The most common outcome is namespace collision and a harder-to-maintain repository. Custom modules and generated modules share the same root, which can make the package look crowded and obscure which files are hand-written versus generated. It can also leave stale generated files behind if upstream protobuf packages are removed, creating orphaned code that is easy to miss.
Why Generated and Hand-Written Protobuf Code Should Not Share the Same Root Package
When generated protobuf modules live in the same top-level package as custom SDK code, the practical problem is not just aesthetics. You are merging two code sources with different lifecycles, ownership, and regeneration behaviour into one namespace. That makes it easier for import paths, symbols, and file ownership boundaries to blur, especially as the repository grows or upstream protobuf definitions change.
The strongest signal that the design is becoming brittle is when developers can no longer tell at a glance what is generated, what is custom, and what should be edited manually. That ambiguity increases review noise and makes repository hygiene harder, because generated files may linger after upstream packages are removed or renamed, leaving orphaned modules behind.
From a maintenance perspective, the shared root also makes accidental coupling more likely. Hand-written SDK helpers can start to depend on generated layout details, and later regeneration can break expectations without an obvious compile-time error. The result is a package structure that still works, but is harder to reason about, refactor, or clean up safely.
What the Namespace Collision Actually Breaks
Namespace collision here usually means two things: symbol overlap and human confusion. Even if the compiler resolves the packages correctly, developers still have to distinguish generated message types from custom client code that sits beside them. As the directory tree fills up, that shared namespace becomes a maintenance tax, because simple changes can affect unrelated files and make code navigation slower.
This setup also creates a lifecycle problem. Generated protobuf output is often regenerated from an upstream schema, but custom SDK code is edited by hand and may evolve independently. When both are co-located under the same root, stale generated artifacts are easier to miss during cleanup, especially if the source protobuf package is removed or renamed. That can leave dead code, misleading imports, or outdated package references in place long after they should have been deleted.
If the repository already has signs of secrets or dependency sprawl, the same pattern tends to worsen operational discipline. Code that looks uniform but has mixed provenance is harder to audit, and a repo with crowded package roots is simply easier to misread during review. For broader packaging and supply-chain hygiene, the same principle applies to the wider open-source ecosystem that OpenSSF works to secure.
Risk and Threat Considerations
This pattern is mainly a maintainability and integrity risk, but it can also create security exposure when stale generated files or ambiguous ownership cause the wrong code to be shipped or trusted. The concern is less about protobuf itself and more about reduced visibility into what is authoritative, current, and safe to remove.
Failure mechanism: Generated code and custom code share the same root package, so reviewers and maintainers lose a clean boundary between source-of-truth schema output and hand-written SDK logic. That increases the chance of orphaned modules, stale imports, and accidental dependence on files that should have been regenerated or deleted.
Impact: Teams spend more time untangling package structure, while the repository becomes easier to misconfigure or leave inconsistent during schema changes. In environments where generated artifacts carry access-related material or interface contracts, that inconsistency can also slow remediation and increase the chance of shipping outdated code paths.
Standards & Framework Alignment
This section maps relevant standards and security frameworks to the operational risks and controls described in this guidance.
CIS Controls v8 and NIST CSF 2.0 set the governance and control requirements practitioners need to meet.
| Framework | Control / Reference | Relevance |
|---|---|---|
| CIS Controls v8 | CIS 16 — Application Software Security | Shared generated and custom code increases release integrity and code hygiene risk. |
| Recommendation — Separate generated artifacts from hand-written code and verify package cleanup during build and release reviews. | ||
| NIST CSF 2.0 | CM-2 — Baseline Configuration | A mixed package root makes it harder to maintain a stable, known-good code baseline. |
| CM-5 — Configuration Change Control | Upstream protobuf changes and stale generated files require controlled updates and removals. | |
| Recommendation — Define and enforce a clear repository baseline for generated protobuf output and custom SDK sources. Require controlled review of regenerated protobuf files and explicit removal of orphaned modules. | ||
Practitioner Guidance
What to verify: Confirm that generated protobuf output has its own clearly named package path, regeneration path, and cleanup rule, so developers can remove upstream modules without leaving dead files behind. If custom SDK code must coexist nearby, make the boundary explicit in naming and directory layout rather than relying on convention alone.
Common mistake: Treating generated code as just another source file tree is what creates the long-term maintenance burden. The safer pattern is to make regeneration and manual editing visibly different in the repository, so code review can spot stale artifacts before they become part of the shipped SDK.
Practitioner takeaway: The real objective is not just to avoid a compiler conflict, but to preserve a clean ownership boundary between generated contracts and hand-written SDK code so repository hygiene remains trustworthy over time.
Related resources from NHI Mgmt Group
- What happens when malicious code is hidden inside a sub-dependency instead of the first-level package?
- What happens when a package imports compiled Python code across different interpreter versions?
- What is the difference between a source schema and generated SDK code?
- When should organisations prioritise transitive dependency review over top-level package updates?
