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Reverse engineering a Viking VOIP phone protocol with Claude Code — Boris Starkov, Eleven Labs
Takeaway
Coding agents can solve legacy integration problems by combining protocol exploration with observed traffic and validation.
Summary
- An ElevenLabs demo connects a legacy Viking phone through Twilio to a conversational voice agent.
- Claude Code explored the undocumented configuration interface and identified valid two-letter commands, but initial settings disappeared after reboot.
- A Windows VM running the original software and a logging TCP proxy exposed the missing persistence message.
- The agent inferred and tested the binary command's one-byte checksum, illustrating iterative hypothesis testing against real hardware.
claude-codereverse-engineeringvoip
Original description
A Viking VoIP phone sat in the ElevenLabs San Francisco office for a year. Three senior engineers and ChatGPT could not get it working. Boris from ElevenLabs cracked the undocumented protocol with Claude Code in a couple of days: brute forced all 676 possible two letter command combinations, found 80 valid ones, then set up a TCP proxy between a Windows virtual machine and the phone to intercept and log what the proprietary Windows XP software was actually sending. The last piece was a one byte checksum in the persistence command. Claude reverse engineered the formula by running known input output pairs through it, confirmed the pattern in a closed loop, and derived a simple subtraction. Boris describes his own role as being the hands: Claude orchestrated, he physically rebooted the phone and reported how many beeps he heard. The protocol is now open sourced as a Claude Code skill so anyone with a Viking phone can configure it directly without the Windows software. The outcome at AI Engineer Europe: a red phone booth on the third floor where picking up the receiver connects you to a Michael Caine voice agent that quizzes you on British AI history.