Release 9.1.0rc2 (2026-04-14)

Bazel 9.1.0 is a minor LTS release. It is fully backward compatible with Bazel 9.0 and contains selected changes by the Bazel community and Google engineers

Configurability

• Fix launcher/launcher_maker for cross build, e.g. build windows binary on linux machine. (#29239)

External Deps

• The `compatibility_level` and `max_compatibility_level` attributes of `module` in MODULE.bazel are now no-ops. Module maintainers should stop specifying those attributes and provide clear build time error messages and actionable migration paths when making major breaking changes. (#28616)
• `package_group` now supports labels with external repositories in the `packages` attribute. (#28893)
• `rctx.symlink` now implicitly watches the target if it falls back to a copy. (#28741)
• The local and remote repo contents cache now include the host OS and CPU architecture in the cache key. (#29195)
• The remote repo contents cache now supports all reproducible repo rules. (#29225)

Remote Execution

• The `requires-worker-protocol` execution requirement is now forwarded to remote execution services as a platform property (`persistentWorkerProtocol`) to support intermixing JSON and Proto remote persistent worker protocols across a build. (#28710)
• Bazel now has experimental support for `--rewind_lost_inputs`, which can rerun actions within a single build to recover from (remote or disk) cache evictions. (#28958)
• Added `--experimental_remote_cache_chunking` flag to read and write large blobs to/from the remote cache in chunks. Requires server support. (#28903)

Starlark / Build Language

• `string.splitlines()` no longer incorrectly treats u+0085 (`NEL`) as a newline character (#28931)

Acknowledgments

This release contains contributions from many people at Google, as well as Armando Montanez, ashutosh0x, Boleyn Su, Fabian Meumertzheim, H5-O5, Joseph Gette, Keith Smiley, Paul Tarjan, Ted Kaplan, Tyler French, and Will Stranton.

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