Changes Announced on January 16, 2026

Prebuilt proto compiler (protoc) for Bazel

In an effort to speed up builds, protobuf 33.4 offers an option to skip re-compiling Protobuf tools and runtimes and use a pre-built protoc binary, available to Bazel 7 and later. Using a pre-built protoc also avoids build failures from incompatible or non-hermetic C++ compilation toolchain installed on your machine.

To use the prebuilt protoc, upgrade to protobuf version 33.4 or later, and set the --incompatible_enable_proto_toolchain_resolution and --@protobuf//bazel/flags:prefer_prebuilt_protoc flags. The first flag is set by default in Bazel 9 onwards.

In the breaking v34 release, protobuf will change the default of --@protobuf//bazel/flags:prefer_prebuilt_protoc to true.

Reasons not to use the prebuilt compiler

There are some use cases in which using the prebuilt protoc is not recommended:

• Your corporate security policy requires all dependencies be built from source.
• You need to build for the exec platform with a specific compiler or specific compiler flags.
• You are making changes to protoc, itself, and want to ensure that those changes are tested.

Troubleshooting

For information on troubleshooting the prebuilt protoc compiler configuration, see Bazel: Resolving Issues with Prebuilt Protoc

For more information on other changes in Bazel 9 that affect Protocol Buffers, see https://bazel.build/about/roadmap.