Bzlmod module resolution transition from WORKSPACE in Bazel 6+

Compatibility Boundary

The activation of Bzlmod mode depends on the --enable_bzlmod flag and the Bazel version, rather than the mere presence of a MODULE.bazel file. In Bazel 6, this flag defaults to false, meaning WORKSPACE remains the primary resolution mechanism. Starting with Bazel 7, the flag defaults to true, activating Bzlmod mode.

Resolution Logic and Determinism

When Bzlmod is enabled and both files exist, MODULE.bazel is authoritative for dependency resolution. The WORKSPACE file is still evaluated to support legacy repositories not defined in the module graph, but these are subordinate to Bzlmod's resolution.

Determinism is not guaranteed across different Bazel versions in mixed mode. Repository canonical names (e.g., those using tilde suffixes) are implementation details that can change between releases. Furthermore, the resolution order and handling of duplicate dependencies may vary across versions, making the combination of a .bazelversion file and a committed MODULE.bazel.lock the only reliable way to ensure reproducible builds across clean clones.

WORKSPACE Deprecation Status

Bazel has signaled an intent to move away from WORKSPACE, with discussions around disabling it by default in later major releases (such as Bazel 9). However, a finalized, fixed date for the total removal of WORKSPACE has not been officially published as a hard deadline; it remains a phased transition.

Verification Steps

1. Check the active version: bazel version.
2. Verify effective flags: bazel info or run a build with --announce_rc to see the resolved value of --enable_bzlmod and --enable_workspace.
3. Test for hidden dependencies: Run --enable_workspace=false to identify repositories that still rely exclusively on the WORKSPACE file.
4. Validate determinism: Commit MODULE.bazel.lock and .bazelversion, then compare bazel query @//external:all across two different clean environments.

To provide a more specific recommendation, please specify the exact Bazel version currently in use, as the default behavior shifts significantly between versions 6 and 7.