Tesla's stock tumbled as much as 6% on Friday, its worst single-day slide in weeks, after the company's long-hyped Cybercab robotaxi finally hit the streets of Austin — and immediately drew a federal safety investigation instead of the fanfare investors wanted.

The National Highway Traffic Safety Administration opened an "Audit Query," an enforcement action examining whether Tesla properly certified that the two-seat, steering-wheel-free Cybercab meets Federal Motor Vehicle Safety Standards. Those standards were written assuming a human driver sits behind a wheel with pedals and mirrors within reach — equipment the Cybercab simply doesn't have. According to NHTSA's own press release, the agency will scrutinize the technical data Tesla relied on to decide those requirements don't apply to a car with no human controls, with the probe reportedly covering roughly 1,000 of the vehicles.

Shares fell to around $354, unwinding a 5.4% pop the day before the launch event and leaving the stock down more than 20% for the year, according to The Motley Fool. Other outlets pegged the intraday drop closer to 3%, with shares changing hands near $364 — still enough to make Tesla the worst performer among the "Magnificent Seven" tech giants Friday, per 24/7 Wall St.

An Invite-Only Event, and Musk No-Showed

Thursday's launch event in Austin was invitation-only, wasn't livestreamed, and had no accompanying press release. CEO Elon Musk didn't appear in person, instead posting prerecorded videos. Tesla said it had registered 45 Cybercabs as part of its Texas robotaxi fleet — a fraction of the roughly 420-vehicle fleet, mostly Model Y SUVs, the company already runs there — and confirmed rides would be limited to a geofenced zone around Austin with no timeline for expanding to other cities, pricing, or production volumes disclosed.

Wall Street's reaction was blunt. Analysts at RBC Capital Markets said the event left "core questions" unanswered on pricing, production cadence and regulatory approvals, while Wells Fargo flagged early operational stumbles, including customer complaints about wrong routes, skipped destinations and unusually long wait times, according to CNBC.

"Tesla's Cybercab event was largely a bust," said Gary Black, managing director of Future Fund, in a widely cited assessment of the launch.

Not every analyst was bearish on the longer arc: Deepwater Asset Management's Gene Munster predicted Tesla could add roughly 300 more Cybercabs in Austin within a month, betting the rocky debut is a speed bump rather than a wall.

The regulatory scrutiny isn't unprecedented, but the timeline is a warning sign for Tesla bulls. Amazon's self-driving unit Zoox faced a similar NHTSA audit query back in 2023 over its own pedal-and-wheel-free design — and didn't win commercial approval until July of this year, nearly three years later. Tesla, by contrast, has already put paying customers in the Cybercab before that approval process has run its course.

For now, Tesla has not said how it will respond to the audit query, and NHTSA has given no timeline for concluding it. Investors will be watching for any expansion of the geofenced Austin zone, additional city announcements, or — just as closely — any sign the agency moves to slow or ground the fleet while it digs through Tesla's compliance paperwork.