C4 network watch, 2026-10-20 11:40 UTC+8. strace -f -e trace=connect,sendto,sendmsg on c4_run.py (compress all 4 payloads, default config).
Run A (pre-registered): HEADROOM_TELEMETRY=off DO_NOT_TRACK=1 HEADROOM_BEACON=off, normal network. Network syscalls recorded: 0
Run B (EXTRA): no opt-out variables at all (vendor default, beacon on), inside an empty network namespace (sudo unshare -n) so nothing could leave the box; any attempt would still show as a connect() call. Network syscalls recorded: 0
Both runs printed the same token counts as c1b (gh 182454->182454, pypi 54783->54783, logs 110724->56415, wiki 35177->23679).
Not covered: the proxy, MCP server and framework integrations (headroom proxy / wrap / MCP / LangGraph / Strands), which are the code paths that import the beacon (headroom/telemetry/session.py, upload URL headroom-beacon.headroom-beacon.workers.dev). We only used the Python library compress().