[bug] Debug logging silently discarded on file creation error

[docker-agent]

🟡 medium - bug

File: cmd/root/root.go (line 191)

Code

logFile, err := logging.NewRotatingFile(path)
if err != nil {
	return err
}
f.logFile = logFile

slog.SetDefault(slog.New(slog.NewTextHandler(logFile, &slog.HandlerOptions{Level: slog.LevelDebug})))

Problem

In setupLogging, if logging.NewRotatingFile(path) returns an error, the error is returned, but slog.SetDefault is never updated to write to the file. This means that if debug mode is enabled and an error occurs during log file creation, all subsequent debug logs will be silently discarded because the default logger remains slog.DiscardHandler from line 186.

Suggested Fix

If logging.NewRotatingFile returns an error, slog.SetDefault should be configured to write to cmd.ErrOrStderr() with debug level, similar to how it's handled in PersistentPreRunE for the initial logging setup. This ensures that debug logs are still visible even if file logging cannot be established.

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Found by nightly codebase scan