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Release 9.1.0 (2026-04-20)

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.

IMPORTANT

Compatibility Note: CcInfo removal and rules_go

If you encounter the error "The CcInfo symbol has been removed", this is due to an intentional change in Bazel 9 regarding C++ Starlarkification. While this change was present in 9.0.0, a bug fixed in 9.0.1 (#28360) now correctly surfaces this error instead of failing silently or with a confusing message. To fix this, please upgrade rules_go, rules_nodejs or any broken rulesets. For example,

# Add repo_name = None if you don't directly depend on them.
bazel_dep(name = "rules_go", version = "0.59.0") 
bazel_dep(name = "rules_nodejs", version = "6.7.3")

CLI

• Reporting of cached test results can now be suppressed with --test_summary=short_uncached or --test_summary=detailed_uncached. (#29263)

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

• 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.

Notice: Bazel installers contain binaries licensed under the GPLv2 with Classpath exception. Those installers should always be redistributed along with the source code.

Some versions of Bazel contain a bundled version of OpenJDK. The license of the bundled OpenJDK and other open-source components can be displayed by running the command bazel license. The vendor and version information of the bundled OpenJDK can be displayed by running the command bazel info java-runtime. The binaries and source-code of the bundled OpenJDK can be downloaded from our mirror server.

Security: All our binaries are signed with our public key 3D5919B448457EE0.