cmux-tui: pass the zig target on a native windows-gnu host

[Somuuuu007]

What's broken

ghostty-vt-sys/build.rs forwards -Dtarget to zig build only when the cargo target differs from the host:

if target != host
    && let Some(zig_target) = zig_target_for_rust_target(&target)

On a native x86_64-pc-windows-gnu toolchain the two match, so zig gets no target and falls back to its Windows default, the msvc ABI:

zig build-lib ... -target native-native-msvc ...
error: failed to find libc installation: WindowsSdkNotFound

A machine with no Visual Studio is exactly why its Rust host is windows-gnu to begin with, so the msvc fallback can never succeed. cargo build -p cmux-tui fails before any crate compiles.

CI doesn't hit this: its Windows runners build from an msvc host to a gnu target, so target != host holds and the target is forwarded.

Fix

Forward the target on a native windows-gnu host too.

zig_target_for_rust_target already maps x86_64-pc-windows-gnu → x86_64-windows-gnu; this just lets the native case reach it. The file already branches on target.contains("windows-gnu") a few lines down for the MinGW archive name, so the shape matches what's there.

Verification

Windows 11, Rust 1.95.0 (gnu host), zig 0.16.0, MSYS2 mingw-w64 gcc 16.2.0 + lld 22.1.8.

Before: zig build fails with WindowsSdkNotFound.

After: cargo build -p cmux-tui finishes, and the binary actually works:

$ cmux --version
cmux 0.1.0

$ cmux server status --session wintest
status   running
socket   C:\Users\...\AppData\Local\Temp\cmux-tui-somes\wintest.sock

$ cmux --session wintest terminal list
TITLE      C:\WINDOWS\System32\WindowsPowerShell\v1.0\powershell.exe
LIFECYCLE  running   RUNNING true   80x24

$ cmux --session wintest terminal <id> screen read
PS C:\...\cmux-tui>
>> echo WINDOWS_PTY_WORKS
WINDOWS_PTY_WORKS
PS C:\...\cmux-tui>

cargo fmt -p ghostty-vt-sys -- --check is clean.

Blast radius

Only the native windows-gnu case changes:

case	before	after
macOS / Linux native	no target passed	unchanged
windows-msvc native	no target passed	unchanged
CI msvc host → gnu target	target passed	unchanged
any cross-compile	target passed	unchanged
windows-gnu native	no target → fails	target passed → builds

Note on the docs

cmux-tui/docs/getting-started.md says Windows support via ConPTY is planned for phase 2, and cmux-tui-artifacts.yml carries "no Windows PTY backend yet". With this build fix the PTY path already works through portable-pty's ConPtySystem — the round-trip above is a real PowerShell child. Happy to send a docs update separately if that reading is right.

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Summary by cubic

Fixes cmux-tui builds on native Windows GNU hosts by passing the zig target even when not cross-compiling.

• Previously, ghostty-vt-sys forwarded -Dtarget only when the Cargo target differed from the host, so a native x86_64-pc-windows-gnu toolchain got no target and zig fell back to the msvc ABI, failing with WindowsSdkNotFound.
• Now the target is passed for any Windows GNU target, matching the existing condition for MinGW archive names. Only the native windows-gnu case changes; other native and cross-compile cases are unaffected.

^{Written for commit 5a0009a. Summary will update on new commits.}

Summary by CodeRabbit

• Bug Fixes
  • Fixed build failures on native Windows GNU environments caused by incorrect target selection.
  • Improved build reliability by ensuring supported Rust targets use the appropriate platform configuration.

Changelog

Fixed: cmux-tui builds on a native Windows GNU host

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• cmux-tui/crates/ghostty-vt-sys/build.rs

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📝 Walkthrough

Walkthrough

The build script now passes -Dtarget= to Zig for known Rust targets, including native *-windows-gnu targets.

Changes

Windows GNU target propagation

Layer / File(s)	Summary
Zig target selection cmux-tui/crates/ghostty-vt-sys/build.rs	The target condition now includes windows-gnu hosts, preventing Zig from defaulting to the MSVC ABI.

Priority: ➖ Normal

Estimated code review effort: 1 (Trivial) | ~5 minutes

Change: Bug fix · Severity of issue fixed: Medium

Suggested reviewers: lawrencecchen

Merge Risk: ⚪ Minimal · up to 1ff7b

The target propagation change is verified for native Windows GNU builds and does not introduce an outstanding merge-blocking risk.

🚥 Pre-merge checks | ✅ 24 | ❌ 1

❌ Failed checks (1 warning)

Check name	Status	Explanation	Resolution
Docstring Coverage	⚠️ Warning	Docstring coverage is 0.00% which is insufficient. The required threshold is 80.00%. Docstring coverage is scoped to functions touched by this diff. Analyzed 1 functions across 1 files.	Write docstrings for the functions missing them to satisfy the coverage threshold.

✅ Passed checks (24 passed)

Check name	Status	Explanation
Cmux Swift Actor Isolation	✅ Passed	PASS: The reviewed range changes only cmux-tui/crates/ghostty-vt-sys/build.rs, a Rust build script. The diff contains no Swift files or Swift actor-isolation constructs. Therefore, the custom check'…
Cmux Swift Blocking Runtime	✅ Passed	PASS: The review-scoped diff changes only cmux-tui/crates/ghostty-vt-sys/build.rs, a Rust build script. No Swift file or Swift runtime synchronization code changed, so the Swift blocking-runtime fai…
Cmux Browser Automation Off-Main	✅ Passed	PASS: The pull request changes only cmux-tui/crates/ghostty-vt-sys/build.rs. The diff adds Zig target selection for native windows-gnu builds and contains no browser.* commands, WebKit/AppKit ac…
Cmux Expensive Synchronous Load	✅ Passed	PASS. The pull request changes only cmux-tui/crates/ghostty-vt-sys/build.rs, a Rust build script. It adds Zig target forwarding for native windows-gnu builds. It does not change production Swift c…
Cmux Cache Substitution Correctness	✅ Passed	PASS: The pull request changes only cmux-tui/crates/ghostty-vt-sys/build.rs, a Rust build script. The diff does not contain production Swift, TypeScript, or JavaScript changes, and it does not repla…
Cmux No Hacky Sleeps	✅ Passed	PASS. The PR changes only cmux-tui/crates/ghostty-vt-sys/build.rs and widens the Zig target condition for native windows-gnu builds. The added lines contain no sleep, timer, polling, fixed backoff…
Cmux Algorithmic Complexity	✅ Passed	PASS. The pull request changes only cmux-tui/crates/ghostty-vt-sys/build.rs, which is Rust build-script code. The algorithmic-complexity check applies to production Swift, TypeScript, JavaScript, sh…
Cmux Swift Concurrency	✅ Passed	The pull request changes only cmux-tui/crates/ghostty-vt-sys/build.rs, a Rust build script. The diff introduces no cmux-owned Swift code and therefore introduces or expands none of the listed legacy…
Cmux Swift @Concurrent	✅ Passed	PASS: The authoritative pull-request diff changes only cmux-tui/crates/ghostty-vt-sys/build.rs and contains no Swift files or Swift declarations. The cmux Swift @concurrent conditions are therefor…
Cmux Swift Package Boundaries	✅ Passed	PASS. The authoritative pull-request diff contains only cmux-tui/crates/ghostty-vt-sys/build.rs, a Rust build script. It contains no Swift source, SwiftPM manifest, or app-target change. Therefore t…
Cmux Swiftpm Lockfiles	✅ Passed	The pull-request diff changes only cmux-tui/crates/ghostty-vt-sys/build.rs. It contains no Package.swift, Package.resolved, .gitignore, workflow, or Xcode project/package-reference changes. Th…
Cmux Swift Logging	✅ Passed	PASS: The review-scoped diff changes only cmux-tui/crates/ghostty-vt-sys/build.rs. It adds Rust comments and target-selection logic for Zig. It adds no Swift code or Swift logging, so the Swift logg…
Cmux User-Facing Error Privacy	✅ Passed	PASS. The only changed file is the developer build script. The diff changes the condition that adds the internal Zig -Dtarget argument and adds developer-only comments. It does not add or modify use…
Cmux Full Internationalization	✅ Passed	PASS. The PR changes only cmux-tui/crates/ghostty-vt-sys/build.rs. The diff adds Zig target-selection logic and developer comments for a Windows build failure. It does not add or change Swift UI tex…
Cmux Swiftui State Layout	✅ Passed	PASS. The pull request changes only cmux-tui/crates/ghostty-vt-sys/build.rs, a Rust build script. The diff introduces no SwiftUI code or state/layout patterns, so the SwiftUI state-layout check does…
Cmux Architecture Rethink	✅ Passed	PASS. The authoritative diff changes only cmux-tui/crates/ghostty-vt-sys/build.rs; it contains no Swift files or Swift architecture changes. The change adds a target argument for native `windows-gnu…
Cmux Swift Auxiliary Window Close Shortcuts	✅ Passed	PASS. The pull request changes only cmux-tui/crates/ghostty-vt-sys/build.rs. The diff contains no Swift or window declaration changes, so the cmux auxiliary-window close-shortcut rule is not applica…
Cmux Source Artifacts	✅ Passed	The PR changes only cmux-tui/crates/ghostty-vt-sys/build.rs. The diff adds source comments and widens a Rust build-script condition. This is intentional hand-written build source, not local tool out…
Cmux No Test Or Debug Seam In Production Source	✅ Passed	PASS: The authoritative PR diff changes only cmux-tui/crates/ghostty-vt-sys/build.rs, a Rust file. It contains no Swift file under a production Sources/ path, so the no-test/debug-seam check is no…
Cmux No Ambient Global State	✅ Passed	PASS: The pull request changes only cmux-tui/crates/ghostty-vt-sys/build.rs, a Rust build script. The authoritative diff contains no Swift or Swift interface files, so the production Swift ambient-g…
Title check	✅ Passed	The title clearly and concisely states the primary change: passing the Zig target on a native Windows GNU host.
Description check	✅ Passed	The description explains the failure, fix, affected cases, verification commands, observed results, and changelog entry. It uses equivalent sections instead of the template headings and omits the chec…
Linked Issues check	✅ Passed	No linked issue is provided, but the description clearly documents the problem, scope, and verification. The supplied template does not require an issue link.
Out of Scope Changes check	✅ Passed	The changes are limited to the stated native Windows GNU build fix and match the pull request objectives. No unrelated changes are reported.

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[github-actions]

Merge receipt for 5a0009aa70: every check was green at merge (12 verified; 15 skipped by policy). Full suite runs on main after merge.

[teamleaderleo]

Merged, thanks @Somuuuu007 :)