Broadcom has extended its long-running relationship with Apple through 2031, signing new multi-year agreements to design and supply a range of custom chips for the iPhone maker.

The deal deepens one of the most important supplier relationships in consumer electronics, and it sent Broadcom’s shares up around 4% as investors read it as a guarantee of years of locked-in revenue. It also lands while the whole industry is scrambling for secure long-term chip supply.

Broadcom has been inside Apple’s products for years, even if its name rarely appears on them. It supplies the radio-frequency components that let iPhones connect to cellular networks, along with Wi-Fi and Bluetooth chips and other networking parts, the unglamorous silicon that makes a phone actually communicate. The new agreements cover custom ASIC products, application-specific chips built for particular jobs, across multiple future generations of Apple hardware.

The commercial weight of the relationship runs both ways. Analysts estimate that Apple accounts for roughly 20% of Broadcom’s annual revenue, which makes the iPhone maker one of its largest customers and gives an extension like this real meaning for Broadcom’s earnings visibility. Knowing a fifth of your revenue is contracted out to 2031 is the kind of certainty chip suppliers rarely get.