bazelbuild/bazel

bootstrap: bootstrap bazel doesn't set correct bazel_version for bazel_features by default

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#27401 opened on Oct 23, 2025

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P2help wantedteam-OSStype: bug

Description

Description of the bug:

As discovered in https://github.com/bazelbuild/bazel/issues/27349 bootstrap ./compile.sh from scratch process doesn't correctly set native.bazel_version in first stage bazel.

Instead bazel_features see version as '' and treat as "dev" 999999 version. Which isn't correct for support branches. Bazel 7.x branch may not have some features of Bazel 8, assuming 999999 then can break the 7.x bootstrap build (even if 8.x feature isn't in use in bazel code, it may still fail to compile due to missing globals)

EMBED_LABEL=/--embed_label isn't setting native.bazel_version BAZEL_DEV_VERSION_OVERRIDE= will set it but it isn't mentioned in the docs https://bazel.build/install/compile-source

Not sure if BAZEL_DEV_VERSION_OVERRIDE is supposed to be the correct way (just docs issue) or there's a bug in how bootstrap bazel own version is being set up.

Note: on bazel_features side https://github.com/bazel-contrib/bazel_features/issues/117 version='' still has a use-case for last_green builds

Which category does this issue belong to?

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What's the simplest, easiest way to reproduce this bug? Please provide a minimal example if possible.

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Which operating system are you running Bazel on?

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What is the output of bazel info release?

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If bazel info release returns development version or (@non-git), tell us how you built Bazel.

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What's the output of git remote get-url origin; git rev-parse HEAD ?

If this is a regression, please try to identify the Bazel commit where the bug was introduced with bazelisk --bisect.

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Have you found anything relevant by searching the web?

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Any other information, logs, or outputs that you want to share?

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Contributor guide

Tech stack
javashell
Domain
build systemdevops
Issue type
bug
DifficultyEstimated implementation difficulty for a new contributor, from 1 for very small changes to 5 for expert-level work.
3
Estimated timeA rough time range for an experienced contributor to investigate, implement, test, and prepare a pull request.
1-3 hours
Activity statusHow available the issue appears right now: fresh, active, stale, blocked, or waiting on maintainer input.
fresh
ClarityHow clearly the issue explains the expected change, acceptance criteria, and next step.
needs investigation
Prerequisites
Understanding of Bazel bootstrap processKnowledge of bazel features
Newbie friendlinessA 1-100 score estimating how approachable this issue is for first-time contributors.
20
Research direction
Investigate compile.sh to see how BAZEL DEV VERSION OVERRIDE and EMBED LABEL are used. Check bazel features issue #117 for context on version=''. Determine if the fix is to set native.bazel version correctly during bootstrap or to document BAZEL DEV VERSION OVERRIDE. Look at the bazel source code for how native.bazel version is populated.