Changes: nonblocking DNS cache writes, one transaction per DNS response, duplicate request coalescing, SQLite WAL, IPv4 fallback for unreachable literal IPv6 with a policy-checked DNS mapping.
Validation: 8 automated tests passed. Actual OPPO CPH2159 with Agent 1.2.1 and VPN enabled: YouTube and TikTok HTTP 200; forced IPv6 YouTube HTTP 200 after fallback; Chrome loaded example.org.
Limitations: these checks do not establish sustained video playback or performance on all phones. Server restart can briefly interrupt existing tunnel sessions.
No user database, credentials or email configuration included.
