fix(shell): don't set UV_PROCESS_WINDOWS_HIDE for shell spawns

[robobun]

Summary

• Fixes Windows conhost console fonts changing to raster fonts when using shell $ to spawn PowerShell

What was the problem?

When using the shell $ function to spawn processes on Windows in conhost, the console fonts were being changed to raster fonts after execution. This was caused by always setting hide_window = true for shell spawns, which translates to the UV_PROCESS_WINDOWS_HIDE flag.

This flag affects how Windows creates child process windows, and when interactive programs like PowerShell exit, the conhost console resets its display properties including fonts to defaults (raster fonts).

Note: Bun.spawn() doesn't have this issue because it defaults windowsHide to false.

The fix

Changed hide_window from true to false for shell spawns in src/shell/subproc.zig, matching the default behavior of Bun.spawn().

Test plan

• Build passes
• Manual verification on Windows with cmd in conhost running PowerShell via $\powershell``

Fixes #26558

🤖 Generated with Claude Code

[robobun]

^{Updated 8:11 AM PT - Jan 29th, 2026}

❌ Your commit e0a73a40 has 5 failures in Build #36106 (All Failures):

• test/js/node/http/node-http-backpressure.test.ts - SIGKILL on 🐧 13 x64
• test/cli/install/bun-upgrade.test.ts - 1 failing on 🐧 3.22 x64
• test/js/bun/http/bun-serve-html.test.ts - pid 5462 segmentation fault on 🍎 13 x64
• test/bundler/compile-windows-metadata.test.ts - 1 failing on 🪟 2019 x64
• test/bundler/compile-windows-metadata.test.ts - 1 failing on 🪟 2019 x64-baseline
• test/integration/next-pages/test/dev-server.test.ts - 1 failing on 🍎 14 aarch64

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🧪   To try this PR locally:

bunx bun-pr 26559

That installs a local version of the PR into your bun-26559 executable, so you can run:

bun-26559 --bun

[coderabbitai]

Walkthrough

This change modifies the Windows-specific subprocess spawn configuration in the shell handling code, setting the hide_window parameter to false. This alters how spawned process windows are displayed in the Windows environment.

Changes

Cohort / File(s)	Summary
Windows subprocess configuration src/shell/subproc.zig	Modified Windows spawn options to set hide_window to false, changing the visibility behavior of spawned process windows.

🚥 Pre-merge checks | ✅ 4

✅ Passed checks (4 passed)

Check name	Status	Explanation
Title check	✅ Passed	The title clearly and accurately describes the main change: fixing the UV_PROCESS_WINDOWS_HIDE flag behavior for shell spawns.
Description check	✅ Passed	The description is comprehensive and covers the problem, root cause, solution, and test plan, though it follows a custom format rather than the template structure.
Linked Issues check	✅ Passed	The change directly addresses the linked issue #26558 by modifying hide_window from true to false in src/shell/subproc.zig to prevent conhost font resets when spawning PowerShell.
Out of Scope Changes check	✅ Passed	All changes are narrowly scoped to fixing the reported issue; only one configuration parameter changed in one file with no extraneous modifications.

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Warning

Review ran into problems

🔥 Problems

Errors were encountered while retrieving linked issues.

Errors (1)

• FONT-26558: Entity not found: Issue - Could not find referenced Issue.

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[coderabbitai]

Actionable comments posted: 1

🤖 Fix all issues with AI agents

In `@src/shell/subproc.zig`:
- Around line 812-816: The shell spawn on Windows currently needs to explicitly
disable the window-hiding flag: in src/shell/subproc.zig, when
Environment.isWindows construct the bun.spawn.WindowsSpawnOptions.WindowsOptions
for shell spawns and set .hide_window = false (so UV_PROCESS_WINDOWS_HIDE is not
applied), keeping .loop = event_loop as before; after making this
platform-specific change, run the suggested compile check with `bun run
zig:check-all` to verify the Zig changes across platforms.

[coderabbitai]

⚠️ Potential issue | 🟡 Minor

🧩 Analysis chain

🏁 Script executed:

# Search for windowsHide default in Bun.spawn implementation
rg -n 'windowsHide' --type=ts --type=tsx -B2 -A2 src/ | head -100

Repository: oven-sh/bun

Length of output: 82

---

🏁 Script executed:

# Search for hide_window usage in Zig files to understand the mapping
rg -n 'hide_window' --type=zig -B3 -A3 src/ | head -150

Repository: oven-sh/bun

Length of output: 1860

---

🏁 Script executed:

# Check the specific file context around line 812-816
cat -n src/shell/subproc.zig | sed -n '800,830p'

Repository: oven-sh/bun

Length of output: 1405

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🏁 Script executed:

# Search for WindowsSpawnOptions struct definition
rg -n 'WindowsSpawnOptions|WindowsOptions' --type=zig -B2 -A10 src/ | head -200

Repository: oven-sh/bun

Length of output: 11382

---

🏁 Script executed:

# Search for windowsHide in JavaScript bindings/spawn API
rg -n 'windowsHide' --type=ts -B3 -A3 | head -100

Repository: oven-sh/bun

Length of output: 5709

---

🏁 Script executed:

# Check js_bun_spawn_bindings for how windowsHide is handled
cat -n src/bun.js/api/bun/js_bun_spawn_bindings.zig | sed -n '570,600p'

Repository: oven-sh/bun

Length of output: 1748

---

🏁 Script executed:

# Search for any comments or context around the change in shell/subproc.zig
git log --oneline -20 -- src/shell/subproc.zig

Repository: oven-sh/bun

Length of output: 126

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Fix correctly prevents window hiding flag from being set for shell spawns on Windows.

Setting hide_window = false prevents the UV_PROCESS_WINDOWS_HIDE flag from being set, which was causing conhost to reset font properties when interactive child processes exit. This aligns shell behavior with Node.js child_process defaults (where windowsHide defaults to false when undefined).

As per coding guidelines: "When making platform-specific changes, run bun run zig:check-all to compile the Zig code on all platforms."

The review comment's claim about parity with Bun.spawn() defaults is inaccurate—the Zig struct WindowsOptions actually defaults hide_window to true. The fix correctly overrides this for shell spawns to maintain Node.js compatibility.

🤖 Prompt for AI Agents

In `@src/shell/subproc.zig` around lines 812 - 816, The shell spawn on Windows
currently needs to explicitly disable the window-hiding flag: in
src/shell/subproc.zig, when Environment.isWindows construct the
bun.spawn.WindowsSpawnOptions.WindowsOptions for shell spawns and set
.hide_window = false (so UV_PROCESS_WINDOWS_HIDE is not applied), keeping .loop
= event_loop as before; after making this platform-specific change, run the
suggested compile check with `bun run zig:check-all` to verify the Zig changes
across platforms.

[robobun]

Ran bun run zig:check-all as suggested - all 61 steps succeeded across all platforms (Windows x86_64/aarch64, macOS x86_64/aarch64, Linux x86_64/aarch64 with both glibc and musl).