[sxlijin]

Native Windows ARM64 wrapper builds select llvm-lib.exe, which treats /Brepro as an input filename and fails with /Brepro: no such file or directory. Clear the ARM64 archiver flags while retaining /Brepro for the x64 MSVC archiver. LLVM's COFF archiver already writes deterministic archives by default.

This is the remaining archiver failure exposed after #5489 stopped MSYS2 from converting the flags into paths. Failure example: https://github.com/BoundaryML/baml/actions/runs/41558436389/job/125663254593.

Validation: reproduced the unsupported-flag failure with LLVM using an ARM64 Windows COFF object, then successfully wrote two byte-identical libraries without the flag after changing the object's filesystem timestamp. Sourcing .envrc clears an inherited ARM64 /Brepro value and preserves the x64 flag. Shell syntax and applicable prek checks pass. LLVM's implementation explicitly enables deterministic output: https://github.com/llvm/llvm-project/blob/main/llvm/lib/ToolDrivers/llvm-lib/LibDriver.cpp.

Summary by CodeRabbit

• Chores
  • Updated build settings for native ARM64 Windows builds. The build no longer passes an unsupported option to the library tool; application behavior is unchanged.

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[coderabbitai]

No actionable comments were generated in the recent review.

Walkthrough

The .envrc configuration now leaves ARFLAGS_aarch64_pc_windows_msvc empty. A new comment states that native ARM64 llvm-lib is deterministic by default and does not support /Brepro.

Changes: ARM64 Archiver Configuration

Layer / File(s)	Summary
Update the ARM64 archiver flag .envrc	ARFLAGS_aarch64_pc_windows_msvc is now empty. A comment documents that native ARM64 llvm-lib is deterministic by default and does not support /Brepro.

Estimated code review effort: 1 (Trivial) | ~3 minutes

Change: Bug fix

Possibly related PRs

• BoundaryML/baml#5487: Adds /Brepro to the ARM64 flag that this change clears.
• BoundaryML/baml#5489: Addresses MSYS2 conversion of the MSVC archiver variables, in the same ARM64 archiver flag flow.

Suggested reviewers: codeshaunted

Merge Risk: Minimal · up to 0e9b2

The ARM64 archiver configuration is ready to merge with no identified actionable risk.

Architecture risk: Low · up to 0e9b2

The changed surface does not map to a changed system, dependency edge, entrypoint, or external dependency.

Changed systems: None identified.

Architecture concerns
No architecture-level concerns identified.

Review details

Before / after behavior

• observed — Modified behavior in .envrc: The ARM64 MSVC archiver flags change from /Brepro to an empty value; a comment identifies native ARM64’s llvm-lib as deterministic by default and without /Brepro support.

Pre-merge checks: 5

Check name	Status	Explanation
Description Check		Check skipped - CodeRabbit’s high-level summary is enabled.
Title check		The title "ci: leave deterministic LLVM ARM64 archives flag-free" matches the main change. The .envrc change clears ARFLAGS_aarch64_pc_windows_msvc so the native ARM64 llvm-lib archiver no longer rece…
Docstring Coverage		No eligible functions found in the changed files. Skipping docstring coverage check. Docstring coverage is scoped to functions touched by this diff with cyclomatic complexity of at least 2. Documentat…
Linked Issues check		Check skipped because no linked issues were found for this pull request.
Out of Scope Changes check		Check skipped because no linked issues were found for this pull request.

Full details: Title check

Explanation

The title "ci: leave deterministic LLVM ARM64 archives flag-free" matches the main change. The .envrc change clears ARFLAGS_aarch64_pc_windows_msvc so the native ARM64 llvm-lib archiver no longer receives /Brepro, which it treats as an input filename and rejects. The x64 MSVC flag is kept, and the title's use of "ci:" fits a change to build configuration. The title is specific and concise, though it names the ARM64 archive behavior rather than the failure it fixes.

Full details: Docstring Coverage

Explanation

No eligible functions found in the changed files. Skipping docstring coverage check. Docstring coverage is scoped to functions touched by this diff with cyclomatic complexity of at least 2. Documentation-only edits and deletions within surviving functions are included; unchanged diff context and fully deleted functions are excluded. Analyzed 0 functions across 0 files. (1 skipped: 1 unsupported.)

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_{A rabbit checks the flags with care,
Finds /Brepro is not for there.
The ARM64 setting clears its space,
While llvm-lib keeps its steady pace.
The burrow hums; the build runs clean.}

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Recent review info

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Commits

Reviewing files that changed from the base of the PR and between 5437493 and 0e9b2d6.

Files selected for processing: 1

• .envrc

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