Per Snyk docs: --debug plus SNYK_LOG_LEVEL=trace gives full API-level tracing of CLI behavior.

Context: Problem: The Snyk CLI behaves unexpectedly on your projects and you need to see what it is doing. Run any command with --debug (or -d) for verbose logs covering the environment, the command, and network interactions with the Snyk API. For maximum detail, raise the log level: snyk test --debug --log-level=trace, or export SNYK_LOG_LEVEL=trace before running. Supported levels are debug (default) and trace (everything in debug, plus more).