Both exist for one diagnostic. KeWaitForSingleObject is declared kHighFrequency, so it is silent even at LOG_LEVEL=3 unless --log_high_frequency_kernel_calls=true is passed - and that flag writes ~157 MB in ten minutes and slows the emulator so far that the title had still not appeared when skip_intro's fixed 600 s budget ran out. The run was then scored "BOOT FAILED" when it was only slow. EXTRA_FLAGS passes one-off diagnostic cvars without making them defaults; SKIP_INTRO_TIMEOUT lets a deliberately-slowed run have the time it needs. Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com> Claude-Session: https://claude.ai/code/session_01PMRJjbxLqZtsb5Vb7KunPE