No error handling when `system-prompt` points to file that does not exist

[StefMa]

I played around with this tool and added a system prompt pointing to a file systempromp.md.
I started the tool and everything "looked fine".
Until I realized, the system prompt wasn't really used.

The problem?
I had a typo in systempromp.md (spot the missing t 😉 ).
The file name is actually systemprompt.md

The "problem" is here:

mcphost/internal/config/config.go

Lines 249 to 266 in 4891f87

	func LoadSystemPrompt(input string) (string, error) {
	if input == "" {
	return "", nil
	}
	// Check if input is a file that exists
	if _, err := os.Stat(input); err == nil {
	// Read the entire file as plain text
	content, err := os.ReadFile(input)
	if err != nil {
	return "", fmt.Errorf("error reading system prompt file: %v", err)
	}
	return strings.TrimSpace(string(content)), nil
	}
	// Treat as direct string
	return input, nil
	}

If os.Stat() returns an error, the tool assumes the input as text.
So the system prompt end up as systempromp.md 🫣 instead of the content of the correct file.

I'm not sure how to handle it better?
Maybe like curl, that requires a @ followed by the file path?
Or different options? system-prompt and system-prompt-file

💭