Windows bootstrap missing libclang and protoc; cargo build fails

[cbeaulieu-gt]

Pre-submit Checks

• I have searched Warp bugs and there are no duplicates. An existing PR (Install libclang and protoc in Windows bootstrap #10911) implements the same fix, but no backing issue exists for it to link to.
• I have searched Warp known issues page and my issue is not there.

Describe the bug

script/windows/bootstrap.ps1 advertises that it installs all required build dependencies, but two hard build dependencies are missing on Windows:

1. protoc (the Protocol Buffers compiler) — required by prost-build, used by the warp_multi_agent_api crate (a git-dep of warpdotdev/warp-proto-apis). This is the first failure a contributor hits.
2. libclang — required by bindgen-style build scripts elsewhere in the workspace. This is the same gap that was fixed on Linux in Add libclang-dev and clang-format to Linux bootstrap deps #9527 (which resolved Linux bootstrap is missing libclang-dev and clang-format, breaking script/presubmit #9526); the Windows side of the same gap has never been closed.

After a fresh bootstrap, cargo build --release fails on protoc first. Once protoc is installed manually, the build proceeds further but is expected to fail again on libclang for the same structural reason.

To reproduce

On a Windows 11 machine with no prior Rust toolchain:

1. Clone warpdotdev/warp (master at b376889).
2. Run .\script\windows\bootstrap.ps1 — completes without error.
3. Open a fresh PowerShell so PATH is refreshed.
4. Run cargo build --release from the repo root.
5. Build progresses through the dependency graph, then fails compiling warp_multi_agent_api.

Exact error:

error: failed to run custom build command for `warp_multi_agent_api v0.0.0 (https://github.com/warpdotdev/warp-proto-apis.git?rev=9a2d2425c5d1eb40fb547956e659511906e03f9e#9a2d2425)`

Caused by:
  process didn't exit successfully: `...\target\release\build\warp_multi_agent_api-...\build-script-build` (exit code: 1)
  --- stderr
  Error: Custom { kind: NotFound, error: "Could not find `protoc`. If `protoc` is installed, try setting the `PROTOC` environment variable to the path of the `protoc` binary. Try installing `protobuf-compiler` or `protobuf` using your package manager. It is also available at https://github.com/protocolbuffers/protobuf/releases" }

Expected behavior

After .\script\windows\bootstrap.ps1 completes, a fresh cargo build --release should succeed without any additional manual setup. Both protoc and libclang are hard build dependencies for any contributor on Windows, so the bootstrap script should install them alongside the existing Visual Studio Build Tools / CMake / InnoSetup / jq steps. This is the Windows analogue of the Linux gap fixed in #9527.

Workaround

For protoc:

winget install protobuf

For libclang, the standard approach is installing LLVM:

winget install LLVM.LLVM

After both, open a fresh shell so PATH refreshes and re-run cargo build --release. Cargo resumes from the failed crate.

Operating system (OS)

Windows

Operating system and version

Windows 11 Pro, 10.0.26200 (build 26200)

Current Warp version

N/A — building from source. Repository state: b376889 on master.

Regression

No, this bug or issue has existed throughout my experience using Warp. This is the first time I've attempted a local build. The protoc gap likely dates to whenever warp_multi_agent_api was added to default workspace members; the libclang gap has the same shape as the Linux issue fixed by #9527.

Does this block you from using Warp daily?

No — this affects local development and contribution, not daily use of the shipped Warp binary.

Is this an issue only in Warp?

Yes — this is specific to Warp's script/windows/bootstrap.ps1 not installing a required build tool.

Additional context

A candidate fix is already proposed in PR #10911 ("Install libclang and protoc in Windows bootstrap" by @AndreKalberer, opened 2026-05-14). That PR's scope matches this issue exactly — both deps. It is currently blocked partly because Oz flagged that it has no linked ready-to-implement issue to back it under Warp's contribution model (per CONTRIBUTING.md). Filing this issue should unblock that linkage.

Related precedents (Linux side of the same gap):

• Linux bootstrap is missing libclang-dev and clang-format, breaking script/presubmit #9526 — Linux bootstrap missing libclang-dev and clang-format
• Add libclang-dev and clang-format to Linux bootstrap deps #9527 — fix that closed Linux bootstrap is missing libclang-dev and clang-format, breaking script/presubmit #9526
• Add fallback protoc install step on Windows build #9230 — earlier protoc-related Windows CI fix (different surface; mentioned in PR Install libclang and protoc in Windows bootstrap #10911 for context)

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🤖 Generated by Claude Code on behalf of @cbeaulieu-gt

[oz-for-oss]

@cbeaulieu-gt

Here's what I found while triaging this issue:

I can confirm the Windows source-build bootstrap flow appears to be missing required build tools for a clean machine. PR #10911 looks scoped to the same dependency gap.

Maintainer details

I concluded that windows source bootstrap appears to omit required build tools (protoc and LLVM/libclang), causing clean Windows builds to fail after bootstrap..

Triage summary

This looks like a valid Windows source-build bootstrap bug. The report includes a clean Windows 11 repro path and a concrete protoc failure after running the Windows bootstrap script. Code inspection supports the core claim: the local Windows bootstrap/install-build-deps path does not install protoc or LLVM/libclang, while Linux/Nix/CI setup paths already account for these dependencies in some form.

Relevant findings for maintainers:

• script/windows/bootstrap.ps1 previews and installs Rust, Visual Studio Build Tools, cargo test dependencies, jq, CMake, Inno Setup, and gcloud, but it does not install Protobuf/protoc or LLVM/libclang.
• script/windows/install_build_deps.ps1, used by the CI environment setup action, only runs Rust setup plus cargo-managed build dependencies; CI then installs protoc in a separate workflow step, so that does not cover local bootstrap users.
• The workspace-level warp_multi_agent_api dependency is pulled into the app and matches the reported prost-build/protoc failure mode.
• The libclang portion is also plausible from the current dependency/setup surface: crates/warpui/Cargo.toml declares bindgen as a build dependency, Linux setup installs libclang-dev, and the Nix shell sets LIBCLANG_PATH.
• PR Install libclang and protoc in Windows bootstrap #10911 is open and appears scoped to this same gap.

No duplicate issue was found in the repository-wide open-issue pass. The closest open bootstrap-related issue found was #9544, but that covers missing Node.js/Yarn checks rather than Windows protoc/libclang bootstrap dependencies.

This is my automated analysis and may be incorrect. A maintainer will verify the details.

Powered by Oz

[kevinchevalier]

Thanks for the report!

[oz-for-oss]

This issue has been labeled ready-to-implement and is open for contributions involving code changes. If you'd like to tackle it, feel free to open a pull request against this issue. You can also comment @oz-agent on this issue to have the bot draft an implementation PR automatically.