Add news announcement for Bazel Starlark flag migration.

PiperOrigin-RevId: 883347678

Author: protobuf-github-bot

content/news/2025-09-19.md

@@ -223,11 +223,43 @@ This release will remove the following public runtime APIs.
 
 **Replacement:** Use `!required && fieldType == GPBFieldTypeSingle` instead.
 
-## Other Changes {#other-changes}
+## Changes in Bazel {#bazel}
 
-The following are additional breaking changes.
+### Migration of Proto Flags to Starlark {#bazel-starlark-flags}
+
+`--proto_toolchain_for*` and `--proto_compiler` are no longer read by Proto
+rules. These toolchain-related flags are deprecated and will be removed in the
+future. Switching to the equivalent Starlark flags is a short-term fix:
+
+*   `--@protobuf//bazel/flags/cc:proto_toolchain_for_cc`
+*   `--@protobuf//bazel/flags/java:proto_toolchain_for_java`
+*   `--@protobuf//bazel/flags/java:proto_toolchain_for_javalite`
+*   `--@protobuf//bazel/flags:proto_compiler`
+
+The longer-term fix is to enable
+`--incompatible_enable_proto_toolchain_resolution` (which is the default in
+Bazel 9 anyway) and to register toolchains using the normal platforms-related
+mechanisms (`register_toolchain()` in `MODULE.bazel` or `WORKSPACE`, or
+`--extra_toolchains`).
+
+All other Bazel Proto flags have also been migrated to Starlark, and the native
+flags will be deprecated with the next Bazel release. Use the following Starlark
+flags to avoid future breakages:
 
-### Bazel: Remove deprecated ProtoInfo.transitive_imports {#bazel-transitive-imports}
+*   `--@protobuf//bazel/flags:strict_proto_deps`
+*   `--@protobuf//bazel/flags:strict_public_imports`
+*   `--@protobuf//bazel/flags:experimental_proto_descriptor_sets_include_source_info`
+*   `--@protobuf//bazel/flags/cc:cc_proto_library_header_suffixes`
+*   `--@protobuf//bazel/flags/cc:cc_proto_library_source_suffixes`
+*   `--@protobuf//bazel/flags:protocopt`
+
+**NOTE:** In v34.0, `--@protobuf//bazel/flags:protocopt` was incorrectly located
+at `--@protobuf//bazel/flags/cc:protocopt`. The flag will be moved to its
+correct location, and the `cc` location will remain as a deprecated alias
+starting in v34.1. This alias should not be used and will be removed in the next
+breaking change.
+
+### Remove deprecated ProtoInfo.transitive_imports {#bazel-transitive-imports}
 
 The deprecated `transitive_imports` field in `ProtoInfo` will be removed. Users
 should migrate to `transitive_sources`.
@@ -237,6 +269,10 @@ should migrate to `transitive_sources`.
 Due to Bazel's recent improvements on Windows, we now plan to continue to
 support Bazel+MSVC. The `--define=protobuf_allow_msvc` flag will be removed.
 
+## Other Changes {#other-changes}
+
+The following are additional breaking changes.
+
 ### Languages Without a Major Version Bump
 
 Java, Ruby, C#, Rust, and JRuby will not have a major version bump in this

content/news/2026-03-13.md

@@ -0,0 +1,44 @@
++++
+title = "Changes Announced on March 13, 2026"
+linkTitle = "March 13, 2026"
+toc_hide = "true"
+description = "Changes announced for Protocol Buffers on March 13, 2026."
+type = "docs"
++++
+
+## Changes in Bazel {#bazel}
+
+### Migration of Proto Flags to Starlark {#bazel-starlark-flags}
+
+`--proto_toolchain_for*` and `--proto_compiler` are no longer read by Proto
+rules. These toolchain-related flags are deprecated and will be removed in the
+future. Switching to the equivalent Starlark versions of the flags is a
+short-term fix:
+
+*   `--@protobuf//bazel/flags/cc:proto_toolchain_for_cc`
+*   `--@protobuf//bazel/flags/java:proto_toolchain_for_java`
+*   `--@protobuf//bazel/flags/java:proto_toolchain_for_javalite`
+*   `--@protobuf//bazel/flags:proto_compiler`
+
+The longer-term fix is to enable
+`--incompatible_enable_proto_toolchain_resolution` (which is the default in
+Bazel 9 anyway) and to register toolchains using the normal platforms-related
+mechanisms (`register_toolchain()` in `MODULE.bazel` or `WORKSPACE`, or
+`--extra_toolchains`).
+
+All other Bazel Proto flags have also been migrated to Starlark, and the native
+flags will be deprecated with the next Bazel release. Use the following Starlark
+flags to avoid future breakages:
+
+*   `--@protobuf//bazel/flags:strict_proto_deps`
+*   `--@protobuf//bazel/flags:strict_public_imports`
+*   `--@protobuf//bazel/flags:experimental_proto_descriptor_sets_include_source_info`
+*   `--@protobuf//bazel/flags/cc:cc_proto_library_header_suffixes`
+*   `--@protobuf//bazel/flags/cc:cc_proto_library_source_suffixes`
+*   `--@protobuf//bazel/flags:protocopt`
+
+**NOTE:** In v34.0, `--@protobuf//bazel/flags:protocopt` was incorrectly located
+at `--@protobuf//bazel/flags/cc:protocopt`. The flag will be moved to its
+correct location, and the `cc` location will remain as a deprecated alias
+starting in v34.1. This alias should not be used and will be removed in the next
+breaking change.

content/news/_index.md

@@ -20,6 +20,8 @@ New news topics will also be published to the
 The following news topics provide information in the reverse order in which it
 was released.
 
+*   [March 13, 2026](/news/2026-03-13) - Breaking changes
+    in Bazel for the upcoming 34.x release
 *   [January 16, 2026](/news/2026-01-16) - Prebuilt proto
     compiler (protoc) for Bazel
 *   [September 19, 2025](/news/2025-09-19) - Breaking

content/news/v34.md

@@ -8,6 +8,8 @@ type = "docs"
 
 The following news topics provide information about changes in the 34.x release.
 
+*   [March 13, 2026](/news/2026-03-13) - Breaking changes
+    in Bazel for the upcoming 34.x release
 *   [January 16, 2026](/news/2026-01-16) - Prebuilt proto
     compiler (protoc) for Bazel
 *   [September 19, 2025](/news/2025-09-19) - Breaking