feat: add platform-specific process attributes support

[nikeshparajuli]

Add platform-specific process attributes support

Problem

When llama-swap spawns child processes on Windows (such as llama-server instances), console windows appear and remain visible throughout the process lifetime, resulting in a poor user experience. On Windows, .exe processes display console windows by default unless explicitly hidden.

Solution

This PR adds platform-specific process attributes using Go build tags:

• process_windows.go: Sets HideWindow: true and CREATE_NO_WINDOW flag to hide console windows on Windows
• process_unix.go: No-op implementation for Unix systems (no changes needed)
• process.go: Calls setProcAttributes() when spawning processes

Changes

• Add setProcAttributes() function with platform-specific implementations
• Apply process attributes to both main command and stop command execution
• No configuration changes required - works automatically per platform

Testing

Tested on Windows 11. Console windows are now completely hidden during model operations.

Thank you for maintaining this project!

Summary by CodeRabbit

• Improvements
  • Added platform-specific process attribute configuration to optimize startup and shutdown operations across all systems. Windows systems now receive enhanced process initialization handling, while Unix systems benefit from streamlined attribute configuration. This ensures consistent and appropriate system-level configurations are properly applied during both command startup procedures and graceful termination sequences across all supported environments.

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[coderabbitai]

Walkthrough

This change introduces platform-specific process attribute configuration for upstream commands in the proxy. Calls to setProcAttributes() are wired into the command startup and stop paths, with Unix (no-op) and Windows (hide window) implementations provided via build-tag-specific files.

Changes

Cohort / File(s)	Summary
Process setup calls proxy/process.go	Adds setProcAttributes(p.cmd) call in start() after command configuration and setProcAttributes(stopCmd) call in cmdStopUpstreamProcess() after constructing the stop command.
Unix implementation proxy/process_unix.go	Defines setProcAttributes(cmd *exec.Cmd) as a no-op function for Unix-like systems (build tag: non-Windows).
Windows implementation proxy/process_windows.go	Defines setProcAttributes(cmd *exec.Cmd) to set SysProcAttr with HideWindow: true and CreationFlags: 0x08000000 (CREATE_NO_WINDOW) for Windows systems (build tag: windows).

Estimated code review effort

🎯 2 (Simple) | ⏱️ ~10 minutes

• Verify that setProcAttributes() calls are placed in the correct execution paths (startup and stop).
• Confirm the Windows CreationFlags value (0x08000000) correctly corresponds to CREATE_NO_WINDOW.
• Validate that the Unix implementation appropriately uses a no-op for the intended behavior.

Pre-merge checks and finishing touches

✅ Passed checks (3 passed)

Check name	Status	Explanation
Description Check	✅ Passed	Check skipped - CodeRabbit’s high-level summary is enabled.
Title check	✅ Passed	The title accurately describes the main change: adding platform-specific process attributes support across Unix and Windows systems.
Docstring Coverage	✅ Passed	Docstring coverage is 100.00% which is sufficient. The required threshold is 80.00%.

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• Create PR with unit tests
• Post copyable unit tests in a comment

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[coderabbitai]

Actionable comments posted: 0

🧹 Nitpick comments (1)

proxy/process_windows.go (1)

14-14: Consider using a named constant for improved readability.

The magic number 0x08000000 represents CREATE_NO_WINDOW. While correct, a named constant would improve code clarity and maintainability.

Apply this diff to use a named constant:

+const (
+	CREATE_NO_WINDOW = 0x08000000
+)
+
 // setProcAttributes sets platform-specific process attributes
 func setProcAttributes(cmd *exec.Cmd) {
 	cmd.SysProcAttr = &syscall.SysProcAttr{
 		HideWindow:    true,
-		CreationFlags: 0x08000000, // CREATE_NO_WINDOW
+		CreationFlags: CREATE_NO_WINDOW,
 	}
 }

📜 Review details

Configuration used: Path: .coderabbit.yaml

Review profile: CHILL

Plan: Pro

📥 Commits

Reviewing files that changed from the base of the PR and between 86e9b93 and fe766f8.

📒 Files selected for processing (3)

• proxy/process.go (2 hunks)
• proxy/process_unix.go (1 hunks)
• proxy/process_windows.go (1 hunks)

⏰ Context from checks skipped due to timeout of 90000ms. You can increase the timeout in your CodeRabbit configuration to a maximum of 15 minutes (900000ms). (1)

• GitHub Check: run-tests

🔇 Additional comments (4)

proxy/process_windows.go (1)

1-16: LGTM! Clean platform-specific implementation.

The use of build tags to separate platform-specific code is appropriate, and the combination of HideWindow: true and CREATE_NO_WINDOW flag correctly prevents console windows from appearing when spawning child processes on Windows.

proxy/process_unix.go (1)

1-12: LGTM! Appropriate no-op implementation.

The build tag correctly targets non-Windows platforms, and the no-op implementation is the right approach for Unix systems where console window hiding is not needed.

proxy/process.go (2)

259-259: LGTM! Correct placement of setProcAttributes.

The call is appropriately positioned after command configuration and before execution, ensuring process attributes are applied to the main upstream command.

---

629-629: LGTM! Consistent application to stop command.

The call ensures that the stop command receives the same process attributes as the main command, maintaining consistent behavior across all spawned processes.

[mostlygeek]

Hi,

I’ve never seen this happen before; though I don’t run Windows. What version of Windows are you using?

[nikeshparajuli]

Hi,

I’ve never seen this happen before; though I don’t run Windows. What version of Windows are you using?

Hi, Windows 11. If it matters, we are spawning llama-swap via nodejs.

Here, I ran two models so two separate terminals appeared.

[mostlygeek]

Interesting. Thanks for the contrib.