS | compile:SKIPPED · contract:PASS · load:PASS · resolve:PASS CONTAINER_RUN · python@1 |
2026-08-18 |
Case
HOW- Goal
- Know which protobuf backend actually loaded: upb ships inside the binary wheel, so a musl/Alpine image with no prebuilt wheel silently gets the pure-Python fallback with different descriptor types and no warning
- Packages
- Symbols
-
- google.protobuf.internal.api_implementation.Type
- google.protobuf.descriptor.Descriptor
- Environment
- python
- Created
- 2026-08-15T11:26:57Z
Contract
- assert the default backend is whatever the platform's wheel provided: upb when the C extension is importable, python when it is not, with no warning either way
- assert the pure-Python fallback carries different descriptor classes (google.protobuf.descriptor rather than google._upb._message), so isinstance and __module__ checks written against upb stop matching
- assert PROTOCOL_BUFFERS_PYTHON_IMPLEMENTATION=python forces the pure-Python backend
- assert PROTOCOL_BUFFERS_PYTHON_IMPLEMENTATION=cpp keeps Type()=='cpp' with no _c_module and then fails loudly on import, rather than falling back
- assert an unsupported backend name raises ValueError naming the supported ones
- assert backend selection is cached at first import, so mutating the environment afterwards changes nothing
Files
- NOTES.md
- csx.json
- requirements.lock
- requirements.txt
- test/contract.py