fix: initialize pseudo console with default size for SSH sessions (coder#20472)

fioan89 · web-flow · commit b89093031e0f · 2025-10-25T14:05:03.000+11:00
Resolved an invalid parameter error (-2147024809) during PTY creation on Windows 11 22H2 (but not only) when connecting via JetBrains Toolbox which spawns the native SSH client with `-tt` forcing PTY allocation even though there is no "terminal" on the client side to query its size. CreatePseudoConsole doesn't accept a 0x0 (zero width and zero height) console size and unfortunately, there is NO explicit documentation in the official Microsoft documentation that states the minimum valid values or explicitly prohibits 0x0. Looking at real-world implementations in the search results, all examples use reasonable non-zero values. I tested this with a local Windows VM registered to dev.coder.com i.e. externally managed workspace. Fixes: coder#20468
diff --git a/pty/pty_windows.go b/pty/pty_windows.go
@@ -54,10 +54,19 @@ func newPty(opt ...Option) (*ptyWindows, error) {
 		return nil, err
 	}
 
-	consoleSize := uintptr(80) + (uintptr(80) << 16)
+	// Default dimensions
+	width, height := 80, 80
 	if opts.sshReq != nil {
-		consoleSize = uintptr(opts.sshReq.Window.Width) + (uintptr(opts.sshReq.Window.Height) << 16)
+		if w := opts.sshReq.Window.Width; w > 0 && w <= 65535 {
+			width = w
+		}
+		if h := opts.sshReq.Window.Height; h > 0 && h <= 65535 {
+			height = h
+		}
 	}
+
+	consoleSize := uintptr(width) + (uintptr(height) << 16)
+
 	ret, _, err := procCreatePseudoConsole.Call(
 		consoleSize,
 		uintptr(pty.inputRead.Fd()),
